MATE 315POLYMERS PROCESSING

Dr. Caroline SchauerLebow 439A 215.895.6797

cschauer@coe.drexel.eduDepartment of Materials Science and Engineering

Drexel University

BooksOsswald: Polymer Processing Fundamentals

• The top 5 polymer processing books are placed on reserve at the library. Plus additional electronic readings– Middleman: Fundamentals of Polymer processing– Tadmor: Principles of Polymer Processing– Baird: Polymer Processing: Principles and Design– Wilkinson: Polymer processing and structure

development• Weekly assigned readings from Polymer Process

Engineering and the reserve books will help with homework

Class Notes• Class Syllabus

– Hang onto your copy. All of the due dates for the quarter have been mapped out for you.

– Note that there are 3 homeworks (20%), 1 midterm (20%), 1 in-class, 4 one page lab reports (20%) plus 1 five page (10%) , egg drop (10%) and one final (20%)

• Academic honesty policy is outlined in the syllabus.

• In.materials!!!!!!!– http://in.materials.drexel.edu/

Egg Drop competition (10%)

– Form teams of 3 people per team (12 teams total)

– Create an all polymer design

– 5% of grade is• Get A for the lab if your

design survives the second round

– 5% for individual write up with photos (1 page)

– I need team names and groupings by Wednesday 01/12/12

Lab notes (20%)• Wednesday 2-5 pm.• Eric Laird is lab TA. His office is Bossone 105, Office

hours 2-3 pm Tuesday, email good way to get in contact wit him

• 1st lab is Wednesday the 18th on Polymer Synthesis-PMMA and Nylon

• Meet 1st in the MATE lounge next to Lebow 336• Bring lab goggles and a good notebook to take notes

for your lab reports• Read the lab beforehand. If it becomes apparent that

you have not read the lab we will start random lab quizzes.

Any Questions?

Polymers (short review)

• Thermosets - solidify after chemical crosslinking (ex. epoxy)

• Elastomers - lightly crosslinked (ex. natural rubber)

• Thermoplastics - polymers which solidify as they cool– Amorphous - remain disordered as they cool

random molecular structure (ex. polystyrene)– Semi-crystalline - solidify with a certain order in their

molecular structure (ex. polypropylene)

Polymers (review slide 2)

• Tg = glass transition temperature – glass to rubber transition

• Tm = crystalline melting point – typically 1.5Tg if the polymer can crystallize

• T = service or “operation” temperature• At ≥ Tg +100˚C polymers form a melt

Long chain molecules

Crosslinked ThermoplasticBranched and Linear

Semi-crystalline(Tm>T>Tg)

Poly(propylene) ( PP)

High crosslink density

Low crosslink density

Thermosets(Tg>T)

Phenolic Resin (PF)

Elastomers(T>Tg)

Natural Rubber (NR) Semi-crystalline(Tm>Tg>T)

Poly(ethylene terephthalate) (PET)

Amorphous(Tg>T)

Polystyrene (PS)

Condensed History of Plastics

• c.1000 BC Lacquer work- A resin from a lacquer tree (Rhus vernicflua) used by the Chinese to form waterproof and durable coatings and until 1950s used to coat domestic tableware.

• c.23-79 BC Amber- A thermoplastic resin from fossilized trees and is found mainly on the Baltic coast. The material can be mixed into lacquers or small pieces can be pressed into compression molds to produce small articles. Amber is first described by Pliny the Elder in his work Natural History.

Condensed History of Plastics (cont)

• c.0 Horn- A typical thermoplastic, which can be split and molded into shape after heating in hot water. 1620s Layers can be laminated together to build thicker products or pressed into wooden molds to form snuff boxes or buttons. The raw material can also be ground up and mixed with a binder (blood) before being compression molded into buttons.

*The ability to produce molded products more cheaply and quickly than their carved counterparts is the prime motivating force behind the development of plastics and the plastics industry

Condensed History of Plastics (cont)

• 1731 Charles Marie de la Condamine reports natives in Amazon using rubber for waterproofing and flexible bottles. Rubber was imported into Europe in 1736 but used by natives for several thousand years.

• 1844 Thomas Hancock and Charles Goodyear prefect the vulcanization process of cooking rubber in sulfur, which joined separate isoprene polymers improving the material’s structural integrity

Condensed History of Plastics (cont)

• 1909 Leo Hendrik Baekelund finds mixtures of phenol and formaldehyde produce and extremely hard material when heated, mixed and allowed to cool. Known as phenolic or phenol-formaldehyde he calls the new material bakelite and is the first synthetic thermosetting resin

• 1927 Wallice Carothers develops the first molecular design of materials

The Development of Plastic• 1868 cellulose nitrate• 1909 phenol-formaldehyde• 1927 cellulose acetate and polyvinyl chloride• 1929 urea formaldehyde• 1931 Duprene• 1935 ethyl cellulose• 1936 acrylic and polyvinyl acetate• 1938 nylon• 1942 polyester and polyethylene terephthalate• 1943 silicone• 1947 epoxy and polypropylene

CHEMISTS

CHEMICAL ENGINEERS

Materials Engineers:The linkage between

processing– structure & properties

Polymers Processing

• Goal: To convert raw plastics to useful final products with desirable properties

• Plastics Polymers• (Plastics = Polymer + Additives)

Case Example

Polyethylene Shampoo Bottle

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Polyethylene is the most popular plastic in the world. This is the polymer that makes grocery bags, shampoo bottles, children's toys, and even bullet proof vests

Polyethylene is polymerized from ethylene a byproduct of the refining of crude oil and is a component of natural gas.

