Effect of molecular weight and content of PDMS on morphology and properties of silicone‐modified epoxy resin

To achieve a stable blend of a bisphenol A type epoxy resin and poly(dimethylsiloxane) (PDMS), reaction between hydroxyl (OH) groups of the epoxy and silanol groups of hydroxyl‐terminated(HT) PDMS has been investigated. The chemical structures of the HTPDMS‐modified epoxies were characterized by Fourier transform infrared (FTIR) and 1H‐ and 13C‐NMR spectroscopy. To allow further understanding of the influence of viscosity and content of HTPDMS on the blend morphology, four different viscosities of HTPDMS were used in three content levels. The morphologies of modified epoxy resins were observed with optical microscopy. The modified epoxies were cured with a cycloaliphatic polyamine. The morphologies of modified epoxies were investigated by using scanning electron microscopy (SEM)/energy dispersive X‐ray (EDX) technique. The cured films showed droplet in matrix morphology with different mean droplets size which was influenced by the viscosity and the content of the incorporated HTPDMS. To illustrate the effect of the morphologies of the cured samples on mechanical properties, tensile strength tests were performed. The introduction of HTPDMS into the epoxy altered the tensile behavior according to its viscosity and content. Surface properties of the cured films were evaluated by sessile drop method. The results clearly indicate that the hydrophilic surface of the epoxy turns to a hydrophobic one due to the modification with HTPDMS.