Plastics obtained by polymerization or polycondensation have no practical value unless they are processed into valuable molded products. Before being molded, plastics are in a state such as liquid, powder, flakes, chips, emulsion, or dispersion, and a molding method must be applied to suit the state. Plastics are divided into thermoplastic resins and thermosetting resins, the former of which are molded by the physical changes of melting → shaping → cooling, while the latter of which are molded using the chemical reactions of shaping → heating → hardening. Source: Heibonsha World Encyclopedia, 2nd Edition Information |
重合あるいは重縮合によって得られるプラスチックは,加工して価値のある成形品にしなければ,実用上の意味をもたない。成形以前のプラスチックは液状物,粉末,フレーク,チップ,乳濁液,分散液などの状態をとっており,それに合わせた成形加工法を適用しなければならない。またプラスチックには熱可塑性樹脂と熱硬化性樹脂があり,前者は溶融→賦形→冷却という物理変化で成形され,後者は賦形→加熱→硬化という化学反応を利用して成形される。
出典 株式会社平凡社世界大百科事典 第2版について 情報 |
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