|
|
马上注册，结交更多热工坛友，更多精彩内容等着您！
您需要 登录 才可以下载或查看，没有帐号？免费注册
x
【丛书名】：Materials Handbook,15 Ed
【作 者】：John A. Vaccari
【装帧项】：Hardcover，P1115
【语言】: English
【出版项】：McGraw-Hill, Inc. 2002 Year
【ISBN号】：0-07-136-076-X, ISBN-13: 978-0071360760
【原书定价】：104.95$
Source: Materials Handbook
Part
1
Materials, Their Properties and Uses
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
2
ABLATIVES
ABLATIVES. Materials used for the outward dissipation of extreme-
ly high heats by mass removal. Their most common use is as an external heat shield to protect supersonic aerospace vehicles from an excessive buildup of heat caused by air friction at the surface. The ablative material must have a low thermal conductivity in order that the heat may remain concentrated in the thin surface layer. As the surface of the ablator melts or sublimes, it is wiped away by the frictional forces that simultaneously heat newly exposed surfaces. The heat is carried off with the material removed. The less material that is lost, the more efficient is the ablative material. The ablative material also should have a high thermal capacity in the solid, liquid, and gaseous states; a high heat of fusion and evaporation; and a high heat of dissociation of its vapors. The ablative agent, or ablator, is usually a carbonaceous organic compound, such as a phenolic plastic. As the dissociation products are lost as liquid or vapor, the char is held in place by the refractory reinforcing fibers, still giving a measure of heat resistance. The effective life of an ablative is short, calculated in seconds per millimeter of thickness for the distance traveled in the atmosphere. Single ablative materials seldom have all the desirable factors, and thus composites are used. Phenolic or epoxy resins are reinforced with asbestos fabric, carbonized cloth, or refractory fibers, such as asbestos, fused silica, and glass. The refractory fibers not only are incorporated for mechanical strength, but also have a function in the ablative process, and surface-active agents may be added to speed the rate of evaporation. Another composite, polyarylacetylene (PAA) reinforced with carbon fiber fabric, proved superior to carbon-reinforced phenolic in tests to develop an alternative ablative and insulative material for nozzle components of solid rocket motors. Favoring the PAA is its high (90%) char yield, lower weight loss and erosion, greater moisture resistance, and more stable ablation. Ablative paint, for protecting woodwork, may be organic silicones which convert to silica at temperatures above 2000°F (1093°C). Metals can resist temperatures higher than their melting point by convection cooling, or thermal cooling, which is heat protection by heat exchange with a coolant. Thus, tungsten can be arc-melted in a copper kettle which is cooled by circulating water. The container metal must have high thermal conductivity, and the heat must be quickly carried away and stored or dissipated. When convection cooling is difficult or not possible, cooling may be accomplished by a heat sink. Heat-sink cooling depends on the heat absorption capability of the structural material itself or backed up by another material of higher heat absorption. Copper, beryllium, graphite, and beryllium oxide have been used. A heat-sink material should have high thermal
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
ABRASIVES
3
conductivity, high specific heat and melting point, and for aerodynamic applications, a low specific gravity.
ABRASIVES. Materials used for surfacing and finishing metals, stone,
wood, glass, and other materials by abrasive action. The natural abrasives include the diamond, emery, corundum, sand, crushed garnet and quartz, tripoli, and pumice. Artificial abrasives, or manufactured abrasives, are generally superior in uniformity to natural abrasives, and are mostly silicon carbide, aluminum oxide, boron carbide, or boron nitride, marketed under trade names. Artificial diamonds are also now being produced. The massive natural abrasives, such as sandstone, are cut into grinding wheels from the natural block, but most abrasive material is used as grains or built into artificial shapes. For industrial grinding, artificial abrasives are preferred to natural abrasives because of their greater uniformity. Grading is important because uniform grinding requires grains of the same size. The abrasive grains are used as a grinding powder; are made into wheels, blocks, or stones; or are bonded to paper or cloth. Abrasive cloth is made of cotton jean or drills to close tolerances of yarns and weaves, and the grains are attached with glue or resin. But the Fabricut cloth of 3M is an open-weave fabric with alumina or silicon-carbide grains of 100 to 400 mesh. The open weave permits easy cleaning of the cloth in an air blast. Abrasive paper has the grains, usually aluminum oxide or silicon carbide, glued to one side of 40- to 130-lb kraft paper. The usual grain sizes are No. 16 to No. 500. Abrasive powder is usually graded in sizes from 8 to 240 mesh. Coarse grain is to 24 mesh; fine grain is 150 to 240. Blasting abrasive for blast cleaning of metal castings is usually coarse grain. Arrowblast, of Norton Co., is aluminum oxide with grain sizes from 16 to 80 mesh. Grinding flour consists of extremely fine grains separated by flotation, usually in grain sizes from 280 to 600 mesh, used for grinding glass and fine polishing. Levigated abrasives are fine powders for final burnishing of metals or for metallographic polishing, usually processed to make them chemically neutral. Green rouge is levigated chromic oxide, and mild polish may be levigated tin oxide; both are used for burnishing soft metals. Polishing powder may be aluminum oxide or metal oxide powders of ultrafine particle size down to 600 mesh. Micria AD, of Monsanto Co., is alumina; Micria ZR is zirconia; and Micria TIS is titania. Gamal, of Fisher Scientific Co., is a fine aluminum oxide powder, the smaller cubes being 59 in (1.5 m), with smaller particles 20 in (0.5 m). Cerox is cerium oxide used to polish optical lenses and automobile windshields. It cuts fast and gives a smooth surface. Grinding compounds for valve grinding are usually aluminum oxide in oil.
