elements 23, issue 2 | 2008 - evonik

1

elements23S C I E N C E N E W S L E T T E R | 2 2 | | 2 4 | 2 5 | 2 0 0 8

C O AT I N G S

SILIKOPON®EF: A Strong Rust-Fighting Network

I N T E R F A C I A L T E C H N O L O G I E S

New Stabilizers for PUR Foams: Saving Energy with Better Refrigerators

I N O R G A N I C P A R T I C L E D E S I G N

Silicone Sealing Compounds: Silicas for Matt Elegance

D E S I G N I N G W I T H P O LY M E R S

Plastics for Photovoltaics: Tapping the Sun on a Shoestringwith Slim Solar Cells

Would you drive an old car that uses 40 liters of gas per 100 kilometers? Probably not. Homes are a differentmatter: In Germany alone, apartments, numbering in the hundreds of thousands, use too much energy. But things are changing. Evonik has improved a residential complex from the 1960s in Düsseldorf – with amini-CHP (combined heat and power) system, photovoltaics unit, decentralized ventilator systems withheat recovery, triple glazing, and thermal insulation. The primary energy demand per square meter andyear dropped from 286 kWh to 36.2 kWh, which is below the specifications of the German Energy SavingOrdinance for new buildings.

Evonik is also going the extra mile for energy generation, as our participation in the three geothermalprojects in Erding, Simbach-Braunau, and Unterschleissheim demonstrates. With a total output of 182,000MWh per year, these plants generate enough heat to supply 20,222 single-family households. Evonik is the market leader in this area.

At the recent Hannover Messe, we displayed a conventional Golf V that we and our partners have made371 kilos lighter and more efficient. The Evonik parts include a lithium-ion starter battery that is 16 kilo-grams lighter; sandwich composite materials for the hood, roof, tailgate, doors, interior, and trunk; low-rolling-resistance tires with silica/silane technology; and motor and gear oils with optimized oil additives that im -prove efficiency. Fuel consumption dropped from 5.7 to 3.9 liters per 100 kilometers, and CO2 emissionsdecreased by 32 percent to 103 grams per kilometer.

Photovoltaics is another example. Soon, we will commence operation of a solar silicon plant that uses90 percent less energy for deposition than established processes. We also plan to make lithium-ion tech -nology useful for storing regenerative energy with new battery components. And even if silicon technologyis positioned to dominate photovoltaics in the near future, we are already looking into alternatives.Currently, the Functional Films & Surfaces Project House is finding out what kind of contribution Evonikcan make in the area of flexible thin-film cells.

With our development initiative Appliance 2010, we are joining forces with customers to improve theenergy efficiency of refrigerators. The goal is to reduce the energy consumption of the next generation ofrefrigerators by up to five percent because PUR rigid foams work even better as an insulating layer. The roadto this objective leads through special additives that improve the cell structure of the PUR and, therefore, itsthermal insulating properties.

We secure the future with projects like these, because the energy supply is central to people’s lives, eco-nomic prosperity and – to the extent that we develop the necessary concepts, products, and technologies –the prosperity of Evonik.

I hope you enjoy the current issue.

2 elements23 E V O N I K S C I E N C E N E W S L E T T E R

E D I T O R I A L

Energy Efficiency

22 COATINGSA dash of color on the sea:Silica makes boat hulls colorful

NEWS25 New distribution channel for homogeneous

catalysts25 Strengthening of exclusive synthesis business

26 DESIGNING WITH POLYMERSPlastics for photovoltaics: Tapping the sun on a shoestring with slim solar cells

NEWS31 MaDriX:

Alliance project for printed electronics launched

32 EVENTS AND CREDITS

elements23 | 2008

The cover picture showsPUR rigid foam. Its cellstructure has an effect onthe energy efficiency ofrefrigerators (p. 12)

4 COATINGSSILIKOPON®EF: A strong rust-fighting network

10 INORGANIC PARTICLE DESIGNPartnership with the Institute for Particle Technology:High-performance electrodes forlarge-scale lithium-ion batteries

12 INTERFACIAL TECHNOLOGIESNew stabilizers for PUR foams:Saving energy with better refrigerators

NEWS17 License for HCN technology to Akzo Nobel 17 Evonik coordinates new BMBF project

18 INORGANIC PARTICLE DESIGNSilicone sealing compounds: Silicas for matt elegance

contents

Dr. Alfred OberholzMember of theExecutive Board ofEvonik Industries AG

elements23 E V O N I K S C I E N C E N E W S L E T T E R 3

Evonik’s Active Oxygens Business Line has successfully concludedthe capacity increase of its hydrogen peroxide plant in Barra do Riacho(Brazil). The expansion raised the plant’s hydrogen peroxide capacityto 70,000 metric tons per year, with the potential to go up to 100,000metric tons. The Barra do Riacho facilities have been in operationsince the mid-1990’s.

“The expansion has concluded at a time when the region is ex -periencing a steady growth in demand for hydrogen peroxide,” saysDr. Alfred Oberholz, the member of Evonik’s Executive Board who isresponsible for the Chemicals Business Area. “The increased capacity

news

+++ Expansion of hydrogen peroxide capacity in Brazil completed

Evonik Industries and Headwaters of South Jordan (Utah, USA) havesubstantially increased production capacity for hydrogen peroxide atthe facility operated by their joint venture EvonikHeadwaters in Ulsan(Korea). The joint venture acquired this facility from the Finnish com-pany Kemira Oyi, Helsinki, in 2006. Using proprietary technologyfrom Evonik, it has more than doubled capacity from the original levelof 34,000 metric tons p. a. within a year.

The hydrogen peroxide (H2O2) produced in Ulsan will be suppliedto customers in Korea and to the adjacent facility operated by theSeoul-based company SKC. Dr. Thomas Haeberle, Head of Evonik’sIndustrial Chemicals Business Unit comments: “The start-up of theadditional production capacity for hydrogen peroxide in Korea bringsus a good deal closer to our goal of supplying large quantities of hy -dro gen peroxide for chemical synthesis reactions.”

+++ Evonik joint venture brings additional production capacity for H2O2 onstream in Korea

In the next few months, here in Ulsan, SKC will start up one of theworld’s first production facilities for propylene oxide based on theHPPO process. Hydrogen peroxide and propylene are the startingprod ucts for this low-cost, environment-friendly method of produc -ing propylene oxide, which is used in the manufacture of polyure -thane, for example for cushioning and instrument panels for autos.SKC has acquired a license for the HPPO process, which was devel -oped by Evonik and Uhde, Dortmund, Germany.

Haeberle explains Evonik’s strategy as follows: “Joint develop-ment of innovative technologies enables us to enter new areas of bu si -ness in collaboration with established partners. One example is indus -trial use of the bleaching and oxidation agent hydrogen peroxide inchemical synthesis reactions.” To provide a long-term basis for thisstrategy, Evonik and Headwaters are currently working on a new cata-lytic direct synthesis route for the production of hydrogen peroxide.

+++ Expansion of plasticizer alcohol capacity in Marl

Evonik Industries is expanding its oxo alcohol production capacity atthe Marl site by 60,000 metric tons per year. The alcohol 2-propyl hep-tanol (2-PH), which is used as a starting material in the manufactureof PVC, for example, in cables and films, will also be produced therefor the first time. The 2-PH facility is scheduled to come onstream inthe latter half of 2009.

Given the globally growing demand for plasticizers, the new 2-PHplant will complement the existing isononanol (INA) business. At theMarl site, Evonik already has an annual INA capacity of 340,000metric tons, which makes the facility the world’s largest single pro-duction plant for this plasticizer alcohol, and Evonik the largest pro -ducer of C9/C10 plasticizer alcohols in Europe. Dr. Klaus Engel,member of Evonik’s Executive Board with responsibility for theChemicals Business Area, says: “With this investment, we are opti -mizing our production network in C4 chemicals, an area where wealready enjoy a leading position worldwide and have expertize goingback several years.”

Plasticizers transform brittle PVC into a flexible material, makingit possible to use the polymer in a greater number of consumer prod -

will enable us to be a much more efficient and reliable supplier to ourcustomers, and underscores our intention of expanding our good po si -tion in the hydrogen peroxide market.”

Following the successful application of Evonik’s proprietaryhigh-performance technology in Barra do Riacho, the technology willnow be applied at Evonik’s hydrogen peroxide production sites ineither Gibbons, Canada, or Mobile, Alabama, depending on marketrequirements. The use of this technology allows existing plants to beexpanded efficiently and economically, obviating the need for costlynew construction.

ucts. They are contained in, for example, floor coatings, cable insula-tion, tarpaulin fabrics, various automotive applications, and films. Inaddition to 2-PH and isononanol, Evonik also produces in Marl thePVC plasticizer VESTINOL™ 9, at a capacity of 220,000 metric tonsper year.

MARKUS HALLACK

he VOC (volatile organic compound) legislation hasbecome a pivotal event in the area of environmentalprotection. Its purpose is to reduce volatile organicsolvents because of their role in forming tropospheric

ozone – the “summer smog” that is so damaging to the environ-ment and human health. With its “Organic Solvent Paint andCoatings Ordinance” of December 2004, Germany implementedthe corresponding EU directive, and aims to eliminate 280,000metric tons of VOCs per year in the paints and coatings industry.Various branches of the industry – including the automobile,rolling stock, and aircraft production sectors – are currentlywork ing on reducing the VOC content of paint formulations to100 grams per liter by the year 2010.

Other countries, such as the United States, are making simi-lar efforts to limit VOCs. Because some states have set their ownVOC standards, information on the success of such restrictionsor goals is difficult to obtain. Experts predict, however, that inthe long run the most stringent requirements will be implemen-ted. Currently, such requirements provide for a VOC content of250 grams per liter for Europe and North America.

Against this backdrop, Evonik has developed new bindersystems with a high solids content. The systems are based onsilicone-epoxy hybrid technology and are as strong as they areenvironmentally compatible. Originally, silicone and siliconecombination resins were used for any application requiring heatresistance. Additional properties are good resistance to weath -ering and yellowing. Fields of application include equipment as -sembly, exhaust systems for cars and two-wheeled vehicles, aswell as stoves and fireproof coatings.

In the past, the focus was on pure silicone resins and silicone-polyester combination resins. The applications were always inthe area of heat-resistant corrosion protection. To expand theproduct range, developers placed a stronger emphasis on weather-resistance when they conceived the new silicone-epoxy hybridbinders. This is where Evonik can leverage its core expertise toproduce an optimal and unique profile of properties by selec -tively combining various organic resins with a silicone resin.

S I L I K O P O N ® E F

elements23 E V O N I K S C I E N C E N E W S L E T T E R4

Base resin with epoxide and alkoxy groups

All silicone resins of Evonik’s Tego brand are produced ac -cording to a uniform reaction scheme in which the resin startingprod ucts are produced with a defined molecular-weight distri-bution. As reactive groups, these resins carry practically noSiOH groups, and almost exclusively SiOR groups. These thenfurther react with OH-functional compounds to a hybrid resinthat contains both epoxide and alkoxy groups.

An amino alkoxy silane is used as the hardener. Its aminogroups react with the epoxide groups, and the three alkoxygroups react under the addition of water and the influence ofatmo spheric humidity with the alkoxy groups in the resin, withthe amine as a catalyst. This “double cross-linking” creates a sili-con-epoxy hybrid backbone chain with an extremely high levelof cross-linking.

