文档介绍：编号：
时间：2021年x月x日
书山有路勤为径，学海无涯苦作舟
页码：
1. Metals and Their Use
It is known that metals are very important in ].
2. Plastics and Other Materials
Plastics[5plAstik, plB:stik] have specific properties which may make them preferable[5prefErEbl] to traditional materials[mE5tIErIEl] for certain uses. In comparison[kEm5pArisn] with metals, for example, plastics have both advantages and disadvantages. Metals tend to be corroded[kE5rEud] by inorganic[7inC:5^Anik] acids[5AsId], such as sulphuric[sQl5fjuErik] acid and hydrochloric[7haidrEu5klC:rik] acid. Plastics tend to be resistant to these acids, but can have dissolved or deformed by solvent[5sClvEnt], such as carbon tetrachloride[7tetrE5klC:raid], which have the same carbon base as the plastics. Color must be applied to the surface of metals, whereas it can be mixed in with plastics. Metals are more rigid[5ridVid] than most plastics while plastics are very light, with a specific[spi5sifik] gravity normally between and . Most plastics do not readily[5redili] conduct[5kCndQkt] heat or electricity[Ilek5trIsItI]. Plastics soften slowly and can easily be shaped[Feip] when they are soft.
塑料具有特殊的性能。对于某种用途而言，这些性能使得塑料比传统材料更为可取。例如，跟金属相比较，塑料既有优点也有缺点。金属易受到无机酸的腐蚀，如硫酸和盐酸，塑料能抵抗这些酸的腐蚀，但可被溶剂所洛解或引起变形，例如溶剂四氯化碳与塑料具有同样的碳基。颜色必定只能涂到金属的表面。而它可以跟塑料混合为一体。金属比大多数塑料刚性要好，而塑料则非常之轻，通常塑料密度在0. 9-1. 8之间。大多数塑料不易传热导电。塑料能缓慢软化，而当其还是在软的状态时，能容易成形。
编号：
时间：2021年x月x日
书山有路勤为径，学海无涯苦作舟
页码：
It is their plasticity[plAs5tisiti] at certain temperatures[5temprItFE(r)] which gives plastics their main advantages over many other materials. It permits the large-scale production of molded[mEuld] articles, such as containers, at an economic unit cost, where other materials require laborious[lE5bC:riEs] and often costly processes involving cutting, shaping, machining, assembly[E5sembli] and decoration.
在某一温度下塑料是处于塑性状态的，这就使塑料具备超过许多其他材料的主要优点。它容许大量生产单位成本低廉的模制式器件，例如，各种容器。于此，若用其他材料则需要大量劳力和往往需要很费钱的加工工艺，比如，切割、成形、加工、装配和装饰。
Plastics