plastics additives and testing (subramanian/plastics) || inorganic additives

6 Inorganic Additives

Inorganic chemicals have existed since the earth solidified. Most of the silicates and aluminosilicates, including mica, clay natu-ral glasses and complex materials, are components in the litho-sphère. Remaining elements such as iron, magnesium, calcium, sodium and potassium, etc., occur as additional components of silicates and aluminosilicates. These materials have been used from prehistoric times up to the polymer age for the needs of mankind.

Metal containing and other inorganic materials have been used for a variety of plastics additive applications. Fillers are among the simplest, high-volume additives widely used. Fillers such as talc, kaolin, calcium carbonate, and other silicates not only improve the economics of the plastics, but also add to product stability and properties such as those that are thermal or mechanical. Thereby, substantial improvements in mechanical and physical properties by the inorganic additives increase their use in the plastics indus-try. The addition of inorganic additives is one of the most com-mon and economical methods used in modifying the properties of plastics.

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Plastics Additives and Testing, by Muralisrinivasan Natamai Subramanian. ©2013 Scrivener Publishing LLC. Co-published by John Wiley & Sons, Inc.

126 PLASTICS ADDITIVES AND TESTING

6.1 Heat Stabilizers There are four main classes of heat stabilizers:

• Lead compounds of sulfate, carboxylate, phosphate • Tin compounds such as dialkyltin carboxlates, dialkyl-

tin dithioglycolates • Combination of barium and cadmium soaps • Combination of calcium and zinc soaps

These inorganic additives are used as thermal stability for PVC. They are very important to PVC. Generally stabilizers may behave in the following ways.

Primary stabilizers are able to reduce long polyene formation, thereby preventing early resin discoloration. They react with labile chlorine atoms in PVC chains (e.g., allylic or tertiary chlorine atoms) preventing further dehydrochlorination.

Secondary stabilizers such as K, Ca or Ba, etc., are reacted with HC1 liberated by the degradation process, and accelerate the ther-mal degradation of PVC. Such stabilizers do not protect against short-term discoloration, but delay the terrific degradation of the material. Zn and Cd carboxylates are both able to scavenge HC1 and react with labile chlorine atoms [1].

Commercial thermal stabilizers are usually either basic lead salts [2] that can trap the evolved hydrogen chloride gas, thus retarding the damaging autocatalytic action of the eliminated HC1 gas [3], or metallic soap [4-6] esters whose stabilizing action occurs through displacement of the labile chlorine atoms on the polymer chains by the ester from the decomposed stabilizer. These metallic soaps also act as lubricant during processing. Recently a new class of stabiliz-ers of an organic nature have been developed [7]. These types of stabilizers claim to work by trapping the radical species in the deg-radation process, by blocking the newly formed radical sites on the polymeric chains, and by absorbing the liberated HC1 gas. Tribasic lead sulphate, 3PbO PbS04 H 2 0 (TBLS), is one of the stabilizers used in this work. However, they do not have the lubricating effect of lead and other heavy metal stabilizers. Because PVC catalyzes its own decomposition, metal stabilizers are added to vinyl for con-struction and other extended-life applications.

Heat stabilizers such as metal stéarates and zinc oxide are acid scavenging additives that are the antacids of the plastics world.

INORGANIC ADDITIVES 127

Without heat stabilizing additives, PVC not only is subject to slow decomposition, as indicated by yellowing and deterioration, but is even corrosive toward steel.

Heat stabilizers such as metal thiolates and carboxylates are com-monly used for long-term PVC stability, replacing labile chlorine found at defect sites in the polymer. Since such sites allow facile initiation of dehydrochlorination, unstabilized PVC is unstable at its melt temperature.

Mixtures of calcium and zinc carboxylates have shown a syn-ergistic stabilizing action. Calcium carboxylates act as ester-exchangers with zinc chloride. Mixtures of Calcium and zinc stéarates are able to form a complex through heating. Such a com-plex has a poor coordination with labile chlorine atoms in PVC because the coordination sites of zinc may be filled with carboxyl-ate anions from calcium soap. Moreover, other authors have sug-gested that only the "free" zinc stéarate is involved in the polymer esterification [8].

6.2 Flame Retardants

All plastics are flammable with the exception of chlorinated polymers such as PVC, which nevertheless produce smoke dur-ing fires. Plasticized PVC can become somewhat flammable. Inorganic flame retardants include aluminum trioxide, magne-sium hydroxide, ammonium polyphosphate, and red phospho-rus. This group represents about 50% by volume of the global flame retardant production [9]. Flame retardant compound using aluminum trihydrate or magnesium hydroxide can improve flame resistance.

Simple and high volume fire retardant additives are hydroxides of aluminum and magnesium. Upon decomposition they remove heat and release water vapor due to their endothermic nature. However, large amounts of these additives are needed to achieve the desired effect. These hydroxide materials must act both as fillers and as fire retardants. The combined additive function is simple to formulate and economical [10].

Antimony oxide produces vapor-phase radical scavengers while used as flame retardants. Antimony halides appear to form an important link in the radical scavenging cycle during flame retardancy. Antimony trioxide and pentoxide are used along with


halogen flame retardant additive or halogenated polymers due to their synergistic interaction arising from the formation of antimony trihalide [11]. The conversion into the trihalide proposed reaction is shown in Equation 6.1.