Varying the siloxane starting products and polyols used alsomakes it possible to produce silicone-epoxy hybrid binders(trademark SILIKOPON®) that are 50 percent silicone. The ali-phatic epoxides contribute good corrosion and chemical resis -tance. The alkoxy siloxanes display good UV stability and resis -tance to yellowing. Both components react with each other tocreate the innovative hybrid binders. For its part, the hardenerfrom the group of the amino alkoxy silanes, which is not addeduntil application, reinforces resistance to corrosion and chem -icals.

Using similar methods, Evonik has already created systemsbased on aromatic epoxides that are distinguished by their ex -treme heat resistance and, therefore, are preferred coatings forthe exhaust systems of two-wheeled vehicles. They also adhereso well to steel substrates that paints formulated with them donot delaminate, even in extreme temperature changes. This kindof binder system is outstanding for the production of paint for-mulations for the exhaust systems of cars and aircraft engines.Both applications must exhibit this material property.

With the new method of using aliphatic epoxides, Evonikhas made it possible to produce formulations that contain >>>

Rust is everywhere – and corrosion protection is a permanent challenge. Experts estimate that one-third of all iron and steel products manufactured worldwide in a year are used to replace corrodedstructural components. The economic damage, therefore, is enormous. According to the BatelleInstitute of Columbus, Ohio, the United States alone suffers damage in the amount of US $300 billioneach year, while the renowned Karl-Winnacker Institute of DECHEMA puts that figure at well over€ 50 billion per year for Germany. A matter of equal importance is sustainable corrosion protectionusing suitable methods and materials. The primary focus here is on systems with high durability and along lifespan, good color retention and stability, that are as good for the economy as they are for theenvironment – systems like the new silicone-epoxy hybrid resins from Evonik.

T

A Strong Rust-FightingMARKUS HALLACK

The new silicone-epoxy hybrid resins are suitable as corrosion pro-tection for steel, but also work well as coatings for wood, concrete,or composite materials. Their key advantages are low flammabilityand, above all, a low VOC content of below 100 grams per liter,which also makes them a clear improvement over existing systems

5

C O A T I N G S

elements23 E V O N I K S C I E N C E N E W S L E T T E R

Network

Aliphatic epoxy•Corrosion resistance•Chemical resistance

Alkoxy silicone resin•UV resistance•Low yellowing

Hardener amino alkoxy silane•Corrosion protection•Chemical resistance

Dynasylan®

SILI

KOPO

N®

EF

O

CH CH2

Reaction scheme for producing silicone-epoxy hybrid resins. An aliphatic epoxide and an alkoxy silicone resin react with OH-func tional compounds to a hybrid resin that carries bothepoxide and alkoxy groups. When cross-linked with an amine alkoxy silane, this amino group reacts with the epoxide groups and the alkoxy groups under the influence of atmospheric humidity with the alkoxy groups in the resin

ORO

R1

Si OR4

R3

H2N

SiORRO

ORR=Me or Et

H2O

-ROH

Gloss retention measured at a 60-degree angle under the challenging conditionsof the Florida test: Compared not only to similar resins currently on the market butto its predecessor SILIKOFTAL® ED, SILIKOPON® EF displays outstanding glossretention, even after two-and-a-half years

■■ SILIKOPON® EF ■■ SILIKOFTAL® ED ■■ Commercial resin

Gloss retention [%]

The ΔE color difference, which describes the change in color as compared to theoriginal color, as well as the yellowing, in the Florida test. Just like its predecessorSILIKOFTAL® ED, the yellowing of SILIKOPON® EF is so minimal that it can hardlybe detected by the naked eye. The commercial resin, on the other hand, showsextreme yellowing

■■ SILIKOPON® EF ■■ SILIKOFTAL® ED ■■ Commercial resin

ΔE color difference


only 5 percent solvent – or 75 grams of VOCs per liter. This issig ni ficantly below the systems currently available on the mar-ket. Typi c ally, a paint formulation consists of over 60 percentSILIKOPON® EF. The hardener – Dynasylan® AMEO or AMMO,for example – is added at a ratio of 100:16. Additionally, “EF” de-notes a considerably more flexible version than its predecessorED (extremely durable), which was formulated to be ex cep -tionally hard. Pigments also contain an equally high share ofmore than 20 percent. The mixtures offer the benefit that boththe manufacturing and processing machines require only veryminimal adaptation. Not least, this means high cost savings forpaint producers and processors.

Outstanding results in the Florida test

The new coating systems performed extremely well in an inten-sive series of tests under Florida conditions, which are acceptedby the paint industry worldwide. There is now over two yearsworth of data from the South Florida test. On the whole, the datareveals extraordinary gloss retention and weather resistance.Yellowing is so minimal that it is barely detectable by the humaneye. The results for corrosion protection are also outstanding.

Because of their low solvent content, these types of systemsare also suitable for ultrahigh-solids coatings. Developers havealso successfully demonstrated that they are easy to clean and

98

96

94

92

90

88

86

84

82

806 12 18 24 30

Months

109876543210

6 12 18 24 30Months

The speed of the hardening reaction can be controlled through the choice of hardener (AMEO stands for 3-aminopropyltriethoxysilane, AMMO for 3-aminopropyltrimethoxysilane) and, if necessary, catalyst (DBTL stands for dibutyl tin laurate). These choices have no effect on the finalhardness of the paint film, however, as the pendulum hardness, illustrated in the figure, shows

■■ ED AMEO 100:16 ■■ EF AMEO 100:16 ■■ EF AMEO/AMMO 100:14

■■ EF AMEO/DBTL 100:18 ■■ EF AMEO/DBTL 100:14

Pendulum hardness [n]

The different drying times for hardeners (AMEO stands for 3-aminopropyltriethoxysilane, AMMO for 3-aminopropyltrimethoxysilane) and catalyst (DBTL stands for dibutyl tin dilaurate):Whether in high atmospheric humidity or extreme temperatures – with SILIKOPON® EF, the speed of harden ing can be adapted to the prevailing conditions

■■ ED AMEO ■■ EF AMEO ■■ EF AMEO/AMMO 100:14

■■ EF AMEO/DBTL 100:18 ■■ EF AMEO/DBTL 100:14

Degree of dryness (touch dry)


can be used as anti-graffiti coatings. Clear coats for these appli-cations have already been formulated. The drying conditionsare comparable to those of conventional two-component poly -urethane systems. In this case, however, because the alkoxycross- links in a hydrolyzation reaction, drying depends not onlyon the temperature but also on the atmospheric humidity.Drying time, therefore, can be controlled through these twoparameters.

All told, Evonik can supply the market with an excellent va -riety of hardeners. Amino-functional silanes – an area in whichEvonik has been active for about 50 years under the trademarkDynasylan® – are the hardeners normally used for epoxide

resins. For the hardening of the new systems, the main com-pounds under consideration are AMEO (3-aminopropyltrieth-oxysilane) and AMMO (3-aminopropyltrimethoxysilane),which can also be used in a 1:1 mixture or catalyzed with dibu-tyl tin dilaurate (DBTL), as well as with bismuth compounds.

The hardness of the lacquer film remains unaffected by thechoice of hardener – the same values are always achieved by theend of the process, no matter which hardener or catalyst is used.The advantage here is that the hardening process can be acce l -erated or slowed, depending on the environmental conditions,through the selection of the hardener and, if needed, the cata -lyst, and still produce the same result – a significant advan- >>>

C O A T I N G S

140

120

100

80

60

40

20

01 2 3 7 14 21 28 35

Days

7

6

5

4

3

2

1

01 2 3 4 5

Hours

poor

good


tage over two-component polyurethane systems. In long-termtests developers also proved that, unlike its predecessor ED,SILIKOPON® EF does not tend toward brittleness.

Another criterion is drying speed. This particularly appliesto larger objects, such as rail cars, that are still painted by hand.For the coating process to proceed as it should, the paint cannotharden too quickly. It must still flow well when the painter ar -rives back at the point where he started his work. These timeperiods can also be adapted to the requirements of the applica -tion by varying the hardener-catalyst system.

There are cases, however, in which large objects have to bebone-dry fast, or even rainproof because the paint shop needsthe space for some other purpose. The same is true of dry docksfor ships, where time means money and every hour counts.Moreover, the important thing in these cases is not the beauty ofthe paint but efficient application and reliable corrosion protec-tion. The new development from Evonik can even bridge the

gap between the extremes of climate that influence the paintingof a metal building in the bitter cold and dry of Murmansk andthe coating of a crane in hot, humid Singapore.

Eco-friendly paint formulations with low VOC content

With the new SILIKOPON® EF systems, highly eco-friendlypaint formulations are available that contain 70 to 90 percentEvonik products, depending on the pigment used. Their specificadvantage lies in their unmatched low VOC content of less than100 grams per liter, which makes them a clear improvement overexisting systems.

But SILIKOPON® EF is not just for steel. It also exhibits anexcellent appearance on a variety of woods. Also, the VOC con-tent can be kept below 100 grams per liter for these applica -tions. Finished coats give the wood a special appeal, drawingattention to grain and color, which are brilliantly enhanced.


Additional benefits for wood applications include flame- andabrasion resistance. These properties open up high-gradeapplications such as the interior design of yachts, aircraft, andhighly durable floors. These solutions are also economical.Today, the interiors of aircrafts and yachts require up to sevencoats – with the new systems, they only need three.

The systems also open up new opportunities in difficultcases of corrosion protection. Filled with a large quantity of zincdust, SILIKOPON® EF can be used as a two-component sili cone-epoxy primer. Several large customers are already re searchingand developing combinations of the two systems to achieve anoptimal property profile. The inorganic solution based on silicaesters delivers the advantages of fast drying and corrosion pro-tection. The organic alternative, on the other hand, earns pointsfor improved adhesion and higher flexibility. Formulationsbased on SILIKOPON® EF combine both properties in oneprod uct.

We may be nowhere near realizing the full potential of thesenew paints, but one thing is certain right now: SILIKOPON® EFcan be used as easily on metals as on concrete or composite ma te -rials like fiberglass- or carbon-fiber-reinforced plastics. The latterare becoming increasingly important in rotor blades for wind-powered plants and in aircraft construction, where single-layerconstruction can also help reduce weight. Lower weight is also akey issue for automobile manufacturing – a field regarded asthe uncontested major leagues for painters. It might well be thatthe industry will one day open its doors to SILIKOPON® EF. ●

C O A T I N G S

MARKUS HALLACKBorn in 1966Markus Hallack is anemployee of the EvonikCoatings & AdditivesBusiness Unit at the site inHopewell (Virginia, USA),where the company op-e rates the technical com -petence center for coatingsand inks. He is seniortechnology manager for

Coating Additives and Specialty Resins for Evonik’sTego brand.

+1 804 541-8658, [email protected]

Multifaceted: SILIKOPON® EF en -hances the grain andcolor of wood, can helpreduce the weight ofplas tics reinforced withglass or carbon fiber, ad -heres extremely well toconcrete, and providesreliable protection for metal structures


ith a market share of over 99 percent, advancedbatteries based on lithium-ion batteries alreadydominate the market for portable applications.They have become indispensable components

in cell phones, laptops, cameras, and home entertainment equip-ment. Given their high energy density, however, these kinds ofsystems are also well-suited to many other applications. Fore -most among these are motor vehicles with hybrid or electricdrives, storage systems for electric drives in machines, and trans-port equipment (mobile and stationary) in the industrial field,as well as storage batteries for industrial and household usepowered by the regenerative energies from wind and solar plants.Other potential fields of application are the markets for cordlesstools, boats, bicycles, and scooters. Success in these segmentsde pends primarily on improving the performance, lifespan, safe-ty, and cost of lithium-ion batteries.

