Morphology of the outermost layer of a compression molded composite based on unsaturated polyester resin

Composites materials, SMC and BMC are widely used for the manufacture of automotive parts. These high performance materials are characterized by their superior surface quality. A strict control of the surface quality goes through a good knowledge of the surface and of the outermost layer. The present work is dedicated to composites surfaces knowledge. The studied material was a compression mold thermosetting composite based on unsaturated polyester resin. Different components like mold release agent, mineral fillers as calcium carbonate and glass fibers were introduced in the resin to prepare the composite. With SEM, XPS and AFM which are techniques dedicated to characterize the surface and the outermost layer, we were able to identify and locate each component in the outermost layer. The mold release agent was found at the surface. The other components were deeper localized. Although they are more than 0.4 μm deep, the glass fibers have an impact on the topography of the surface. A surface layer model was proposed.