高分子材料与应用（英文版） Chapter 2 Commodity Plastics

1、Chapter 2Chapter 2 Thermoplastics Thermoplastics Introduction Thermoplastics vs Thermosets Thermal properties Strength Uses Processing Types of Thermoplastics Amorphous plastics Semi-crystalline plastics Amorphous vs. Crystalline Thermoplastics Amorphous (a-morphous = without shape) - The polymer ch

2、ains are in random arrangement. Molecular structure is incapable of forming regular order (crystallizing) with molecules or portions of molecules regularly stacked in crystal-like fashion. Molecular arrangement is randomly twisted, kinked and coiled. Crystalline - The polymer chains form a regular p

3、attern. Molecular structure forms regular order (crystals) with molecules or portions of molecules regularly stacked in crystal-like fashion. Molecular arrangement is arranged in an ordered fashion. Amorphous Commodity Thermoplastics MaterialsMaterials Acrylic (PMMA) Polystyrene (PS) Acrylonitrile -

4、 Butadiene - Styrene (ABS) Polyvinyl Chloride (PVC) Polyethylene Terepthalate Glycol (PETG) Cellulose Acetate Butyrate (CAB) Amorphous Commodity Thermoplastics Key CharacteristicsKey Characteristics Low cost, temperature resistance and strength Good dimensional stability Bonds well Typically, but no

5、t always, transparent Semi-Crystalline Commodity Thermoplastics MaterialsMaterials Polyethylene (PE) High Density Polyethylene (HDPE) Low Density Polyethylene (LDPE) Polypropylene (PP) Polymethylpentene (PMP) Semi-Crystalline Commodity Thermoplastics Key CharacteristicsKey Characteristics Low cost,

6、temperature resistance and strength Excellent chemical resistance Low COF Near zero moisture absorption Very good electrical properties Good toughness Commodity Resins Big Four Polyethylene (PE) Polypropylene (PP) Polyvinyl Chloride (PVC or Vinyl) 1.Polystyrene (GPPS General Purpose Polystyrene also

7、 includes Styrofoam or expanded polystyrene eps) Of the seven symbols used for domestic recycling, 5 of them are for commodity plastics. Polyolefins PP and PE are often given a special name, polyolefins Polyolefins means oil like & refer to oily and waxy feel these materials have Consists of only ca

8、rbon and hydrogen, they are all aliphatic groups Polyethylene (PE) Mer unit Polymer chain CH2 CH2 Polyethylene LDPE High Pressure/High Temperature processing High “H” activationbranching HDPE Low Pressure/Ziegler-Natta catalyst Little branching Highly crystalline LLDPE “Copolymer”side chains prevent

9、 crystalization Improve toughness, strength, ESCR Crosslinked PE Karl ZieglerGuilio Natta Forms of PE Branched or low density polyethylene (LDPE) b) High density polyethylene (HDPE) c) Linear low density polyethylene (LLDPE) Commodity Plastics Polyethylene History Polyethylene (PE) was developed in

10、1898 by a German chemist named Hans von Pechmann. He prepared it by accident while heating diazomethane. Structure The structure of PE is probably the simplest in the polymer world. It is made up of the monomer Ethylene and contains only C-C and C-H bonds which makes it very stable. The most common

11、application for polyethylene that everyone can identify with is the polyethylene milk jug. Commodity Plastics Polyethylene Forms PE comes in a wide variety of forms made by changing the density, branching, and crystalline structure of the basic polyethylene chain. HDPE is probably the most common fo

12、rm people are familiar with so the properties provided will be for HDPE LDPE Low Density Polyethylene Commodity Plastics Polyethylene Forms LLDPE Linear Low Density Polyethylene UHMWPE Ultra High Molecular Weight Polyethylene Usually around 8-10,000 monomers need to be linked up in order to make the

13、 polyethylene useable as a polymer. For UHMWPE the number of monomers is around 70,000. PEX Cross-Linked Polyethylene HDPE is probably the most common form people are familiar with so the properties provided will be for HDPE Commodity Plastics Polyethylene - Considerations Density HDPE has a specifi

14、c gravity of 0.95 which means that it will float in water. Crystallinity HDPE is semi-crystalline (around 65%) Hygroscopy HDPE is not hygroscopic and does not require drying when processed Tg HDPE has a glass transition temperature of -180F Tm HDPEs crystals melt at around 280 F, but it is commonly

