Plastic Product Material and Process Selection Handbook Part 3 ppt

54 Plastic Product Material and Process Selection Handbook Polyolefin Thermoplastic Elastomer TPEs are blends of various amorphous rubbers such as ethylene- propylene and of polyolefin semicrystalline plastics such as PP. They are part of the family of TP olefins (TPOs). TPOs are mechanical blends consisting of a hard plastic and softer rubber. They are considered different from blends that are dynamically thermoplastic vulcanized (TPV) a process in which the elastomer phase is cured during mixing of the polymers. 84, 94 Ethylene-Propylene Elastomer EP elastomcrs arc random, amorphous polymers with outstanding resistance to ozone, aging and weathering, mainly because of the saturated structure in their hydrocarbon backbone. These TPs also possess good low temperature flexibility and heat resistance and have excellent electrical properties. Their resistance to hydrocarbons and solvents is poor. The low density of these elastomers plus their ability to accept very high levels of extender oils and fillers often gives them a cost advantage over other elastomers in many applications. Principal applications are in automotive products, single-ply roofing, thermo- plastic olefins and viscosity index improvers for lubricating oils. EP elastomers are the third-largest synthetic rubber consumed worldwide, after styrene-butadiene rubber and polybutadiene rubber. World consumption of EP elastomers in 1998 was about 800 thousand metric tons. Polypropylene PPs arc in the polyolefin family of plastics representing a major plastic used worldwide providing different performances. They have low specific gravity and good resistance to chemicals and fatigue. PP made with metallocene catalysts (mPP) has improved characteristics such as toughness, stiffness, heat resistance, clarity, barrier properties, high melt flow, and high melt strength. 14, 95 Their densities are slightly lower than PEs but are much stiffer, more heat resistant, and have the same chemical and electrical resistance. They arc semi-translucent and milky white in color, with excellent colorability. Their chemical structure makes them stronger than other members of the polyolcfin family. These versatile plastics are available in many grades as well as copolymers like ethylene propylene. NEAT PP has a low density of 0.90, which, combined with its good balance of moderate cost, strength, and stiffness as well as excellent fatigue, chemical resistance, and thermal and electrical properties, makes PP extremely attractive for many indoor and outdoor applications. There arc hundreds of formulations that are produced. 2 9 Plastic property 55 PP is widely known for its application in the integral so called living hinges that are used in all types of applications; PP's excellent fatigue resistance is utilized in molding these integral living hinges. 59 They have superior resistance to flexural fatigue stress cracldng, with excellent electrical and chemical properties. This versatile polyolefin overcomes poor low temperature performance and other shortcomings through copolymer, filler, and fiber additions. It is widely used in packaging (film and rigid), and in automobile interiors, under-the-hood and underbody applications, dishwashers, pumps, agitators, tubs, filters for laundry appliances and sterilizable medical components, etc. 96 Electrical properties are affected to varying degrees by their service temperatures. Its dielectric constant is essentially unchanged, but its dielectric strength increases and its volume resistivity decreases as temperature increases. They are unstable in the presence of oxidation conditions and UV radiation. Although all its grades arc stabilized to some extent, specific stabilization systems are often used to suit a formulation to a particular environment, such as where it must undergo outdoor weathering. PPs resist chemical attack and staining and are unaffected by aqueous solutions of inorganic salts or mineral acids and bases, even at high temperatures. Most organic chemicals do not attack them, and there is no solvent for this plastic at room temperature. Halogens, fuming nitric acid, and other active oxidizing agents attack the plastics. Also attacked by aromatic and chlorinated hydrocarbons at high temperatures. PPs have limited heat resistance, but heat-stabilized grades are available for applications requiring prolonged use at elevated temperatures. The useful life for products molded from such grades