Materials Handbook 15th ed - G. Brady_ H. Clauser_ J. Vaccari (McGraw-Hill_ 2002) Episode 10 ppsx

species is also called buttonwood and buttonball. It is a yellowish, compact wood with a fine, open grain. The density is about 40 lb/ft 3 (641 kg/m 3 ). It resembles maple and gives a beautiful grain when quartered. It is employed in cabinetwork. PLASTIC ALLOYS AND BLENDS. Alloys consisting of two thermoplas- tics compounded into a single resin. The two polymers must be melt- compatible. Some polymers are naturally compatible; others require the use of compatibilizing agents. The purpose of alloying polymers is to achieve a combination of properties not available in any single resin. Acrylonitrile butadiene styrene (ABS) is a common alloy ingredient, alloys including polycarbonate-ABS (PC-ABS), ABS- polyurethane (ABS-PUR), ABS-nylon, ABS-polysulfone, and ABS-polyvinyl chloride (ABS-PVC). Besides PC-ABS there are polycarbonate-polybutylene terephthalate (PC-PBT), polycar- bonate-acrylonitrile styrene acrylate (PC-ASA), and polycar- bonate acrylic (PC-Acrylic) and polyetherimide-polycarbonate (PEI-PC) alloys. And besides ABS-PVC, there are polyvinyl chlo- ride-acrylic, polyvinyl chloride-chlorinated polyethylene (PVC-CPE), and acrylic-polyvinyl chloride alloys. There are also polyethylene alloys, polyphenylene oxide-polystyrene, and polyphenylene oxide-polybutylene terephthalate (PPO-PBT) alloys. PC-ABS alloys extend the exceptionally high impact strength of car- bonate plastics to section thicknesses over 0.0625 in (0.16 cm). Tradenames of PC-ABS alloys include Cycoloy of General Electric Plastics; Pulse of Dow Plastics; Bayblend of Bayer.; and Celstran of Polymer Composites Inc. Cycoloy C2950 HF features a 30% greater flow rate than Cycoloy C2950 and a UL94 V-O flame retardance at a thickness of 0.06 in (1.5 mm) and a UL94 5VB at 0.10 in (2.5 mm). Cycoloy LG9000 is a low-gloss, or matte-finish, grade for unpainted, interior auto parts. It provides 60% less gloss than standard grades and has a tensile strength of 7,900 lb/in2 (54 MPa), a flexural strength of 12,300 lb/in2 (85 MPa), a flexural modulus of 335,000 lb/in2 (2,310 MPa), a heat deflection temperature of 225°F (107°C) at 264 lb/in2 (1.8 MPa), and a notched Izod impact strength of 10 ft . lb/in (534 J/m). The Dow grades include Pulse 830, 1725, 1735, and 1745. Pulse 1725 is a brominated (flame-retardant), ignition-resistant grade; Pulse 1735 is a nonbrominated, ignition-resistant grade. Pulse 1745 is brominated, but it does not contain polybrominated diphenyl ether, which may generate environmentally harmful dibenzodioxin and dibenzofuran. This alloy and antimony-, bromine-, and chlorine-free, flame-retardant Bayblend FR2000 and FR 2010 are intended for computer and business-machine housings. Both have a specific gravity of 1.18, a tensile strength at yield 720 PLASTIC ALLOYS AND BLENDS Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses of 8,700 lb/in 2 (60 MPa), a flexural strength at 5% strain of 13,800 lb/in 2 (95 MPa), and a flexural modulus of 390,000 lb/in 2 (2,689 MPa). The notched Izod impact strength is 8 and 10 ft . lb/in (430 and 530 J/m), respectively, and the 264-lb/in 2 (1.8-MPa) deflection temperature is 180 and 200°F (82 and 93°C). Celstran PC-ABS alloys are reinforced with 25 or 40% long, glass fibers. The RTP 1800 A PC-acrylic alloys, from RTP Co., are tougher than polycarbonate, having an unnotched impact strength of 39 ft . lb/in (2,081 J/m) and a notched Izod impact strength of 16 ft . lb/in (854 J/m) and the processing ease of acrylics. Tensile strength is 7500 lb/in (52 MPa) and the flexural strength is 12,000 lb/in 2 (83 MPa). They are white in color and can be modified for coloring, flame retar- dance, abrasion resistance, electromagnetic shielding, and antistatic characteristics. Triax Nylon 6-ABS, from Bayer, are semicrystalline injection-mold- ing and extrusion alloys that combine good chemical and fatigue resis- tance with excellent abrasion resistance. General-purpose 1120 and 1180 grades have, respectively, a specific gravity of 1.06 and 1.07, and, dry, as-molded, a tensile strength at yield of 6,300 and 5,800 lb/in 2 (43 and 40 MPa), a flexural modulus of 300,000 and 250,000 lb/in 2 (2,069 and 1,724 