Against this backdrop, the Evonik subsidiary Litarion hascom menced production of high-performance electrodes forlarge-scale lithium-ion battery systems at its site in Kamenz,Sax ony, where the systems are manufactured by site residentLi-Tec Battery GmbH & Co. KG in a tightly integrated produc -

tion network. To improve the key elements of the battery, it isessential to understand and optimize the physicochemicalaspects not only of the entire manufacturing process but of thefinished elec trode bands themselves. To this end, the develop-ment team of Evonik Litarion is also cooperating with selecteduniversity in st itutes. Student research projects and theses pro-vide fertile ground for partnership opportunities.

Together with the renowned Institute for Particle Tech nol -ogy (iPAT) of the Technical University of Brunswick, EvonikLitarion has embarked on a joint project for transferring knowl -edge from physicochemical basic research to industrial practice.The transfer of knowledge between production and universityunder the coordination of the Evonik Process Tech nology & En -gineering Service Unit allowed both sides to benefit from theex is ting experience of each partner.

Along with Evonik, the Institute for Particle Technology,directed by Prof. Arno Kwade, is a member of the DFG (Germanresearch foundation) project initiative “Functional Materialsand Material Analytics for Lithium High-Performance Bat te r -ies.” The Institute has unique expertise in the areas of milling,mixing, and dispersion, as well as powder handling and compac-

P A R T N E R S H I P W I T H T H E I N S T I T U T E F O R P A R T I C L E T E C H N O L O G Y

High-Performance Electrodes for Large-Scale

TORBEN HÖFEL (IPAT, TU BRUNSWICK), DR. ANDRÉ MECKLENBURG, DR. ANDREAS SCHORMANN, DR. CLAUDIA VEIT

Nearly a year ago at its site in Kamenz near Dresden, Evonik Litarion GmbH, a wholly owned sub -si diary of Evonik Industries, began commissioning the serial production of electrodes for large-scalelithium-ion batteries – a new market, still in the embryonic stage, that promises attractive growth in the areas of hybrid vehicles and stationary storage systems. Consistent with its objective, Litarion is not limiting itself to pure production of the newly developed electrodes but is also searching foroppor tunities to make improvements. The company is working side-by-side with leading universitypartners such as the Institute for Particle Technology of the Technical University of Brunswick.

Serial production of electrodes for large-scalelithium-ion batteries inKamenz involves coatinga metal film – the “current collector” –with particles a fewmicrometers in size.Graphite particles can beused for the anode, andlithium-metal oxide particles for the cathode.The finished layer is from20 to 200 micrometersthick

W



11

tion. The equipment at iPAT, some of which already existed, andsome of which was procured just for the DFG project initiative,allows small-scale implementation and testing of the manufac-turing process for lithium-ion electrodes. It offers opportunitiesranging from material pretreatment, through dispersion of sus-pensions, to coating, drying, and compaction of the electrodelayers.

Development objective: a longer lifespan for electrodes

Among its analytical equipment, iPAT has a variety of particlesize measuring devices down to the nano-range, rheometers,and devices for measuring micromechanical properties. Theseinclude an atomic force microscope and a nano indenter that canbe used for determining hardness and elastic properties. iPAT iscurrently developing or adapting various methods just for de ter-mining the physical strength and durability of electrode coat ings,which have a significant influence on the cyclical and calendri-cal lifespan of the electrodes: nano indentation, the pull-off test –the most conventional and widely developed quantitativemethod for measuring the adhesive strength of thin surface coat -ings – and the three-point bending test for measuring bondstrength.

Electrodes for lithium-ion batteries are made of particleson ly a few micrometers in diameter – for example, graphiteparticles on the anode and lithium-metal oxide particles on thecathode. These are bound on a metal film, the “current collec-tor,” in a layer roughly 20 to 200 μm in strength. The key charac-teristics of the layer are its coating weight, height and width,porosity, and contour. Prior to coating, the particles must be dis -persed in a solvent along with a binding agent. A variety of pro-cesses are available for the coating operation itself, with the

selection depending on such factors as the size of the instru-ment – lab- or production-scale. The formula for the dispersionmust be adapted to the coating process while maintaining thedesired electrochemical parameters of the electrodes.

One of the objectives of the partnership between EvonikLitarion and iPAT is to study how key formulation and disper -sion parameters affect geometric and physical properties –including height, contour and porosity – of electrode layers.Specifically, the researchers are trying to answer the followingquestions:

• How do formula and dispersion parameters such as solidscontent, dispersion time and intensity, temperature, and vacu-um affect the rheological properties and stability of the disper-sion for the coating?• How does the layer generation process in the productionplant proceed under precise variation of the dispersion charac-teristics, especially the rheological properties, and taking intoaccount the coating process, if necessary?• What is the interrelationship between the porosity of var -ious electrode layers and the electrochemical performance ofthe finished product?

More in-depth knowledge of the essential structure-prop -erty relationships of the systems in the study will enable elec-trode bands to be better coordinated with the application inquestion, and to be custom-manufactured for the customer.Under these conditions, the electrodes will then also help im -prove lithium-ion batteries – another reason the partnershipwith iPAT, which has already born fruit, should be expanded inthe future. ●

Lithium-Ion Batteries

DR. ANDRÉ MECKLENBURGProcess Technology & Engineering Service UnitEvonik Degussa GmbH+49 6181 59-4223

[email protected]

DR. ANDREAS SCHORMANNProduction ManagementEvonik Litarion GmbH+49 3578 37487-314

[email protected]

DR. CLAUDIA VEITElectrodes DevelopmentEvonik Degussa GmbH+49 2365 49-5093

[email protected]

CONTACTTogether with iPAT,Evonik Litarion is studying, for example,the generation of layersin the production plantunder precise variation of dispersion characte r-is tics, especially rheo -logical properties. Thegraph shows how theviscosity of the disper -sion changes dependingon the solids content andtemperature

■■ T = 20 °C

■■ T = 35 °C

■■ T = 50 °C48 50 52 54 56 58 60 62 64 66

Solids content [%]

Viscosity [Pa•s]

●

●

●

●

●

●●●

●

●

●

●

9

8

7

6

5

4

3

2

1

0


With its Appliance 2010 development initiative, Evonik and its customers have set their sightson the energy efficiency of refrigerators. Their objective is to reduce the energy consumptionof the next generation of refrigerators by up to five percent by improving the insulating propertiesof the PUR rigid foams used as the insulating layer. To this end, Evonik researchers are makinga tiny but effective adjustment in the foam. Specially developed additives that make up less thanone percent of the foam improve its cell structure and, in turn, its heat-insulating properties.

N E W S T A B I L I Z E R S F O R P U R F O A M S

Saving Energy with Better

The finer the cells of the rigid polyurethane foam used to insulate refrigerators,the better the heat insulation. A new method for two-dimensional visualizationand evaluation, which enables routine analysis of large-scale rigid foam materialsfor the first time, was developed for checking the fineness of the foam cells. The result of a devel opment partnership, the method uses a combination ofmicroscope and digital camera to make photos of the foam, which is dyed be-forehand, under special illumination. A customized software solution then determines the size and number of the cells

DR. CHRISTIAN EILBRACHT, DR. CARSTEN SCHILLER



13

t best, useful for producing imitations of Swisscheese, wrote the technician who had tested a pieceof foamed polyurethane (PUR) in 1941. Since then,the plastic for which Otto Bayer obtained the basic

pa tent in 1937 has proven that it can do just about anything. Thisversatility is owed not least to the availability of a vast array ofpolyols and isocyanates – the basic chemicals for manufacturingpolyurethane materials. In a polyaddition process, appropriatemachines are used to react these chemicals to the desired prod -ucts in the presence of water and/or physical foaming agentsand processing aids.

Polyurethane – youth through versatility

The range of properties between hard and brittle and soft andelastic alone points to the opportunities latent in this material.The applications are just as diverse. Shoe soles and sealing mate-rials, mattresses and floor coverings, car seats, expanding foams,and insulating boards – polyurethanes are everywhere. Theyalso play an essential role as insulating material in refrigerators,coolers, and commercial construction. For these applications,the rigid polyurethane foam is used as an insulating layer be -tween covering layers of steel sheeting, aluminum, or plastic,where it also plays a constructive role as the sandwich elementthat glues the two cover layers together. This profile of charac-teristics makes polyurethane foam an irreplaceable material inthe construction of commercial cooling units and freezers.

Refrigerators

A Additives for the optimal foam

Evonik has already spent years developing additives, especiallyfoam stabilizers, that are indispensable to the production andoptimization of the properties of foams. The latest develop-ments in this field allow ultrafine cell structures that improvethe heat-insulating properties of refrigerators and, therefore,also make an indirect contribution to climate protection. Thefoam stabilizers are based on organically modified siloxanes, sothey are derived from a type of chemistry in which Evonik al -ready has broad expertise. A network of sites researches and de -velops the stabilizers: The synthesis and application screen ing ofnew or developed molecules takes place in Essen; Hope well(Virginia, USA); and Shanghai, while semi-industrial testing isthe responsibility of the laboratory at the Hopewell site.

With its Appliance 2010, Evonik has now started a develop-ment initiative that follows similar projects implemented bycustomers. The focus of the initiative is the refrigerator of thefuture, which must be designed for maximum energy savingsand environmental compatibility. Tests using eco-efficiencymeth ods show that new Class A energy-efficient refrigeratorsalready save so much electricity that selecting them over oldermodels (power consumption 330 kWh per year) is not only en -vironmentally wise, but also makes good economic sense. For anominal extra cost, purchasing this kind of refrigerator can go along way toward protecting the environment, and also pay offfinancially through reduced power consumption. >>>

It is a stated aim of the industry to im -prove the thermal conductivity of rigidpolyurethane foam systems for refriger -ator applications by as much as ten per-cent by the year 2010. This challengingjob requires the efforts of system housesand additive suppliers. There are threeparts to the thermal conductivity of rigidfoam materials: thermal conductionthrough the cell gas, thermal conductionthrough the poly mer matrix, and thermalradiation. The first two depend on thechemical nature of the blowing agent andthe basic raw material; the system housescan have an influence on this aspect offormulation development, but they mustalso take market realities into account.Thermal radiation, on the other hand,depends on the cell structure. The finerthe cells of the foam, the less thermalradiation can pass through them. This iswhere the additives from Evonik comeinto play. They allow a finer cell structureand, therefore, play an essential role inreducing overall thermal radiation

0

Typical thermal conductivity ofPUR refrigerator systems

■■ Share depending on cell structure

■■ Share of thermal conductivity dependenton blowing agent and basic raw materials

Current system generation

mW/m•K

2 4 6 8 10 12 14 16 18 20

Up to 10 % reduction in thermal conductivity

Contribution of the Evonik additives

v v

Development goal for 2010

Market launch in 2008


The Chemistry of Foam

Foam stabilizers are polydimethylsiloxane polyether copolymers,which belong to the silicon surfactant group. Despite a low weightpercen tage of less than one percent of the entire formulation, theyperform several tasks: They simplify the mixing of the various com-ponents by reducing surface tension. Intensive mixing of the compo-nents is required for a uniform re action sequence and the formationof a ho mo geneous material.

