Water resistance and thermal insulation properties of modified expanded vermiculite composites

In this study, in order to enhance the water resistance of expanded vermiculite (EV) composites. Three hydrophobic modifiers, hydrogenated silicone oil (HO), sodium methylsiliconate (SM), and waterborne polyurethane (WP), were used to prepare the EV/HO, EV/SM, and EV/WP composites. The microstructure, water resistance, thermal insulation and fire resistance of the composites were studied. The results indicate that the EV/HO composite exhibit the best water resistance. Rough structure appears on the surface of the EV/HO composite. The water contact angle (WCA) of the EV/HO composite reaches 128.8° when the HO content is 2.4 wt%. The water absorption ability of the composites decreased, softening coefficient and WCA increased with the increase of HO content. The backside temperature of the EV/HO composite was recorded to be 381.2 ℃ after 90 min single-side fire-resistance test, 13.3 % lower than that of the EV composite. The EV/HO composites maintain better integrity after fire-resistance test. Besides, the fiber-like network structures appear in the EV/SM and EV/WP composites. This structure enhances the thermal insulation properties of the EV/SM and EV/WP composite. The thermal conductivity of the composites modified with 8.97 wt% of SM and WP decreased by 9.29 % and 8.70 % respectively.