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
4
ABRASIVES
Mild abrasives, used in silver polishes and window-cleaning compounds, such as chalk and talc, have a Mohs hardness of 1 to 2. The milder abrasives for dental pastes and powders may be precipitated calcium carbonate, tricalcium phosphate, or combinations of sodium metaphosphate and tricalcium phosphate. Abrasives for metal polishes may also be pumice, diatomite, silica flour, tripoli, whiting, kaolin, tin oxide, or fuller’s earth. This type of fine abrasive must be of very uniform grain in order to prevent scratching. Cuttle bone, or cuttlefish bone, is a calcareous powder made from the internal shell of a Mediterranean marine mollusk of the genus Sepia, and it is used as a fine polishing material for jewelry and in tooth powders. Ground glass is regularly marketed as an abrasive for use in scouring compounds and in match-head compositions. Lapping abrasives, for finish grinding of hard materials, are diamond dust or boron carbide powder. Aluminum oxide wheels are used for grinding materials of high tensile strength. Silicon carbide is harder but is not as strong as aluminum oxide. It is used for grinding metals that have dense grain structure and for stone. Vitrified wheels are made by molding under heat and pressure. They are used for general and precision grinding where the wheel does not exceed a speed of 6,500 surface ft/min (33 m/s). The rigidity gives high precision, and the porosity and strength of bond permit high stock removal. Silicate wheels have a silicate binder and are baked. The silicate bond releases the grains more easily than the vitrified, and is used for grinding edge tools to reduce burning of the tool. Synthetic resins are used for bonding where greater strength is required than is obtained with the silicate, but less openness than with the vitrified. Resinoid bonds are used up to 16,000 surface ft/min (81 m/s), and are used especially for thread grinding and cutoff wheels. Shellac binder is used for light work and for high finishing. Rubber is used for precision grinding and for centerless-feed machines. 3M’s Trizact abrasives are microreplicating aluminum oxide or silicon carbide pyramid-like grains on flexible polyester cloth or film. Continued use keeps exposing fresh cutting grains. Grading of abrasive wheels is by grit size number from No. 10 to No. 600, which is 600 mesh; by grade of wheel, or strength of the bond, which is by letter designation, increasing in hardness from A to Z; and by grain spacing or structure number. The ideal condition is with a bond strong enough to hold the grains to accomplish the desired result and then to release them before they become too dull. Essential qualities in the abrasive grain are penetration hardness, body strength sufficient to resist fracture until the points dull and then break to present a new edge, and an attrition resistance suitable to the work. Some wheels are made with a porous honeycombed strucDownloaded 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
ABS PLASTICS
5
ture to give free cutting and cooler operation on some types of metal grinding. Some diamond wheels are made with aluminum powder mixed with a thermosetting resin, and the diamond abrasive mix is hot-pressed around this core wheel. Norton diamond wheels are of three types: metal bonded by powder metallurgy, resinoid bonded, and vitrified bonded.
ABRASIVE SAND. Any sand used for abrasive and grinding purposes,
but the term does not include the sharp grains obtained by crushing quartz and used for sandpaper. The chief types of abrasive sand include sandblast sand, glass-grinding sand, and stone-cutting sand. Sand for stone sawing and for marble and glass grinding is usually ungraded, with no preparation other than screening, but it must have tough, uniform grains. Chats are sand tailings from the Missouri lead ores, used for sawing stone. Banding sand is used for the band grinding of tool handles and for the grinding of plate glass, but is often replaced by artificial abrasives. Banding-sand grains are fine, 95% being retained on a 150-mesh screen. Burnishing sand, for metal polishing, is a fine-grain silica sand with rounded grains. It should pass a 65-mesh screen, and be retained on a 100-mesh screen.
ABS PLASTICS. The letters ABS identify the family of acrylonitrile-
butadiene-styrene. Common trade names for these materials are Cycolac, Magnum, and Lustran. They generally are opaque and distinguished by a good balance of properties, including high impact strength, rigidity, and hardness over a temperature range of 40 to 230°F ( 40 to 110°C). Compared to other structural or engineering plastics, they are generally considered to fall at the lower end of the scale. Medium impact grades are hard, rigid, and tough and are used for appearance parts that require high strength, good fatigue resistance, and surface hardness and gloss. High impact grades are formulated for similar products where additional impact strength is gained at some sacrifice in rigidity and hardness. Low-temperature impact grades have high impact strength down to 40°F ( 40°C). Again, some sacrifice is made in strength, rigidity, and heat resistance. Heatresistant, high-strength grades provide the best heat resistance— continuous use up to about 200°F (93°C), and a 264 lb/in2 (1.8 MPa) heat deflection temperature of around 215°F (102°C). Impact strength is about comparable to that of medium impact grades, but strength, modulus of elasticity, and hardness are higher. At stresses above their tensile strength, ABS plastics usually yield plastically instead of rupturing, and impact failures are ductile. Because of relatively low creep, they have good long-term load-carrying ability. This low creep plus low water absorption and relatively high heat resistance provide ABS plastics with good dimensional stability. Transparent grades are
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
6
ACAROID RESIN
available. ABS plastics are readily processed by extrusion, injection molding, blow molding, calendering, and vacuum forming. Resins have been developed especially for cold forming or stamping from extruded sheet. Typical applications are helmets, refrigerator liners, luggage tote trays, housings, grills for hot air systems, and pump impellers. Extruded shapes include tubing and pipe. ABS plated parts are now in wide use, replacing metal parts in the automotive and appliance field Lustran 266 Mediclear, from Monsanto, offers better than usual clarity with toughness and chemical resistance. Modified with methyl methacrylate, it has excellent gloss and haze values while providing an Izod impact strength of 3.25 ft.lb/in (173 J/m) for 0.125 in (3.175 mm) thickness. Of interest for medical applications, it can be sterilized by gamma radiation with little color loss. Lustran 752, from Bayer Corp., is a high-gloss, tough ABS with low color to ease coloring with ABS color concentrates. The density is 0.038 lb/in3 (1.04 g/cm3) and, at 73°F (23°C), it has a tensile strength at yield of 5100 lb/in 2 (35.2 MPa), tensile and flexural moduli of 270,000 lb/in2 (1.9 GPa), and a notched Izod impact strength of 6.3 ft.lb/in (336 J/m) for 0.125 in. thickness. Cycolac Magix, a metallicflake ABS from General Electric Plastics, can provide a variety of colors and surface effects: the high gloss of a marble surface; the shadow, light, and 3D visual effect of granite; the look of gun metal; and the glitter of quartz or gold dust.
