Preparation and Characterization of Some NR and SBR Formulations Containing Different Modified Kaolinite

Kaolinite clay (KC) surface was modified with different surface modifiers such as methacrylic acid (MAA), polymethacrylic acid (PMAA1, mol wt 10,000) and polymethacrylic acid (PMAA2, mol wt 11,500). The adsorption isotherms of the above modifiers on the surface of KC were determined. The concentrations required for building up monolayer coverage of these modifiers on the surface of KC were determined from the adsorption isotherms. The optimum amount of modifier required for monolayer surface coverage on kaolinite was equal to 31 x 10(-5) mol/g for MAA, 35 x 10(-5) mol/g for PMAA and 23.5 x 10(-5) mol/g for PMA. Different rubber mixes containing unmodified and modified KC were prepared. The rheometric characteristics of the rubber mixes and physico-mechanical properties of the rubber vulcanizates were measured. There was remarkable decrease in both the optimum cure time (tc(90)) and scorch time (ts(2)), following increase in the maximum torque of the SBR mixes by adding unmodified or modified KC. With the maximum torque increase, the values of both of the optimum cure time (tc(90)) and scorch time (ts(2)) decreases for the NR mixes by adding unmodified and modified KC. Also the mechanical properties of the investigated rubber vulcanizates as tensile strength and hardness were improved using unmodified KC and modified KC.