RHEOLOGICAL BEHAVIOR OF NATURAL AND SYNTHETIC RUBBER LATTICES IN THE PRESENCE OF SURFACE-ACTIVE AGENTS

The rheological properties of natural rubber (NR), epoxidised natural rubber (ENR) and styrene butadiene rubber (SBR) lattices have been stu died with reference to the effect of shear rate, temperature and vario us surface active agents such as casein, poly(vinyl alcohol) and sodiu m methyl cellulose. NR latex showed pseudoplastic behaviour due to its high solid content which was evidenced by the decrease in viscosity w ith an increase in shear rate. Due to the low solid content, the visco sities of both ENR and SBR lattices were virtually constant over the e ntire range of shear rate, indicating Newtonian behaviour. Addition of surface active agents increased the viscosities of NR and SBR lattice s. The increase in viscosity upon the addition of a surface active age nt is due to the occlusion of rubber particles in the network formed b y the surface active agents in the aqueous phase. However, viscosity o f ENR latex decreased with the addition of surface active agents. ENR latex containing surface active agents showed dilatant behaviour.