ACAROID RESIN.
A gum resin from the base of the tufted trunk leaves of various species of Xanthorrhoea trees of Australia and Tasmania. It is also called gum accroides and yacca gum. Yellow acaroid from the X. tateana is relatively scarce, but a gum of the yellow class comes from the tree X. preissii of western Australia, and is in small hollow pieces yellow to reddish. It is known as black boy resin, the name coming from the appearance of the tree. Red acaroid, known also as red gum and grass tree gum, comes in small dusty pieces of reddish brown. This variety is from the X. australis and about 15 other species of the tree of southeastern Australia. The resins contain 80 to 85% resinotannol with coumaric acid, which is a hydroxycinnamic acid, and they also contain free cinnamic acid. They are thus closely related chemically to the balsams. Acaroid resin has the property unique among natural resins of capacity for thermosetting to a hard, insoluble, chemical-resistant film. By treatment with nitric acid it yields picric acid; by treatment with sulfuric acid it yields fast brown to black dyes. The resins are soluble in alcohols and in aniline, only slightly soluble in chlorinated compounds, and insoluble in coal-tar hydrocarbons. Acaroid has some of the physical characteristics of shellac, but is difficult to bleach. It is used for spirit varnishes and metal lacquers, in coatings, in paper sizing, in
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
ACETAL RESINS.
7
inks and sealing waxes, in binders, for blending with shellac, in production of picric acid, and in medicine. Highly crystalline resins that have the repeating group (OCH2)x. The resins are polyformaldehyde. The natural acetal resin is translucent white and can be readily colored. There are two basic types: a homopolymer, such a Du Pont’s Delrin, and a copolymer, such as Hoechst Celanese’s Celcon. In general, the homopolymers are harder and more rigid and have higher tensile, flexural, and fatigue strengths, but lower elongation. The copolymers are more stable in long-term high-temperature service and have better resistance to hot water. Glass-filled acetals provide greater strength and stiffness, and tetrafluoroethylene (TFE)-filled acetals provide low friction and high wear resistance. The 500 Series of Glidestar, from EM Corp., consists of acetal-based selflubricating (oil or TFE) compounds. Acetals are among the strongest and stiffest of the thermoplastics. Their tensile strength ranges from 8,000 to about 13,000 lb/in2 (55 to 89 MPa), the tensile modulus of elasticity is about 500,000 lb/in2 (3,445 MPa), and fatigue strength at room temperature is about 5,000 lb/in2 (34 MPa). Their excellent creep resistance and low moisture absorption (less than 0.4%) give them excellent dimensional stability. They are useful for continuous service up to about 220°F (104°C). Acetals’ low friction and high abrasion resistance, though not as good as nylon’s, rates them high among thermoplastics. Their impact resistance is good and remains almost constant over a wide temperature range. Acetals are attacked by some acids and bases, but have excellent resistance to all common solvents. They are processed mainly by molding or extruding. Some parts are also made by blow and rotational molding. Typical parts and products made of acetal include pump impellers, conveyor links, drive sprockets, automobile instrument clusters, spinning reel housings, gear valve components, bearings, and other machine parts. Acetal homopolymers are used for mechanical and electrical parts. They have a specific gravity of 1.425, a tensile strength of 10,000 lb/in2 (69 MPa), 15% elongation, a dielectric strength of 500 V/mil (19.6 106 V/m), and Rockwell hardness M94. They retain their mechanical strength close to the melting point of 347°F (175°C). Acetal copolymers are thermoplastic linear acetal resins produced from trioxane, which is a cyclic form of formaldehyde. The specific gravity is 1.410, flexural strength 12,000 lb/in2 (83 MPa), Rockwell hardness M76, and dielectric strength 1,200 V/mil (47 106 V/m). It comes in translucent white pellets for molding. Tenac SH, a homopolymer from Asahi Chemical, uses a Nylon 3 heat stabilizer to enhance processibility but retains the thermal stability and mechanical properties of the standard homopolymer.
ACETAL RESINS.
