Rheological and physical properties of natural rubber modified by admicellar polymerization of styrene

Abstract

Admicellar polymerization is a fine-coating technique to form ultrathin polymer films on the charged surface of another polymer that could possibly improve its mechanical properties. According to this technique, the thin polystyrene (PS) film covers each natural rubber (NR) particle by using bilayers of cetyltrimethylammonium bromide (CTAB) as a reaction template for the admicellar polymerization of PS-NR by varying styrene concentrations from 50 to 300 mM and using a ratio of styrene to initiator at 1:0.04. The comfirmation of synthesizing admicelled PS-NR was investigated by FTIR. The TGA curves revealed that the thermal property of the admicelled PS-NR was improved when a higher styrene concentration was used. The cure rate and the minimum torque of admicelled PS-NR with any styrene concentration were lower than that of NR, but the maximum torque was vice versa. In the physical properties study, the cured admicelled PS-NR with 300 mM-styrene has the highest tensile strength, modulus and hardness buty lowest elongation at break. The rheological behavior of the admicelled PS-NR, using a Capillary Rheometer, indicated better processability after blending and mixing with 50 wt.% NR and 30 phr silica, respectively.