Sb203 + 2ΗΧ -> 2SbOX + H 2 0 ( )

5SbOX -» Sb4OsX2 + SbX3

Boron compounds such as boric acid and borax are economical flame retardants. The retardation appears as a formation of a glass-like coating on the polymer surface.

6.3 Fillers Fillers are inorganic additives that play an important role in technically demanding applications [12-17]. They improve stiff-ness, modulus of elasticity, hardness, and tensile stress at break and melt viscosity at optimum level of addition. However, they reduce the elongation in plastics such as polypropylene. They also reduce impact strength and melt flow index [18-19]. Many properties are changed by good matrix adhesion of filler with plastics. Fillers also improve the modulus and dimensional stabil-ity, along with decreased penetration and permeability [20-25]. Inorganic filler plastics represent an important class of engineer-ing materials [26-27]. Filler with fine materials tend to agglom-erate to obtain good particle dispersion in plastics. The mineral fillers seem to modify the mechanical properties at three levels:

1. by their nature; 2. by their size, shape and distribution [28-29]; and 3. by the changes they bring about in the microstructure

of the matrix.

Tailor-made plastics are produced with the addition of fillers with new and enhanced properties with respect to the unfilled matrix. To achieve significant changes in the macroscopic behavior, high-volume filler with micrometer-sized particles is required [30].


The effects of filler on the properties strongly depend on [31-32]

• its origin; • particle shape and size; • aggregate size; • fraction of filler; • surface characteristics; • degree of dispersion.

6.3.1 Calcium Carbonate

Calcium carbonate is classified as inert non-reinforcing filler. However, when present in concentrations greater than 10%, it does increase the tensile strength of composites to some extent. The more readily dispersible surface-treated varieties of calcium carbonate fillers also contribute to a significant increase in tensile strength of polyester resins [33]. Calcium carbonate filler is also used with PVC, polyolefins, epoxy and PF resins.

Calcium carbonate is one of the most abundant materials on our planet. Early on it has been used in ground form to produce plastic composites. There are no less than three minerals or phases of CaC03 (calcite, aragonite and vaterite), but calcite is most widely found in nature. In contrast to precipitated calcium carbonate, ground natural calcite is usually micron-sized (easier to disperse) with a broad size distribution and irregular shape. To reduce its high surface energy and its particle-particle interactions, which lead to agglomerates, it is often coated by a variety of surface modifiers such as fatty acids, phosphates, silanes, titanates or zirconates [26,34-36].

The most widely used calcite coating is the surface treatment with stearic acid or one of its salts. As a result, an ultra-thin layer of hydrophobic alkyl chains is chemically bonded to the surface. The coated organic film represents the interface between the filler and the polymer matrix, and hence influences the wetting and adhesion properties of the two phases involved. It also influences the growth of the interphase and consequently determines the final properties of the composite, besides reducing the particle—particle interactions and the filler surface energy. Studies on the structure and properties of the coated organic thin film have shown that one stearic moiety is attached to each surface Ca2+ [37-39]. This results in a vertical orien-tation and close packing of the alkyl chains, leading to a high trans


population and an ordered state. To ensure complete surface cover-age, an excess of the surfactant is often used in commercial products. It has been reported that surfactant excess often leads to process-ing problems and inferior mechanical properties, but no detailed study on the influence of over coating on the tensile properties of polyolefin-calcite composites can be found in the literature [38-42].

Calcium carbonate with a broad range of particle size distribu-tion favors mass/volume costs [19, 43-44]. It is commonly used as filler in the plastics industry. Calcium carbonate can be com-pounded with polyolefins, PVC, phenolics, polyesters and epoxies. Its broad usage can be attributed to both economic and perfor-mance considerations.

Calcium carbonate is used either to fill the plastics or to modify some physical property. The plastics and filler interface has to exert a considerable influence on mechanical response, and correlation with acid-base characteristics of filler [45].

Calcium carbonate is an inexpensive and widely used particulate filler in the plastic industry. Before incorporation into the polymer, CaC03 is often surface treated to change the basic character of the particle surface induced by the presence of Ca2+ on the surface of the CaC03 particles. CaCOs can be modified with higher fatty acids, unsaturated acids, hydroxyl acids, silanes, amino acids and their derivatives. This modification decreases the ability of CaC03 to form specific interface interactions with hydrocarbon elastomers [46].

The reaction of CaC03 with fatty acids and other acids, particu-larly with stearic acid, has been used for many years [47]. It is com-monly known as coated filler and is much more hydrophobic than uncoated ones. The coated fillers have been shown to have an effect on polymer morphology, hence modifying properties result from rendering the surface more hydrophobic thereby altering the com-patibility with the plastics. Coating is used to improve compatibility with, and dispersion in plastics materials, which leads to improved properties. By enabling the filler to bond through hydrogen or ionic bonds the physical nature of the interface is changed [48]. However, a certain degree of chemical modification of filler surfaces could result in changes of the interfacial layer. This leads to the change in failure mechanism due to the cohesive failure in plastics materials [49].

6.3.2 Nanofillers

Nanofillers reduce the oxygen-permeability rate by at least 10% compared to values obtained for pure resins, while preserving the


transparency [50-52]. In order to work as a good barrier there is a direct relation to the nanofiller dispersion in the polymeric matrix. The barrier property significantly improves if the filler dispersion takes place preferentially as single layers or individual particles [53-54]. Incomplete dispersion is responsible for the presence of agglomerates or tactoides, with a consequent reduction in the bar-rier, thermal, and mechanical properties [54].

