Crystallization of forms I′ and form II of polybutene-1 in stretched polypropylene/polybutene-1 blends

In this work, the effects of orientated crystal morphology of polypropylene (PP) induced by tensile stretching on the subsequent crystallization behavior of polybutene-1 (PB-1) in the incompatible PP/PB-1 (50/50) blends were studied. When the PP/PB-1 blends were stretched at a temperature above melting temperature (Tm) of PB-1 but below the Tm of PP, strong orientation of PP crystals was observed under stretching. As temperature dropped below Tm of PB-1, orientated form II and I′ of PB-1 appeared. In the framework of PP crystals, form I′ of PB-1 was formed due to the confined effect which suppressed the formation of form II crystals. Interfacial interaction played a role in guiding the nucleation of both form II and I’ crystals resulting in highly oriented structures. The mechanism of PB-1 orientation and confined crystallization under stretching in PP/PB-1 (50/50) blends was discussed.