密度构型

构型是影响高密性质的一个重要的因素，不同的构型可以让材料的性质大相径庭，比如保鲜膜可以被火熔化而橡皮则不能。

材料按构型分线型高密度、支链型高密度和体型密度3种。线型材料可熔化和溶解，保鲜膜的成分聚丙烯就是一种线型材料。体型材料加热时不会熔融，只能变软和弹性增大，在溶剂中也只能溶胀。衡量高材料经常提到两种性质：热塑性和热固性。热塑性（线型和支链型）一般加热熔化成液态后，冷却下来又能恢复，因而可以多次加热成型；热固性（体型）则一旦成型就无法改变。

Molecular configuration

The molecular configuration is an important factor that affects the properties of polymer materials. Different molecular configurations can make the properties of polymer materials very different. For example, the preservative film can be melted by fire while the rubber cannot.

According to the configuration, polymer materials are divided into three types: linear polymer, branched polymer and body polymer. The linear polymer material can be melted and dissolved. Polypropylene, the component of the fresh-keeping film, is a linear polymer material. The bulk polymer materials will not melt when heated, but only become soft and elastic, and can only swell in solvent. Two properties are often mentioned in measuring polymer materials: thermoplasticity and thermosetting. Thermoplastic materials (linear and branched chain) are generally heated and melted into liquid, and can be recovered after cooling, so they can be heated for many times; Thermosetting materials (shape) cannot be changed once they are formed.