PA80/NBR blends: Optimizing the processability, mechanical and swelling properties for extrusion applications

PA80, a partially crosslinked form of natural rubber, was blended with a polar synthetic rubber (acrylonitrile butadiene rubber (NBR)) in variable proportions via a three-step dry rubber mixing procedure. The effect of PA80 in imparting superior processability and retaining the physical properties of NBR vulcanizates was evaluated to select an optimum blend proportion appropriate for extrusion applications. The polarity mismatch between PA80 and NBR was minimized and the blend properties were improved with a suitable compatibilizer (polychloroprene rubber). The fast-curing accelerators resulted in uniform rheological characteristics. A partial replacement of NBR with PA80 (up to 30 phr) satisfactorily maintained the mechanical and transport properties with minimum deviation. Under similar proportions, the thermal behaviour of the blends was also measured and was comparable with the NBR reference system. Moreover, the filler dispersion was found excellent for all the samples studied. The effect of PA80 in improving the processability was evident from the smoother appearance and lower die swell of extruded profiles. So, a strategy of blending synthetic rubbers with an optimum level of a secondary elastomer like PA80 is highly recommended to achieve a good balance of technical properties, cost-effectiveness and processability.