SURFACE MODIFICATION OF DIATOMITE WITH TITANATE AND ITS EFFECTS ON THE PROPERTIES OF REINFORCING NR/SBR BLENDS

摘要

Diatomite is a biogenic silicolites with porosity. Its main component is amorphous silica formed from the skeleton of single cell of diatom, and the chemical formula is SiO2-nH2O. In mineralogy, it belongs to opal-AG. Owing to low cost, good chemical stability, safe and nontoxic, diatomite is often used as filter aid, adsorbent, catalyst carrier and functional filler. Although precipitated amorphous silica is an important reinforcing agent for rubber, the problems such as high cost and severe pollution during its production process drive people to find the substitute to replace it. It is demonstrated that modified attapulgite and fly ash can substitute (or partly substitute) amorphous silica in rubber. Diatomite, as a natural mineral, is rich in resources and of low cost. Diatomite and precipitated amorphous silica share the same chemical composition, and they both posses porous structure and appear acidic on the surface.4 In addition, diatomite added into rubber or plastic can enhance its rigidity, hardness and wear-resistance significantly.5 As a filler, it can obviously increase strength, aging, curability, recovery, compression, permanent deformation and workability of fluorubber.6 Therefore, substituting amorphous silica with diatomite to reinforce rubber is significant. Due to its low dispersity in organic matrix and poor compatibility in polymer matrix caused by high surface energy and hydrophilicity, diatomite should be surface modified first. Diatomite modified by stearic acid was used in natural rubber/styrene butadiene rubber blends (NR/SBR). The results showed that diatomite took on good dispersion in organic matrix and enhanced mechanical properties of rubber.7 At present, the study of surface modification of diatomite is aiming at improving the adsorb-ability in wastewater treatment,8"10 while little in reinforcing rubber.