热固性塑料Thermosetting polymer

固化前树脂是低分子量的线型或支化预聚物，可以流动成型；固化时官能团反应形成共价交联，达到凝胶点后体系不再流动，最终成为一个“巨大分子”。高交联密度带来高硬度、高模量、耐热、尺寸稳定和耐溶剂性，但也使材料较脆。

Before curing the resin is a low-molar-mass linear or branched prepolymer that can flow into shape; during cure its functional groups react to form covalent crosslinks, flow stops at the gel point, and the whole part becomes in effect one giant molecule. High crosslink density gives hardness, stiffness, heat resistance, dimensional stability and solvent resistance, but also brittleness.

1839 年固特异的硫化橡胶是最早的交联高分子材料。1907 年贝克兰发明的酚醛塑料是第一种全合成热固性塑料。1920 年代脲醛树脂、1930 年代三聚氰胺-甲醛树脂、1940 年代环氧树脂和不饱和聚酯先后出现，后者与玻璃纤维结合制成“玻璃钢”。

Goodyear's vulcanised rubber of 1839 was the first crosslinked polymer material, and Baekeland's phenolic plastic of 1907 the first fully synthetic thermoset. Urea–formaldehyde resins (1920s), melamine–formaldehyde (1930s), and epoxies and unsaturated polyesters (1940s) followed; the last, reinforced with glass fibre, became fibreglass.

热固性塑料用于电器绝缘件、电路板、胶黏剂、涂料、复合材料（风电叶片、飞机机身、船体）和厨具（密胺餐具）。由于不能重熔，回收十分困难，废弃风电叶片已成为难题。可逆交联的“类玻璃高分子”（vitrimer，2011 年莱布勒提出）和可降解交联键是解决方向。

Thermosets are used in electrical insulators, circuit boards, adhesives, coatings, composites for wind blades, aircraft and boat hulls, and melamine tableware. Because they cannot be remelted, recycling is very hard, and retired wind-turbine blades have become a problem. Vitrimers with exchangeable crosslinks, introduced by Leibler in 2011, and cleavable crosslinks are possible solutions.