6.3.3 Silica

Silica, which has a specific gravity of 2.6, is available as finely divided amorphous diatomaceous earth and as fumed silica, as well as in the form of large crystalline particulates such as sand and ground quartz. Reactive silica ash has been produced by burning rice hulls. Finely divided silicas are also produced by a comminuta-tion process in a fluid energy mill or by the acidification of sodium silicate solutions. Pyrogenic, or fumed silica, is produced by heat-ing silicon tetrachloride in an atmosphere of hydrogen and oxygen, and by the programmed thermal reduction and oxidation of silicon dioxide. Fumed silica is used to increase the viscosity and thixot-ropy of liquid resins.

Hydrated finely divided silicas consist of aggregates of quasi-spherical particles which are fused together [55]. These fillers, which contain surface silanol groups, are used for the rein-forcement of polydiene and silicone elastomers. The modulus, compressive strength, tensile strength, and toughness of epoxy resins are increased when silica is added to these polymers [56].

The interaction of silica fillers and polymers has also been improved by the addition of silanes [57]. The flexural strength of polyesters is markedly improved when these composites contain silane-treated silica fillers [58]. The temperature resistance of PP has been increased by filling with silica that has been treated with stea-ric acid or zinc stéarate. Silica treated with ortho-hydroxybenzyl alcohol [59] was used to produce Nylon 6 composites with high tensile strength.

6.3.4 Mica

Mica, which has a specific gravity of 2.8 and a Mohs hardness of 3, is a naturally occurring lamellar or platelike filler which is available in a particle size range of 10 to 80 pm. The aspect ratio for commer-cially wet or dry ground mica is usually below 30, but flakes with


an average aspect ratio as high as 300 have been produced by the ultrasonic delamination of mica [60].

Mica is also available in the form of paper-like sheets. When the aspect ratio is low, the mica plates may be pulled out of the resin matrix, but when this ratio is greater than 49, the plates will frac-ture when the composite fails. Composites with excellent electrical properties and good impact resistance are produced when Nylon 66, or ABS copolymers, are reinforced by suitably prepared mica platelets. Mica also increases the moisture and corrosion resistance of plastics [61].

Mica has been extensively used as reinforcing filler for thermo-sets and thermoplastics because of its influence on the physical, mechanical, and electrical properties of the mica-filled composites [62-65]. Mica has a modulus of 172GN/m2 against 73GN/m2 of the glass flakes. Mica has excellent chemical and corrosion resistance, good electric properties, and low thermal expansion, and it causes less wear and abrasion to the processing equipment.

Mica agglomeration, distribution, wetting, and adhesion with polymer resin determine the composite properties. Upgradation of mica by increasing the aspect ratio and coupling efficiency, and combining mica with other fibers, can improve the reinforcing effect of the composites [66].

Mica addition to polymers also shows significant changes in dielectric properties of the plastics [67-69].

6.3.5 Solid Glass Spheres

Solid glass spheres have been used for centuries for adornment and decorative effects. For the past four decades, on America high-ways, tiny glass beads have also been used to provide retro-reflec-tivity. The use of such readily available and economical product as a filler in plastics is relatively new [70]. Glass sphere compos-ites have been produced from high density polyethylene (HDPE), silicone resins, poly(vinyl chloride) (PVC), and SAN and ABS copolymers.

They are made from a soda lime or Type A glass formulation with specific gravity of 2.5. Glass beads produce isotropic composites which, because of reduced internal stress, have less shrinkage and warpage. Glass spheres increase stiffness and reduce the strength of polypropylene (PP). In poly(propylene oxide), They increase the elongation and impact strength [71].


6.3.6 Talc

Talc is a naturally occurring hydrated magnesium silicate with a specific gravity of 2.4 and a hardness of 1 on the Mohs scale. Because it has a fiber-like structure, talc provides some reinforce-ment to polymer composites. Talc-filled PP is more rigid, harder, and more resistant to creep at elevated temperatures than the unfilled polymer [72].

6.3.7 Asbestos

Asbestos is a naturally occurring magnesium silicate which has been used for over 2500 years as a flame-resistant fiber. Much of this filler is mined in Canada and the USSR. Anthophyllite, which is a short fiber belonging to the amiphibole class, and crocidolite, which is a blue fiber belonging to the same class, are discussed under the section on polymer reinforcements [73].

Chrysotile is used to increase the hardness, impact resistance, and heat deflection temperature of poly (vinyl chloride) tile [74]. This type belongs to the serpentine class and accounts for 95% of the world's production of asbestos. Short asbestos fibers, called "shorts," have been used to reinforce phenolic resins, but because of Occupational Safety and Health Administration (OSHA) regula-tions this filler has been replaced to some extent by less hazardous products [75].

OSHA requires that each individual not be exposed to more than two fibers longer than 5 pm/cm 3 of air during an 8-hr period. The World Health Organization (WHO) has found that the concentra-tion of asbestos in urban atmospheres is much less than the estab-lished safety limits. Accordingly, asbestos reinforced polyolefins and polystyrene (PS) are being produced in Western Europe, and over 250 thousand metric tons of asbestos are used annually in the United States for the production of PVC tile.

