Adhesion and Surface Chemistry of Sheet Molding Compound

The surface chemistry of styrene-crosslinked polyester sheet molding compound (SMC) and its interface with epoxy adhesives was investigated. A readily extractable thermoplastic material in the SMC contributed to the formation of weak boundary layers which could lead to near-interface failures and allow the growth of bubbles in the curing adhesive near the interface. The distribution of components in near-interface failure specimens was determined using FTIR and ESCA. A mathematical model of pore penetration by a curing liquid was developed to investigate dynamic wetting phenomena.