Reducing surface tension also benefits the nucleation of thefoam cells, because it promotes the formation of small gas bubblesfrom the air released in the raw materials. The number of these gas bubbles is vital to the creation of a fine-celled foam.

The stabilizer’s most important job is to stabilize the foam againstthe bursting of cell walls, which would result in a coarsening of the foam and the loss of volume yield – and in extreme cases thecomplete collapse of the foam. Here, too, the extraordinary surface activity of silicon surfactants is the decisive factor. Silicon-freesurfactants, on the other hand, are inadequate stabilizers. After thepoly u re thane ma trix is cured, the foam structure is fixed and the stabilizer’s task is finished.

The polydimethylsiloxane polyether co polymers are synthesizedin two steps. First, there is an equilibrium reaction in which the oligomer silicon components are converted into polymer silicons. Inthe second step, polyethers produced from ethylene and propyleneoxide are linked to this silicon intermediate. The latest generation of rigid foam stabilizers from Evonik displays an optimized geometricarrangement of these polyethers on the siloxane backbones, whichallows improved properties. The siloxane component guaranteeshigh surface activity, while the polyether component ensures suffi-cient compatibility with or solubility in the remaining components of the polyurethane formulation.

Rigid polyurethane foam is producedfrom the liquid raw materials with thehelp of high-pressure foaming ma -chines. Laboratory foaming molds likethe “Bosch lance” or brett mold preventhaving to foam an entire refrigeratorfor the purpose of testing the additives.The molds are temperature-controlledand enable the manufacture of rigidfoam testing blocks, which allowresearchers to draw inferences aboutthe behavior of the foam under realproduction conditions. These tests alsoclearly show that the flow behavior ofthe foam depends on the foam stabi -lizer. Custom-produced stabilizers,therefore, can have a significant impactnot only on flow height but on flowdefects, which are visible after the testblocks are sliced

Chemical structure of the polydimethyl -siloxane polyether co poly mers used as a stabilizer for PUR rigid foams

Si OH3C

CH3

CH3

Si O

CH3

CH3

Si

CH3

OR

C3H6

O

C2H4

O

CH2

CH2

CH2

O CH3

CH3

CH3

Si

n

m

x

y

Broad structural diversity can be obtained from the basic reaction. The molecular weight of the copolymer and the ratio ofsiloxane to polyether offer a great many potential variations. The molecular weight influences the mobility and availability ofthe molecules on the surface. This is why stabilizers with a highmolecular weight are better suited for minimally catalyzed systems that require a lot of physical stabilization.

On the other hand, stabilizers with a low molecular weight areespecially suitable for fast, highly catalyzed systems in which thechemical cross-linking essentially promotes stability during pro -cess ing. Other opportunities for fine-tuning include the relation-ship and arrangement of ethylene oxide or propylene oxide in the polyether, as well as the end group used on the polyether, bothof which have a strong influence on the solubility of the productsin the raw materials and on their effectiveness.


15elements23 E V O N I K S C I E N C E N E W S L E T T E R

The largest buyers for these polyurethane additives fromEvonik are the leading multinational chemical companies, whichnot only operate in the PUR market in their function as producersof a central raw material (diphenylmethane diisocyanate (MDI)),but also operate as system houses. In this role, they supply re -frigerator producers with preformulated polyurethane sys tems,consisting of a mixture of polyols and additives (A components)and the isocyanate (MDI, B components). Evonik assists thesystem houses in finding custom-tailored solutions for indi -vidual refrigerator manufacturers. A proven success factor forEvonik has been its broad expertize in application engineering,coupled with its close development networks with all leadingsystem houses. These assets allow the company to perceive cus -t omer needs early on and quickly develop creative approachesto customer-oriented solutions.

The early entry of Evonik into the development process asan additive supplier allows it, together with the system houses,to exploit synergies and tread paths that are possible only >>>

With the help of the new cell structureanalysis method, the positive effect ofthe optimized foam stabilizers andnucleation agents from Evonik on thefineness of the cells of rigid polyurethanefoams becomes visible: The photo onthe left shows a micrograph of the cellstructure of a foam system currentlyused for refrigerator applications; thephoto on the right shows – at the samemagnification – a foam containing thesame polyurethane system, but in whichthe standard additives were exchangedfor the new additives from Evonik

According to calculations by the Wuppertal Institute, replac-ing refrigerators over ten years old with the average Class Aenergy-efficient appliance could reduce power consumption inGerman households (about 130 terrawatt hours) by between2.5 and 4.0 percent. The objective of the joint developmentwork by Evonik and its customers is to realize another signifi-cant increase in the efficiency of refrigerators by the year 2010.

A custom-tailored solution for each refrigerator manufacturer

The work in connection with Appliance 2010 is carried out invery close contact with customers, and is focused not only onsystem-specific customer requirements but on regional differ -ences between the large markets in Europe, the United States,and Asia. Pentane isomers, for example, are the preferred blow -ing agents in Europe, while 1,1,1,3,3-pentafluoropropane(HFC-245fa) is the first choice in the United States.

DR. CHRISTIAN EILBRACHTBorn in 1969As technical director in the Evonik Consumer SpecialtiesBusiness Unit, Christian Eilbracht is globally responsiblefor development and application engineering for poly -urethane additives. After studying chemistry and thenearning his doctorate in solid state chemistry at theUniversity of Dortmund in 1997, Eilbracht began hiscareer at Hoechst in the High Temperature Super con -duc tivity unit. He then moved to Pigments and Additivesat Clariant, where he was responsible for re search anddevelopment of flame retardants for thermoplastic

materials and polyurethane foams. He came to Evonik Industries in 2001.


DR. CARSTEN SCHILLERBorn in 1973Carsten Schiller works in the Consumer SpecialtiesBusiness Unit at Evonik as technical manager RigidFoam Development in the application engineeringdepartment of the Polyurethane Additives Product Line.His responsibilities include product development, tech-nical customer service and technical key account man -agement. After studying chemistry at the Univer sity ofHamburg and earning his doctorate at the Ruhr Uni -versity Bochum in 2003, Schiller researched absorptivebiomaterials at the University of Duisberg-Essen before

coming to Evonik Industries in early 2005.



through simultaneous optimization of the polyol formulationand foam stabilizer. The company’s solid expertise in siliconchemistry en ables Evonik to construct customized foam stabi -lizers – a kind of modular system – that meet the individualrequirements of a wide variety of polyurethane foam systems.

Making refrigerators ready for the future

The thermal conductivity of the insulating material, the lambda(λ) value, is considered the most important property in the pro-duction of refrigerators because it supplies the evaluation cri -terion for the insulating effect. The entire industry, includingEvonik, has set itself the goal of improving the λ value by up toten percent. As a general principle, the finer the cells of thefoam, the better the heat insulation. The cell structure can belargely influenced by the selection and design of the additives, especially the foam stabilizers. The additives, therefore, play alarge role in reaching maximum energy efficiency.

But the fineness of the foam cells is not the only factor thatdetermines energy efficiency: Even and unbroken distributionof the foam is also important. In refrigerator production, thesheet metal surface skin and the plastic inner skin of the refrig -erator cabinet are fixed in supporting molds, and the free spacein between is injected with the liquid polyurethane reactionmixture – most of the time, in a single spot. The foam that devel -ops and expands must cover complex flow paths that subject itto mechanical stresses and can damage it before it completelyfills the cavity in the wall and cures. Any imperfection, any de -fect, can lead to thermal bridging, which will diminish the insu-lating effect of the entire system. This is why improving the flowproperty of foams is another important objective for additivemanufacturers.

By developing foam stabilizers with a new, innovative typeof structure, Evonik has addressed the need for fine cell structureand good flow behavior at the same time. These substances areparticularly effective at reducing the surface tension of the poly -urethane reaction mixture, which promotes nucleation – or thedevelopment of finer cells. Reducing surface tension also effec-tively stabilizes the expanding foam, which improves the flowproperty and minimizes defects.

While improving the fineness of foam cells by optimizingfoam stabilizers represents a great achievement, it does have adrawback: The surface tension cannot be reduced as much asmight be desired. This is one reason Evonik has made additionalefforts to promote heterogeneous nucleation through the use ofan innovative solids concept. This kind of supplementarynucleation agent could further increase the number of nucleiand, in turn, the fineness of the cells. Evonik has now found asolution for this problem and applied for a patent.

Stabilizers for polyurethane foams are important formula -tion components that not only play an essential role in systemoptimization but often allow rational production to proceed atall. The new silicon surfactants demonstrate this clearly – aboveall in their interplay with the supplementary nucleation throughselected solids. They improve productivity and lower costs.Thanks to the abundance of opportunities for fine-tuning in -herent in the system, and the deep technical understanding of

structure-effect relationships at Evonik, customer-specific so -lu tions can be created based on a modular system and closedevelopment partnerships. Evonik is also making an importantcontribution to environmental protection with this specialty –in keeping with its motto: Just a little goes a long way. With aningredient that makes up less than one percent of the entire sys -tem, this is without doubt a fitting statement. ●

The cross-section of a refrigeratorshows the complex flowpaths of thepolyurethanereaction mixture,which is usuallysprayed in just one spot


coating material on flexible substrates to the industrial productionscale.

The project partners have all the expertize required in the fields ofdispersion technology, process engineering, and process technologyto reach the goals and can rely on prior achievements and extensiveknow-how. Evonik is experienced in the development and productionof materials and their conversion into dispersions, as well as in thecoating of substrates. The South Westphalia University has expertknowledge, technical equipment, and a staff qualified in the produc-tion and development of innovative materials and their processing tonanoscale coatings and coating systems. The Particle Institute of theTechnical University of Brunswick has spent over 20 years re search -ing the comminution and dispersion of micro- and nanoparticles, aswell as the solubilization of microorganisms. Ystral has been active inthe field of mixing and dispersion technology for over 30 years, andmanufactures machines and complete plants. SUNCOAT GmbH hasyears of experience in the field of coating technology. The companyis providing the machine platform for applying the sol to the film sub-strate. EHA-Spezialmaschinenbau GmbH is participating as a subcon-tractor. The company develops and manufactures machines andplants for coating web-shaped substrate materials and is a highly spe-cialized supplier of unique solutions. The results of the project will beused primarily to supply a process for industrial-scale coating of fle x -ible web-shaped substrates with a sol-gel-based nanoscale coatingmaterial.

news

In its Nanotronics Science-to-Business Center in Marl, Evonik Indus -tries is coordinating the new project “Industrial Sol Production andCoating of Flexible Substrates with Nanoscale Sol-Gel Materials(SolGel)” sponsored by the Federal Ministry of Education and Re -search (BMBF). Evonik’s collaborators on the project include theSouth Westphalia University of Applied Sciences, the Particle Insti -tute of the Technical University of Brunswick, and the companiesYstral GmbH, Ballrechten-Dottingen, and SUNCoat GmbH, Zittau.The R&D project, which started on January 1, 2008, and is scheduledto run for three years, receives funding from the BMBF as part of itsframework concept “Research for the Production of Tomorrow” andis managed by the project’s sponsor, the Karlsruhe Research Center.