6.3.8 Zinc Oxide

Zinc oxide, which has a Mohs hardness of 2.5, is used primarily in the compounding of rubber. However, because of its ability to convert high energy radiation to lower energy radiation, zinc oxide is also used to improve the weatherability of polypropylene and polyesters. Both anatase and rutile titanium dioxide have been


used as white filler pigments. Composites with superior weather resistance are produced when rutile is added to PVC, polyethylene, PS, and ABS copolymers [76].

6.3.9 Barium Sulfate

Ground barytes, or barium sulfate, is a white filler with a specific gravity of 4.5 and a Mohs hardness of 3. Barium sulfate has been used to produce x-ray opaque poly(vinyl chloride) and to provide composites of controlled density. This filler improves the "drape" and "hand" of PUR foams. Grinding and polishing devices have been produced by adding finely divided silicon carbide to Nylon 6 or to PUR foams. The abrasion resistance of PF plastics has been increased by the addition of corundum.

6.3.10 Calcined Alumina

Calcined alumina, which has a Mohs hardness of 9, has also been used to produce abrasive composites. However, hydrated alumina, which has a Mohs hardness of less than 3, is used as a soft, fire-retardant filler for plastics [77].

6.3.11 Aluminum Trihydrate (ATH)

Aluminum trihydrate (ATH)-polyester composites have oxy-gen index values that are superior to flame-resistant composites containing antimony trioxide and chlorinated paraffin. The oxy-gen index, or candle test, is defined in ASTM standard D 2863 as the minimum concentration of oxygen in air that will support combustion when the specimen is ignited at its upper end, like a candle.

ATH-polyethylene composites have excellent adhesion to steel. The track resistance, dimensional stability, and heat resistance of cycloaliphatic epoxy resins have been improved by the addition of ATH [78].

6.3.12 Zirconia and Zirconium Silicate

Zirconia and zirconium silicate which have specific gravities of 5.5 and 4.7, respectively, have been used to produce composites with high densities. High concentrations of yiron oxide in polyethylene


composites cause an increase in density, hardness, and tensile strength, and a corresponding decrease in elongation. This filler has a specific gravity of 5.2.

6.3.13 Reinforcing Fillers

Reinforcing, usually with glass fibers because of the economics, normally at least doubles the tensile strength of the basic resin and provides a low temperature impact equal to, or exceeding that, of the room temperature impact strength. Such reinforcements almost always include specific coatings designed for specific functions within the polymer system.

Carbon fibers are known for their lightness, high strength and electrical conductivity, whereas glass fibers offer high strength and more elongation at break than is seen with carbon fibers. Natural fibers exhibit higher elongation at break than glass or carbon fibers, while their thermal conductivity is low, making them good candi-dates for thermal barrier materials [79].

Reinforcement of polymer products is well known to be suc-cessfully accomplished using a range of inorganic fillers, includ-ing glass fibers and flakes, smectite clays, talc and many other minerals [80-90]. While such fillers can substantially increase the moduli and thermal properties (heat deflection temperature, glass transition temperature, onset of thermal degradation), these prop-erty enhancements generally come at the expense of ductility and processability.

6.3.14 Glass Fiber

Glass fiber has a true reinforcing effect and gives extremely high strength and modulus combined with moderately high impact strength. Although conditioned glass fiber reinforced material results in some increase in impact strength, the increase is propor-tionately much smaller than for unfilled material. According to the old convention, glass filled materials were expected to have inferior surface appearance, however, new product innovations by leading manufacturers of resins make it possible to have superior gloss and surface by material characteristics and mold developments.

The inclusion of reinforcements is essential in achieving high lev-els of thermo-mechanical performance, as shown by the tempera-ture of deflection under load (heat distortion temperature). Glass


fiber reinforcement is particularly effective, raising the heat distor-tion temperature. A 30% glass filled material can raise the HDT to over 200°C.

Glass fiber reinforcements in polymers such as nylon will give very high strength and rigidity even at high temperatures. The processing temperature of Nylon 66 is about 30°C higher than that of Nylon 6. Hence, Nylon 6 has a slight processing advantage in terms of material stability, particularly where functional fillers are incorporated. The alignment of the glass fibers along the flow direction while processing, results in materials being "anisotropic." Glass fiber filled products will tend to distort, depending on flow in the mold. The alignment of the fiber will show property varia-tions in different directions. Problems in processing is to be con-trolled during the compounding and introduction of glass fibers. Many new applications are being contemplated with long fiber use in compounding.

Filled nylons and glass-reinforced nylons have melt flow charac-teristics which must be taken into account to produce a good surface finish. Generally, these materials are much more viscous than unfilled nylons, and to obtain, the requisite flow in the mold, high rates of shear are necessary. The higher shear rate is obtained by using high injection speed to fill the mold in order to prevent "freeze-off" in the gates, runners and mold cavity. The use of hot mold (80°C-100°C) will also greatly assist in providing a good surface finish.

Fiberglass is used in almost all of the traditional composite struc-tures in the form of unidirectional rovings, woven fabric, braiding fabric, or chopped strand mat. The popularity of this glass fiber comes from its relatively low cost and good in-plane mechanical properties [91].

6.3.15 Other Applications of Fillers

Silicate fillers such as talc, silica and zeolites, function as antiblock-ing agents that allow separation of film layers. Additives containing metals such as copper, zinc, and silver ions, are used as antimicro-bial additives. Nickel compounds are used as antioxidants.

