The Surface Modification of Diatomite, Thermal, and Mechanical Properties of Poly(vinyl chloride)/Diatomite Composites

Pristine diatomite was first purified by acid treatment and then modified with gamma-methacryloxy propyl trimethoxysilane molecule (KH570) to introduce hydrophobic chains on the surface of acid-treated diatomite. Fourier-transform infrared spectroscopy and thermogravimetric analysis (TGA) indicated that the silane coupling agent (KH570) was successfully grafted on the diatomite through covalent bonding. The digital photos showed that the silanization process changed the surface property of the diatomite. The poly(vinyl chloride) (PVC)/pristine diatomite and PVC/modified diatomite composites were prepared via two-roll mill. The thermal stability and mechanical properties of PVC composites were investigated by TGA, mechanical properties tests, and dynamic mechanical analysis. The results showed that the thermal stability of the composites improved and maximum weight loss temperature (T-max) of the PVC composite with 1 phr modified diatomite was about 20 degrees C higher than that of PVC composite without diatomite. The PVC/modified diatomite composites exhibited better mechanical properties owing to the stronger interfacial interaction between PVC matrix and modified diatomite. But the impact strength reduced sharply when the addition of diatomite was more than 1 phr. The reason of the phenomenon is that the diatomite plays the role of defects in PVC and it works against the absorption of impact strength energy. It was proved by the results of scanning electron microscopy. (C) 2018 Society of Plastics Engineers