15、processed in a melt range of 375 525 F. Commodity Plastics Polyethylene - Considerations Price HDPE is one of the cheapest polymers in terms of cost. The commodity polymers are generally cheaper than the engineering grade polymers depending on the quantity purchased. Mechanical Properties HDPE is ge

16、nerally considered to have poor mechanical properties with the exception of impact strength. Its tensile strength averages around 4,000 psi and its tensile modulus around 150,000 psi. Chemical Resistance HDPE has excellent chemical resistance. It is one of the most chemically resistant thermoplastic

17、 resins. This is the reason it is commonly used in bottles for detergents and other household chemicals. Commodity Plastics Polyethylene - Considerations Optical Properties- HDPE has a high degree of crystallinity making its optical properties quite poor. Flammability- Unmodified HDPE is classified

18、in the “quite flammable” category which is the lowest rating a plastic can achieve. This rating is determined by a flammability test. HDPE not only burns and continues to burn, but usually also drips flaming melt which continues to burn. This is not a good property for a plastic material to have. El

19、ectrical Properties- The electrical properties of HDPE are moderate but it is used for some types of wire coatings. Commodity Plastics Polyethylene - Considerations Weatherability- HDPE is very susceptible to weathering making its uses in outdoor applications somewhat limited unless it is modified t

20、o withstand the ultraviolet rays of the sun. Processability HDPE is easily processed in virtually all standard plastic forming processes. Thermal Sensitivity HDPE is not very thermally sensitive. It can remain at high temperatures for long periods of time without suffering thermal degradation. It is

21、 commonly used to purge other materials out of the processing machinery because of its thermal resistance. Commodity Plastics Cl Chlorosulfonated polyethylene Properties Good resistance to ozone, heat, flame, chemicals and solvents Low temperature flexibility Heat-ageing resistance Uses & Applicatio

22、ns Hose products, roll covers, tank linings, wire and cable covers, footwear, and building products Random chlorination of PE (25-45% Cl) Incorporation of infrequent chlorosulfonic groups (SO2Cl) as preferred cross-linking sites Caused by Cross-linking unit Highly polar unit Commodity Plastics Ethyl

23、ene copolymer series Ethylene vinyl acetate (EVA) Low crystallinity gives it a low melting point and excellent low temperature toughness. EVA based hot-melts are able to fulfill various requirements in applications such as packaging, bookbinding or label sticking Polar functionality promotes adhesio

24、n to polar substrates (paper, polyester, wood, and leather) Polar functional moiety : packaging, adhesives, wire, cable and health care. Applications Commodity Plastics Ethylene copolymer series Acrylic ester decreases the crysta llinity of the polymer Key benefits of ethylene acrylic ester copolyme

25、rs Excellent thermal stability Excellent adherence to many substrates (polyethylene, polystyrene, polypro pylene, OPP, etc.) Good chemical resistance Good elastic properties Excellent mechanical behavior at low temperature Ethylene - Acrylic Ester copolymers Commodity Plastics Ethylene copolymer ser

26、ies They can be divided into several product families depending on the acrylic ester type (methyl, ethyl or butyl acrylate) Third monomer - MAH : maleic anhydride - GMA : glycidyl methacrylate. - Increase final adhesion properties - Heat resistance or long term ageing properties. The roles of third

27、monomer Ethylene acrylic ester terpolymers Commodity Plastics Ionomers : An ionomer is an ion containing polymer. It is more than just a polymer with ionic groups. We call any old polymer with ionic groups a polyelectrolyte special kind of polyelectrolyte. containing both nonionic repeat units and s

28、mall amounts of ion containing repeat units less than 15% of polymer Characteristics : The polar groups tend to cluster together, away from the nonpolar polymer backbone chains not closslinked polymer a type of thermoplastic called a reversible crosslinker Commodity Plastics This phenomenon allows f

29、or a polymer with the properties of an elastomer and the pr ocessability of a thermoplastic. These ionomers are sometimes known as thermoplastic elastomers When heated, ionic groups lose their attractions and the chains more around freely. Reversible crosslinking behavior of ionomers Ionomers Commod

