Effect of masterbatch drying methods on the properties of rubber reinforced with renewable hydrophilic filler

Abstract

Hydrophilic fillers contain functional groups capable of forming hydrogen and/or ionic bonds. Many recent developments with biobased fillers are masterbatch process with rubber latex. The effect of the different process influences the characteristics of filler network and therefore rubber properties. In this study, the rubbers reinforced with hydrophilic filler, soy protein particles, and carbon black processed in two different methods, casting and freeze-drying methods, are investigated using crosslink density, dynamic mechanical properties, stress softening effect, stress relaxation, tensile properties, and thermal degradation. Stress softening effect is analyzed with the Kraus model and shows that the characteristic strains shifted to smaller strains for the rubbers prepared by a casting process. Stress relaxation of the reinforced rubber prepared from the two different processes shows that the rubbers from the casting process have slower relaxation rates because of higher crosslink density and modulus. Overall, the rubber composites prepared by casting method have higher crosslink density, greater softening effect, slower rate of stress relaxation, and higher moduli attributed to greater interactions between hydrophilic components in the reinforced rubber.