may be at least as long as five years at 120C (250F), 10 years at 130C (230F), and 20 years at 99C (210F). Specially stabilized grades are UL rated at 120C (248F) for continuous service. Basically, PP is classified as a slow burning material, but it can also be supplied in flame-retardant grades. Polybutylene Part of the polyolcfin family are PBs. They are similar to PPs and HDPEs but exhibit a more crystalline structure. This crystallinity produces unusual high strength and extreme resistance to deformation over a temperature range of-10 to 190F. Its structure results in a rubberlikc, elastomeric material with low molded-in stress. Tensile stress that does not plateau after reaching its yield point makes possible films that look like PE but act more like polyester (TP) films. Compared to other polyolefins, they have superior resistance to creep 56 Plastic Product Material and Process Selection Handbook and stress cracking. PB films have high tear resistance, toughness, and flexibility. Their chemical and electrical properties arc similar to those of the PEs and PPs. Use includes pipe/tube, packaging, hot-melt adhesives, and sealants. Piping for cold-water use out of PBs has a higher burst strength than pipe made from any other polyolefin. Large diameter pipe has been successfully used in mining and power generation systems to convey abrasive materials. PBs can be alloyed with other polyolefins to provide its inherent advantage. Film made into industrial trash bags gives improved resistance to bursting, puncturing, and tearing. Cyclic Polybutylene Terephthalate CBT| plastic is being developed by Dow with target date to have them commercially available by 2005. 422 These plastic polymerize reactively like TSs but have the material properties of a TP. Because its initial viscosity is like water it is easy to process. CBT will provide significant performance improvements over traditional plastics as well as weight reduction, minimized scrap rates, lower tooling costs, and lower processing costs. These cyclics with fiber reinforcements offers stiffness and toughness with a high level of resistance to heat and chemical attack. They are dimensionally stable with low water absorption, provide electrical insulation, and can be made to be flame retardant. Standard composites fabricating processes can be used (injection, compression, thermoforming, etc.). Parts can be welded, adhesively bonded, and painted. Fabricated products are completely recyclable. It is possible to separate them back into their original components without any loss of properties. Applications include auto products such as vertical and horizontal external body panels, truck boxes and tailgates with Class A high quality surface appearances. Other grades will be available for applications where structural strength is required. Dow predicts many more traditional steel components being made of fiber reinforced plastic (FRP). Vinyl Vinyls are one of the most versatile families of plastics. The term vinyl usually identifies the major very large production of polyvinyl chloride (PVC) plastics. The vinyl family, in addition to PVCs, consists of polyvinyl acctals, polyvinyl acetates, polyvinyl alcohols, polyvinyl carbazoles, polyvinyl chloride-acetates, and polyvinylidene chlorides. As a family, they are strong and abrasion resistant. They are unaffected, for the most part, by prolonged exposure to water, common chemicals, 2 9 Plastic property 57 and petroleum products. However, they should be kept away from chlorinated solvents, such as many household-cleaning fluids. Vinyls can withstand continuous exposure to heat up to 130F (54C) and perform satisfactorily at food freezing temperatures. 98q~ Most vinyls arc naturally clear, with an unlimited color range for most forms of the materials. They generally have in common excellent strength, abrasion resistance, and self-extinguishable. In their elastomeric form vinyls usually exhibit properties superior to those of natural rubber in their flcxural life, resistance to acids, alcohols, sunlight, wear, and aging. They are slow burning and some types are self-extinguishing but they should be kept away from direct heat. The vinyls may be given a wide range of colors and may be printed or embossed. They generally have excellent electrical properties but with relatively poor weathering qualities are recommended for indoor use only unless stabilized wit suitable additives. Vinyls literally can be processed by more techniques than any other plastic. Reason