MPa), a notched Izod impact strength at 73°F (23°C) of 14 to 15 and 15 to 16 ft . lb/in 2 (747 to 801 and 801 to 854 J/m), and a 264- lb/in 2 (1.8-MPa) deflection temperature of 149 and 165°F (65 and 74°C) and 129 and 142°F (54 and 61°C). The alloys absorb mois- ture and should be dried to 0.15 and 0.35% moisture before pro- cessing. Electrafil ABS-1200/SD, of DSM Engineering Plastics, combines ABS with a static-dissipative polymer for protection against electro- static discharge. At 15% relative humidity, the static decay rate is less than 2 s compared with 99 s or more for unmodified ABS. Although the alloy’s flexural modulus is reduced considerably—270,000 lb/in 2 (1,862 MPa) versus 340,000 lb/in 2 (2,344 MPa)—tensile strength and heat-deflection temperature are only slightly less, and impact strength is unaffected. ABS-PUR alloys combine the excellent abra- sion resistance and toughness of the urethanes with the lower cost and rigidity of ABS. ABS-PVC alloys are available commercially in several grades. One of the established grades provides self-extinguishing properties, thus eliminating the need for intumescent (nonburning) coatings in ABS applications, such as power tool housings, where self-extinguishing materials are required. A second grade possesses an impact strength about 30% higher than that of general-purpose ABS. Also ABS-PVC alloys can be produced in sheet form. The sheet materials have improved hot strength, which allows deeper draws than are possible PLASTIC ALLOYS AND BLENDS 721 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses with standard rubber-modified PVC base sheet. They also are nonfog- ging when exposed to the heat of sunlight. Some properties of ABS-PVC alloys are lower than those of the base resins. Rigidity, in general, is somewhat lower, and tensile strength is more or less depen- dent on the type and amount of ABS in the alloy. Another sheet material, an alloy of about 80% PVC and the rest acrylic plastic, combines the nonburning properties, chemical resistance, and toughness of vinyl plastics with the rigidity and deep-drawing mer- its of the acrylics. The PVC-acrylic alloy approaches some metals in its ability to withstand repeated blows. Because of its unusually high rigid- ity, sheets ranging in thickness from 0.60 to 0.187 in (1.5 to 0.5 cm) can be formed into thin-walled, deeply drawn parts. Kydex 200, of Kleerdex Co., is an acrylic-PVC alloy in the form of sheet 0.04 to 0.25 in (1 to 6.4 mm) thick in various surface textures and colors. The tensile strength is 6,000 lb/in 2 (41 MPa), flexural modulus is 350,000 lb/in 2 (2,413 MPa), and the notched Izod impact strength is 4 to 6 ft и lb/in (214 to 320 J/m). PVC is also alloyed with chlorinated polyethylene (CPE) to gain materials with improved outdoor weathering or to obtain better low-temperature flexibility. The PVC-CPE alloy applications include wire and cable jacketing, extruded and molded shapes, and film sheeting. Acrylic-base alloys with a polybutadiene additive have also been developed, chiefly for blow-molded products. The acrylic content can range from 50 to 95%, depending on the application. Besides blow-molded bottles, the alloys are suitable for thermoformed products such as tubs, trays, and blister pods. The material is rigid and tough and has good heat-distortion resistance up to 180°F (82°C). Polyphenylene oxide (PPO) can be blended with polystyrene to pro- duce a PPO-polystyrene alloy having improved processing traits and lower costs than nonalloyed PPO. The addition of polystyrene reduces tensile strength and heat-deflection temperature somewhat and increases thermal expansion. Gemax is a PPO-PBT alloy of General Electric Plastics. GTX alloys, also of this company, combine PPO and nylon and have heat-deflection temperatures up to 302°F (150°C) and good stiffness without glass or mineral fillers. Variations of this alloy combine various levels of stiffness, impact strength, and heat resistance. GTX 990EP is nanotube-filled and has been used for auto mirror housings and fuel filler caps. Xenoy is a PC-PBT alloy of the same company, for, among other uses, auto-bumper impact beams, and Ultem LTX alloys are PC-ASA alloys. LTX100A and 100B are aimed at thick-wall connectors and