Compression and Transfer Molding

Abstract

Compression and transfer molding (CM and TM) are the two main methods used to produce molded parts from thermoset (TS) resins. Compression molding (CM) was the major method of processing plastics during the first half of this century because of the development of a phenolic resin (TS) in 1909 and its extensive use at that time. By the 1940s this situation began to change with the development and use of thermoplastics (TPs) in extrusion and injection molding (IM) processes. CM originally processed about 70 percent (by weight) of all plastics, but by the 1950s its share of total production was below 25 percent, and now that figure is about 3 percent. This change does not mean that CM is not a viable process; it just does not provide the much lower cost to performance of TPs, particularly at high production rates. In the early 1900s resins were almost entirely TS (95 percent by weight); that proportion had fallen to about 40 percent by the mid-19408, and now is about 3 percent.