Study On Synthesis Of PS-b-PDMS By Anionic Polymerization And Its Application In Epoxy Coatings

Epoxy resins are widely used as coatings because of their distinguished adhesion properties and mechanical properties; However, high surface energy and the hydrophilic properties of epoxy resins, resulting in a decrease in its protectiveness for metal underneath. It is well known that polysiloxane has an extremely low surface energy and exhibits excellent performance water repellency. Modification of an epoxy resin by polysiloxane is an effective way to enhance the hydrophobicity, and toughness, for a highly crosslinked epoxy resin system.In this study, a diblock copolymer of poly(styrene-block-dimethylsiloxane) (PS-b-PDMS) was synthesized by the sequential anionic polymerization of styrene and D3, and then was used to modify the surface properties of the epoxy coatings by blending technique.Firstly, we reported the epoxy varnish modified by the copolymer of PS-b-PDMS. It was found that the leveling properties of coating films was remarkably improved, the modified epoxy coatings also showed good water repellency and low surface energy properties.According to the experimental results, the copolymer of PS-b-PDMS(with PDMS 28.6%) had good compatibility with epoxy resin (E-44), The epoxy resin varnish modified by different content of PS-b-PDMS (with 28.6wt% )were studied. The best performance was observed for coating system modified by 7wt% PS-b-PDMS content. It indicated that when the dosage of PS-b-PDMS was 7wt%, the surface energy was reduced to 13.8mN·m^-1, the contact angle for water was 115.9°. Furthermore, the impact resistance and flexibility of the modified epoxy coatings were also improved. The values of that two parameters were 50kg·cm and 0.5mm,respectively. The commercial epoxy paints modified by PS-b-PDMS were also investigated. The surface properties of pure epoxy coating was changed from hydrophilic to hydrophobic when PS-b-PDMS was introduced into the epoxy paints. The coatings modified with 7wt% PS-b-PDMS, which static contact angle for water was increased up to114.4°,showed good water repellency. The hardness and adhesion of the coatings were not affected. The impact strength and flexibility of the coatings were also improved by adding PS-b-PDMS. As the PS-b-PDMS increases the anti-corrosion resistence of epoxy coatings is promoted.