Shear-induced conformational ordering in the melt of isotactic polypropylene

The shear-induced coil-helix transition in the melt of isotactic polypropylene (iPP) was studied by using a model system of synthetic polymer isotactic polypropylene (iPP). The isothermal crystallization of iPP studied at 140 °C denote the presence of regular bands, indicating the existence of short helices in the melt. Shear-induced conformational order is observed at higher temperatures and the intensity of the vibration bands show an inflection point that depends on the melting of helical structures and crystallization of the polymer. The results show that shear induces an increase of length and the concentration of helices in the melt of iPP. The results also show that the helical structure of iPP propagates from both sides of short helices without primary nucleation and the long helixes can relax back in initial state and grow and align to create crystallization.