is that it contains a relatively polar polymer that allows a large range of formations. Polyvinyl Chloride The high volume PVCs worldwide market provides a wide range of low cost flexible to rigid plastic with moderate heat resistance and good chemical, weather and flame resistance. The manufacture of a wide range of products is possible because of PVC's miscibility with an amount and variety of plasticizers. PVC has good clarity and chemical resistance (Figures 2.2 and 2.3). PVC can be chlorinated (CPVC) and be alloyed with other polymers like ABS, acrylics, polyurethanes, and nitrile rubbers to improve its impact resistance, heat deflection, and processability. Although these vinyls differ in having literally thousands of varying compositions and properties, there are certain general characteristics that are common to nearly all these plastics. Most materials based on vinyls are inherently TP and heat sealable. The exceptions are the products that have been purposely compounded with TSs or crosslinldng agents arc used. Rigid PVC, so-called poor man's engineering plastic, has a wide range of properties for use in different products. It has high resistance to ignition, good corrosion, and stain resistance, and weatherability. However, aromatic solvents, ketones, aldehydes, naphthalenes, and some chloride, acetate, and acrylate esters attack it. In general, the normal impact grades of PVCs have better chemical resistance than the high-impact grades. Most PVCs arc not recommended for continuous use above 60C (140F). Chlorination to form CPVC increases its heat Mixer I mLmm. r 1 I possiuy I extruder t -J I ' ~o,e~e; I L Fll'ms =- =. I 1 I ' prin#ng machines Iomtr~ating machine J Decorahve. podded Sheets or webs wafter htm (e. g. flooring) 80-50 ports PVC powder 20-50 ports ploshctzer (extendeC, fillers) slabilizers, pigments I Mt In,, ,rJ f .o, oodc~"l mixer I Sheets and h'Ims Granules Extruder Profiles Covernngs and tubes Agglomerates, dry blends' injection I I Costing and molding machine dipping mactu)~es Moldings Moldings~ coverings and tapes I Agitaler mixer, ! * Chemical or roll mill, if need ~ e~- physical blowing be de~erated i agents J PVC pastes Foam-forming (ptastisots) PVC pastes r Spreodu~g machines High- and low- pressure foaming plants Solid and foamed coab'ngs artificial leather, floor covc~ing, paneling Open or closed flexible foams, sheet foams Figure 2°2 Examples of plasticized-flexible PVC 0"1 CO D3 ¢/t "0 8 e e-i, Pe ,-t D3 m "13 8 I'D t/I I'D ¢'D "! "r" ~3 (::r" 0 0 M;xe.,r l | ! ~ntin k,~er Co~'endPr F~lrns o~ s~P~hr 1 L ~.r~fhecm (oi~dK i F~ne l¢Im_~ F!~ 2~3 Ex~,Tplescf'icd FVC PVC pow#er torso copo(mxn's o¢ blends) * ~¢~zer~ ~ub~canr, ptgraents 1 Pohshed ~ee~ and b~k5 t [ rhera',elormr~ ~chine~ ] Granu/es ' t I Hot and cold I mixer ! I F#ms an# sheets ~atruder I Pipes profile.s, rn~Is Powder mixing _J l i J Blow moldings Injection- molding nx~i~ine 1 Molding5 ,~ Blowing agen/ Mizer tnjech~ extrusion hlgh - pressure loaning Slruclural ¢oom products, rigid foams ho "0 P~ .Z Ltl ¢JO 60 Plastic Product Material and Process Selection Handbook resistance, flame retardancy, and density, depending on the amount of chlorination introduced. In regard to flammability, note that the vinyls release a limited amount of hydrochloric acid during processing. Different blends can be prepared providing different properties. Blends with non-compatible polymers such as polyolefin elastomers (POEs) are made to blend by using compatibilizers. 143 These flexible PVC blends can be made with no plasticizers resulting in improved properties. They are nontoxic, tasteless, odorless, and suitable for use as packaging materials that will come in contact with foods and drugs, as well as for decorative packaging requiring ordinary protection. The vinyl plastics can be used in printing inks and be effectively used in coating paper, leather, wood, and, in some cases, plastics. In most forms vinyl can be printed. They qualify in many markets such as for packaging, pipe, outdoor construction products (siding, window profiles, etc), and a host of low- cost disposable products [including FDA-grade medical uses in blood transfusion, storage, etc.96]. Foam-vinyl strippables are used for metal parts packaging. These PVC dispersion plastics are applied in liquid form. Foaming takes place during their cure cycle (Chapter 8). PVCs come in a variety of grades, flexible to rigid. They are tough, can be transparent (as in blow molded bottles and jugs), and are also