Clays have long been used as fillers and blocking agents. Sodium and potassium ions, along with water, occupy the space between aluminosilicate layers in the clay. Organic anti-cations can cause the aluminosilicate sheets to delaminate during blending. They allow intercalation of polymer strands between sheets. Because


aluminosilicate sheets have a very high aspect ratio and great strength they tend to act as reinforcement with the polymer matrix. Polymer clays have increased thermal and mechanical properties along with fire retardance. Organoclay's functionality is clearly based on both the concentration and the type used in order to work as a oxygen and humidity barrier. Polyethylene (PE) and polypropylene (PP) are the most widely used polyolefin polymers. However, because of their nonpolar backbones, it is a challenge to make nanocomposites of PE and PP by melt blending with organically modified clay.

Inorganic nucleating agents, such as talc, mica, barium sulfate (BaS04) and calcium carbonate (CaC03), are added to reduce the cost and improve mechanical properties such as modulus and heat stability. They enhance the crystallization rate with phase behavior that controls the cell size, and to some extent, the properties in the final product [92].

The addition of fillers such as carbon and ceramics (silica, alu-mina, aluminum nitride, etc.) is commonly used to induce thermal conductivity into conventional polymers. Higher thermal conduc-tivity can be achieved by the addition of high volume fractions of a filler and the use of a suitable filler. Fillers have to form a random close packed structure to maximize a pathway for heat conduction through the polymer matrix [93]. Along with epoxy resins, various fillers have been used to improve flame-retardant properties [94-96].

Fillers with a high aspect ratio have been regarded as good can-didates for retardant additive. Fillers like montmorillonite (MMT) and carbon nanotube (CNT) are widely used to improve not only the flame-retardant properties, but also the mechanical properties [97-99]. They do not generate toxic smoke or corrosive fumes during combustion, unlike halogen compounds. They can produce environ-mentally friendly products with high thermal properties [100-101].

In polypropylene, CaC03 is added to improve mechanical prop-erties such as modulus and heat stability, to reduce cost of the end product, and enhance crystallization rate. Glass beads and talcum enhances mechanical and thermal properties, including phase behavior [102-104].

6.4 Blowing Agents

Inorganic blowing agents, namely sodium bicarbonate, ammo-nium carbonate, sodium boron hydride, silicon oxy-hydride, etc.,


gas rather slowly. The gas generation is difficult to control. Sodium bicarbonate decomposes over a broader temperature range start-ing at about 150°C. Thus, they do not have many applications. The significant advantage possessed by NaHC03 is its extremely low cost. Blowing agent cost per hundred pounds of compound, with NaHC03, will be in cents rather than dollars. The decomposition products are also nontoxic and odorless.

Minimum foam densities obtainable from NaHCOs are approxi-mately 30 Ib./cu. ft., with cell structure somewhat coarser than with other blowing agents. The main reason for the higher densities of NaHC03 foams is that water is one of the decomposition products. Generated in equimolar quantities with the CÖ2, the vaporized water contributes to expansion at processing temperatures, but a much larger percentage of cell contraction occurs during cooling as the water condenses. Five-six phr NaHC03 is the optimum concen-tration for good cell structure. Above this level a large overblow is evidenced with an almost complete collapse of cell structure. When the content of blowing agent in the compound increases, the com-pound containing too much blowing agent and processing aid is unable to efficiently decrease the extrudate density.

6.5 Inorganic Colorants

Inorganic pigments with cadmium have given increased brightness and freedom from soluble impurities. The ultramarines have been extended towards the violet end of the spectrum. The increasingly stable yellow, orange, and scarlet chrome pigments have made con-tributions towards solving problems in processing. Acrylic sheet pigmented with anatase grade titanium dioxide begins to crack and flake after exposure for 12-18 months. However, with rutile grade, even after exposure for 10 years, there is no cracking or flaking in the sample [105].

Titanium dioxide is the most important pigment. It provides an opaque white appearance. Titanium dioxide (Ti02) is a great scien-tific and technological versatile inorganic chemical. As a biocompat-ible, chemically inert semiconductor, it shows a high photostability. It is readily available and cheap [106].

Synthetic mixed-metal oxides encompassing a wide range of colors are used for high temperature plastics processing. Metal


powders such as aluminum and bronze also find use as pig-ments. Color concentrates help avoid handling problems, and can be blended during processing. Aluminum sulfosilicates and cadmium sulfides are used as color pigments for red to blue, and yellow to blue, respectively. Barium sulfate, calcium silicate, titanium dioxide and zinc oxide or sulfide are used as white pig-ments. Chromâtes are used for yellow pigmentation. Iron oxides are used in yellow to beige, tan to brown, and black and are among the other colors to be used for coloring plastics. However, use of metallic pigments used in PVC creates higher viscosity due to the reactions of metal with hydrogen chloride liberated during pro-cessing. Molybdates are used to tune the color from yellow to orange. Ferri-ferrocyanides are used as coloring agents for metallic blue. The overwhelming majority of fillers and pigments are neu-tral additives in respect to polymer thermal degradation, except sometimes in the case of additives like zinc derivatives and some fluorescent pigments [107].

