Compression molding is a process in which the molding polymer, called the “charge” or “compound,” is squeezed into a preheated mold to form the shape of the mold cavity with heat and pressure until the charge has cured.
Compression moulding is the original plastics processing method and was initially used for early polymers such as horn and rubber. With the advent of thermosetting materials such as the phenol-formaldehydes and urea-formaldehydes the natural processing choice was compression moulding. Compression moulding is now also used for materials such as fibre reinforced polyester resins in the form of Bulk Moulding Compound (BMC) or Sheet Moulding Compound (SMC).