extrusions; LTX300A and 300B provide greater heat resistance. Ultem ATX alloys, from General Electric Plastics, combine polyetherimide and polycarbonate for impact strength and heat resistance. Du Pont’s “low-warp” PBT-ASA 722 PLASTIC ALLOYS AND BLENDS Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses alloys, Crastin LW9020 and LW9030, with 20 and 30% glass filling, respectively, are intended mainly for electrical housings and connec- tors. Also for electrical applications is Bayer Corp.’s Makroblend DP4-1389, an alloy of polyethylene terephthalate (PET) and polycar- bonate. Ultradur S, of BASF Corp., is a glass-filled PBT, ASA, and PET alloy. It is slightly lighter in weight than PBT, has better flow, is less prone to distortion and moisture absorption, and provides a bet- ter surface appearance. GE Plastics’ Geloy XP4034 PC-ASA alloy fea- tures high impact strength and heat resistance as well as low moisture absorption. An alloy of polypropylene modified with non-cross-linked ethylene-propylene-diene monomer and Surlyn ionomer provides “soft-touch” auto instrument panels. Hostalloy 731, of Hoechst Celanese, is an alloy of several polyethyl- enes of different molecular weights. It has a density of 0.034 lb/in 3 (941 kg/m 3 ), a tensile yield strength of 5,000 lb/in 2 (35 MPa), and a flexural modulus of 170,000 lb/in 2 (1,170 MPa). The alloy approaches the abrasion resistance and impact strength of ultrahigh-molecular-weight polyethyl- ene but is more readily processed. Hivalloy, of Montell North America, is a line of propylene-based copolymer and terpolymer alloys that combine the strength of the semicrystalline monomer with the attributes of vari- ous amorphous monomers. They are intended to compete with amor- phous plastics such as acrylonitrile butadiene styrene and polycarbonate as well as with semicrystalline acetal, nylon, and thermoplastic polyester. The styrene-propylene G series has a specific gravity as low as 0.92, a melt flow as high as 0.055 lb/10 min (25 g/10 min), a Gardner impact strength of up to 27 ft . lb (36 J), and a flexural modulus as high as 1 ϫ 10 6 lb/in 2 (6,900 MPa). Toughened G-series alloys include ethylene propylene and styrene-ethylene-butadiene-styrene modifiers to boost impact strength, especially at low temperatures (Ϫ22°F, Ϫ30°C). Hivalloy W alloys are of polypropylene and acrylic. PLASTIC BRONZE. A name once applied by makers of bearing bronzes to copper alloys that are sufficiently pliable to assume the shape of the shaft and make a good bearing by running in. These bronzes have a vari- ety of compositions, but the plasticity is always obtained by the addition of lead, which in turn weakens the bearing. In some cases the lead con- tent is so high, and the tin content so low, that the alloy is not a bronze. These copper-lead alloys have been referred to as red metals. The plas- tic bronze ingot marketed by one large foundry for journal bearings con- tains 65 to 75% copper, 5 to 7 tin, and the balance lead. Semiplastic bronze usually contains above 75% copper and not more than 15 lead. ASTM alloy No. 7 has about 10% lead, 10 tin, 1 zinc, 1 antimony, and 78 copper. The compressive strength is 12,500 lb/in 2 (85 MPa). PLASTIC BRONZE 723 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses PLASTIC LAMINATES. Resin-impregnated paper or fabric, produced under heat and high pressure. Also referred to as high-pressure plastic laminates. Two major categories are decorative thermoset- ting laminates and industrial thermosetting laminates. Most of the decorative thermosetting laminates are a paper base and are known generically as papreg. Decorative laminates are usually com- posed of a combination of phenolic- and melamine-impregnated sheets of paper. The final properties of the laminate are related directly to the properties of the paper from which the laminate is made. Early laminates were designated by trade names, such as Bakelite of Union Carbide, Textolite of General Electric, Micarta of Westinghouse, Phenolite, Condensite, Dilecto, Haveg, Spauldite, and Synthane. Formica, of Formica Corp., designated various types of laminates with a decorative facing layer for such uses as tabletops. Trade names now usually include a number or symbol to describe the type and