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|Section2= |Section8= }} Acrylonitrile butadiene styrene (ABS) (chemical formula (C8H8)x· (C4H6)y·(C3H3N)z) is a common thermoplastic polymer. Its glass transition temperature is approximately 105 °C (221 °F).〔(ABS ). Stratasys Inc. (2007).〕 ABS is amorphous and therefore has no true melting point. ABS is a terpolymer made by polymerizing styrene and acrylonitrile in the presence of polybutadiene. The proportions can vary from 15 to 35% acrylonitrile, 5 to 30% butadiene and 40 to 60% styrene. The result is a long chain of polybutadiene criss-crossed with shorter chains of poly(styrene-co-acrylonitrile). The nitrile groups from neighboring chains, being polar, attract each other and bind the chains together, making ABS stronger than pure polystyrene. The styrene gives the plastic a shiny, impervious surface. The polybutadiene, a rubbery substance, provides toughness even at low temperatures. For the majority of applications, ABS can be used between as its mechanical properties vary with temperature.〔(Plastic Properties of Acrylonitrile Butadiene Styrene (ABS) ) Small table of ABS properties towards the bottom. Retrieved 7 May 2010〕 The properties are created by rubber toughening, where fine particles of elastomer are distributed throughout the rigid matrix. ==Properties== The most important mechanical properties of ABS are impact resistance and toughness. A variety of modifications can be made to improve impact resistance, toughness, and heat resistance. The impact resistance can be amplified by increasing the proportions of polybutadiene in relation to styrene and also acrylonitrile, although this causes changes in other properties. Impact resistance does not fall off rapidly at lower temperatures. Stability under load is excellent with limited loads. Thus, by changing the proportions of its components, ABS can be prepared in different grades. Two major categories could be ABS for extrusion and ABS for injection moulding, then high and medium impact resistance. Generally ABS would have useful characteristics within a temperature range from .〔 The final properties will be influenced to some extent by the conditions under which the material is processed to the final product. For example, molding at a high temperature improves the gloss and heat resistance of the product whereas the highest impact resistance and strength are obtained by molding at low temperature. Fibers (usually glass fibers) and additives can be mixed in the resin pellets to make the final product strong and raise the operating range to as high as . Pigments can also be added, as the raw material original color is translucent ivory to white. The aging characteristics of the polymers are largely influenced by the polybutadiene content, and it is normal to include antioxidants in the composition. Other factors include exposure to ultraviolet radiation, for which additives are also available to protect against. ABS polymers are resistant to aqueous acids, alkalis, concentrated hydrochloric and phosphoric acids, alcohols and animal, vegetable and mineral oils, but they are swollen by glacial acetic acid, carbon tetrachloride and aromatic hydrocarbons and are attacked by concentrated sulfuric and nitric acids. They are soluble in esters, ketones, ethylene dichloride and acetone.〔Benj Edwards (Vintage Computing and Gaming | Archive » Why Super Nintendos Lose Their Color: Plastic Discoloration in Classic Machines ). Vintagecomputing. January 12, 2007〕 Even though ABS plastics are used largely for mechanical purposes, they also have electrical properties that are fairly constant over a wide range of frequencies. These properties are little affected by temperature and atmospheric humidity in the acceptable operating range of temperatures.〔Harper C.A. (1975) ''Handbook of plastic and elastomers'', McGraw-Hill, New York, pp. 1–3,1–62, 2–42, 3–1, ISBN 0070266816〕 ABS is flammable when it is exposed to high temperatures, such as a wood fire. It will melt then boil, at which point the vapors burst into intense, hot flames. Since pure ABS contains no halogens, its combustion does not typically produce any persistent organic pollutants, and the most toxic products of its combustion or pyrolysis are carbon monoxide and hydrogen cyanide. ABS is also damaged by sunlight. This caused one of the most widespread and expensive automobile recalls in US history due to the degradation of the seatbelt release buttons. ABS can be recycled, although it is not accepted by all recycling facilities.〔(【引用サイトリンク】url=http://www.heathland.nl/abs-recycling.html )〕〔(【引用サイトリンク】url=http://www.brisbane.qld.gov.au/environment-waste/rubbish-tips-and-bins/recycling-reducing-waste/recycling-at-home/recycling-plastic/index.htm )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Acrylonitrile butadiene styrene」の詳細全文を読む スポンサード リンク
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