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
8
ACETIC ACID
ACETIC ACID. Also known as ethanoic acid. A colorless, corrosive liq-
uid of pungent odor and composition CH3 COOH, having a wide variety of industrial uses as a reagent, solvent, and esterifier. A carboxylic acid, it is employed as a weak acid for etching and for soldering; in stain removers and bleaches; as a preservative; in photographic chemicals; for the manufacture of cellulose acetate and vinyl acetate; as a solvent for essential oils, resins, and gums; as a precipitant for latex; in tanning leather; and in making artificial flavors. Acetic acid is found in the juices of many fruits and in combination in the stems or woody parts of plants. It is the active principle in vinegar, giving it the characteristic sour taste, acid flavor, and pungent odor. It is made commercially by oxidation of acetaldehyde (in the presence of manganese, cobalt, or copper acetate), butane, or naphtha. Its specific gravity is 1.049, its boiling point is 244°F (118°C), and it becomes a colorless solid below 61.9°F (16.6°C). The pure 99.9% solid is known as glacial acetic acid. Standard and laundry special grades contain 99.5% acid, with water the chief impurity. Standard strengths of water solution are 28, 56, 70, 80, 85, and 90%. Acetic anhydride, CH3COOCOCH3, a colorless liquid with boiling point 283°F (139.5°C), is a powerful acetylating agent and is used in making cellulose acetate. It forms acetic acid when water is added. Hydroxyacetic acid, HOCH2COOH, or glycolic acid, is produced by oxidizing glycol with dilute nitric acid and is intermediate in strength between acetic and formic acids. It is soluble in water, is nontoxic, and is used in foodstuffs, dyeing, tanning, electropolishing, and resins. Its esters are solvents for resins. Diglycolic acid, O(CH2CO2H)2, is a white solid melting at 298°F (148°C). It is stronger than tartaric and formic acids and is used for making resins and plasticizers. Thioacetic acid has the formula of acetamide but with HS replacing the NH2. It is a pungent liquid used for making esters for synthetic resins. Chloroacetic acid, CH2ClCOOH, is a white crystalline powder melting at 143°F (61.6°C) and boiling at 372°F (189°C). It is used for producing carboxymethylcellulose, dyes, and drugs. Sequestrene, used as a clarifying agent and water softener in soaps and detergents, and to prevent rancidity in foods and sulfonated oils, is ethylene bisaminodiacetic acid, (HOOCCH2)2-NCH2CH2N(CH2COOH)2. It is a liquid, but in the form of its sodium salt is a water-soluble white powder. Trifluoroacetic acid, CF3COOH, is one of the strongest organic acids. It is a colorless, corrosive liquid, boiling at 160°F (71.1°C) and freezing at 4.5°F ( 15.3°C). It is used in the manufacture of plastics, dyes, pharmaceuticals, and flame-resistant compounds. Paracetic acid, CH3 O COOH, is a colorless liquid of strong odor with the same solubility as acetic acid. It has 8.6% available
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
ACETONE
9
oxygen and is used as a bleaching agent, a polymerization catalyst, for making epoxy resins, and as a bactericide. Acetin is an ester of acetic acid made from glycerin and acetic acid, used as a solvent for basic dyes and tannins. It is a neutral straw-colored liquid of specific gravity 1.20 and boiling point 271 to 307°F (133 to 153°C). It is also used in low-freezing dynamites and smokeless powder. The triacetic ester, triacetin, is a water-white liquid of specific gravity 1.16 and flash point 271°F (133°C), soluble in aromatic hydrocarbons. It is used as a plasticizer and in propellants. Phenylacetic acid, C6H5CH2COOH, is a white flaky solid melting at 166°F (74.5°C). The reactive methylene group makes it useful for the manufacture of fine chemicals. Cyanoacetic acid, CN CH2 COOH, has an active methylene group and an easily oxidized cyano group, and is used for producing caffeine, while the derivative ethyl cyanoacetate, NC CH2COO CH2 CH3, a liquid boiling at 405°F (207°C), is used for making many drugs. Malonic acid, CH2(COOH)2, or propanedioic acid, is a very reactive acid sometimes used instead of acetic acid for making plastics, drugs, and perfumes. It decomposes at 320°F (160°C), yielding acetic acid and carbon dioxide. Methyl acetic acid, CH3CH2COOH, is propionic acid or propanoic acid, a by-product in the extraction of potash from kelp. Modifications of this acid are used for cross-linking plastics.
ACETONE. An important industrial solvent, used in the manufacture
of lacquers, plastics, smokeless powder; for dewaxing lubricating oils; for dissolving acetylene for storage; for dyeing cotton with aniline black; and as a raw material in the manufacture of other chemicals. It is a colorless, flammable liquid with a mintlike odor and is soluble in water and in ether. The composition is CH3 CO CH3, specific gravity 0.790, boiling point 133°F (56°C), and solidification point 137°F ( 94°C). Acetone is mainly produced as a by-product in the cleavage of cumene hydroperoxide into phenol. A secondary route is by catalytic dehydrogenation of isopropyl alcohol. Diacetone, or diacetone alcohol, is a colorless liquid of composition CH3 CO CH2 COH(CH3)2 with a pleasant odor. It is used as a solvent for nitrocellulose and cellulose acetate, for gums and resins, in lacquers and thinners, and in ink, paint, and varnish removers. Because of its low freezing point and miscibility with castor oil it is used in hydraulic brake fluids. The specific gravity is 0.938, boiling point 331°F (166°C), and freezing point 65°F ( 54°C). Synthetic methyl acetone is a mixture of about 50% acetone, 30 methyl acetate, and 20 methanol, used in lacquers, paint removers, and for coagulating latex. Dihydroxyacetone, a colorless crystalline solid produced from glycerine by sorbose bacteria
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
10
ACETYLENE
reaction, is used in cosmetics, and in preparing foodstuff emulsions, plasticizers, and alkyd resins. It is soluble in water and in alcohol.
