Investigation of hydroxyl-terminated polydimethylsiloxane-modified epoxy resin

Epoxy resin coatings are characterized by a high concentration of hydroxyl groups, making them inherently hydrophilic and prone to corrosion. Additionally, the brittleness of epoxy resin limits its practical uses. In this study, epoxy resin (EP-51) was modified using hydroxyl-terminated polydimethylsiloxane (HTPDMS), which possesses a low surface energy due to its -Si-O- bonds, to improve the hydrophobicity and toughness of the coating. The effect of varying HTPDMS concentrations on the properties of epoxy resin was evaluated in terms of mechanical, thermodynamic, and electrochemical properties, as well as contact angle measurements. The findings reveal that as the HTPDMS content increases, the tensile strength of the modified EP diminishes, while the elongation and impact strength are enhanced. However, higher HTPDMS levels lead to reduced compatibility with EP, causing phase separation and the formation of an "island structure". The glass transition temperature of the EP declines with added HTPDMS, resulting in an increased swelling rate and reduced pencil hardness and adhesion grade of the coatings. Notably, the hydrophobicity of the EP improved significantly, with its contact angle rising from 74.8° to 99.0° post-modification. Electrochemical impedance spectroscopy and polarization curve analyses revealed optimal protective performance of the coating at an epoxy resin to HTPDMS mass ratio of 8:2.