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Classes of Polymeric Materials

Classes of Polymeric Materials. Professor Joe Greene CSU, CHICO. Topics. Introduction Thermoplastics General Commercial plastics Thermosets General Commercial thermosets Elastomers General Commercial elastomers. Introduction. Polymeric materials can be either

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Classes of Polymeric Materials

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  1. Classes of Polymeric Materials Professor Joe Greene CSU, CHICO

  2. Topics • Introduction • Thermoplastics • General • Commercial plastics • Thermosets • General • Commercial thermosets • Elastomers • General • Commercial elastomers

  3. Introduction • Polymeric materials can be either • Thermoplastics, thermosets, and elastomers. • Each section is presented in appropriate groups • Thermoplastics come in a variety of forms • Pellets, powder (1-100 microns), flake, chip, cube, dice, • Shipped in packages of choice • Bags (50 lbs), drums (200 lbs), boxes, cartons, gaylords (1000 lb), • Tank-truck loads (15 tons), rail cars (40 – 80 tons) • Bulk supplies are stored in silos and conveyed pneumatically • Thermosets are supplied in powder or liquid form • Supplied in drums, tank-trucks, and railroad cars. • Rubbers are supplied in bale form.

  4. Commercial Thermoplastics • Olefins • Unsaturated, aliphatic hydrocarbons made from ethylene gas • Ethylene is produced by cracking higher hydrocarbons of natural gas or petroleum • LDPE commercialized in 1939 in high pressure process • Branched, high pressure, and low density polyethylene • HDPE commercialized in 1957 in low pressure process • Linear, low pressure, high density • The higher the density the higher the crystallinity • Higher the crystallinity the higher the modulus, strength, chemical resistance, • PE grades are classified according to melt index (viscosity) which is a strong indicator of molecular weight. • Injection molding requires high flow, extrusion grade is highly elastic, thermoforming grade requires high viscosity or consistency

  5. Principal Olefin Monomers H H C C H H H H H H H H C C C C C C C2H5 CH3 C5H6 H H H CH3 • Ethylene Propylene • Butene-1 4-Methylpentene

  6. Several Olefin Polymers H H H H C C C C H H n CH3 H n H H C C C2H5 H n • Polyethylene Polypropylene • Polyisobutene Polymethylpentene H H C C C5H6 H n CH3

  7. Polymers Derived from Ethylene Monomer X Position Material Name Abbreviation H Polyethylene PE Cl Polyvinyl chloride PVC Methyl group Polypropylene PP Benzene ring Polystyrene PS CN Polyacrylonitrile PAN OOCCH Polyvinyl acetate PvaC 3 OH Polyvinyl alcohol PVA COOCH Polymethyl acrylate PMA 3 F Polyvinyl fluoride PVF Note : | Methyl Group is: H – C – H | H Benzene ring is:

  8. Addition Polymerization of PE H H H H H H H H H H H H H H H H H H H H C C C C C C C C C C C C C C C C C C C C H H H H H H H H H H H H H H H H H H H … … … … H H C H C H • Polyethylene produced with low (Ziegler) or high pressure (ICI) • Polyethylene produced with linear or branched chains OR n

  9. Mechanical Properties of Polyethylene • Type 1: (Branched) Low Density of 0.910 - 0.925 g/cc • Type 2: Medium Density of 0.926 - 0.940 g/cc • Type 3: High Density of 0.941 - 0.959 g/cc • Type 4: (Linear) High Density to ultra high density > 0.959

  10. Physical Properties of Polyethylene

  11. Processing Properties of Polyethylene

  12. Special Low Versions of PolyethyleneProduced through catalyst selection and regulation of reactor conditions • Very Low Density Polyethylene (VLDPE) • Densities between 0.890 and 0.915 • Applications include disposable gloves, shrink packages, vacuum cleaner hoses, tuning, bottles, shrink wrap, diaper film liners, and other health care products • Linear Low Density Polyethylene (LLDPE) • Densities between 0.916 and 0.930 • Contains little if any branching by co-polymerizing ethylene at low pressures in presence of catalysts with small amounts of -olefin co-monomers (butene, hexene, octene) which play the role of uniform short branches along linear backbone. • Properties include improved flex life, low warpage, improved stress-crack resistance, better impact, tear, or puncture versus conventional LDPE • Applications include films for ice, trash, garment, and produce bags at thinner gage.

