Rheological behavior of blends of natural rubber and, hydrogenated nitrile rubber

The influence of dichlorocarbene modified natural rubber (DCNR) as a modifying agent on the rheological behavior of blends based on natural rubber (NR) and hydrogenated nitrile rubber (HNBR) was investigated. The binary blends of NR and HNBR showed a pseudoplastic flow behavior. The blends recorded a viscosity lower than both the constituents showing a behavior, characteristic of immiscible blends. The addition of small quantities of DCNR to the 50/50 blend resulted in an increase in the viscosity due to the interactions with the blend constituents. The temperature sensitivity of the DCNR containing blend decreased with incorporation of filler. The higher elasticity of NR was indicated by higher values of principal normal stress difference (tau(11) - tau(22)), recoverable shear strain (S-R) and lower values of elastic modulus (G) in comparison with other mixes. Blending of NR with HNBR considerably reduced the elasticity of the blend. At lower shear rates, DCNR containing blends recorded a die swell lower than both the blend constituents. Filled blends exhibited very low die swell and showed slight variation with shear rate.