a good alloying plastic to improve properties and reduce costs. PVCs inherent characteristics generally require special considerations to ensure the best melt processing conditions and the tool will not be damaged (corrode due to hydrochloric acid) by the PVC. One such consideration is specifying the correct tool steel in order to meet products demanding appearances, meet long run production, etc. (Chapter 17). Ultra High Molecular Weight Polyvinyl Chloride UHMWPVCs are versatile plastics that can provide superior mechanical properties and be formulated to produce a variety of products. Because changes in formulations or equipment conditions may be required for processing, these plastics are generally used in plasticized applications; it is in highly plasticized uses that they show the greatest advantages in producing compounds with improved properties. They can bring to flexible vinyls improved tensile, modulus, abrasion, and solvent resistance; low and high temperature performance; and retention of properties during aging. Polyvinyl Acetate The PVAc copolymers are odorless, tasteless, nontoxic, slow burning, lightweight, and colorless, with reasonably low water absorption. They 2 9 Plastic property 61 are soluble in organic ketones, esters, chlorinated hydrocarbons, aromatic hydrocarbons, and alcohols, but insoluble in water, aliphatic hydrocarbons, fats, and waxes. Water emulsions have extended the use of this plastic. Used perhaps most extensively as adhesives, they are also employed as coatings for paper sizing for textiles, and finishes for leathers, as well as bases for inks and lacquers, for heat-sealing films, and for flashbulb linings. They include vinyl acetate homopolymers and all copolymers in which vinyl acetate is the major constituent (50% or greater). The major PVAc copolymers are vinyl acetate-ethylene (VAE) and vinyl acetate-acrylic ester (vinyl acrylic). Vinyl acetate-versatic acid (vinyl versatate) and vinyl acetate- maleate are major PVAc copolymer emulsions used. Polyvinyl Chloride Acetate PVCA is a copolymer of vinyl chloride and vinyl acetate. It is a colorless thermoplastic solid with good resistance to water as well as concentrated acids and alkalis. It is obtainable in the form of granules, solutions, and emulsions. Compounded with plasticizers, it yields a flexible material superior to rubber in aging properties. It is widely used for cable and wire coverings, in chemical plants, and in protective garments. Polyvinyl Chloride, Chlorinated CPVC is a plastic produced by the post-chlorination of PVC. Adding more chlorine raises the glass transition tempe::ature of CPVC at 115 to 135C (239 to 275F) and the resultant heat deflection under load from that of PVC at 70C (158F) to a level of 82 to 102C (180 to 219F) depending on formation. CPVC has improved resistance to combustion and smoke generation with higher tensile strength and modulus while maintaining all the good properties that rigid PVC possesses. Traditional uses are hot and cold-water distribution piping and fittings and industrial chemical liquid handling pipe, fittings, valves, and other different applications. Polyvinyl Alcohol PVOH (or tradename PVAL) is a crystalline, white powder soluble in water and alcohols. It is characterized by water solubility, low gas permeability barrier, high resistance to organic solvents other than alcohol, and crystallinity when stretch oriented. Crystallinity allows the material to polarize light. A series of hydrolysis levels of the plastic are available that range from room temperature solubility to those not soluble at all. The major applications of the PVOHs are in elastomeric products, adhesives, films, and finishes. Extruded PVOH hoses and tubing are excellent for use subjected to contact with oils and other chemicals. PVOH is used as a sizing in the manufacture of nylon. 