  13. Special High Versions of PolyethyleneProducedthrough catalyst selection and regulation of reactor conditions • Ultra High Molecular Weight Polyethylene (UHMWPE) • Extremely high MW at least 10 times of HDPE (MW=3M to 6M) • Process leads to linear molecules with HDPE • Densities are 0.93 to 0.94 g/cc and Moderate cost • High MW leads to high degree of physical entanglements that • Above Tmelt (130 C or 266F), the material behaves in a rubber-like molecule rather than fluid-like manner causing processing troubles, high viscosities • Processed similar to PTFE (Teflon) • Ram extrusion and compression molding are used.

  14. Special High Versions of PolyethyleneProduced through catalyst selection and regulation of reactor conditions • Ultra High Molecular Weight Polyethylene (UHMWPE) • Properties include outstanding properties like engineering plastic or specialty resin • Chemical inertness is unmatched; environmental stress cracking resistance and resistance to foods and physiological fluids, • Outstanding wear or abrasion resistance, very low coefficient of friction, excellent toughness and impact resistance. • Applications: • pump parts, seals, surgical implants, pen tips, and butcher-block cutting surfaces. , chemical handling equipment, pen tips, prosthetic wear surfaces, gears

  15. Special Forms of Polyethylene • Cross-linked PE (XLPE) • Chemical cross-links improve chemical resistance and improve temperature properties. • Cross-linked with addition of small amounts of organic peroxides • Dicumyl peroxide, etc. • Crosslinks a small amount during processing and then sets up after flowing into mold. • Used primarily with rotational molding • Extruded Products • Films (shrink wrap film in particular) • Pipes • Electrical wire and cable insulation

  16. Copolymers of Polyethylene H H H H C C C C H H H O C = O C n m • Ethylene-Vinyl Acetate (EVA) • Repeating groups is ethylene with a vinyl acetate functional that reduces the regularity of the chain; thus the crystallinity and stiffness • Part of the pendent group are highly polar which makes film with increased water vapor permeability, increased oil resistance and cling. • Vinyl acetate reduces crystallinity and increases chemical reactivity because of high regions of polarity. • Applications include flexible packaging, shrink wrap, auto bumper pads, flexible toys, and tubing with vinylacetate up to 50%

  17. Copolymers of Polyethylene • Ethylene-vinyl alcohol (EVOH) • Contains equal amounts of two repeat units that act as • Barrier layers or as interlayers (tie layers) between incompatible materials due to strong bonding of vinylalcohol repeat units. • Ethylene-ethyl acrylate (EEA) Ethylene-methyl acrylate (EMA) • Properties range from rubbery to tough ethylene-like properties • Applications include hot melt adhesives, shrink wrap, produce bags, bag-in-box products, and wire coating. • Produced by addition of methyl acrylate monomer (40% by weight) with ethylene gas • reduces crystallinity and increases polarity • Tough, thermally stable olefin with good rubber characteristics. • Applications include food packaging, disposable medical gloves, heat-sealable layers, and coating for composite packaging

  18. Copolymers of Polyethylene • Ethylene-carboxylic acid (EAA, EMAA) • Small amounts of acrylic acid (AA) or methacrylic acid (MAA) that feature carboxyl acid groups (COOH) are notable adhesives, especially to polar substrates, including fillers and reinforcements • Problems include tackiness and corrosive to metals and crosslinking nature • Ionomers • Modified ethylene-methacrylic acid copolymers where some of the carboxyl acid groups are converted into corresponding metallic salts (metal metacrylate), where the metals are sodium or zinc. • Ionic bonds are formed between these cationic and the remaining anionic acid groups. Results in a quasi crosslinked polymer at low temperature and is reversible at high temperature • Useful properties, e.g., adhesive and paints to metals (polarity), resistance to fats and oils, Flex, puncture, impact resistance • Applications: golf balls, bowling pin covers, ski boot shells, films