grade. Textolite, for example, embraces more than 70 categories of laminates subdivided into use-specification grades, all produced in many sizes and thicknesses. Textolite 11711 is an electronic laminate for such uses as multilayer circuit boards. It is made with polyphenylene oxide resin and may have a copper or aluminum cladding. The tensile strength is up to 10,000 lb/in 2 (69 MPa), and the dielectric strength is 400 V/mil (16ϫ10 6 V/m). Phenolyte Y240 is a paper-base laminate bonded with a polyester- modified melamine which gives high dielectric strength and arc resis- tance together with good punching or blanking characteristics in thicknesses up to 0.125 in (0.32 cm). Doryl H17511, of Westinghouse, has glass fabric laminations bonded with a modified phenolic resin based on diphenyl oxide and polyphenyl ether. This laminate has a flexural strength of 27,400 lb/in 2 (184 MPa) at 480°F (249°C). Luxwood, of Formica Corp., for furniture, is a 0.0625-in (0.16-cm) laminate with photographic reproductions of wood grains on the face, while Beautywood is this material in thicker sizes for wall panels. Industrial thermosetting laminates are availabile in the form of sheet, rod, and rolled or molded tubing. Impregnating resins commonly used are phenolic, polyester, melamine, epoxy, and silicone. The base material, or reinforcement, is usually one of the following: paper, woven cotton or linen, asbestos, glass cloth, or glass mat. NEMA (National Electrical Manufacturing Association) has published standards covering over 25 standard grades of these laminates. Each manufacturer, in addition to these, usually produces a range of special grades. Laminating resins may be marketed under one trade name by the resin producer and other names by the molders of the laminate. Paraplex P resins, of Rohm & Haas, for example, comprise a series of polyester solutions in monomeric styrene which can be blended 724 PLASTIC LAMINATES Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses with other resins to give varied qualities. But Panelyte, of St. Regis Paper Co., refers to the laminates which are made with phenolic, melamine, silicone, or other resin, for a variety of applications. PLASTIC POWDER COATINGS. Although many different plastic pow- ders can be applied as coatings, vinyl, epoxy, and nylon are most often used. Vinyl and epoxy provide good corrosion and weather resistance as well as good electrical insulation. Nylon is used chiefly for its out- standing wear and abrasion resistance. Other plastics frequently used in powder coating include chlorinated polyethers, polycarbon- ates, acetals, cellulosics, acrylics, and fluorocarbons. Several different methods have been developed to apply these coat- ings. In the most popular process, fluidized bed, parts are preheated and then immersed in a tank of finely divided plastic powders, which are held in a suspended state by a rising current of air. When the powder particles contact the heated part, they fuse and adhere to the surface, forming a continuous, uniform coating. Another process, electrostatic spraying, works on the principle that oppositely charged materials attract each other. Powder is fed through a gun, which applies an electrostatic charge opposite to that applied to the part to be coated. When the charged particles leave the gun, they are attracted to the part, where they cling until fused together as a plas- tic coating. Other powder application methods include flock and flow coating, flame and plasma spraying, and a cloud-chamber technique. PLASTICS. A major group of materials that are primarily noncrys- talline hydrocarbon substances composed of large molecular chains whose major element is carbon. The three terms—plastics, poly- mers, and resins—are sometimes used interchangeably to identify these materials. However, the term plastics has now come to be the commonly used designation. The first commercial plastic, Celluloid, was developed in 1868 to replace ivory for billiard balls. Phenolic plastics, developed by Baekeland and named Bakelite after him, were introduced around the turn of the twentieth century. A plastic material, as defined by the Society of the Plastics Industry, is “any one of a large group of materials consisting wholly or in