Versatile one-pot synthesis of grafted-hydrogenated natural rubber

Abstract

Natural rubber, one of the widely used renewable resources, is susceptible to degradation upon exposure to sunlight, oxygen, heat and ozone due to the presence of double bonds in cis-polyisoprene. This work describes a versatile means to improve the stability of natural rubber by saturating the double bonds through grafting and hydrogenation reactions as a one-pot method. Graft copolymerization of methyl methacrylate onto natural rubber latex was carried out using emulsion polymerization in the presence of cumene hydroperoxide/tetra-ethylene pentamine mixture as initiator whereas hydrogenation of the natural rubber was performed using the diimide reduction method. The effects of initiator concentration, monomer concentration, reaction temperature, and reaction time on reaction efficiency were investigated. In addition, the thermal, mechanical, ozone ageing, and solvent resistance properties of modified natural rubbers were characterized and found to be superior to the unmodified natural rubber. The decomposition temperature of the grafted-hydrogenated natural rubber is almost 30 °C better than that of the unmodified rubber. The mechanical strength was also improved. In order to test the versatility of this one-pot technique, styrene was also used as a monomer to graft onto the natural rubber. These results show that the one-pot method developed in this work is a simple, versatile means for improving the chemical and physical properties of the natural rubber. This work is also a proof-of-concept for other combinations of reactions or other polymers.