为了使生产的塑胶符合要求的一些特性、符合经济的需求，一定都会加入或多或少『添加剂』。塑胶添加剂有很多种，有润滑剂、氧化防止剂、热稳定剂、强化剂等等。部份原料必须加入添加剂才能做的出塑胶成品。

早在聚合物工业（The Polymer Industry）发展的早期，人们就已经知道把一些添加剂加到聚合物结构（Polymer Matrix）中，以得到某些产品，最初把这种过程叫掺和（Compounding。）

In chemistry a stabilizer is a chemical which tends to inhibit the reaction between two or more other chemicals. It can be thought of as the antonym to a catalyst. The term can also refer to a chemical that inhibits separation of suspensions, emulsions, and foams. Heat and light stabilizers are added to plastics and elastomers because they ensure safe processing and protect products against premature aging and weathering. The trend is towards fluid systems, pellets, and increased use of masterbatches. There are monofunctional, bifunctional, and polyfunctional stabilizers. In economic terms the most important product groups on the market for stabilizers are compounds based on calcium (calcium-zinc and organo-calcium), lead, and tin stabilizers as well as liquid and light stabilizers (HALS, benzophenone, benzotriazole). Cadmium-based stabilizers largely vanished in the last years due to health and environmental concerns.