part of combinations of carbon with oxygen, hydrogen, nitrogen, and other organic and inorganic elements which, while solid in the finished state, at some stage in its manufacture is made liquid, and thus capable of being formed into various shapes, most usually through the application, either singly or together, of heat and pressure.” There are two basic types of plastics based on intermolecular bond- ing. Thermoplastics, because of little or no cross-bonding between PLASTICS 725 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses molecules, soften when heated and harden when cooled, no matter how often the process is repeated. Thermosets, on the other hand, have strong intermolecular bonding. Therefore, once the plastic is set into permanent shape under heat and pressure, reheating will not soften it. Within these major classes, plastics are commonly classified on the basis of base monomers. There are over two dozen such monomer families or groups. Plastics are also sometimes classified roughly into three stiffness categories: rigid, flexible, and elastic. Another method of classification is by the “level” of performance or the general area of application, using such categories as engineering, general-purpose, and specialty plastics, or the two broad categories of engineering and commodity plastics. In general, plastics are lightweight, are dielectric, and provide low thermal conductivity. They are resistant to many environments, have low softening temperatures, and can be formed into complex shapes. They are also viscoelastic—that is, after an applied load is removed, plastics tend to continue to exhibit strain or deformation with time. Plastics can be built of one, two, or even three different monomers, and are termed homopolymers, copolymers, and terpolymers, respectively. Their geometric form can be linear or branched. Linear or unbranched polymers are composed of monomers linked end to end to form a molecular chain that is like a simple string of beads or a piece of spaghetti. Branched polymers have side chains of molecules attached to the main linear polymer. These branches can be composed either of the basic linear monomer or of a different one. If the side molecules are arranged randomly, the polymer is atactic; if they branch out on one side of the linear chain in the same plane, the poly- mer is isotactic; and if they alternate from one side to the other, the polymer is syndiotactic. Plastics are produced in a variety of different forms. Most common are plastic moldings, which range in size from less than 1 in to several feet (2 cm to several meters). Thermoplastics, such as polyvinylchloride and polyethylene, are widely used in the form of plastic film and plas- tic sheeting. The term film is used for thicknesses up to and including 10 mils (0.25 cm), while sheeting refers to thicknesses over that. Rigid- rod polymers are high-performance thermoplastics characterized by long, stiff molecules and high strength and stiffness. Until the 1992 development by Maxdem Inc. of injection and compression moldable and extrudable Poly-X grades, they could only be spun into fibers or cast as film from acid solutions. The moldable grades, described as substituted chains of benezene rings called polyparaphenylene, have tensile moduli of 0.9 ϫ 10 6 lb/in 2 to 2.6 ϫ 10 6 lb/in 2 (6,205 to 17,927 MPa). Potential uses include printed-circuit boards, electronic connectors, scratch-resis- tant windows, lenses, bearings, bushings, and valves. 726 PLASTICS Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses Both thermosetting and thermoplastic materials are used as plas- tic coatings on metal, wood, paper, fabric, leather, glass, concrete, ceramics, or other plastics. There are many coating processes, includ- ing knife or spread coating, spraying, roller coating, dipping, brush- ing, calendering, and the fluidized-bed process. Thermosetting plastics are used in high-pressure laminates to hold together the reinforcing materials that comprise the body of the finished product. The reinforcing materials may be cloth, paper, wood, or glass fibers. The end product may be plain, flat sheets, or decorative sheets as in countertops, rods, tubes, or formed shapes. PLASTICS ADDITIVES. Almost all plastics