Coatings of PDMS-modified epoxy via urethane linkage: Segmental correlation length, phase morphology, thermomechanical and surface behavior

Modification of an aliphatic epoxy resin with silicone was carried out through urethane route. Hydroxy-terminated polydimethylsiloxane (HTPDMS) was reacted with toluene diisocyanate to form an isocyanate-capped prepolymer. The -NCO group of the prepolymer was further reacted with -OH group of an aliphatic epoxy adipate resin, obtained by reaction of adipic acid with an epoxy resin, to obtain silicone-modified epoxy resin. Silicone-modified epoxy resins containing 15 and 30wt% of silicone prepolymer have been synthesized by this procedure. TGA analysis of the silicone-modified epoxy resin showed considerable improvement in thermal stability over the unmodified epoxy resin. Modulated differential scanning calorimetry (MDSC) was used to find the segmental correlation length of the silicone-modified polymers. The cured films of silicone-modified resins showed biphasic morphology as evidenced from scanning electron microscopy. Further, the thermomechanical property of the samples was investigated by dynamic mechanical analysis. The surface properties of the silicone-modified matrices were studied by atomic force microscopy and contact angle goniometry. The silicone-modified samples showed considerably lower surface energy, surface roughness and contact angle hysteresis compared to the unmodified resins. (C) 2009 Elsevier B.V. All rights reserved.