6.6 Antimicrobial Agents

Heavy metals have long been recognized for their broad-spectrum biocidal effects, being the most commonly used inorganic antimi-crobials. Among them, ionic silver is known to have the largest antimicrobial capacity, with long-term biocidal properties, low volatility and low toxicity to eukaryotic cells. Thus, silver-based antimicrobial fillers in polymer matrices base their antimicrobial activity on a sustained release of silver ions [108-110].

Recently, silver and zinc ions have been trapped within zeolites (inorganic ceramics), expanding the applications of silver in dif-ferent fields [111-113]. Alkaline or alkaline-earth metal ions com-plexed with aluminosilicates are partially replaced in zeolites with silver or zinc ions by ion exchange. Silver containing zeolites are microscopic in size, and their main antimicrobial activity is almost certainly due to the action of released silver ions on cell metab-olism. Additionally, zinc ions could reinforce the antimicrobial activity of silver by interfering with proton transfer and inhibit-ing nutrient uptake [114]. Silver-zinc zeolites are being used for the decontamination of surfaces, the disinfection of medical devices, and for food preservation purposes [115-116].

140 PLASTICS ADDITIVES A N D TESTING

References

1. R. Bacaloglu, M.H. Fisch. PVC stabilizers. In Plastics additives hand-book. H. Zweifel, ed. 5th ed. Munich: Hanser., (2001) Chap. 3.

2. R.D. Dworkin. /. Vinyl. Technol. (1989) 11(1), 15. 3. P. Simon, L. Valko. Polym. Degrad. Stab. (1992) 35, 249. 4. M. Statheropoulos, G. Kakali. Eur. Polym. ]. (1989) 25(4), 405. 5. Gy. Levai, Gy. Ocskay, Z.S. Nyitrai. Polym. Degrad. Stab. (1994) 43,159. 6. H.I. Gokcel, D. Balkose, U. Kokturk. Eur. Polym. J. (1999) 1501;35 7. M.W. Sabaa, N.A. Mohamed, E.H. Oraby, A.A. Yassin. Polym. Degrad.

Stab. (2002) 76,367. 8. M.W. Mckensey, H.A. Willis, R.C. Owen, A. Michel. Eur. Polym. } .

(1983) 19,511-7. 9. S.M. Lomakin, G.E. Zaikov. Ecological aspects of flame retardancy. VSP

International Science Publishers: Zeist, Holland, (1999) p. 170. 10. R.D. Pike. Journal of Vinyl & Additive Technology (2004) 10,1. 11. E.D. Weil. Additivity, synergism and antogonism in flame retardance.

Plastics Inst. of America, Hoboken, NJ (1971). 12. G. Pritchard. Plastic additives. Chapman and Hall, London, (1998) 13. H.D. Rozman, B.K. Kon, A. Abusamah, R.N. Kumar, Z.A.M. Ishak. /.

Appl. Polym. (1998) 69,1993. 14. N. Sharma, L.P. Chang, Y.L. Chu, H. Ismail, U.S. Ishiaku, Z.A.M.

Ishak. Polym. Degrad. Stab. (2001) 71,381. 15. G. Yu, M.Q. Zhang, H.M. Zeng. /. Appl. Polym. Sei. (1998) 70,559. 16. Y Nakamura, S. Okabe, T. Iida. J. Polym. Compos. (1999) 7, 33. 17. J. Jancar, J. Kueera. Polym. Eng. Sei. (1990) 30, 707. 18. H.G.B. Premalal, H. Ismail, A. Baharin. Polym. Test. (2002) 21,833. 19. M. Fujiyama, T. Wakino. /. Appl. Polym. Sei. (1991) 42,2749. 20. F.M. Fowkes. /. Adhesion (1972) 4,155. 21. F.M. Fowkes, F.H. Hielscher. Symposium on surface chemistry

of composite materials. 163rd National Meeting of the American Chemical Society, Boston, Mass., (April 1972).

22. L.E. Nielsen. Mechanical properties of polymers and composites: Vol. 2. Marcel Dekker. Inc., New York, N.Y., (1975).

23. J.A. Manson, L.H. Sperling. Polymer blends and composites. Plenum Publishing Company, New York, N.Y., (1976).

24. L.E. Nielsen. /. Macromoi. Sei. (1967) A1,929. 25. J.A. Manson, E.H. Chiu. /. Polym. Sei. Symp. (1973) 41, 95. 26. R.N. Rothon, ed. Particulate-filled polymer composites. Harlow:

Longman Scientific and Technical; (1995). 27. B. Pukanszky, and J. Karger-Kocsis, eds. Polypropylene: Structure,

blends and composites, Vol 3: Composites. Chapman & Hall, London, UK (1995).


28. L. Averous, J.C. Quantin, D. Lafon, and A. Crespy, Inf.}. Polym. Anni. Charact. (1995), 1, 339-347.

29. L. Averous, J.C. Quantin, D. Lafon, and A. Crespy. Determination of 3D fiber orientations in reinforced thermoplastics, using scanning electron microscopy. Ada Stereol. (1995) 14(1), 69-74 (Stermat '94).

30. F. Hussain, M. Hojjati, M. Okamoto, R.E.J. Gorga. Compos. Mater. (2006)40,1511.

31. Y. Wang, and J.J. Wang. Polym. Eng. Sei. (1999) 39,190. 32. G. Guerrica-Echevarria, J.I. Eguiazabal, and J. Nazabal. Eur. Polym. ].