ACETYLENE.
A colorless gas of the composition HC CH, used for welding and flame cutting of metals and for producing other chemicals. It contains 92.3% carbon and is therefore nearly gaseous carbon. When pure, it has a sweet odor, but when it contains hydrogen sulfide as an impurity, it has a disagreeable odor. Acetylene burns brightly in air, and was widely used for theater stage lighting before the advent of electric light. When mixed with oxygen as oxyacetylene for flame cutting and welding, it gives a temperature of 6332°F (3500°C). In air it is an explosive gas. The maximum explosive effect is with a mixture of 7.7% gas and 92.3% air. Acetylene has a specific gravity of 0.92. It is nontoxic and is soluble in water, alcohol, or acetone. It liquefies under a pressure of 700 lb/in2 (4.8 MPa) at 70°F (21°C). It is easily generated by the action of water on calcium carbide, but the newest methods involve pyrolysis, or cracking, of hydrocarbons, principally methane. It is also recovered from ethylene feedstock prior to polymerization. About 80% of acetylene usage is for synthesis of industrial chemicals, such as vinyl chloride, vinyl acetate, acrylonitrile, polyvinylpyrrolidone, trichloroethylene, and acetic acid. Acetylenic alcohols and diols include propargyl alcohol, butynediol, butenediol, butanediol, and butyrolacetone; these are used in metal pickling and plating and for making agricultural chemicals, polyesters, and vinyl esters. It is marketed compressed in cylinders, dissolved in acetone to make it nonexplosive. One volume of acetone will dissolve 25 volumes of acetylene at atmospheric pressure, or 250 volumes at 10 atm (10.3 kg/cm2). Prest-O-Lite is a trade name of Union Carbide Corp. for acetylene dissolved in acetone. Acetylene snow, or solid acetylene, is produced by cooling acetylene below the melting point and compressing. It is insensible to shock and flame and is thus easier to transport. A replacement for acetylene for producing plastics is methyl acetylene propadiene, which contains 70% methyl acetylene and 30 of the isomer propadiene. It has the reactions of both acetylene and its isomer. Mapp, of Dow Chemical Co., for metal cutting, is methyl acetylene, CH:C CH3. It is safer to handle and gives about the same flame temperature.
ACRYLIC RESINS.
Colorless, highly transparent, thermoplastic, synthetic resins made by the polymerization of acrylic derivatives, chiefly from the esters of acrylic acid, CH2:CH COOH, and methacrylic acid, CH2:C(CH3) COOH, ethyl acrylate and methyl acrylate. Glacial acrylic acid is the anhydrous monomer with less than 2% moisture. It can be esterified directly with an alcohol. Vinyl acrylic
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
ACRYLIC RESINS
11
acid, CH2:CHCH:CHCOOH, with a melting point of 80°C, is made from acrolein and malonic acid. It polymerizes on heating. The resins vary from soft, sticky semisolids to hard, brittle solids, depending upon the constitution of the monomers and upon the polymerization. They are used for adhesives, protective coatings, finishes, laminated glass, transparent structural sheet, and molded products. Acrylic resins, or acrylate resins, are stable and resistant to chemicals. They do not cloud or fade in light when used as laminating material in glass and are used as air-curing adhesives to seal glass to metals or wood. Water-based acrylics are used for the formulation of caulks and sealants. They have better adhesion and weather resistance than butyl rubbers and dry more quickly. The sealants usually contain about 80% solids. A hydrogel sealant of acrylates and water, developed at Germany’s Fraunhofer Institute, automatically seals underground pipe joints by swelling on water contact in the event of a leak from a crack in service. Most acrylic plastics are based on polymers of methyl methacrylate, which may be modified by copolymerizing or blending with other monomers. Noted for excellent optical properties, they have a light transmission of about 92%. Clarex DR-III, from Astra Products, is an acrylic light-diffusion material to guide light from lowlevel sources to display surfaces. Light transmission ranges from 45 to 92%, and the material is available in white or specially formulated to transmit peak wavelengths of various colors. Besides the transparent grades, they can be obtained in translucent or opaque colors as well as the natural color of water white. Moldings have a deep luster and high surface gloss, and for this reason are widely used for decorative parts. Acrylics have excellent weathering characteristics. Because they are little affected by sunlight, rain, and corrosive atmospheres, they are well suited for outdoor applications. In general, the majority of grades can be used up to about 212°F (100°C). Thermal expansion is relatively high. Acrylics are hard and stiff. They are also a relatively strong plastic; their tensile strength ranges from 5,000 to about 11,000 lb/in2 (34 to about 76 MPa). However, regular grades are somewhat brittle. High impact grades are produced by blending with rubber stock. The high strength is useful only for short-term loading. For long-term service, to avoid crazing or surface cracking, tensile stresses must be limited to about 1,500 lb/in2 (10 MPa). Acrylic plastics are available as cast sheets, rods, tubes, and blocks. They are also processed by injection or compression molding. Sheets are produced in thicknesses from 0.125 to 0.375 in (0.32 to 0.95 cm) and in sizes up to 10 by 12 ft (3 by 4 m). A special process that produces molecular orientation in the cast product is used to make crack-resistant
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
12
ACRYLIC RESINS