Sol-gel technology is an innovative process for the manufactureof thin, functional coatings on a variety of substrates. Sol-gel coatingsare highly scratch- and abrasion-resistant without impeding substrate-specific flexibility. Depending on customer requirements, the coat -ings can be customized for additional properties, such as temperatureand chemical resistance, easy-to-clean, antigraffiti and heat reflection.Just a few of the fields of applications include the protection of furni-ture surfaces, self-adhesive films for the film-coating of vehicles, dirt-repellant and perspiration-resistant synthetic leather surfaces, and UVprotection for textile fabrics.

The project will concentrate on the development of industrial pro-cesses and plants for the surface coating of flexible substrates such asplastic films, polyester fabric, and textiles with nanoscale sol-gel ma te -rials. The new processes shall enable theproject partners to obtain products withnew surface properties unrivaled so far. Thisis to heigh ten the products’ added valueand sustainably improve the companies’competitiveness. The primary objective istransferring the processes for dispersion,sol production, and application of the

+++ Evonik coordinates new BMBF project

Evonik Industries with its subsidiary Evonik Röhm GmbH has enteredinto an agreement with Amersfoort-based Akzo Nobel FunctionalChemicals B. V. for licensing its hydrocyanic acid (HCN) productiontechnology based on the Andrussov process. Akzo Nobel will use thetechnology to produce chelating agents – which find application in,for example, the manufacture of soaps and detergents – in a world-scale plant at Ningbo Chemical Industry Zone (NCIZ) in China. Un -der the license, Evonik will provide to Akzo Nobel an extensive tech-nology package, including advice and consulting services from theplanning stage to the startup of the plant.

Evonik can look back at more than 50 years of experience in hy dro -cyanic acid production. Vast expertize is available in three of the fourdirect synthesis processes that are used industrially: the Andrussov,the BMA, and the formamide processes. The Andrussov process is themost widely used direct synthesis process for hydrocyanic acid pro duc -tion. In this process, ammonia and methane are reacted on a platinum

gauze serving as a catalyst, at temperatures exceeding 1,000 de greesCelsius. The waste heat from the reaction is used to produce steam.This process is currently the most important method for commercialscale production of hydrocyanic acid.

“In making available extensive expertize and wealth of experi-ence, we are enabling our partner to rapidly attain the benchmark inregard to safety, ecology, and economy in hydrocyanic acid produc -tion,” said Gregor Hetzke, head of Evonik Industries’ PerformancePolymers Business Unit. Evonik operates a number of plants world -wide and possesses, in ad dition to technological expertize, a fund ofoperational know-how. The processes have been continually opti -mized ever since the first plant started operating in the 1950s. Thecompany has taken out var ious patents for hydrocyanic acid produc-tion by the Andrussov process. These include the latest developmentssuch as the use of oxygen-enriched air for the synthesis, which allowscapacity to be significantly increased.

+++ License for HCN technology to Akzo Nobel

Silicone Sealing Com

Matted surfaces are not just a growing trend: They also have the benefit of being non-glare. A newly developed matting

agent from Evonik enables the matting of translucent and pigmented silicone sealing com pounds without sacrificing quality. Fields of application include electronic LCD displays, but also ex pansion joints on paths and terraces made of natural stone, and the seams of shower stalls.


Because silicone sealing compounds arewater-resistant and highly elastic, they are used most often for sanitaryinstallations, in the kitchen, on win dows,and for exterior applications, but also in electronic displays

DR. JÜRGEN MEYER, DR. MARIO SCHOLZ

pounds: Silicas for Matt Elegance

In the past, the inherently glossy silicone sealing compoundscould be matted only by adding either mixtures of fatty acids,fatty acid esters, and polybutadiene, or large amounts of specialtychalks. The drawback of these processes is that they impair thedesired properties of the silicone sealing compound: Fast cross-linking and good storage stability are no longer a guarantee.

Matting agents based on silicas, which are used to matt paintsand coatings, are unsuitable for silicone sealing compounds be -cause of their water content. Since water and humidity triggerthe cross-linking reaction and hold it until the joint filler is cured,they are desirable only when the sealing compound is appliedfrom a cartridge. If traces of water cause the cross-linking tooc cur in the cartridge, the compound can no longer be injectedinto the joint.

Now, for the first time, the newly developed matting agentVP AEROPERL® R806/30 of the Evonik Inorganic Materials Busi-ness Unit makes it possible not only to matt translucent and pig-mented silicone sealing compounds without sacrificing quality,but to improve some of their mechanical properties. Whileother products from the relatively new AEROPERL® brand arehy dro philic and used as substrates for catalysts, active ingre-dients, oils, and cosmetics, the new product variant is a hydro-phobic granulate.

Production of the starting material for VP AEROPERL®

R806/30 is based on the AEROSIL® process: High-temperaturehydrolysis of silicon tetrachloride in an oxyhydrogen flame ge n-erates silicon dioxide in the form of extremely small primaryparticles. These particles aggregate and agglomerate with theformation of the three-dimensional network of the fumed silicaAEROSIL®.

Spray granulation produces a granulate of spherical part -icles that are several micrometers in size. These particles, how -ever, are still hydrophilic because they carry silanol groups ontheir surface. Through a continuous after-treatment process,the silanol groups are reacted with an appropriate hydrophobi-zation agent and converted into trimethylsilyl groups. The re -sultant hydrophobic, fumed silica granulate absorbs significantlyless moisture than hydrophilic AEROSIL® grades. This, along withits defined particle size, makes it the most suitable for mattingsilicone sealing compounds.

How much matt is enough matt?

Developers tested the suitability of the hydrophobic silica granu-late as a matting agent for silicone sealing compounds in a seriesof experiments that determined the residual gloss, transmissionfactor – the translucency – and the surface roughness of thevulcanized product. They also defined the rheological behaviorand thixotropic properties. Thixotropic behavior, for example,prevents the joint filler from running or forming drip marks, be -cause it solidifies when the filler is at rest after being squeezedinto the joint. >>>

atted surfaces are more pleasing to the eye andsometimes safer than shiny surfaces. For example,matt silicone sealants on electronic LCD displaysof signboards, cell phones, or pocket calculators

sup press disturbing light reflexes and make the displays easierto read. Stylistic aspects are the focus when it comes to installingmatt expansion joints in natural stone decking, where the jointsblend harmoniously into the overall scene because they are notshiny in sunlight.

Recently, a new matting agent became available for applica-tions involving translucent and pigmented silicone sealants – aspecially granulated and hydrophobized fumed silica marketed byEvonik under the trademark VP AEROPERL® R806/30. Add ingjust small quantities to formulations containing the fumed si l i caAEROSIL® 150 as a thixotropic agent achieves a remarkable mat-ting effect in cold-curing silicone polymers. At the same time, thetranslucency of the cured sealing compound is retained and itsrheological behavior is hardly affected.

Matting agents change surface properties

Shine and mattness are visual impressions that occur when view-ing a certain surface. The angle of incidence of the light and thequality of the surface play a decisive role in this effect. Followingthe law of reflection, which states that the angle of incidence isequal to the angle of reflection, smooth surfaces reflect lightrays directionally. To the human eye, this kind of surface appearsshiny. Rough, uneven surfaces, on the other hand, scatter the lightin all directions, causing the viewer to perceive them as matt.

Matting agents are used to convert smooth, shiny surfaces tomatt. They contain particles that, because they are sized in themicrometer range, prevent the formation of smooth surfaces.Ideally, they have no effect on the other physical and chemicalpro perties of the material to be matted.

19



Light reflection on smooth and rough surfaces. Smooth surfaces reflect rays of light directionally – they shine. Rough, uneven surfaces, on the other hand,scatter the light in all directions, so they appear matt

M

Shiny Matted

micrographs taken with an optical microscope also confirm thisconnection between the concentration of matting agent andsurface rough ness. As the photomicrograph shows, the surfaceis even and smooth without VP AEROPERL® R806/30. As morematting agent is added to the compound, spherical structuresproliferate on the surface, making it rougher.

Another advantage of VP AEROPERL® R806/30 is that it im -proves the mechanical properties of silicone sealing compounds,because it not only acts as a matting agent but as a reinforcingfiller. The filler that producers of silicone sealing compoundsnormally use is AEROSIL® 150, which has a specific surface areaof 150 m2/g. A more efficient option would be AEROSIL® 300,which has twice as much surface area and is likewise more active.But because it is extremely difficult to disperse, manufacturerscan not use it in silicone sealing compounds.

This is where the new matting agent scores: While it is a de -ri vative of AEROSIL® 300, it is far easier to disperse. As a result,both the elongation at break and the tensile strength of thecross-linked sealing compounds is improved. When added to astandard formulation containing AEROSIL® 150, VP AEROPERL®

For their series of tests, scientists prepared the silicone sealingcompounds based on a standard formulation of 62.4 percentsilicone polymer, 24.6 percent silicone oil, 4 percent crosslinker,1 percent adhesion promoter, 0.1 percent catalyst and 8 percentAEROSIL® 150 as the thixotropic agent. They varied the propor-tion of matting agent by replacing a portion of the thixotropicagent with VP AEROPERL® R806/30. This allowed them to di -rect ly determine the influence of the matting agent on the rheol-ogical properties of the silicone sealing compound and on theoptical and mechanical properties of the vulcanized product.

Using a reflectometer to determine the matting effect of thehydrophobic granulate, they found that adding very smallamounts of VP AEROPERL® R806/30 reduced the residual glossdramatically, while causing only minimal changes to the trans -lucency of the vulcanized product.

Measurements taken of surface roughness by surface-scan-ning with a Hommel tester confirmed the results of the residualgloss measurements: If the matting agent is not added, the sur-face is smooth. The surface becomes considerably rougher asthe concentration of matting agent is increased. Photo -


The scanning electron micrograph of VP AEROPERL® R806/30 shows the uniform particle size distribution in the micrometer range

Optical properties of the cured silicone sealing compounds: Adding only 0.8 percent VP AEROPERL® R 806/30 reduced the residual gloss by 75 percent compared to the formulation with pure AEROSIL® 150.Translucency was not significantly affected

■■ Reflection [at 20 °] Transparency [DE] ■■

Photomicrograph of a silicone sealant without VP AEROPERL® R806/30

Photomicrograph of a silicone sealant with VP AEROPERL® R 806/30 (100 percent re lated to AEROSIL® 150)

The viscosity of the silicone sealing compound depends on the concentration of VP AEROPERL® R 806/30. As expected, adding AEROPERL® to a stan dard formulation with eight percent AEROSIL® 150 increases viscosity, sinceAEROPERL® also acts as a thickening agent. Reducing the amount of AEROSIL® 150, however, can compensate for this effect

Viscosity Pa•s45

40

35

30

25

20

15

10

5

0

200

180

160

140

120

100

25

100% 50% 20% 10% 0%

Amount of AEROSIL® 150, replaced by the matting agent VP AEROPERL® R 806/30

20

15

10

5

0100% 50% 20% 10% 0%

Amount of AEROSIL® 150, replaced by the matting agent VP AEROPERL® R 806/30

● ●

● ●●

●●

●●


R806/30 enhances viscosity while lowering extrusion perfor-mance. Reducing the amount of AEROSIL® 150, however, cancompensate for this effect.

Based on their experiments, developers recommend using0.8 percent of the matting agent VP AEROPERL® R 806/30 andonly 7.2 percent of the AEROSIL® 150 filler – instead of theusual eight percent AEROSIL® 150 of standard formulations.Even with the addition of such a small quantity of matting agent,residual gloss is lowered by 75 percent, translucency remainsgood, and viscosity barely changes. It can also be easily dis -persed into the conventional formulations for silicone sealingcompounds.