contain one or more addi- tive materials to improve their physical properties and processing characteristics or to reduce costs. There are a wide range of additives for use with plastics, including antimicrobials, antistatic agents, clar- ifiers, colorants, fillers, flame retardants, foaming agents, heat stabi- lizers, impact modifiers, light stabilizers, lubricants, mold-release agents, odorants, plasticizers, reinforcements, and smoke retardants. Fillers are probably the most common of the additives. They are usually used to either provide bulk or modify certain properties. Generally, they are inert and thus do not react chemically with the resin during processing. The fillers are often cheap and serve to reduce costs by increasing bulk. For example, wood flour, a common low-cost filler, sometimes makes up 50% of a plastic compound. Other typical fillers are chopped fabrics, asbestos, calcium carbonate, talc, gypsum, and milled glass. Besides lowering costs, fillers can improve properties. For example, asbestos increases heat resistance, and cotton fibers improve toughness. Plasticizers are added to plastics compounds either to improve flow during processing by reducing the glass transition temperature or to improve properties such as flexibility. Plasticizers are usually liquids that have high boiling points. Polyvinyl chloride accounts for about 80%, but phthalates and polyesters are also used. Stabilizers are added to plastics to help prevent breakdown or deterioration during molding or when the polymer is exposed to sunlight, heat, oxygen, ozone, or combinations of these. Thus there are a wide range of compounds, each designated for a specific function. Stabilizers can be metal compounds, based on tin, lead, cadmium, barium, and others. And phenols and amines are added antioxidants that protect the plastic by diverting the oxidation reactions to them- selves. The trend, however, is away from toxic lead and cadmium for environmental reasons. For heat stabilizers, the lead can be diluted by adding calcium-zinc compounds. These compounds are intended mainly for use with polyvinyl chloride for window profiles and pipe. PLASTICS ADDITIVES 727 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses Some are also alternatives for barium-zinc compounds, which are alternatives for cadmium heat stabilizers. Catalysts, by controlling the rate and extent of the polymerization process in the resin, allow the curing cycle to be tailored to the pro- cessing requirements of the application. Catalysts also affect the shelf life of the plastics. Both metallic and organic chemical compounds are used as catalysts. Colorants, added to plastics for decorative pur- poses, come in a wide variety of pigments and dyestuffs. Colorants have been metal-base pigments such as cadmium, lead, and selenium, but here, too, environmental concerns have led to a trend away from these metals. More recently, liquid colorants, composed of dispersions of pigments in a liquid, have been developed. Titanium dioxide, the most common pigment, is usually surface treated (coated) to aid dis- persion in processing and reduce power in mixing. Alumina is the most common coating; silica and zirconia are also used. Organic coat- ings include polyols, the most common, plus amines, siloxanes, and phosphated fatty acids. Clarifiers are used to impart clarity to plastics for packaging and other applications. Sorbitol, for example, is used for polypropylene in food packaging and other uses. Coupling agents based on organometallic titanates, zirconates, and aluminates bond to the sur- face of glass, carbon, aramid, and other reinforcements for plastics, making them more dispersible. Silane coupling agents, for example, are used for both thermosets and thermoplastics. Flame retardants are added to plastic products that must meet fire-retardant require- ments, because polymer resins are generally flammable, except for such notable exceptions as polyvinyl chloride. In general, the function of fire retardants is limited to the spread of fire. They do not normally increase heat resistance or prevent the plastic from charring or melt- ing. Some fire-retardant additives include compounds containing chlorine or bromine, phosphate-ester compounds, antimony