aircraft cabin windows and fighter plane canopies. Acrylic moldings as large as 1 yd2 (1 m2) have been produced. Typical moldings include knobs, handles, escutcheons, parts for vending machines, and a wide variety of lenses for light control, signal lamps, and the like. Tough molding resins are made by copolymerizing methyl methacrylate with styrene. These molding resins have a flexural strength of 17,600 lb/in2 (121 MPa). Acrylate rubbers, having a tensile strength of 2,500 lb/in2 (17 MPa) and an elongation of 350%, are used for gaskets, wire insulation, and hose. Allyl methacrylate is a liquid of the empirical formula C7H10O2, boiling at 145°F (63°C) and insoluble in water. It can be polymerized to form liquid or hard solid resins, but is used chiefly as a cross-linking agent for other resins to raise the softening point and increase hardness. Polymethyl alphachloroacrylate, (CH2:CCl COOCH3)x, is a transparent and craze-resistant resin used for aircraft windows. The heat distortion point is 260°F (127°C), and it has higher tensile and flexural strength than other acrylics. Cyclohexyl methacrylate has optical properties similar to those of crown glass and is used for cast lenses, where its softness and low softening point, 160°F (71°C), are not objectionable. Lucite is methyl methacrylate of Du Pont, marketed as molding powder and in rods, tubes, and cast and molded sheets. Lucitone, of Dentsply International, is this material molded in dentures in pink and translucent. Lucite HM-140 is this material compounded for high-temperature injection molding. Acrylic syrup is a liquid Lucite for use as a low-pressure laminating resin. It produces strong, stiff, tough laminates adaptable to translucent or bright colors. Reinforced with glass fibers, a panel with contact cure has a flexural strength of 25,000 lb/in2 (172 MPa), elongation 1.5%, distortion point at 233°F (112°C), Rockwell hardness R121, and light transmission up to 65%. Crystalite, of Rohm & Haas Co., is an acrylic molding powder. Plexiglas, of this company, is transparent methyl methacrylate in sheets and rods. All these plastics are used for aircraft windows. Plexiglas V is for injection molding, while Plexiglas VM is a molding powder to resist heat distortion to 174°F (79°C). Vernonite, of Rohm & Haas Co., is an acrylic denture resin. Quarite and Quarite Plus, of Aristech Chemical, are mineral-filled sheets with a pebbly surface texture for spas, plumbing ware, and architectural applications. Acrystone, of the same firm, is a mineral-filled, solid-surfacing, cast acrylic sheet. The Acryloid resins, of the same company, are acrylic copolymer solid resins, and the Acrysol resins are solutions for coatings. Plexene M, of the same company, is a styrene-acrylic resin for injection molding. The specific gravity of the molded resin is 1.08, the
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
ACRYLIC RESINS
13
dielectric strength 350 V/mil (14 106 V/m), and tensile strength 2 15,000 lb/in (103 MPa). Rhoplex resins, of the same company, are acrylic resin emulsions for paints, textile finishes, and adhesives. Water-soluble acrylic copolymer is used for thickening natural or synthetic rubber latex for paper and textile coatings. Coatings made with acrylics have good adhesion and gloss, are resistant to oils and chemicals, and have good dielectric strength. Carboset 511 is a water solution of acrylic resin for protecting polished metal surfaces and precision parts against scratching. It is resistant to water, but can be washed off with soap and water. Cavalon, of Du Pont, is a polyacrylic resin for coatings that has high hardness and resistance to abrasion. Cyrolite HP sheet, from Cyro Industries, has 90% light transmission and is thermoformable at 240 to 320°F (116 to 160°C). It has a Rockwell hardness of 60 M, a tensile strength of 7800 lb/in2 (54 MPa), a flexural strength of 13,800 lb/in2 (95 MPa), a flexural modulus of 440,000 lb/in2 (303 GPa), an Izod notched impact strength of 0.7 ft.lb/in (37 J/m), and a maximum continuous service temperature of 160°F (71°C). Shinbolite P UT-100, UT-200, and UT-300, a heatresistant acrylic copolymer from Mitsubishi Rayon Co. and Franklin Polymers Inc. is intended for lens applications. Density is 0.043 lb/in3 (1190 kg/m3), light transmission is 92 to 93%, refractive index is 1.49 to 1.51, and haze is 0.3 to 0.5%. Tensile and flexural strengths are 11,000 to 11,500 lb/in2 (76 to 79 MPa) and 16,100 to 18,100 lb/in2 (111 to 125 MPa), respectively; ultimate elongation is 4.3 to 8.8%; the flexural modulus is 470,000 to 480,000 lb/in2 (3240 to 3310 MPa); and the heat deflection temperature at 264 lb/in2 (1.8 MPa) is 230 to 248°F (110 to 120°C). Volan, of the Du Pont Co., is a methacrylate-chromic oxychloride, CH2:C(CH3)C(OH)(OCrCl2)2, in which methacrylic acid is joined with two CrCl2 groups to form resonant bonds. It is a dark-green liquid with a specific gravity of 1.02, boiling point at 180°F (82°C). When applied to negatively charged surfaces such as cellulose, polyamides, or silica materials, the chromium complex is strongly held while the chlorine is lost. In attaching to glass, the CrO forms a chemical bond to the silica of the glass, Cr O Si. With polyamides, the CrO attaches to a carbon atom, Cr O C, and thus provides strong bonds in plastic laminates. Korad films, from Polymer Extruded Products, are weatherable, wood-grain, acrylic laminating films for outdoor window and door profiles and for adhesive-free bonding to polypropylene sheet for thermoformed products. Acumer 3000, a water-treatment acrylate polymer from Rohm and Haas Co., controls silica and prevents formation of magnesium-silicate scale. Treated with the polymer, recirculated water can tolerate as much as 300 parts per million of silica without scale formation. Acumer 5000,
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
14
ACRYLONITRILE
an acrylate terpolymer of the same company, controls iron and inhibits scale formation in boiler water.
