High impact polystyrene, also known as HIPS, is a thermoplastic material made of elastomer modified polystyrene. The two-phase system consisting of rubber phase and continuous polystyrene phase has developed into an important polymer commodity in the world. This general-purpose product has a wide range of impact properties and processing properties, making it widely used, such as in automobile, apparatus, electric products, furniture, household appliances, telecommunications, electronics, computers, disposable goods, medicine, packaging and entertainment markets.

There are two basic processes for HIPS production: intermittent process and continuous process. The two processes generally use prepolymerization first. After the completion of prepolymerization, the polymerization is continued in the form of suspension in the intermittent process and in the form of solution in the continuous process. Therefore, intermittent process is also called bulk suspension process, and continuous process is also called solution process.