Morphology and dynamic mechanical properties of natural rubber/nitrile rubber blends containing trans-polyoctylene rubber as a compatibilizer

The use of trans-polyoctylene rubber (TOR) as a compatibilizer for blends of natural rubber (NR) and acrylonitrile-butadiene rubber (NBR) was investigated using atomic force microscopy (AFM) and dynamic mechanical analysis (DMA). The NR/NBR blends containing varying proportions of TOR were prepared in an internal mixer. AFM micrographs of NR/NBR blend at 50/50 (w/w) composition showed heterogeneous phase morphology with NR as a matrix and NBR as a dispersed phase. Inclusion of TOR in the NR/NBR blend altered the phase morphology by reducing the size of the NBR phase. DMA of NR/NBR/TOR showed reduction in tan δ peak height of NBR and an increase in storage modulus E′ in the rubbery region for the NR/NBR blends. A comparison of the E′ obtained from experimental data with that from theoretical models was made to deduce the location of TOR in the blend. Based on the fittings of calculated and experimental values of E', it was inferred that TOR was incorporated into the NR phase at lower proportion as well as at the interfacial region at higher proportion. The Cole-Cole plot illustrated the compatibilizing effect of TOR.