ACRYLONITRILE. Also called vinyl cyanide and propene nitrile. A
liquid of composition CH2:CHCN, boiling at 172°F (78°C), used in insecticides and for producing plastics and other chemicals. It is made by the addition of hydrocyanic acid to acetylene, by using propylene as the starter and reacting with ammonia, or from petroleum. Acrylonitrile fiber, originally developed in Germany as a textile staple fiber and as a monofilament for screens and weaving, and known as Redon, has good dimensional stability and high dielectric strength and is resistant to water and to solvents. The polymerized acrylonitrile has a molecular structure that can be oriented by drawing to give fibers of high strength. Orlon, of Du Pont, is a polymerized acrylonitrile fiber. It is nearly as strong as nylon and has a softer feel. It can be crimped to facilitate spinning with wool. It is used for clothing textiles and for filter fabrics. Dynel, of Union Carbide Corp., is an acrylonitrile-vinyl chloride copolymer staple fiber. It produces textiles with a warmth and feel like those of wool. It has good strength, is resilient, dyes easily, and is mothproof. Verel, of Eastman Chemical Products, Inc., is a similar acrylic fiber produced from acrylonitrile and vinylidene chloride, and Creslan, of American Cyanamid Co., called Exlan in Japan, is an acrylic fiber. Acrilan, of Monsanto, is a similar textile fiber and is an acrylonitrile-vinyl acetate copolymer. Acrylonitrile-styrene is a copolymer for injection molding and extruding that produces rigid thermoplastic parts of higher tensile strength than those of the methacrylates, and has good dimensional stability and scratch resistance. Saran F-120, of Dow Chemical Co., is a similar material. Centrex polymers from Bayer Corp. are acrylonitrile styrene acrylate (ASA), acrylonitrile-ethylene-propylene-styrene (AES), and ASA/AES resins. All are noted for good resistance to weather aging in unpainted, outdoor applications. ASA grades include medium-impact, low- or high-gloss types, and a high-impact, highgloss type. AES grades include high-impact, low- or medium-gloss grades suitable for coextrusion over ABS or PVC substrates. ASA/AES grades are medium-impact, low-gloss or high-impact, highgloss grades, most of which are suitable for coextrusion over ABS. Acrylonitrile also is polymerized with vinyl pyrrolidone or other dye-receptive monomer. The fiber has a molecular structure called a nitrile alloy, with a continuous polyacrylonitrile backbond with close-packed hydrophilic groups which hold the dye molecules. It resists heat to 490°F (254°C). Crystal-clear styrene-acrylonitrile copolymer is used for molding such articles as dinnerware and food
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
ACTIVATED CHARCOAL
15
containers. Acrylonitrile-styrene copolymers are also combined with alkyl-substituted phenolic resins to produce hard, glossy, flexible coatings. Itaconic acid, or methylene succinic acid, CH2:CCH(COOH)2, is also polymerized with acrylonitrile to produce fibers. When this acid is polymerized with styrene, it produces transparent plastics of good optical properties. Ultrapure succinonitrile (SCN) is a transparent organic material that melts at 134°F (58°C) and forms crystals much like common metals. Produced at Rensselaer Polytechnic Institute, it was used by the National Aeronautics and Space Administration on the Space Shuttle to observe dendritic crystal formation in gravityfree space to validate or modify crystal-growth theories for metals on earth. For jet aircraft tires, an extremely wear-resistant rubber is made of acrylonitrile-butadiene with an organometallic catalyst that has alternating groups in the copolymer. Acrylonitrile reacts with cellulose to form a wide range of resins from soluble ethers useful for textile finishes to tough, resistant materials useful for fibers. It can be reacted directly with cotton to improve the fiber. Sodium salts of acrylonitrile are used as soil conditioners. They are more efficient than peat moss.