(1998) 34,1213. 33. W.C. Jones, and A.L. Fricke. Mod. Plast. (1972) 49(4), 88. 34. J. Jancar, ed. Mineral fillers in thermoplastics: Advances in polymer sci-

ence 139. Berlin: Springer; (1999). 35. J. Karger-Kocsis, ed. Polypropylene: Structure, blends and composites.

London: Chapman and Hall; (1995). 36. T. Nakatsuka. Molecular characterization of composite interfaces. New

York: Plenum Press; (1985). 37. E. Papirer, J. Schultz, C. Turchi. Eur. Polym.}. (1984) 20(12), 1155. 38. E. Fekete, B. Pukânszky, A. Toth, I. Bertoti. /. Colloid. Interface Sei.

(1990) 135(1), 200. 39. M.A. Osman, U.W. Suter. Chem. Mater. (2002) 14,4408. 40. B. Pukânszky, ed. Polypropylene structure, blends and composites: Vol. 3.

London: Chapman and Hall; (1995). 41. E. Fekete, B. Pukânszky. /. Colloid. Interface Sei. (1997) 194, 269. 42. T. Ahsan, D.A. Taylor. /. Adhes. (1998) 67, 69. 43. B. Pukânszky, K. Belina, A. Rockenbauer, F.H.J. Maurer. Composites

(1994) 25,205. 44. W.C.J. Zuiderduin, C. Westzaan, J. Huetink, R.J. Gaymans. Polymer

(2003)44,261. 45. H.P. Schreiber, and F.J. St.Germain. /. Adhes. Sei. Technol. (1990) 4(4),

319. 46. M. Lipinska, M. Zaborski, L. Slusarski. Macromol. Symp. (2003)

194, 287. 47. P. McGenity, C D . Paynter, J.M. Adams, and A.H. Riley. Plastics

Rubber Process Appl. (1990) 14, 85. 48. R. Rothon. Particulate-filled polymer composites. Longman Scientific &

Technical, Harlow, England (1995). 49. L.C. Sawyer, and D.T. Grubb. Polymer microscopy. Chapman & Hall,

London (1996). 50. S. Arunvisut, S. Phummanee, A. Somwangthanaroj. /. Appl. Polym.

Sei. (2007) 106,2210. 51. M.A. Osman, V. Mittal, U.W. Suter. Macromol. Chem. Phys. (2007)

208, 68.


52. K. Yano, A. Usuki, A. Okada. /. Polym. Sei. Part A: Polym. Chem. (1997) 35, 2289.

53. T. Sakaya, R. Kuroda, T. Ogawa. US Patent 5,854,326 (1998). 54. S. Bagrodia, L.T. Germinario, J.W. Gilmer, T. Lan, V. Psihogios. US

Patent 6,586,500 (2003). 55. A.I. Medalia. Rubber Chem. Technol. (1974) 47(2), 411. 56. F. Swanson, and N. Gregomik. Mod. Plast. (1972) 49(11), 106. 57. A.M. Gessler, H.K. Wiese, and J. Rehner. Rubber Age (1955) 78, 73. 58. H.A. Freeman, and E.P. Plueddemann. Proc. Electron. Micros. Soc. Am.

(1973) 31,130. 59. K. Newbould. /. Appl. Polym. Sei. (1975) 19(3), 907. 60. S.H. Kauffman, et al. Am. Chem. Soc. Div. Org. Coat. Plast. Chem. Prepr.

(1973) 33(2), 41. 61. A.J. Eickkoff. Paint Varn. Prod. (1974) 64(10), 55. 62. P. Bataille, and TV. Bui, Polym. Compos. (2004) 2(1), 8-12. 63. C.J. Marshall, R. Rozett, and A.C. Kunkle, Plast. Compd. (1985) 8(7),

69-70, 73. 64. C. Richard, K. Hing, and H.R Schreiber. Polym. Compos. (2004) 6(4),

201-208. 65. D. Maldas, and B.V. Kokta, /. Vinyl Addit. Technol. (1993) 15(1), 38^4 . 66. M. Fenton, and G. Hawley, Polym. Compos. (1982) 3(4), 218-229. 67. M.A. Osman, A. Atallah, M. Muller, and U.W. Suter, Polymer (2001)

42, 6545-6556. 68. P. Bajaj, N.K. Jha, and R. Anand Kumar, /. Appl. Polym. Sei. (1992)

44(11), 1921-1930. 69. A. Tripathi, A.K. Tripathi, and P.K.C. Pillai, /. Mater. Sei. Lett. (1990)

9(4), 443^45. 70. J.B. Milewski. Am. Chem. Soc. Div. Org. Coat. Plast. Chem. Prepr. (1973)

33(2), 57. 71. R.B. Seymour, Polymer-Plastics Technology and Engineering (1976) 7:1,

49-79. 72. J.A. Radosta. Plast. Compounding (1979) 2,2. 73. J.W. Axelson. Am. Chem. Soc. Div. Org. Coat. Plast. Chem. Prepr. (1973)

33(2), 22. 74. A.M. Litman, and A.M. Crugnola. Ibid. (1973) 33(2), 164. 75. G.R. Smoluk. SPE } . (1970) 28(12), 49. 76. H.C. Jones. Mod. Plast. (1972) 49(1), 90. 77. C.V. Lundberg. Am. Chem. Soc. Div. Org. Coat. Plast. Chem. Prepr.