thrioxide, alumina trihydrate, magnesium hydroxide, ammonium phosphates and melamine amyl phosphate, and zinc borate. Halogen compounds have long dominated but have lost favor in recent years due to con- cern over generating toxic combustion products, such as bromides, hydrochloric acid, and brominated dioxins and furans, on burning. Thus, the use of halogens has been reduced (the most widely used having contained as much as 80%) or eliminated. Reinforcement materials in plastics are not normally considered additives. Usually in fiber or mat form, they are used primarily to improve mechanical properties, particularly strength. Although asbestos and some other materials are used, glass fibers are the pre- dominant reinforcement for plastics. 728 PLASTICS ADDITIVES Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses PLATINUM. A whitish-gray metal, symbol Pt. It is more ductile than silver, gold, or copper and is heavier than gold. The melting point is 3217°F (1769°C), and the specific gravity is 21.45. The Brinell hard- ness of the annealed metal is 45, and its tensile strength is 17,000 lb/in 2 (117 MPa); when hard-rolled, the Brinell hardness is 97 and tensile strength 34,000 lb/in 2 (234 MPa). Electrical conductivity is about 16% that of copper. The metal has a face-centered-cubic lattice structure, and it is very ductile and malleable. It is resistant to acids and alkalies, but dissolves in aqua regia. Platinum is widely used in jewelry, but because of its heat resistance and chemical resistance it is also valued for electrical contacts and resistance wire, thermocou- ples, standard weights, and laboratory dishes. Generally too soft for use alone, it is almost always alloyed with harder metals of the same group, such as osmium, rhodium, and iridium. An important use of the metal, in the form of gauze, is as a catalyst. Platinum gauze is of high purity in standard meshes of 45 to 80 per inch (18 to 31 per centimeter), with wire from 0.0078 to 0.003 in (0.020 to 0.008 cm) in diameter. Dental foil is 99.99% pure and of maximum softness. Platinum foil for other uses is made as thin as 0.0002 in (0.0005 cm). Platinum powder comes in fine submesh particle size. It is made by chemical reduction and is at least 99.9% pure, with amor- phous particles 12 to 138 ␮in (0.3 to 3.5␮m) in diameter. Atomized powder has spherical particles of 50 to 200 mesh, and is 99.9% pure and free-flowing. Platinum flake has the powder particles in the form of tiny laminar platelets which overlap in the coating film. The particles in Platinum flake No. 22 have an average diameter of 118 ␮in (3 ␮m) and thickness of 3.9 ␮in (0.1 ␮m). Because of the high resistance of the metal to atmospheric corro- sion even in sulfur environments, platinum coatings are used on springs and other functioning parts of instruments and electronic devices where precise operation is essential. Electroplating may be done with an electrolyte bath of platinum dichloride, PtCl 2 , or platinum tetrachloride, PtCl 4 . Hard plates may be produced with an alkaline bath of platinum diamine nitrite, Pt(NH 3 ) 2 (NO 2 ) 2 . Coatings are also produced by vapor deposition of platinum com- pounds; thin coatings, 0.0002 in (0.0005 cm) or less, are made by painting the surface with a solution of platinum powder in an organic vehicle and then firing to drive off the organic material, leaving an adherent coating of platinum metal. Platinum occurs in small, flat grains or in pebbles usually in alluvial sands, and the native metal generally contains other metals of the plat- inum group. The largest nugget ever found came from South America and weighed 2 lb (0.9 kg). The chief sources of the metal are Russia and Colombia, with smaller amounts from Alaska, Canada, and South Africa. PLATINUM 729 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses [...]