ACTIVATED CHARCOAL. A nearly chemically pure amorphous carbon made by carbonizing and treating dense material such as coconut shells, peach pits, or hardwood. When made from coal, or in the chemical industry, it is more usually called activated carbon, or filter carbon. It may be made by dry distillation or by leaching the charcoal with steam or by treatment with zinc chloride or potassium thiocyanate. It is used as an adsorbent material for gas masks, for cigarette filters, and for purifying acids, recovering solvents, and decolorizing liquids. Activated carbon woven into garments protects members of the armed forces from chemical warfare. Garments with superactivated carbon are lighter in weight and much more absorbent. Coconut charcoal, valued for gas masks, is an activated charcoal usually made by heating coconut shells in a closed retort, crushing, and steam treating. An activated charcoal made from coconut shells will adsorb 68% of its weight of carbon tetrachloride. A requirement of activated charcoals, besides high adsorbing power, is that they possess strength to retain a porous structure to pass the air or liquid. Activated carbon CXC4-6, of Union Carbide Corp., produced from petroleum and used as a catalyst support, is in 3⁄16-in (0.48-cm) pellets of high hardness and strength. Activated charcoal powder is usually ground to 300 mesh. An acid-washed coconut-shell activated carbon from Barnebey Sutcliffe Corp. is effective for removing mercury, ketones, and methylene chloride from solutions. For water purification it should be fine enough to wet easily, but not
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
16
ACTIVATED CHARCOAL
so light that it will float on the top. For decolorizing or deodorizing oils and chemicals, it is mixed in the liquid and settles out in a few hours. A single drop of water will hold 10,000 particles of powdered charcoal. HiPur, from Barnebey Sutcliffe, is intended for high-purity water and process applications, especially medical dialysis service and semiconductor manufacturing. HiPur Plus is useful in sweetener decolorization and for purifying select organic, mineral, and food acids as well as pharmaceuticals and vitamins. In sugar and oil refining, it removes color but does not bleach like chemicals. Color removal is measured by the molasses number, which is the index of color removed per gram of carbon when tested on a standard molasses solution. Kelpchar is activated carbon made from seaweed. Tec-Char, of Tennessee Eastman Co., is a by-product charcoal obtained in wood distillation and in graded grains for various uses. Nuchar is an activated carbon. The activated carbon of the Masonite Corp. is made by subjecting wood chips to high steam pressure and disintegrating by sudden release of the pressure. The doughy mass is briquetted and carbonized. Activated carbon of Calgon Carbon Corp. serves as an adsorbent to stabilize organic chemicals such as halogenated aromatic compounds in contaminated soil and sludge. After stabilization, the treated soil and sludge are mixed with pozzolanic materials such as portland cement, fly ash, and kiln dust for disposal as landfill. Granular activated carbon is used in a system from Envirex Inc. for the removal of benzene, toluene, ethylbenzene, and xylenes from groundwater. It is especially effective in cleaning sites having low levels of these contaminants. Activated carbon derived from coal is harder than organic carbons and does not crumble easily, permitting a higher flow of liquid to be filtered. It has a high density and high activity. SGL carbon has an iodine number of 1,000 compared with 650 for ordinary carbons. Its color-removal index is about 40% higher than that of organic carbons. Filt-o-cite, of Shamokin Filler Co., is finely ground anthracite used to replace sand as a filtering agent for industrial wastes. Filtrasorb 600, from Calgon Carbon, is made from bituminous coal and designed to remove methyl tert-butyl ether from water. Picabiol is a wood-based activated carbon from Pica USA for biological filtration of potable water. Picacarb, of this company, is a series of coal-based activated carbons for removing taste and odor compounds and adsorption of pesticides, herbicides, and other micropollutants from water. Hydrodarco B and C, from Norit Americas, are activated carbon in powder form for potable-water production and wastewater treatment. Bentonrit, of the same company, is activatedcarbon powder bonded with betonite into cylindrical pellets that sub-
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
ADHESIVES
17
merge in liquids without creating excess dust. The pellets are effective for dosing systems used for purifying and decolorizing pharmaceuticals, foods, beverages, chemicals, potable water, and wastewater. Centaur, an adsorptive-catalytic carbon from Calgon Carbon, is made by modifying the surface properties of granular activated carbon to speed chemical reactions. In effluent-cleaning operations, it has removed virtually all the hydrogen sulfide and converted it to sulfuric acid. The 55% copper–45% zinc KDF55 redox alloy, from KDF Fluid Treatment Inc., is used to prolong the life and reduce replacement frequency of activated-carbon beds. The alloy is quite effective in removing chlorine, which deactivates carbon, from water. A woven cloth made by Calgon Carbon from bundles of activatedcarbon filaments and fiber has surface areas of 4.89 106 to 8.79 6 2 2 10 ft /lb (1000 to 1800 m /g) and densities of 0.045 to 0.203 lb/ft2 (220 to 990 g/m2). It is less vulnerable to humidity than granular activated carbon and provides a greater rate of chemical absorption, which can be further improved by impregnation with copper, silver, or potassium iodide. Kothmex, a pressed rather than knitted carbon-fiber cloth supplied in rolls by Taiwan Carbon Technology, is 0.016 in (0.4 mm) thick and has surface areas of 4.89 106 to 9.78 106 ft2/lb (1000 to 2000 m2/g). BPS (bonded particulate structure), of Filtration Group, is made by binding activated carbon into a monolithic structure with a polymeric binder. The material is formable into various shapes, its open-pore structure exceeds 9.78 106 ft2/lb, and its reduction in micropore volume, despite the binder, is less than 2%
ADHESIVES.
Materials employed for sticking, or adhering, one surface to another. Forms are liquid, paste, powder, and dry film. The commercial adhesives include pastes; glues; pyroxylin cements; rubber cements; latex cement; special cements of chlorinated rubber, synthetic rubbers, or synthetic resins; and the natural mucilages. Adhesives are characterized by degree of tack, or stickiness, by strength of bond after setting
Materials Handbook,15 Ed.PDF
(4.25 MB, 下载次数: 66, 售价: 5 枚热加工币)
|
|
[复制链接]
|手机版|Archiver|热加工行业论坛
( 苏ICP备18061189号-1|豫公网安备 41142602000010号 )
发表于 2011-11-18 13:16:02
