Characterization of the surface of bulk-molded compounds

The automotive industry more and more frequently uses composite materials s uch as molded compounds (sheet-molded compounds, SMC, or bulk-molded compou nds, BMC). Bonding is then the only way of assembling two pieces. Consequen tly, and in order tentatively to predict the adhesive behavior of such mate rials, if is necessary to have a good knowledge of their surface properties . Here, different complementary techniques of surface analysis allowed us, on the one hand, to reach this aim for BMCs prepared by compression molding and, on the other hand to show the influence on the surface properties of the concentration and composition of the internal release agent added to th e blend. The surface heterogeneity and the organic nature of the surface of the compounds are shown and no phase separation occurs there as in the bul k. Mold release agents remain in the surface layer and induce some acid-bas e character to the surface material which depends on the type of stearate i ntroduced in the blend. Copyright (C) 1999 John Wiley & Sons, Ltd.