... Teijin Chemical Lexan F-8000 is a polycarbonate sheet that can be laminated with polyvinyl fluoride film, such as Du Pont’s Tedlar, and thermoformed Among other applications, it is intended for aircraft cabin windows Lexan Nu-View is a glazing laminate intended to keep mass-transit windows free of graffiti It comprises Lexan MR5 sheet with a 0 .1 0- in (2.54-mm )- thick abrasion-resistant film on either... wear-resistant and have high melting points A platinum-rhenium alloy with 10% rhenium has an electrical conductivity of only 5.5% that of copper compared with 16% for pure platinum Its melting point is 3362°F (1850°C), and the Rockwell T hardness of the cold-rolled metal is 91 compared with 78 for cold-rolled platinum Platinum-ruthenium alloy, with 10% ruthenium, has a PLATINUM ALLOYS Downloaded from... containers, automotive, materials handling, consumer products, medical, wire and cable insulation, furniture, housewares, toys, and novelties Quantum Chemical’s carbon-black-filled Petrothene PR92941 LLDPE permits laserprinting, which is more durable than traditional ink-jet printing Glidestar compounds, from EM Corp for oil-filled, self-lubricated products, include the polyethylene-based 400 Series The... processing High-molecular-weight low-density polyethylene resins are used to extrude high-clarity, tough film used in shrink packaging and for making heavy-duty bags High-molecular-weight high-density polyethylene resins (MW 200,000 to 500,000) have excellent environmental stress cracking resistance, toughness, high moisture barrier properties, and high strength and stiffness The HMW-HDPE resins are used in... thermal expansion It is intended for producing hot-pressed shapes Biaxially oriented polypropylene (BOPP) film (film stretched in two ways) has greatly improved moisture resistance, clarity, and stiffness It is used for packaging tobacco products, snack foods, baked goods, and pharmaceuticals Metallized grades also are available for packaging designed for extended shelf life Foamed polypropylene includes... widely used for consumer products The impact grades and glass-filled types are used quite widely for engineering parts and semistructural applications Because of good processing characteristics, polystyrenes are produced in a wide range of forms They can be extruded; injection-, compression-, and blow-molded; and thermoformed They are also available as film sheet and foam Polystyrenes can be divided into... flexural modulus 2.1 ϫ 106 lb/in2 (14,480 MPa), heat-deflection temperature 549°F (287°C), and impact strength 2.5 ft и lb/in (133 J/m) Thermocomp UF -1 00 6, of LNP Engineering Plastics, is a 30% glass-reinforced grade based on Amodel Its continuous-use temperature is 545°F (285°C) versus 480°F (249°C) for similarly reinforced Nylon 6/6 RTP Co makes a line of lubricated compounds based on PPA for gears... to 100 0% and more They are intended to replace plasticized polyvinyl chloride in autoclavable health care products and other plastics in extruded profiles and injection-molded parts Petrothene random copolymers from Quantum Chemical are based on BASF’s gas-phase polymerization process and markedly increase optical quality and, having melt flow rates (MFRs) up to 0.0075 lb/min (34 g /10 min), speed cycle... J/m) notched Izod impact strength, and 2% optical haze Foamed polystyrene is used in many forms, including extruded sheet (which is then thermoformed, e .g., egg cartons, trays); expandable polystyrene (EPS) beads, which contain a blow agent (usually pentane) and which are processed into low-density [0.7 to 10 lb/ft3 (11 to 160 kg/m3)] foamed products, such as hot and cold drink cups and Downloaded from... resins can be injection-molded, extruded, and blow-molded, and sheet can be thermoformed These resins also are blended with other engineering thermoplastics and reinforcements POLYARYLATES POLYARYLENE ETHER BENZIMIDAZOLES PAEBI polymers, developed at NASA-Langley in 1991, combine high-gloss transition temperature and optical transmission with inherent resistance to high-energy particles, especially . each other. Powder is fed through a gun, which applies an electrostatic charge opposite to that applied to the part to be coated. When the charged particles leave the gun, they are attracted. cat- alyst. This approach eliminates the need for toxic phosgene gas with BPA dissolved in an excess of the chloride. The molecular structure is in double-linked zigzag chains that give high rigidity a paper-base laminate bonded with a polyester- modified melamine which gives high dielectric strength and arc resis- tance together with good punching or blanking characteristics in thicknesses