In situ micro and nano fibrillar reinforced elastomer composites based on polypropylene (PP)/olefinic block copolymer (OBC)

In situ micro and nano fibrillar reinforced blends with olefin block copolymer as matrix and polypropylene (PP) as dispersed fibrils were successfully prepared by a simple extrusion-stretching process. Four parameters, that are screw rotating speed, post stretch ratio, die dimension, and PP content, are explored to study how they affect PP fiber morphology and the mechanical performance of the composites. At high stretch ratio, refined PP fibrils are obtained at three different screw rotating speeds and the diameters of the fibrils decrease as the speed increases; at low stretch ratio, only short fibrils with elongated ellipsoids are found in the composites whatever the screw rotating speeds are. When other processing parameters are kept constant, the blends prepared with smaller die exhibit a more impeccable fibrils structure. As the PP contents vary from 5 wt% to 20 wt%, all the composites nearly have same PP morphologies and the diameters of PP fibrils seem to be independent of PP content. Particularly, even refined nano-sized PP fibrils are formed under high screw rotating speed and post stretch ratio with smaller die. Rheological and mechanical analysis show that once the continuously PP fibrils network are established, the property of OBC could be well improved. This structure is proved to be superior to PP component of spheres, elongated ellipsoids and short fibrils.