1. Intro-2007

© Caroline L. Schauer 2007

MATE 315POLYMERS PROCESSING

Dr. Caroline SchauerLebow 439A currently CAT 179

[email protected]

Department of Materials Science and EngineeringDrexel University


Books• Polymer Process Engineering by Richard Griskey• The top 5 polymer processing books will be placed

on reserve at the library.– Middleman: Fundamentals of Polymer processing– Tadmor: Principles of Polymer Processing– Osswald: Polymer Processing Fundamentals– 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.

– It is posted on In.Materials which was introduced last term. If there are any problems let me know and I can always switch to WebCT if necessary

– Note that there are 4 homeworks, 2 midterms, 5 labs and one final


Kamikaze Egg Drop competition

– 6 teams at 2 people per team *one team of 3*

– Get an A for the lab if your design survives the first round

– The team that does the best using the provided guidelines gets 5 extra class points

– I need team names and groupings by next class (Thurs.)


Lab notes

• Monday and Wednesday 2-5 pm. If you have not signed up for lab and Wed fits please sign up for Wed.

• Aaron Sakulich is lab TA. His office is Alumni 177 Office hours 1-2 pm Monday.

• 1st lab is Monday the 22rd on Polymer Synthesis-PMMA and Nylon

• Meet 1st in the MATE Lab conference room, Lebow335

• Bring lab goggles and a good notebook to take notes for your lab reports


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 1950sused 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



• 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



• 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


The Graduate (1968)


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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H H

H H

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[CH2-CH2]n

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 polyethylenesfrom 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 samefacility!

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 termsof 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

• μm < 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 stageat 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


PROCESSING AND PROPERTIESA case study

• Film blow molding of polybutelyne(PB1)– most film made by PE

but PB1 is cheaper– obtaining good properties is an issue

• Processing– Pellets are feed into an extruder– The melt is homogenized and

pressurized through a slit die– Air is blowing through the center of

the die to expand the bubble


Film blow molding of polybutelyneA case study

Note that:1. Gap >> Thickness

Obvious because we want to induce stretching - high molecular orientation = high strength

2. Die gap ↑ Land length ↓Why?

Land Length


Effect of Land Length on Tear Strength

Land Length ↑ ⇒Tear Strength ↓

BUR (Blow-up Ratio=gap/thickness)

Reasons: Low Land Length ⇒ More Swelling ⇒ Higher effective BUR

BUR ↑ Higher orientation

Thickness=


Die Gap Effect on Strength

MD = molding directionTD = transverse direction

What causes this change?

Large gap - more relaxation of orientation in die?Crystallinity / Spherulitic size ?


Melt Temperature Effect on Strength

What causes this change?How does temperature effect orientation?Crystallinity / Spherulitic size ?Other????


Anisotropy of Strength

As orientation in MD increases the corresponding orientation in the TD decreases?

Is there an optimum - it depends on the application...


Other effects

Line Speed(FPM)

14203040

Higher speed: higher strength in MD - lower in TDlower ductility both in MD/TDless impact resistance in MD/TDless tear strength in MD/TD

Multiple and complex interactions


HOW TO OPTIMIZE SUCH A COMPLEX OPERATION

POSSIBLE CHOICES:

– Mathematical / Computational Modeling• needs expertise, data, software

– Design of Experiments• needs statistics, valid over a narrow window

– Trial and Error• depends on experience - usually most costly


\http://www.eng.uc.edu/~gbeaucag/Classes/Processing/Chapter1html/Chapter1.htmlpubs.acs.org/hotartcl/cenear/ 980112/coal.html

Documents

1. Intro-2007