30、ity Plastics Example: Polymerization between ethylene and methacrylic acid ionomer Acidic property ethylene methacrylic acid Poly(ethylene-co-methacrylic acid) Semipermeable membrane Ion filter Fuel cells Electrodialysis Applications Dupon : Surlyn TMDupon : Nafion TM Functional moiety Commodity Pla

31、stics Ethylene propylene rubber EP rubber (EPR), poly(ethylene-co-propylene) Glass transition temperature: -50 deg.C : A random copolymer of ethylene and propylene. A rubbery noncrystalline material Properties Non-polar elastomers Good electrical resistivity Resistance to polar solvents (i.e., water

32、, acids, alkalies, ketones, alcohols) radiator, appliance hose, tubing, belts, electrical ins ulation, roofing membrane, rubber mechanical good s High-voltage tape Rubber mechanical goods Commodity Plastics Polyethylene - Considerations Decoration and Assembly HDPE can be difficult to decorate and a

33、ssemble with some methods because of its low surface energy. Inks tend to bead-up on it and adhesives can have a hard time sticking to it. It has a waxy feel to it due to its low Tg and many assembly methods that use friction to generate heat for bonding have difficulty processing HDPE. Creep HDPE c

34、reeps badly due to its low glass transition temperature. This leads to low dimensional stability and is reason it is not used in some applications. Recyclability HDPE and all other PEs are highly recyclable. Recycled products made from PEs include trash cans, detergent bottles, flower pots, grocery

35、bags, and composite decking. Commodity Plastics Polyethylene - Applications Consumer goods- Toys, food storage containers, buckets Commodity Plastics Polypropylene History Polypropylene (PP) was developed in Spain in 1954 by professor Giulio Natta. He was able to produce the resin by using catalysts

36、 from the Polyethylene industry and applying them to propylene gas. Structure The PP monomer is a single bond between two carbon atoms and can be seen below. It is similar to Polyethylene in many ways, but the methyl group that takes the place of the hydrogen reduces the chain flexibility, making po

37、lypropylene a stiffer material. Methyl group Commodity Plastics Polypropylene Forms PP comes in a few varieties: Homopolymer - General purpose grade, very versatile Block Copolymer - 5-15% ethylene, improved impact strength to below 20 C Random Copolymer - Co-monomers arranged randomly on the molecu

38、lar chain, more flexibility and better clarity Commodity Plastics Polypropylene - Considerations Density PP has a specific gravity of 0.93 which means that it will float in water. Crystallinity PP is semi-crystalline (around 75%) Hygroscopy PP is not hygroscopic and does not require drying when proc

39、essed Tg PP has a glass transition temperature of -9 C Tm PPs crystals melt at around 176C, but it is commonly processed in a melt range of 215 280 C. Commodity Plastics Polypropylene - Considerations Price PP is a very cheap and extremely common polymer. The commodity polymers are generally cheaper

40、 than the engineering grade polymers depending on the quantity purchased. Mechanical Properties PP has a tensile strength that averages around 31 MPa and its tensile modulus around 1200 MPa. Chemical Resistance PP has excellent chemical resistance. It is one of the most chemically resistant thermopl

41、astic resins. It is not quite as good as HDPE, but it is still one of the best in terms of chemical resistance. Commodity Plastics Polypropylene - Considerations Optical Properties- PP has a high degree of crystallinity making its optical properties quite poor. Flammability- PP is classified in the

42、“quite flammable” category which is the lowest rating a plastic can achieve. PP not only burns and continues to burn, but usually also drips flaming melt which continues to burn. This is not a good property for a plastic material to have in certain applications. Electrical Properties- PP has excelle

43、nt electrical properties making it very useful as an insulating material on high voltage capacitors. Commodity Plastics Polypropylene - Considerations Weatherability- PP has a poor weathering resistance and is especially susceptible to extreme cold and high degrees of UV rays Processability PP is ea

44、sily processed in virtually all standard plastic forming processes Thermal Sensitivity PP is not very thermally sensitive. It can remain at high temperatures for long periods of while suffering little if any thermal degradation Commodity Plastics Polypropylene - Considerations Decoration and Assembl

45、y PP is difficult to decorate but when it is decorated the most common method is using a hot stamp. Hot stamping is a fairly simple process which has an endless variety of colors, metals, designs, etc. Creep PP creeps badly due to its low glass transition temperature This is another reason it is not