With the development of the new AEROPERL® variant forsilicone sealing compounds, Evonik is answering the user’s de -mand for matting, and has once more demonstrated the versatil -ity and adaptability of fumed silicas. This success is founded onthe company’s wide-ranging expertize in modifying the size,structure, and surface quality of inorganic particles such as sili-cas, and customizing them for the application at hand. ●

21elements23 E V O N I K S C I E N C E N E W S L E T T E R

DR. MARIO SCHOLZBorn in 1959Mario Scholz is head of applicationstechnology for silicone rubber in theInorganic Materials Business Unit. Afterstudying chemistry and earning his doc-torate at Georg-August University ofGöttingen, he began his employment atDegussa (now Evonik Degussa GmbH)in 1990 in the former Inorganics Re -search unit, where he was responsiblefor the development of carbon black for

the tire industry and for the development and production of zeolitecatalysts for the petrochemical industry. He moved to his current position in 2004.


DR. JÜRGEN MEYERBorn in 1959Jürgen Meyer is responsible for the areaof particle modification in the AEROSIL®

R&D unit of the Inorganic MaterialsBusiness Unit of Evonik. After studyingchemistry and earning his doctorate atJulius Maximilian University Würzburg,he began his career in 1988 at Degussa(now Evonik Degussa GmbH) in the for-mer Inorganics Research unit, workingwith precipitated and fumed silicas, as

well as matting agents. Meyer held various positions in production inRheinfelden, where he was in charge of the construction and com -missioning of the plant for manufacturing the different grades of structure-modified AEROSIL®, before assuming his current duties.


Scan of a silicone sealant with VP AEROPERL® R 806/30(100 percent related to AEROSIL® 150) with a Hommel tester

Adding VP AEROPERL® R 806/30 improves the elongation at break of the vulcanized product. An exception is a formulation with ten percent mattingagent. In this case, the elongation at break is slightly diminished compared to the standard formulation with no additive. The same effects are observedwith regard to tensile strength

Elongation at break [%]800

600

400

200

0100% 50% 20% 10% 0%

Amount of AEROSIL® 150, replaced bythe matting agent VP AEROPERL® R 806/30

Silica Makes Boat Hulls A D A S H O F C O L O R O N T H E S E A

pear – that is, when stirring stops – the substance slowlyreturns to its original viscosity. The thixotropy of the gel coatsmust be high enough that the coat does not liquefy and drip afterit is sprayed on the fiberglass hull. If it is too thixotropic, how -ever, the coat can cure unevenly, which can deform the surfaceof the hull.

Gel coats have to have two significant properties that affectresistance to weathering: Their porosity and their percentage ofmetallic ions must be as low as possible. Porosity results whentrapped air is not removed before the gel coat cures. Just howmuch air escapes depends on the average particle size and themorphology of the silica. Seawater is better able to penetratewhen air remains in the coat and can settle in the pores. Over thelong term, this accelerates the weathering of the gel coat.

The purity of silica determines how many metallic ions thereare later in the gel coat. The more there are, the more likely un -wanted processes can occur. A good example is osmosis, whichcan ultimately lead to fogging and the formation of bubbles inthe gel coat.

The precipitated silica SIPERNAT® 22LS and the fumed sili-ca AEROSIL® 200, which are both produced by Evonik, are twoexamples of established gel coat additives. SIPERNAT® 22LS

t is fall 2006, and a trade show for sailboats and motorboats isheld in the United States. The show attracts the Who’s Whoof the industry – manufacturers, suppliers, event organizers.Representatives of the Inorganic Materials Business Unit of

Evonik are also on hand, strengthening contacts with their busi-ness partners from the supplier industry. “So is there no way wecan offer a colored fiberglass boat?” a customer suddenly asksthem in a conversation. Apparently, Evonik employees werehearing over and over again from boat manufacturers that theircustomers were tired of the basic white of today’s boat hulls –and might even be willing to pay extra for custom colors. Theproblem was that dark or colored boat hulls had always begun toshow signs of weathering and discoloration over time throughextensive contact with seawater.

Fiberglass hulls have a gel coat on their exterior that servestwo functions: It provides the aesthetic appearance of the hulland, at the same time, protects it against rapid weathering byaggressive seawater. A gel coat consists of an unsaturated poly-ester resin, to which silica is added to ensure the correct rheologyduring processing. Stirring can influence the thinness of suchgel coats, which are thixotropic: The longer the coat undergoesshear stress, the lower its viscosity. If the shearing forces disap-

Let’s say there was once a day when the automobile industry produced only white cars. Hard toimagine? For years, the manufacturers of fiberglass boats found themselves in just this situation. But all that has changed, thanks to an additive by Evonik. This case is also a great example of how the customer benefits from intra-company teamwork across three continents.


JIM TOTH, DR. STEFAN UHRLANDT

I

Colorful

Because time was short, developers at the Inorganic Ma te -rials Business Unit shipped SIPERNAT® FPS-5 to several cus -tomers for initial experimentation. At the same time, they devel -oped their own tests for evaluating weather-resistant coloredformulations. Because the laboratory for these tests would haveto break completely new ground, the greatest hurdle was gen -erating the required results in a very short time. All available HRresources were funneled into the project. Based on the positiveresults of the tests, and about six months after the customer orig-inally approached Evonik, the company applied for a patent inthe United States in July 2007. Colleagues in Germany wereresponsible for handling the legalities of the patent application.As it turned out, then, the search for the right silica led to global,intra-Group teamwork over three continents.

In the exposure tests carried out by Evonik, formulations ofblue and red gel coats yielded impressive results: When laborato-ry employees exposed fiberglass sheets with the new gel coat toseawater warmed to 65 °C (149 °F) for seven and fourteen days,the sheets showed significantly fewer changes than comparablesheets coated with formulations containing other silicas. De pen d -ing on the polyester resin used, the share of SIPERNAT® FPS-5fluctuated between two and six percent. The business >>>

displays average purity for a precipitated silica but ensures lowporosity in the gel coats. AEROSIL® 200, on the other hand, isextremely pure but generates higher porosity. For these rea-sons, both silicas were eliminated as ingredients for weather-resistant colored formulations.

Japanese silica gives colors longer-lasting shine

Following more discussions with manufacturers of gel coats andan analysis of the portfolios of Evonik in the United States andEurope, the employees of Inorganic Materials declared that noneof the company’s in-house products had the required purity. Sothey turned to DSL, a joint venture between Evonik and Shionogi& Co in Japan. Based on the specifications, Japanese colleaguesidentified several potentially suitable silicas pro duced in Japan.SIPERNAT® FPS-5, a precipitated silica, finally proved to be apromising candidate: Its rheological properties are somewhatbetter than those of SIPERNAT® 22LS, it has the re quired highpurity, and generates only minimal porosity compared to fumedsilica. SIPERNAT® FPS-5 is tradionally utilized in the Japanesecoatings industry as a thickening additive and also in the elec-trodeposition coating process where high purity is essential.

23

C O A T I N G S


With SIPERNAT® FPS-5, the fiberglass hulls of the futurewill be any color desired


partners of Evonik saw test results that were just as convincing.From then on, nothing more could stand in the way of coloredgel coats for boat hulls.

So far, there has been no product comparable with SIPERNAT®

FPS-5 on the market: Competing products offer either goodrheology or improve weather resistance – but nothing can sup-ply both at the same time like SIPERNAT® FPS-5. This Silicaallows Evonik’s customers to offer high-quality gel coats, and thefree dom to choose coloring opens up a completely new marketfor them.

The strong demand for colored boat hulls is evidenced bythe swift introduction of products containing SIPERNAT® FPS-5:Although this silica is a markedly more expensive than SIPERNAT®

22LS, for example, business is doing very well. For the first time,manufacturers of gel coats can advertise that their products pre-vent blister formation and fogging, porosity, and color fading –even below the waterline. The days when all boats had to bewhite, it seems, are over. ●

DR. STEFAN UHRLANDTBorn in 1967Stefan Uhrlandt is currently DirectorApplied Technol ogy Performance Solu -t ions, NAFTA, for the Evonik InorganicMaterials Business Unit. After studyingchem istry and earning his doctoratedegree at the University of Hanover inGermany, he came to Evonik Industries in 1995, where he was initially in chargeof the research and development of silica as antifoaming agents and for tire

applications. Beginning in 1998, he was responsible for the expansionand operation of the pilot plant for precipitated silica. Four years later,he moved to Applied Technology in Piscataway (New Jersey, USA),where he assumed his current position in 2004.+1 732 981-5326, [email protected]

JIM TOTHBorn in 1971Jim Toth received B.S. and M.S. degreesin chemical engineering from the OhioState University in 1993 and 1995respectively. His masters’ research wasfunded by General Motors and focusedon liquid injection/com pres sion mold -ing of large parts. Upon graduation, hejoined the Bombardier RecreationalProducts as a prod uct engineer wherehe was responsible for the composite

and chemical components of several vehicles. He then worked forAkzo Nobel as technical service manager providing support for organicperoxide initiators in the thermoset polymer industry. He joinedEvonik Degussa in 2005 and is currently em ployed as an applicationmanager promoting silica to the unsaturated polyester industry. +1 732 981-5015, [email protected]

The Δ E color difference describes the change in color as compared to the original color.The top part of the figure shows the values for a blue gel coat exposed to warm seawater(65 °C) for seven and fourteen days. The formulation with SIPERNAT® FPS-5 surpassesthe formulations with other silicas by a wide margin. The same is true of a red gel coat. The bottom part of the figure shows the values afterseven days in 65 °C seawater

■■ Seven days ■■ 14 days

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6

Color difference Δ E

4.5% SIPERNAT® FPS-5

4.5% SIPERNAT® 22LS

4.5% Comparative standard product

3.25% SIPERNAT® FPS-5

3.25% SIPERNAT® 22LS

3.25% Comparative standard product

Blue

gel

coa

tRe

d ge

l coa

t


Since February 1, Sigma-Aldrich offers Evonik’s catASium® andcataCXium® product families. Sample amounts of these homogene-ous catalysts are being made available, for research purposes, fromthe Sigma-Aldrich Corporation based in St. Louis (Missouri, USA).The range will consist of ligands and metal complex catalysts forasymmetric hydrogenations (catASium® family) as well as for pal -ladium catalyzed C-X coupling reactions (cataCXium® family). “Withthese ligands we are covering a broad spectrum of organic synthesesto prepare complex molecules starting from simple starting materi-als,” said Dr. Jürgen Krauter, responsible for marketing in Evonik’sCatalysts Business Line. “Through the broad distribution capabilitiesof Sigma-Aldrich we are offering chemists in research and develop-ment easy access to these homogeneous catalysts.”

“This means a significant step forward for us to become a leadingprovider in (asymmetric) catalysis, one of today’s most importantareas in organic chemistry,” said Dr. Daniel Weibel, product managerfor asymmetric synthesis at Sigma-Aldrich. Commercial amounts ofthe homogeneous catalysts will continue to be distributed by Evonik.

Sigma-Aldrich is a leading Life Science and High Technologycompany. Its biochemical and organic chemical products and kits areused in scientific and genomic research, biotechnology, pharmaceuti-

news

+++ New distribution channel for homogeneous catalysts

cal development, the diagnosis of disease, and as key components inpharmaceutical and other high technology manufacturing.

