ABSTRACT
Two successful variants of compression molding in the composites industry involve the use of Sheet Molding Compound (SMC) and Bulk Molding Compound (BMC). BMC can be molded immediately after mixing or may be stored like SMC in order to increase the viscosity to specified levels. For molding, both SMC and BMC are preweighed to specific size charges and placed into the mold prior to application of heat and pressure. In thick moldings, cure cycles must be increased so that the exothermic chemical reaction does not cause material degradation. The process involves specialized mixing techniques for preparing an easily handled putty-like molding compound containing all the ingredients of the composite formulation. Other processing conditions such as resin paste mixing and sheet take-up are quite similar to those for SMC. All molding compounds require close quality control of the ingredients in the formulation and of the processing steps during manufacture.