(1973) 33(2), 195. 78. J.Z. Keating. Plast. Compounding 3,23 (1980). 79. R. Kozlowski, M. Wladyka-Przybylak. Polym. Adv. Technol. (2008) 19,

446-53. 80. A.T. Dibenedetto. Mater. Sei. Eng. A (2001) 302, 74-82. 81. L.A. Goettler, K.Y. Lee, H. Thakkar. Polym. Rev. (2007) 47,291-317.


82. P.C. Lebaron, Z. Wang, TJ. Pinnavaia. Appl. Clay Sei. (1999) 15,11-29. 83. S. Pavlidou, C D . Papaspyrides. Prog. Polym. Sei. (2008) 33,1119-98. 84. B. Chen. Bri. Ceram. Trans. (2004) 103(6), 241-9. 85. S. Ray, A.J. Easteal. Mater. Manuf. Processes (2007) 22, 741-9. 86. Q.P. Zhong, M. Li, R. Srinivasa, J.H. He. US Patent 18,890,852; 2006. 87. O. Yutaka, S. Takashi, L. Toshikazu, M. Masatoshi, N. Takao. Polym.

Eng. Sei. (2001) 41(3), 408-16. 88. J. Liu, W.J. Boo, A. Clearfield, HJ. Sue. Mater. Manuf. Processes (2006) 20,

143-51. 89. P.K. Sudeep, T. Emrick. Polym. Rev. (2007) 47,155-63. 90. M. Gupta, Y.J. Lin, T. Deans, A. Crosby, E. Baer, A. Hiltner, et al.

Polymer (2009) 50, 598-604. 91. L. Onal, and S. Adanur, Journal of Reinforced Plastics and Composites

(2005) 24, 775. 92. D. Murray, H.H. Hassel. Plastics Design and Processing 20, No.2,

Feb.1980, pp. 20-3. 93. G.W. Lee, M. Park, J. Kim, J.I. Lee, H.G. Yoon, Compos A 2006; 37,

727-34. 94. N. Huang, J. Wang. /. Anal. Appl. Pyrol. (2009) 84,124-130. 95. P. Rupper, S. Gaan, V. Salimova, M. Heuberger. /. Anal. Appl. Pyrol.

(2010) 87, 93-98. 96. S. Gaan, G. Sun. /. Anal. Appl. Pyrol. (2009) 84,108-115. 97. CF. Dai, P.R. Li, J.M. Yeh. Eur. Polym. J. (2008) 44, 2439-2447. 98. H. Ma, L. Tong, Z. Xu, Z. Fang. Appl. Clay Sei. (2008) 42, 238-245. 99. T. Kashiwagi, E. Grulke, J. Hilding, K. Groth, R. Harris,

K. Butler, J. Shields, S. Kharchenko, J. Douglas. Polymer (2004) 45,4227-4239.

100. F. Laoutid, L. Bonnaud, M. Alexandre, J.M. Lopez-Cuesta, P.H. Dubois. Mater. Sei. Eng. R Rep. (2009) 63,100-125.

101. H. Tuulia, H. Kari. Trac-Trends Anal. Chem. (2002) 21,13-30. 102. F. Strieker, M. Bruch, R. Mülhaupt. Polymer (1997), 38, 5347. 103. F. Stricker, R. Mülhaupt. Polym. Eng. Sei. (1998) 38,1463. 104. F. Stricker, R.-D. Maier, M. Bruch, R. Thomann, R. Mülhaupt. Polymer

(1999) 40,2077. 105. D.G.C. Thornley. Pigments, plastics and progress. Symposium on

Progress in Pigments, London 7 February 1969. 106. I. Truijen, A. Hardy, M.K. Van Bael, H. Van den Rul, J. Mullens.

Thermochimica Acta (2007) 456,38-47. 107. V.F. Struber. Theory and practice of vinyl compounding. Argus, New York,

(1968). 108. L.E. Hoffman, J.L. Hendrix Biotechnol. Bioengr. (1976) 18,1161-5. 109. R. Kumar, S. Howdle, H. Münstedt /. Biomed. Mat. Res. (2005) 75B,

311-9.


110. R. Silvestry-Rodriguez, E.E. Sicairos-Ruelas, P.G. Gerba, R.B. Nelly Rev. Environ. Contam. Toxicol. (2007) 191, 23-45.

111. K. Im, Y Takasaki, A. Endo, M. Kuriyama /. Antibact. Antifungal Agents (1996) 24, 269-74.

112. K. Kawahara, K. Tsuruda, M. Morishita, M. Uchida Dental Mater. (2000) 16, 452-5.

113. Y Inoue, M. Hoshino, H. Takasashi, T. Noguchi, T Murata, Y Kanzaki, H. Hamashima, M. Sasatsu /. Inorg. Biochem. (2002) 92, 37-42.

114. B. Galeano, E. Korff, W.L. Nicholson. Appl. Environ. Microbiol. (2003) 69,4329-31.

115. M. Cowan, K.Z. Abshire, S.L. Houk, S.M. Evans. /. Ind. Microbiol. Biotechnol. (2003) 30,102-6.

116. M. Rai, A. Yadav, A. Gade Biotechnol. Adv. (2009) 27, 76-83.

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