Polystyrene (expandablepolystyrene, EPS), also known as polystyrene foam, is a relatively small density (1.05g/cm3), low thermal conductivity, low water absorption, impact resistance, heat insulation, sound insulation, moisture-proof, anti oscillation, good dielectric properties and so on. It is widely used in mechanical equipment, instrumentation, household appliances, Shockproof packaging materials and fast food packaging for handicrafts and other valuable products. With the rapid development of the world economy, the consumption of styrofoam plastics is increasing. The waste polystyrene foam is small in volume, light in weight, resistant to ageing and not easy to corrode. It is a major problem in garbage disposal. In recent years, recycling of foam plastics has become one of the focuses of the industry.

polystyrene impregnation process: there are two methods to prepare polystyrene particles: 1. One step impregnation process (or one-step impregnation process). Firstly, styrene monomer, foaming agent, dispersant, water, foaming agent (usually pentane and butane) and others were added to the reactor to polymerize the resin particles containing foaming agent, and then washed, centrifuged and dried to obtain polystyrene particles with good foaming performance; 2. Two step impregnation process, referred to as two-step impregnation process, is the styrene monomer in the reactor, first synthesis of a certain particle size of styrene particles, and then add, emulsifier, other additives, impregnated in the reactor from the developable products.

molding process: there are two main molding methods for EPS:

1. Extrusion route, i.e. direct hot extrusion of EPS particles after foaming, is usually used to manufacture thin plates and films. 

2. Molding route: first, the EPS particles were pre foamed with air (or water vapor) at 100 ℃ for 30 ~ 50 times, and then matured after 24 hours, and then the matured particles were put into aluminum or casting mold, and evaporated in air at 115 ~ 120 ℃.

EPS products are generally safe and non-toxic, but the raw materials are in different states during processing, and there are certain dangers. The respiratory tract and skin will be stimulated by polystyrene powder, and the stored EPS particles will release pentane vapor, which is a gas that is very easy to burn and form explosive mixture with air. After polystyrene is heated, styrene monomer will be released, which is a dangerous substance.