62 Plastic Product Material and Process Selection Handbook Polyvinyl Butyral PVB is colorless, flexible, very tough solid plastic, soluble in esters, ketones, alcohols, and chlorinated hydrocarbons but insoluble in the aliphatic hydrocarbons. They are stable in dilute alkali; but slowly decompose in dilute acids. Since the year 1930s PVBs have been extensively used as shatterproof safety-glass interlayers and between sheets of acrylic to protect the enclosures of pressurized cabins in aircraft against shattering. PVB film interlayers range from 10 to 40 mils. They continue to be used as an important resource for the building glass windows, automotive, architectural industries, etc. PVBs are also used as coatings for textiles and paper and also as adhesives. Polyvinyl Carbazole PVCB is brown in color, obtained by reacting acetylene with carbazole. The plastic has excellent electrical properties and good heat and chemical resistance. Use includes high frequency dielectrics, impregnant for paper capacitors, and photoconductive plastics. Polyvinyl Pyridine PVP is primarily used as a constituent in copolymers as adhesives. Polyvinyl Pyrrolidone PVPO is highly polar and water-soluble plastic. It finds applications in adhesives and as a water thickener. Water solutions can be used as blood plasma substitute or artificial blood. Po lyvi n yl fluoride PVF products are strong and tough, with good abrasion and staining resistance up to fairly high temperatures of 100 to 150C (212 to 302F) and they are classified as slow burning. They are generally less chemical resistant than fully fluorinated plastics but show excellent UV resistance and good color retention and are not affected by water. Their excellent weatherability has made them a choice material for exterior applications such as coatings for metals (slides, gutters, etc.), plywood finishes, architectural sheets, lighting panels, and glazing for solar energy collection. Also for electrical wrapping tape and parting layers for laminates. Polyvinyl Formal PVFO finds applications as temperature-resistant coatings for containers and electric wires. It resistant greases and oils. Polyvinylidene Chloride There are flexible and rigid PVDCs. They have high strength, abrasion resistance, strong welds, dimensional stability, toughness, and durability. This material is especially suited for injection molding at high speed that provides heavy, thick cross-sections. Molded fittings and 2 9 Plastic property 63 parts are particularly valuable in industries involving the use of chemicals. For example pipes of this material are superior to iron pipes to dispose of waste acids. As an extruded monofilament it is woven into upholstery fabric and screening. Films produced from PVDC exhibit an extremely low water-vapor transmission rate, as well as flexibility over a wide range of temperatures and heat sealability. They are particularly suitable for various types of packaging, including medical products, metal parts, and food. Food packaging for the home refrigerator uses the highly popular Saran (PVDC) wrap from Dow. Polyvinylidene Fluoride PVDF is a fluorine-containing TP unlike other plastics. It is a crystalline, high molecular weight polymer of vinylidene fluoride. Compounds are available that contain at least 60wt% fluorine. This nonflammable plastic is mechanically strong and tough, thermally stable, resistant to almost all chemicals and solvents. It is also stable to UV and extreme weather conditions with higher strength and abrasion resistance than PTFE; however, it does not match the high chemical and temperature resistance of PTFE. Where unfavorable combinations of chemical, mechanical, and physical environments may preclude the use of other materials, PVDF has been successfully used. Examples include valve and pump parts, heavy wall pipefittings, gears, cams, bearings, coatings, and electrical insulations. Its limitations include lower service temperatures than the highly fluorinated fluoropolymers, no anti-stick qualities, and the fact that it produces toxic products upon thermal decomposition. Polystyrene PS is a high volume worldwide consumed plastic. It is used in many different formulations. PS is noted for its sparlding clarity, hardness, low water absorption, extreme ease of processing general purpose PS (GPPS), excellent colorability, dimensional stability, and relatively low cost. This amorphous TP often competes favorably with higher-priced plastics. It is available in a wide range of grades for all types of processes. In its basic crystal PS form it is brittle, with low heat and chemical resistance, poor weather resistance. High impact polystyrene is made with butadiene modifiers that provides significant improvements in impact strength and elongation over crystal polystyrene, accompanied by a loss of transparency and little other property improvement. Modifications available to the basic GPPS include grades for high heat and for various degrees of impact resistance. Clarity and gloss are [...]