Preparation and surface properties of polydimethysiloxane/polycaprolactone/epoxy resin composites

Silyl-terminated polycaprolactone/polydimethysiloxane (PCL-TESi/PDMS-TESi) was directly synthesized via -OH and -NCO nucleophilic addition reaction. A series of resin composites were prepared by blending epoxy and PCLTESi/PDMSTESi. The morphologies and the surface elements of the composite system were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. The surface tension of the composite system was obtained based on the contact angle by Owens-Wendt-Kaelble model. The water-resistance properties of the composites were also studied. The results show that the morphologies, surface tension and water resistance properties of the composites are quite dependent on the content of PCL-TESi/PDMS-TESi and the curing temperature. The surface tension decreases with increasing PCL-TESi/PDMS-TESi content because of the Si element migrating toward the surface to some extent. The compatibility of the two phases at 50°C curing systems is better than that at room temperature curing systems, which results in that the composites cured at 50°C have higher surface tensions than those cured at room temperature. When the mass ratio of PCL-TESi/PDMS-TESi to the epoxy is 5:5, the mass change of composite cured at room temperature is below 1% after soak in distilled water at 50°C for 7 days.