Renewable Interfacial Modifier for Silica Filled Natural Rubber Compound

Abstract

A main problem of using silica as reinforcing filler in natural rubber (NR) compound is a poor dispersion of silica in the rubber matrix due to incompatibility between them. As silica contains high silanol groups on its surface, these polar groups promote strong filler-filler interactions leading to high degree of aggregation and agglomeration of silica particles. To overcome this drawback, many types of modifiers have been applied into silica filled recipes. In this work, a renewable and sustainable interfacial modifier, namely low molecular weight hydroxyl terminated natural rubber (HTNR). HTNR was prepared by controlled epoxidation and cleavage of natural rubber, following by reduction reaction of the obtained carbonyl telechelic natural rubber. Influence of the prepared interfacial modifier on enhancement of rubber-filler interaction was studied by focusing on the cure characteristics and the mechanical properties of silica filled natural rubber at a fixed silica content of 30 phr. In comparison with silica filled compound without silane coupling agent, shorter scorch and cure times, lower Payne effect and higher tensile strength of silica filled natural rubber were achieved with the presence of interfacial modifier at 2.4 parts per hundred parts of rubber (phr). This was attributed to an active reaction of silanol groups with interfacial modifier and compatibility between modifier and natural rubber. For HTNR-treated compound to obtain optimum properties, mixing should be carried out at initial mixing temperature of 300C, mixing time of 12minutes, and rotor speed of 60rpm. However, TESPT is more effective than HTNR because it imposes better properties than HTNR.