  19. Copolymers of Polyethylene H H H H C C C C H CH3 H H n m • Ethylene-Propylene (EPM) • Ethylene and propylene are copolymerized in random manner and causes a delay in the crystallization. • Thus, the copolymer is rubbery at room temp because the Tg is between HDPE (-110C) and PP (-20C). • Ethylene and propylene can be copolymerized with small amounts of a monomer containing 2 C=C double bonds (dienes) • Results in a co-polymer, EPR, or thermoplastic rubber, TPR

  20. Mechanical Properties of PE Blends

  21. Processing Properties of PE Blends

  22. Polypropylene History • Prior to 1954 most attempts to produce plastics from polyolefins had little commercial success • PP invented in 1955 by Italian Scientist F.J. Natta by addition reaction of propylene gas with a sterospecific catalyst titanium trichloride. • Isotactic polypropylene was sterospecific (molecules are arranged in a definite order in space) • PP is not prone to environmental stress-cracking like PE • Polypropylene is similar in manufacturing method and in properties to PE • Tg of PP = -25C versus Tg of PE of -100C

  23. Chemical Structure H H H H H H H H H H H H C C C C C C C C C C C C CH3 CH3 CH3 CH3 CH3 CH3 H H H H H H • Propylene • Isotactic- CH3 on one side of polymer chain (isolated). Commercial PP is 90% to 95% Isotactic n

  24. Polypropylene Stereostatic Arrangements H H H H H H H H H H CH3 H CH3 H H H CH3 H CH3 CH3 C C C C C C C C C C C C C C C C C C C C CH3 CH3 H CH3 CH3 H H H CH3 H H H H H H H H H H H • Atactic- CH3 in a random order (A- without; Tactic- order) Rubbery and of limited commercial value. • Syndiotactic- CH3 in a alternating order (Syndio- ; Tactic- order)

  25. Addition Polymerization of PP • Polypropylene produced with low pressure process (Ziegler) • Polypropylene produced with linear chains • Polypropylene is similar in manufacturing method and in properties to PE • Differences between PP and PE are • Density: PP = 0.90; PE = 0.941 to 0.965 • Melt Temperature: PP = 176 C; PE = 110 C • Tg of PP = -25C versus Tg of PE of -100C • Service Temperature: PP has higher service temperature • Hardness: PP is harder, more rigid, and higher brittle point • Stress Cracking: PP is more resistant to environmental stress cracking

  26. Advantages/Disadvatages of Polypropylene • Disadvantages • High thermal expansion • UV degradation • Poor weathering resistance • Subject to attack by chlorinated solvents and aromatics • Difficulty to bond or paint • Oxidizes readily • flammable • Advantages • 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 resistance

  27. Mechanical Properties of Polypropylene

  28. Physical Properties of Polyethylene

  29. Processing Properties of Polyethylene

  30. Several Olefin Polymers H H H H C C C C HCH H n H3C C CH3 C2H5 H n • Polybutylene (PB) • Based on butene-1 monomer • Plus comonomers (small amt) • Melt Point 125C similar to PE • Tg, -25C is closer to PP • Good creep & ESC resistance • Good for pipe and film extrusions • Polymethylpentene (PMP) • Trade name is TPX • Crystallizes to high degree (60%) • Highly transparent (90% transmis) • Properties similar to PP • Density is 0.83 g/cc, Tg =30C • Stable to 200C, Tm=240C • Creep and chemical resistance is good and low permeability. • Electrical properties are excellent • Process by injection & extrusion • Good for lighting, packaging, trays, bags, coffee makers, wire covering, connectors, syringes. • Poor ESC and UV H

  31. Polyolefin_Polybutylene H H CH3 C C CH2 H • History • PB invented in 1974 by Witco Chemical • Ethyl side groups in a linear backbone • Description • Linear isotactic material • Upon cooling the crystallinity is 30% • Post-forming techniques can increase crystallinity to 55% • Formed by conventional thermoplastic techniques • Applications (primarily pipe and film areas) • High performance films • Tank liners and pipes • Hot-melt adhesive • Coextruded as moisture barrier and heat-sealable packages