A large oil company separates ethylene from crude oil in a refinery and sells the ethylene to a relatively small company that owns an ethylene pipeline.

Ethylene pipelines exist throughout the southern United States along the Gulf Coast.

The pipeline company is usually a small company due to the high liability associated with the maintenance of this critical system (pipelines periodically blow-up!).

The pipeline industry is a high-risk/high-profit industry. Sales of ethylene, is a lower-risk, commodity industry that is basically subject to the price of oil.

Various grades offered by a large polyolefin producer are partly composed of blends of different branch content, molecular weight and density polyethylenes from different synthetic reaction conditions. A film blowing grade of polyethylene for clear bags might contain a blend of linear low density polyethylene, controlled branch content metallocene polyethylene and low density polyethylene. These blends might include polymers made in-house as well as some components from competitor olefin producers.

Polyolefin producers often purchase or "rent" each others synthetic technology (license patents) and such patent royalties can often be a large component of profits for some polyolefin companies (Phillips Petroleum for instance). Blending of different grades and production of pellets from the usually powder reactor products involve a variety of processing steps and require process engineers.

The polyethylene industry is a commodity product industry governed on the supply-side by the price of oil on the world market and on the demand-side by the consumer product, housing and automotive industries. metallocene

An example: A shampoo bottle is injection molded from a high density grade of PE sold by a company such as Equistar. The shampoo is sold by a company like P&G and there is extensive interaction between them, although P&G may never purchase Equistar PE at all. The purchaser of the PE pellets is usually a small processing company that owns a number of injection molders and proprietary molds. The molds are provided by P&G, for instance, under a proprietary license to the processing company. The processing company is typically a high throughput, low profit margin facility and may be producing bottles from competitive brands in the same facility!

In the end, the bottle for the shampoo product may represent only a small fraction of the total cost of the product (1 to 5 cents) but may be of utmost importance to the consumer product company in terms of product recognition and in terms of effective storage and dispensing of the product.

Dec 28, 2004• AP: Encouraged by a milk

industry study that shows children drink more dairy when it comes in round plastic bottles, a growing number of schools are ditching those clumsy paper half-pint cartons

• a 2002 Dairy Council study found milk consumption increased 18 percent in schools that tested bottles. The study also found that children who drank bottled milk finished more of it

High density polyethylene (HDPE)

Nylon

Everything came to an unfortunate halt with the outbreak of World War II, when nylon production was commandeered for the war effort. Women resorted to using makeup to decorate their legs, like drawing faux seams up the back of their legs with an eyebrow pencil.

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RAW MATERIALS• Most polymers are supplied in particulate

form (pellets, beads, granulates) which is convenient– transport and handle– blend (with additives) and compound– store– feed and process

• m < Size < mm

MIXING• Additives - a wide range of second phases

added to polymers for processing and/or properties– Stabilizers (degradation), Colors (pigments and

dies), Plasticizers (molecular level) Fillers and Reinforcements, Lubricants (granule level).

• Other polymers (co-extrusion, co-injection molding etc.)

• UNIFORMITY IS A MAJOR ISSUE!...

DEVOLATILIZATION

• Entrapped air (between granules)– source of defects

• Absorbed gases and humidity– greatly affect processing and properties1. Water (solvent)2. Residual monomers

PROCESSING IN THE MELT

• The majority of processing operations for polymers are performed in the liquid stage at temperatures between RT and 300-400oC

• Essential knowledge:– thermal aspects of melting– cooling and effect on properties

• Melting is often the rate limiting step!...

FLOW UNDER PRESSURE

• The molten plastic is forced through “channels” in order to be shaped into products. Size of machine is an issue.– EXTRUSION (80% of plastics processed by

extrusion)– INJECTION MOLDING – BLOW MOLDING – THERMOFORMING– COMPRESSION MOLDING

FINISHED PRODUCTS

• Die forming – (profiles, fibers, blow molding)

• Molding – (conventional, reaction molding, compression

molding, casting, blow molding)• Secondary shaping

– (fiber stretching, blowing, thermoforming)• Calendering (films and sheets) and coating• Mold coating

PROPERTIES

• Shape/Size Tolerances• Mechanical Properties• Optical Properties• Electrical Properties• Appearance and Aesthetics

FUNDAMENTAL KNOWLEDGE REQUIREMENTS

• Transport phenomena• Mixing principles• Solid Mechanics• Polymer Melt Rheology• Polymer Physics (Properties)• Polymer Chemistry

OTHER ISSUES

• Empiricism vs Mathematical Modeling - Computer Modeling.

• Equipment and Automatic Control

• Properties, and Quality (control, statistics)

• Cost, Investment, Financial Issues

EXTRUSION

FIBER SPINNING

FLAT FILM FORMING

TUBULAR FILM BLOWING

INJECTION MOLDING

BLOW MOLDING

THERMOFORMING

ROTATIONAL MOLDING

CASTING

REACTION INJECTION MOLDING

COMPRESSION MOLDING

CALENDERING

COATING

POLTRUSION

High qualitycomposites