Advances in Thermoset Injection Molding
Injection molding of thermosetting materials such as low profile SMC/BMC composites found increasing application in the transportation industry in the eighties. Such automotive parts as front end panels and rear/hatchback doors have grown in usage. The rear doors have reached exceptional production levels of 2600/day in a single plant. The injection process offers the advantages of greater automation for the mass production of body panel parts compared in compression molding. However, the injection molding of fiber reinforced low profile composites suffers from a severe reduction in physical properties. This is particularly true for impact strength which can be one-third that of similar compression molding materials. A primary reason for this is due to the degradation of the reinforcement during the processing/molding. Efforts at increasing the physical properties through processing changes have many times caused problems with the surface smoothness of the moldings.