  32. Properties of Polybutylene

  33. Polyolefin_Polymethylpentene (PMP) H H C C CH2 H • Description • Crystallizes to 40%-60% • Highly transparent with 90% transmission • Formed by injection molding and blow molding • Properties • Low density of 0.83 g/cc; High transparency • Mechanical properties comparable to polyolefins with higher temperature properties and higher creep properties. • Low permeability to gasses and better chemical resistance • Attacked by oxidizing agents and light hydrogen carbon solvents • Attacked by UV and is quite flammable • Applications • Lighting elements (Diffusers, lenses reflectors), liquid level • Food packaging containers, trays, and bags. H3C-CH-CH3

  34. Properties of Polymethylpentene

  35. PVC Background • Vinyl is a varied group- PVC, PVAc, PVOH, PVDC, PVB • Polyvinyls were invented in 1835 by French chemist V. Regnault when he discovered a white residue could be synthesized from ethylene dichloride in an alcohol solution. (Sunlight was catalyst) • PVC was patented in 1933 by BF Goodrich Company in a process that combined a plasticizer, tritolyl phosphate, with PVC compounds making it easily moldable and processed. • PVC is the leading plastic in Europe and second to PE in the US. • PVC is made by suspension process (82%), by mass polymerization (10% ), or by emulsion (8%) • All PVC is produced by addition polymerization from the vinyl chloride monomer in a head-to-tail alignment. • PVC is amorphous with partially crystalline (syndiotactic) due to structural irregularity increasing with the reaction temperature. • PVC (rigid) decomposes at 212 F leading to dangerous HCl gas

  36. PVC and Vinyl Products • Rigid-PVC • Pipe for water delivery • Pipe for structural yard and garden structures • Plasticizer-PVC or Vinyl • Latex gloves • Latex clothing • Paints and Sealers • Signs

  37. PVC and PS Chemical Structure H H H Cl H H C C C C C C H H H Cl OH Cl n n n n H H H H C C C C H n H OCOCH3 • Vinyl Groups (homopolymers produced by addition polymerization) • PVC - poly vinylidene - polyvinylalcohol (PVOH) chloride (PVDC) • polyvinyl acetate (PVAc) - PolyStyrene (PS)

  38. Mechanical Properties of Polyvinyls

  39. Physical Properties of Polyvinyls

  40. Processing Properties of Polyvinyls

  41. Vinylchloride Co-Polymers • Chlorinated PVC (CPVC) • Possible to chemically modify PVC by substituting Cl for H • Cl content can be raised from 56.8% in PVC to 62%-72% • CPVC has improved chemical and temperature resistance that can be used for pipe and hot water applications, even boiling water. • Vinylchloride-vinylacetate (PVC-VAC) • Internally plasticizing PVC with 3% to 30% vinyl acetate • Impact properties and processing ease are improved for • Floor coverings, phonograph records. • Polyalloys • Improves impact resistance of rigid PVC by blending with elastomers, e.g., EVA, Nitrile rubber (NBR), Chloronated PE. • Blend PVC with PMMA and SAN for better transparency • Blend PVC with ABS for improved combustion resistance

  42. Vinylchloride Co-Polymers H Cl C C H Cl n H H C C n H OCOCH3 • Polyvinylidenechloride (PVDC) • Homopolymer can crystallize. Tg = -18C, Tm = 190C • Decomposition temperature is slightly above melt temperature of abut 200C • PVDC has outstanding barrier properties for O2, CO2, and H2O. • Copolymerized with 10-15% vinyl chloride to create Saran Wrap. • Copolymerize with acrlonitrile and acrylate esters up to 50%. • Coplymerization reduces crystallinity to 35-45% and the Tmelt ot 175C • Polyvinyl acetate (PVAC) • Not used as a plastic • Noncrystallizing • Low Tg = 30C, it is • It is best as a major ingredient in adhesives and paint, Elmers Glue • Vinylacetate repeat units form the minor component in imporant copolymers with vinylchloride (PVC-PVAC) and ethylene (EVA)

  43. Vinylchloride Co-Polymers H H C C OH H n CH2 CH3 H H C C n H CH2 • Polyvinylalcohol (PVAL or PVOH) • Homopolymer is very polar can crystallize • Water soluable. Tg = 80C, Tm = 240C • Random copolymer that is derived from PVAC • Used as a release film for reinforced plastics or barrier film. • Polyvinylbutyral (PVB) • Random copolymer (PVB-PVAL) • containing 10-15% VAL • Low Tg = 50C • Used in plasticized form as adhesive interlayer • For windshield safety glass (Saflex from Monsanto) • Powder is extruded into sheet and then placed between two layers of glass • Requires • Toughness, transparency, weatherability, and adhesion to glass.

