EPP is engineered polypropylene resin, formed into small, closed-cell foam beads. Expanded polypropylene (EPP) was developed in the 1980s. This is particle foam based on polypropylene. As opposed to EPS, EPP is not impregnated with a foaming agent, meaning that subsequent foaming agent-based expansion is not possible. Two main processes are used to manufacture EPP: the autoclave process (standard) and direct foam extrusion (rare).