46、 used in some applications. Recyclability PP is recyclable but not in any meaningful quantities. Recycled products made from PP include plastic lumber, and car battery cases. Many times it is mixed in with the PE regrind and processed together due to their similar processing qualities. Commodity Pla

47、stics Advantages of Polypropylene Low Cost Excellent flexural strength Good impact strength Processable by all thermoplastic equipment Low coefficient of friction Excellent electrical insulation Good fatigue resistance Excellent moisture resistance Service Temperature to 126 C Very good chemical res

48、istance Commodity Plastics Disadvantages of Polypropylene High thermal expansion UV degradation Poor weathering resistance Subject to attack by chlorinated solvents and aromatics Difficulty to bond or paint Oxidizes readily flammable Commodity Plastics Polypropylene - Applications Consumer goods- Fo

49、od storage containers, weather resistant clothing, indooroutdoor carpeting Polypropylene is usually used for food storage containers so that they dont warp and lose their shape in the microwave or in the dishwasher. Commodity Plastics Polypropylene Applications Medial Applications- Syringes, storage

50、 containers for needles, surgical disposable fabric Automotive- Instrument panels, fender liners, and brake/coolant reservoirs Commodity Plastics Polypropylene - Applications Packaging-Notably anything with a living hinge is usually made from PP like tic-tac container lids and shampoo bottle lids, f

51、ood storage containers, water bottles, pill bottle lids, etc. Construction- Non-electric fuses, insulating material for power capacitors Commodity Plastics Polypropylene Polyvinylchloride (PVC) Mer unit Polymer chain C Cl CH2 H Commodity Plastics Polyvinyl Chloride History Polyvinyl was discovered b

52、y accident on two separate occasions. The first discovery occurred in 1835 by Henri Victor Regnault (1810-1878), a French chemist and physicist. The second finding came 37 years later, in 1872 by Eugene Baumann. Structure PVC is made up of hydrogen, carbon, and Chlorine. The large Chlorine atom help

53、s to protect the polymer chain from chemical attack, but makes the material more shear and heat sensitive. Commodity Plastics Polyvinyl Chloride - Considerations Forms PVC comes in a wide variety of forms: Plasticized PVC (PPVC) Rigid PVC (RPVC) Semi-Rigid PVC The mechanical properties and hardness

54、of PVC are frequently modified with the use of plasticizers. The properties provided will mostly be for Rigid PVC (RPVC) unless otherwise stated. Commodity Plastics Polyvinyl Chloride - Considerations Density RPVC has a specific gravity of 1.4 which means that it will not float in water. It is one o

55、f the densest unfilled thermoplastics. Crystallinity RPVC is an amorphous material, it only achieves around 8% crystallinity Hygroscopy RPVC is not hygroscopic(吸湿性) and does not require drying when processed Tg RPVC has a glass transition temperature of 85C Tm RPVCs has a melt temperature of 240C, b

56、ut it is commonly processed in a melt range of 196 204C. Commodity Plastics Polyvinyl Chloride - Considerations Price Pricing on RPVC is almost directly related to construction and industrial activity. Mechanical Properties RPVC is generally considered to have good mechanical properties. Its tensile

57、 strength averages around 55 MPa and its tensile modulus around 2700 MPa. Chemical Resistance RPVC has an excellent chemical resistance. PVC is resistant to most oils, fats, alcohols, and petrol. PVC is also resistant to the most severe oxidizing conditions. 1psi6895Pa Commodity Plastics Polyvinyl C

58、hloride - Considerations Optical Properties RPVC is usually a tan or white color and is not transparent. Plasticized grades are usually transparent, but have a blue tint. Flammability- RPVC has a very low natural combustibility and is usually self-extinguishing. This is a very advantageous property

59、to have in buildings and homes. Electrical Properties- PVC has excellent electrical properties making it very useful for wire insulation among many other uses. Commodity Plastics Polyvinyl Chloride - Considerations Weatherability- RPVC has a good weather resistance which makes it great for many outd

60、oor uses like pipes and house siding. Processability RPVC can be processed by most commercial methods Thermal Sensitivity PVC is very thermally sensitive. A temperature of -9 less than the recommended melt temperature can drastically increase the viscosity of the melt and cause discoloration and bur