Evonik is a leading supplier of catalytic system solutions. It offersa broad portfolio of homogeneous and heterogeneous catalysts fromone hand as well as a comprehensive service package for customersfrom Life Sciences, fine chemistry, industrial chemicals, intermediates,and polymers.

+++ Strengthening of exclusive synthesis business

Evonik Industries has acquired the remaining 49 percent of its formerjoint venture Degussa Lynchem Co. Ltd., Dalian (China), from theChinese shareholders Yuncai Wang and Jingkun Wang. By this trans-action Degussa Lynchem has become a wholly owned subsidiary ofEvonik. The shares are held through Evonik Degussa China Co. Ltd.Financial details of the acquisition have not been disclosed. The trans-action is subject to the approval of government authorities.

The joint venture between Evonik and its Chinese partners wasestablished in 2006 by the purchase of a 51 percent stake in LynchemCo. Ltd. in Dalian. “In taking over the remaining shares, we are

strength ening our global Exclusive Synthesis business and further ex -pan ding it in line with our successful concept of horizontal integration,”says Dr. Alfred Oberholz, member of the Executive Board of EvonikIndustries AG with responsibility for the Chemicals Business Area.

Evonik is the first European supplier to have implemented theconcept of horizontal integration in exclusive synthesis. This allowsfor intermediates and starting materials, as well as active ingredientsthat are not patent protected, to be produced at competitive cost inChina. At its European sites, Evonik concentrates on refined interme-diates and patent-protected active ingredients. At the same time, cus -

t omers benefit from Evonik’s technology port-folio at its European sites, and from its longexperience in governmental and patent lawregulations regarding the manufacturing ofpatent-protected intermediates and activeingredients.

Evonik’s Exclusive Synthesis Business Lineconcentrates on cus tomer-specific productionof pharmaceutical intermediates, active ingre-dients, and fine chemicals with stringent qualityrequirements. With its worldwide productionand research network, the business line offers acomprehensive service, ranging from synthesisdevelopment on the laboratory scale to com-mercial production in FDA-certified facilities(FDA = Food and Drug Administration, USA).The Exclusive Synthesis Business Line is part ofthe Health and Nutrition Business Unit.

The cataCXium® product family is suitable for palladium-catalyzed C-X coupling reactions. The picture showsexemplarily cataCXium® A, a bisada-mantyl butylphosphine ligand

The catASium® product family is usedin asymmetric hydrogenation. The picture shows exemplarily catASium®

MN(R), a biphospholane-pyrrole-2,5-dione ligand

Tapping the Sun on a ShoestringP L A S T I C S F O R P H O T O V O L T A I C S


Regardless of the attractiveness of photovoltaics, the cost ofsolar energy will have to drop from its current level of roughlyø 3 per Watt-peak to at least ø 1 to be competitive without gov -ern ment subsidies. Watt-peak (Wp) is a standar dized measure-ment for power rating of solar cells and modules, the prices forwhich are normally expressed in ø/Wp for comparison purpo-ses. The Wp rating corresponds to the electrical output reachedwhen 1,000 W per m2 of solar radiation reaches the module at aperpendicular angle and the temperature of the solar cells ismaintained at 25 °C (77 °F).

Solar energy must become competitive

The European Photovoltaics Technology Platform, a coalition ofthe most important players in photovoltaics in Europe, pub -lished a strategic research agenda (SRA) in June 2007. To con-solidate Europe’s worldwide leading role in photovoltaics, thedocument sets short-term, medium-term, and long-term re -search priorities. According to the SRA, solar power will becom petitive with conventional power sources in southernEurope by 2015, and nearly everywhere in Europe by 2020.Moreover, grid parity – the term for this ability to compete –will be reached through strong market trends, to the extent thatthe necessary market launch instruments are established in as

DR. CLAUDIUS NEUMANN, DR. JOCHEN ACKERMANN

espite all attempts to save, the demand for energywill keep climbing over the next few decades. Ac - cor ding to its latest World Energy Outlook, the Inter -national Energy Agency (IEA) predicts worldwide

energy demand to grow from the current 10.8 billion metrictons of oil equivalents to 16.3 billion metric tons by 2030, anincrease of over 50 percent. Prognoses also indicate that thenext decades will continue to see a mix of energies, with analmost certain disproportionate rise in the share of renewableenergies. Today, over 180 GW of electrical power from renew -able energies is installed globally, which makes up about 18 per-cent of the global energy supply.

Among the range of choices, photovoltaic energy generationis considered a particularly promising form of renewable ener-gy. Although solar power still accounts for just a fraction of apercentage of total electricity consumption in Germany, annualgrowth in the sector is in the double-digit range. This makesphotovoltaics the fastest-growing renewable energy technol -ogy with the brightest prospects. One reason is that the solarmodules required for this energy can be placed on the roofs ofhouses or in open spaces, in total harmony with the environ-ment. Moreover, with an energy supply more than 10,000times larger than the worldwide demand for energy, the sun is avirtually endless resource.

D

The solar industry is urgently seeking new, low-costmaterials. Despite an ongoing boom, unsubsidized photo-voltaics is still not as competitive as other regenerativeenergy sources. To pave the way for solar cells in a sustain-able and promising energy market, manufacturing andinstallation costs will have to be reduced considerably.Advanced thin-film technology, combined with powerfulplastics, could hold the key to greater economic efficiency.Scientists from the Functional Films & Surfaces ProjectHouse at Evonik have already developed a strategy for ap proaching this idea.

with Slim Solar Cells

27

D E S I G N I N G W I T H P O L Y M E R S


Grid parity

Grid parity will be reached when power from a photo-voltaics plant can be supplied at the same price as theend-user price of electricity from a wall receptacle. If,for example, electricity from a wall receptacle one daycosts about 25 cents/kWh (2007: approx. 19 cents),and the feed-in compensation for solar power costs,for example, 24 cents, it might make more sense forthe individual homeowner to consume his solar powerdirectly than to hook up to the public grid. Grid parityshould not be confused with a comparison of the pro-duction costs of solar energy and conventional power.The pure production costs for atomic or coal-firedpower, for example, are only three to eight cents/kWh (production costs plus costs for CO2 certificatesplus network fees). Solar energy will become genui-nely competitive only when it can be produced at thesame cost. Only then will it be practical from a purebusiness standpoint to construct a solar power stationrather than a coal-fired power station.

many European countries as possible. The German RenewableEnergy Sources Law (EEG) is cited as an example.

One thing is already clear. Compared to established solar cellsbased on mono- or polycrystalline silicon, the competitiveness ofsolar power can be realized significantly faster through thin-filmtechnology. Right now, CIGS (copper indium gallium selenide)technology is considered one of the most powerful thin-film pro-cesses, and unlike silicon wafers of 150 –350 μm thickness, isbased on photo voltaic active CIGS layers a few micrometersthick. Pro duction involves the evaporization of the semiconduc-tor materials in a vacuum and deposition on a glass substrate(Fig 1, p. 28). Over the last ten years, this process has maturedenough to allow serial production of modules 120 x 80cm in size.

Modules must become lighter and slimmer

The advantage of the process is that it frees manufacturers fromdependence on silicon, a raw material that is currently scarce; itis also an elegant technological alternative to the establishedcrystallization process for solar silicon production. Another be n-e fit of thin-film technologies is that, unlike silicon-based mod -ules, they are capable of supplying energy even under weak ordiffuse light, and on roof planes that are not optimally aligned tothe incidence of the sun. >>>


A persistent disadvantage, however, is the expensive andheavy glass plates of the thin-layer modules, between which thephotovoltaic layers are embedded. In these laminates, the lowerglass sheet acts as substrate, while the upper sheet serves as abarrier to moisture and oxygen, which ensures the requiredguaranteed longevity of at least 20 years. The installation of suchglass-on-glass modules on the roofs of houses normally requiresa solid subconstruction, whereby installation accounts for aboutone third of the total costs. This is why the next logical step in thecontinued development of thin-film technology is a significantreduction in the weight and cost of solar modules. And this isexactly where the Functional Films & Surfaces Proj ect House atEvonik starts its development.

The objective of the “Polymer Materials for Solar EnergyGeneration” project is to replace the glass barriers of the solar

Glass front sheet

EVA* lamination

TPT* backsheet

• Protection against deteriorating environmental influences

• Transmission > 90%

• Structural and mechanical support of photovoltaic

• Electrical isolation• Thermal conduction

• Protection against deteriorating environmental influences

• Electrical

isolationagainst environment

Solar cells

Ethylene vinyl acetatePolymer film composed of poly(vinyl fluoride) – polyester - poly(vinyl fluoride)

* *

cell layers

Float glass cleaning

Substrate

Mo, DC sputtered

Applying back contact

Laser patterning

Isolating cut

CIGS, inline co-evaporation

Absorber layer

CdS, chemical bath i-ZnO, RF sputtered

Buffer layer

Mechanical patterning

Open back contact

ZnO:Al, RF sputtered

Applying front contact

Mechanical patterning

Isolating cut Applying contacts

EVA/tempered glass framing

Encapsulation

k k k

k k

v

k

v v

Figure 1With CIGS technology,thin film solar cells and modules can bemanufactured in a continuous process fromsubstrate to finishedmodule

Figure 2Structure of a conven-tional silicon-basedsolar module. Glazing,encapsulation, and framing are potentialfields of innovation forplastics manufacturersin the PV industry

modules with a suitable film system. The film will have to provideultra-reliable protection against environmental influences forthe photovoltaic layer and transmit light at least as well as glass –requirements that could be met with polymethyl methacrylate(PMMA) films. For the development work, Evonik can drawupon years of experience with this material for applicationswith high requirements in weatherability.

Plastics as a key construction element in solar modules

Polymer-based film materials are already making a significantcontribution to the longevity, the mechanical stability, and theoperational safety of conventional silicon-based solar modules(Fig. 2). The soldered solar cells are embedded in a thermallycured plastic, which protects them against mechanical >>>

D E S I G N I N G W I T H P O L Y M E R S


10-6

10-2

10-1

100

Flexible LCDs and organic

solar cells

Solar cell encapsulation

Packaging of technical parts

Flexible OLED

Permeabilityrange forbarriermaterials

Two inorganic layers One inorganic layer

Single polymer layer

Polymer

EB evaporation

PECVD (plasma enhancedchemical vapour deposition)

Sputtering

+ Hybrid (sol-gel) 10-4 10-2

10-2 10-1

10-2 100

10-1 100

100 102

Backcontact

Photovoltaiclayer

Frontcontact

Deposition

Barrierand top

cover filmroll

Flexiblesubstrate

roll

Flexiblephotovoltaic cell roll

Encapsulation

High temperature polymersubstrate (e.g. PI, PEEK)

Flexible polymer barrier film(e.g. EVA, silicones, TPU)Flexible transparent polymertop cover (e.g. PMMA, ECTFE)

Figure 3The requirements for the water vaportransfer rate (WVTR) and oxygentransfer rate (OTR) of a barrier materialvary depending on the application.While packaging films with a value ofone are sufficient for technical parts,flex ible organic light-emitting diodes(OLEDs) require a high level of pro -tection against humid ity and oxygenthat can be pro vided only by inorganiclayers, which have transfer rates ofabout 10-6. For this reason, plastic filmsfor flex ible thin film modules will require new barrier film concepts

Figure 4 Coating with inorganic metal oxidescan enhance the barrier properties of a conventional plastic to protect itagainst humidity and oxygen

Figure 5Developers from Evonik’s FunctionalFilms & Surfaces Project House areworking on such projects as plasticfilms for flexible solar cells that couldbe produced in a continuous roll-to-roll process

WVTR [g/(m2•d)], OTR [cm3/(m2•d•bar)]

10-4 10-3 10-2 10-1 100 101 102

OTR [cm3/(m2•d •bar)]WVTR [g/(m2•d)]


loading. While the front side is made of glass to allow light toenter, the backside of the module is insulated by a film thatprotects it against the influences of weather and prevents theelectric discharge through the backside of the module.

