Interfacial enhancement of fibrillar silicates (FSs)/EPDM nanocomposites by surface modification of FS in supercritical CO₂

In this work, surface modification of fibrillar silicate (FS) is conducted by using supercritical CO₂(sc-CO₂) technique. For comparison purpose, conventional modification method is also carried out. The results showed that physical adsorption of the modifier (KH570) on FS surface dominated by using conventional method, whereas chemical adsorption dominated by using sc-CO₂ technique. In addition, a more uniform adsorption of the modifier on FS surface is successfully obtained by using sc-CO₂ method. This is ascribed to the special gaseous and liquid characteristics of sc-CO₂, which can facilitate the diffuse and the full contact of KH570 on the whole surface of FS. The modified FS are then melt blended with ethylene-propylene ethylidene norbornene terpolymer (EPDM) to prepare rubber composites with excellent high temperature performance and good ageing resistance. The results showed that a more uniform dispersion of FS in EPDM matrix and a stronger interfacial interaction between FS and EPDM are successfully achieved by surface modification of FS in sc-CO₂, which lead to the obviously enhanced mechanical properties of the composites. Our work demonstrates a better surface modification technique for FS to largely improve the interfacial interaction between FS and EPDM and to obtain a high performance FS/EPDM elastomer composites for its wide application such as transmission belts of automobile.