Simultaneously improving toughness and hydrophobic properties of cycloaliphatic epoxy resin through silicone prepolymer

Abstract To improve the toughness and hydrophobic property of the cycloaliphatic epoxy resin (CEP), which is vital to application in high voltage insulation of outdoor transmission lines, 3‐aminopropyltriethoxysilane was used as the intermediate to prepare the silicone prepolymer by the interaction of the end groups of the CEP and the hydroxy‐terminated polydimethylsiloxane. The results showed that the silicone prepolymer segments were self‐assembled to form solid dispersion phases distributed uniformly in the CEP. The size of the dispersed phase gradually increased in CEP with more concentration of silicone prepolymer. The tensile strength and static contact angle of the CEP were simultaneously improved when content of the silicone prepolymer reached 10 phr. The tensile strength and static contact angle were mainly affected by the distribution of dispersed phase and by surface tension, respectively. With the increase of Si/C on the surface, surface tension decreased and tended to saturate. Due to small molecule migration, the CEP containing silicone prepolymer was also endowed with hydrophobic transfer properties. This paper affords a method to simultaneously enhance toughness and hydrophobic properties of CEP and deepens fundamental understanding of hydrophobic properties.