  44. PS Background • PS is one of the oldest known vinyl compounds • PS was produced in 1851 by French chemist M. Berthelot by passing benzene and ethylene through a red-hot-tube (basis for today) • Amorphous polymer made from addition polymerization of styrene • Homopolymer (crystal): (2.7 M metric tons in ’94) GPPS (General Purpose PS) • Clear and colorless with excellent optical properties and high stiffness. • It is brittle until biaxially oriented when it becomes flexible and durable. • Graft copolymer or blend with elastomers- High Impact Polystyrene (HIPS): • Tough, white or clear in color, and easily extruded or molded. • Properties are dependent upon the elastomer %, but are grouped into • medium impact (Izod<1.5 ft-lb), high impact (Izod between 1.5 to 2.4 ft-lb) and super-high impact (Izod between 2.6 and 5 ft-lb) • Copolymers include SAN (poly styrene-acrylonitrile), SMA (maleic anhydride), SBS (butadiene), styrene and acrylic copolymers. • Expandable PS (EPS) is very popular for cups and insulation foam. • EPS is made with blowing agents, such as pentane and isopentane. • The properties are dependent upon cell size and cell size distribution

  45. Polystyrene Polymers CH3 CH3 n n H H H C C C C H H • Poly-para-methyl-styrene (PPMS) • Similar to PS (Tg=100C) with a slightly higher Tg=110C • Low cost alternative to PS in homo and co-polymers • Poly-alpha-methyl-styrene (PAMS) • High Tg =160C and better Temp resistance • Not much commercial importance by itself • Has significant use in copolymers • Rubber-toughened impact polystyrene (HIPS) • Random copolymerization with small fraction of elastomer type repeat units. Lowers Tg • Block copolymerization of elastomeric component is more expensive, but keeps Tg same as PS

  46. PSB, SAN, ABS Chemical Structure H H H H C C C C H H H H H CH3 C:::N CH3 n m C C C C CH3 CH3 H C:::N n m H H H H H H C C C C C C H H H k k k • PSB (copolymer -addition) * Styrene- acrylonitrile (SAN) • ABS acrylonitrile butadiene styrene (Terpolymer- addition)

  47. Polystyrene Co-Polymers • Styrene-Butadiene (PSB) • Tg= % of each PS (100C) and Butadiene (-80C) • Example, 50% PS and 50% B, Tg=10C • Easy to copolymerize and can be rubbery (butadiene-dominant) or plastic like (styrene-like), out 70% of the PSB is styrene dominant • Random (styrene dominant) copolymers have been used in emulsion (latex) form to produce coatings (paints). • Block copolymers are commercial butadiene styrene-plastics • Styrene Acrylonitrile (SAN) • Random copolymer of 30% polyacrylonitrile repeat units yields • Increased Temp performance and transparent, ease to process • Resistant to food and body oils • Used for transparent medical products, houseware care items • Polyalloys (blends) with polysulphone

  48. Polystyrene Co-Polymers • Acrylonitrile Butadiene Styrene (ABS) • First introduced in the late 1940s as replacement for rubber. • Terpolymer: Three repeat units vary according to grade (20%A, 20%B, 60%S) • Acrylonitrile for chemical and temperature resistance • Butadiene for impact resistance; Styrene for cost and processability • Graft polymerization techniques are used to produce ABS • Very versatile applications that are injection molded and extruded • Rigid pipes and fittings, thermoformed refrigerator door liners, Legos toys • Small boat hulls, telephone and computer housings • Family of materials that vary from high gloss to low matte finish, and from low to high impact resistance. • Additives enable ABS grades that are flame retardant, transparent, high heat-resistance, foamable, or UV-stabilized • ABS-based polyalloys (blends) • PVC/ABS for flame resistance • TPU/ABS for polyurethane; PSU/ABS for polysulphone • PC/ABS for temperature and impact resistance (Saturn door) • .

  49. Mechanical Properties of PS, ABS, SAN n H H C C H Tg =100C

  50. Physical Properties of PS, ABS, SAN

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