The unique challenge with thin-film modules is in replacingthe front glass cover with a transparent film that is not onlyhighly light-transmitting but also protects the photovoltaic layeragainst weathering and mechanical damage. For this purpose,conventional plastics must be surface-modified to have barrierproperties that significantly reduce the permeation of moistureand oxygen. One measure for these barrier properties is thewater vapor and oxygen transfer rate. The two variables mustbe low ered by one to two orders of magnitude for thin-layer mod -ules, compared to conventional packaging films (Fig. 3, p. 29).

Coating technologies that are commonly used today in themanufacture of packaging materials offer ways of approachingthis challenge. These processes involve the evaporation of metaloxides such as those of silicon or aluminum by electron excita -t ion in a vacuum and depositing them in an only nano meter thicklayer onto the surface of the plastic substrate. The bar rier effect ofthis coating process can be enhanced even further by applyingan additional organic or hybrid coating (Fig. 4, p. 29).

Gluing modules like roofing sheets

Over the intermediate term, however, project house developerswill not be satisfied with half measures. In fact, they alreadyhave some specific ideas about producing plastic films for mod -ules in which also the second supporting layer of glass will bereplaced by a polymer material. Such modules would be fullyflexible, and could – according to the developers – be manufac-tured far more economically than before in a continuous roll-to-roll process (Fig. 5, p. 29). Such a process could yield extremelylightweight solar cells in the form of roofing sheets, which couldsimply be attached to the roof without an additional substructure.

Apart from this, the modules could also be installed in placesthat are difficult to access, or on any shape of surface – areaswhere solar cells have commonly not been installed yet. Currentdevelopments aim to convert polymers into high-temperaturesubstrates for compatibility with the deposition process.

The decisive factor for entry into the new technology has

been market demand. Driven by the enormous market growth,particularly in thin-film photovoltaics, the solar industry issearching for new products to make the manufacture of the mo d-ules cost competitive, above all for the construction of large-scale solar power plants in regions with plenty of sun. Because itmakes it possible to generate power even under relatively unfa-vorable lighting conditions, thin-film technology with flexiblefilms ap pears to hold much promise for successfully – and thatmeans above all economically – tapping the sun, even in middlelati tudes. On the whole, future R&D will focus on developingeach technology for applications in a certain market segment ofthe solar industry. ●

DR.-ING. JOCHEN ACKERMANNJochen Ackermann has been head of Evonik’sFunctional Films & Surfaces Project House in Hanau-Wolfgang since July 2006. After studying chemicalengineering at the University of Erlangen-Nurembergand after receiving his doctorate from the university’sInstitute for Chemical Technology, he began his careerin 2000 as a development engineer with MonomerProcess Technology at Evonik Röhm GmbH. After a station as group manager for Monomer ProcessTechnology in Darmstadt, he transferred to CYROIndustries, an Evonik subsidiary in Fortier (Louisiana,

USA), where he was responsible for the construction of a new monomer productionplant until he took over his current position.+49 6181 59-6375, [email protected]

DR. CLAUDIUS NEUMANNDr. Claudius Neumann is responsible for the project“Polymer Materials for Solar Energy Generation” atEvonik’s Functional Films & Surfaces Project House. He studied chemistry at the Universities of Erlangen andMainz (Germany), and Dijon (France). After obtaininghis doctor’s degree at the University of Mainz, he joinedEvonik in 1997, where he initially improved and devel -oped superabsorbent polymers. In 2000, he took re -sponsibility as head of technical service and applica tiontechnology in the Performance Monomers Busi ness Lineof the former Methacrylates Business Unit. Be gin n ing

2005, he joined the R&D department of the former Advanced Polymer ShapesBusiness Unit until end of 2006, when he joined the newly founded project house.+49 6181 59-6287, [email protected]

Because of its high weathering resistance and light transmission, PMMA satisfies stringent requirements as a substitute for the glass cover sheets of solar modules. With its R&D, Evonik can draw upon several years of experience in film production. The picture on the right shows one such plant in Weiterstadt that produces the material


PolyIC, BASF, Evonik Industries, Elantas Beck, and Siemens have an -nounced the launch of a new German Federal Ministry of Educationand Research (BMBF)-sponsored alliance project called MaDriX toadvance the development of high-performance printable radio fre -quency identification (RFID) tags.

The current generation of RFID tags contain silicon chips and aremainly used for high-priced products because of the complex manu-facturing processes involved. Printed electronic technology willreduce the cost of RFID tag production thanks to the development ofnew materials such as electrically conductive and semiconductingplastics that can be employed in high throughput printing processes.This will make printed radio frequency identification tags suitable foruse in cheaper consumer goods so that they may even come to replaceprinted bar codes.

PolyIC leads the consortium engaged in the three-year joint proj -ect. The total investment sum amounts to some € 15 million, with theBMBF contributing approximately € 8 million. The project is fundedas part of the BMBF’s 5th Framework Program “Key Technologies –Research for Innovations, Communications Technology Sector.” TheGerman Aerospace Center, DLR, is acting as project sponsor. WithMaDriX, the companies involved in the alliance and the federal min -istry will secure Germany’s current leadership as a research base inthe printable electronics sector.

Goods labeled with RFID tags can beidentified by radiowaves and are used inapplications from logistics through tosupermarket checkouts. They also makeproducts harder to fake. The graduallaunch of printed RFID tags within thenext ten years is a realistic prospect.

The close cooperation between thecompanies involved is a key to the successof the MaDriX project. PolyIC engageswith the issues of component characteri-zation, process development and settingup demonstrators. BASF, Evonik Indus -tries, and Elantas Beck will supply newmaterials to produce semiconductors andinsulators for use in electronic circuits.Siemens is developing new real-time visualprint inspection processes for quality con-trol in the printing process. A number ofuniversities and research institutes are alsoinvolved in the MaDriX project.

news

+++ MaDriX: Alliance project for printed electronics launched

Innovative semi-conductor systems are a top priority at Evonik

Evonik will play a dual role in the MaDriX alliance project: the synthe-sis of innovative semiconductor systems through various subcontrac-tors, and the transfer of the findings to industrial processes, followedby upscaling. As part of the project, Creavis Technologies & Inno -vation, the strategic research and development unit of the ChemicalsBusiness Area, is cooperating externally with the University ofWup pertal, the Technical University of Berlin, the University ofErlangen-Nuremberg, and the Max Planck Institute for PolymerResearch in Mainz.

In addition to the activities at Creavis, Evonik will contribute itsexpertise in the fields of nanomaterials and PMMA to the project.“We maintain close contact in these areas with Dr. Sven Hill, NewBusiness Development Aerosil, and Dr. Günter Schmitt of the NewBusiness Development unit in the Coatings & Additives BusinessUnit,” explains Dr. Heiko Thiem, MaDriX project manager for Creavis.

The Evonik Nanotronics Science-to-Business Center tests thesemiconductors and dielectric systems developed in the MaDriXproj ect for use in standardized test assemblies. Transferring thematerial systems to various printing processes is another task Evonikwill perform for the project.

First printed polymer RFID tag (13.56 MHz) (Photo: PolyIC)

Mile long printed logic circuitsfor RFID tags (Photo: PolyIC)

Credits

Published byEvonik Degussa GmbHInnovation Management ChemicalsRellinghauser Strasse 1–11

45128 EssenGermany

Scientific Advisory BoardDr. Norbert FinkeEvonik Degussa GmbHInnovation Management [email protected]

Editor in ChiefDr. Karin Assmann Evonik Services GmbHEditorial [email protected]

Contribution EditorsDr. Angelika Fallert-MüllerDr. Rolf FroböseKlaus JoppMichael Vogel

DesignMichael Stahl, Munich, Germany

PhotosEvonik IndustriesDieter DeboMarkus SchmidtStefan WildhirtWürth Solar, Andi Schmid (p. 26)DIGITALstock (p. 8, left)Getty Images (p. 22)Mauritius Images (p. 18)

Printed byMediahaus Biering GmbHMunich, Germany

Reproduction only with permissionof the editorial office

06/01– 06/04/20084th International Conference onRenewable Resources & BiorefineriesROTTERDAM (THE NETHERLANDS)

www.rrbconference.com

J U N E 0 8

07/20 – 07/24/200848th Symposium on Polymer ColloidsPRAGUE (CZECH REPUBLIC)

www.imc.cas.cz/sympo/48micros

J U LY / A U G U S T 0 8

09/07– 09/10/20087th European Symposium on Biochemical Engineering ScienceFARO (PORTUGAL)

www.esbes2008.org

S E P T E M B E R 0 8

09/28– 10/01/2008Green SolventsKONSTANZ (GERMANY)

events.dechema.de/gspsa.html

S E P T E M B E R / O C T O B E R 0 8

06/01– 06/05/2008Nanotech 2008BOSTON (MASSACHUSETTS, USA)

www.nsti.org/Nanotech2008

09/07– 09/11/20084th International Symposium on Macro- and SupramolecularArchitectures and MaterialsDÜSSELDORF (GERMANY)

www.chemie.uni-duesseldorf.de/Faecher/Organische_Chemie/OC2/ritter/MAM_08/index_html

09/28– 10/02/20085th International Conference on Combinatorial and High ThroughputMaterials ScienceSEEON (GERMANY)

www.dechema.de/seeon

07/28– 08/01/200823rd IUPAC Symposium on PhotochemistryGOTHENBURG (SWEDEN)

photoscience.la.asu.edu/Goteborg2008

08/31– 09/03/20085th International Conferenceon Environmental CatalysisBELFAST (UNITED KINGDOM)www.centacat.qub.ac.uk/5icec/index.html

10/07– 10/09/2008ProcessNet Annual Conference 2008KARLSRUHE (GERMANY)

www.dechema.de/jt2008

07/27– 08/01/200817th International Conference on Photochemical Conversion andStorage of Solar EnergySYDNEY (AUSTRALIA)

www.ips17.com

Evonik Industries AGRellinghauser Strasse 1–11

45128 EssenGermany

www.evonik.com

events

06/02– 06/03/2008American Coatings ShowCHARLOTTE (NORTH CAROLINA, USA)

www.american-coatings-show.com

06/22– 06/25/20087th World Surfactants CongressPARIS (FRANCE)

www.cesio2008.com/index.htm

09/16– 09/20/20082nd EuCheMS Chemistry CongressTURIN (ITALY)

www.euchems-torino2008.it

10/07 – 10/09/2008European BioPerspectivesHANOVER (GERMANY)

www.bioperspectives.org

09/28– 09/30/20086th International Conference on Inorganic MaterialsDRESDEN (GERMANY)

www.im-conference.elsevier.com/index.htm

elements 23, issue 2 | 2008 - evonik

Documents