... moisture, which then has to be carefully removed before the plastics can be processed into acceptable products Low concentrations, as specified by the plastic supplier, can be achieved through efficient drying systems and properly handling the dried plastic prior to and during molding, 31 68 Plastic Product Material and Process Selection Handbook devices, etc Used as an opaque colored sheeting thermoformed... crystalline structure, etc 82 Plastic Product Material and Process Selection Handbook psi), an elongation at yield of 6% at 23C (74F) and of 2% at 160C (32 0F), and no break using an unnotched Izod impact test PAEKs arc plastics in which phcnylcne tings arc linked together via oxygen bridges [ether and carbonyl groups (ketone)] and may be viewed as the family name of this class of plastics Their ratio influences... during the product design to processing the plastics In addition to matcrial variables, thcrc arc a number of factors in 35 72 Plastic Product Material and Process Selection Handbook or precursor in the manufacture of certain carbon and graphite reinforcement fibers (Chapter 15) Cellulosic These plastics have been used for over a century They are tough, transparent, hard or flexible natural materials... able to maintain their structural integrity and 66 Plastic Product Material and Process Selection Handbook include foamed food trays, packaging, disposable cups, and printed displays Syndiotactic Polystyrene SPS is a crystalline plastic with far higher heat resistance than standard amorphous PS, lower moisture pick-up, and improved warp-resistance, and outstanding dimensional stability (eliminates the... creep and fatigue behaviors These type products have performed in service for long periods of time with some performing well over a half-century For certain plastic products there are definite properties 41 78 Plastic Product Material and Process Selection Handbook of nylons arc increased at room and elevated temperatures by incorporating glass fibers (Chapter 15) Thcy have good resistance to creep and. .. product, and so on 1 80 Plastic Product Material and Process Selection Handbook resistant to acids and alkalis, have poor solvent resistance (especially in ketones) but good resistance to aliphatic hydrocarbons, and resist staining from common household agents rather well They are exceptionally useful in primer plastic applications where drying speed, compatibility with various ldnds of topcoats, and. .. the proper method Designers, material selectors, and processors to produce products meeting requirements at the lowest cost have unconsciously used the basic concept of the FALLO approach (Follow ALL Opportunities) This approach makes one aware that many steps arc involved to be 37 74 Plastic Product Material and Process Selection Handbook Their common properties are outstanding chemical inertness, resistance... strength, lightweight, low cost, and processability Other HDPE formulations include a high-flow HDPE that is suited to injection molding thin-wall products like food containers, drink cups, 88 Plastic Product Material and Process Selection Handbook attacked by such partially halogenated solvents as methylene chloride trichloroethane, and strong acids These amorphous engineering plastic are characterized by... to survive an earthquake better than more rigid materials such as PVC or ductile iron They have a slow 47 84 Plastic Product Material and Process Selection Handbook electrical properties remain relatively constant over a wide range of temperatures and humidity They resist water, acids, and oxidizing and reducing agents but can be dissolved in aromatic and chlorinated solvents Typical mechanical properties... MWD The melt index and density often have opposite effects on properties, necessitating compromises in plastic selection (Figure 2.1) MW and density affect the optical properties of LDPE High MW molecules produce a rough, low gloss surface; HDPEs contain more or larger crystalline areas that scatter light and cause a hazy appearance 86 Plastic Product Material and Process Selection Handbook cleanup, . resistance to creep 56 Plastic Product Material and Process Selection Handbook and stress cracking. PB films have high tear resistance, toughness, and flexibility. Their chemical and electrical properties. 54 Plastic Product Material and Process Selection Handbook Polyolefin Thermoplastic Elastomer TPEs are blends of various amorphous rubbers such as ethylene- propylene and of polyolefin. loaning Slruclural ¢oom products, rigid foams ho "0 P~ .Z Ltl ¢JO 60 Plastic Product Material and Process Selection Handbook resistance, flame retardancy, and density, depending