PARTIAL MELTING AND RECRYSTALLIZATION OF ISOTACTIC POLYPROPYLENE

A relatively high predetermined crystallization temperature (135°C) was chosen to grow well developed iPP spherulites, then the partial melting was carried out at a temperature of 165°C, where the preformed spherulites were seen to only decrease their size but not completely melted. The crystallization behavior of partially melted isotactic polypropylene (iPP) has been carefully examined by different scanning calorimetry (DSC) and polarized light microscopy (PLM). The experimental results show that at a special annealing temperature (165°C) the melting behavior of iPP includes two parts with different mechanism, one part is the melting of iPP spherulite outside, another is the partial lamellae perfection during longer annealing time in the unmelted spherulite. The conformational orders of the iPP melt decrease with the increase of the annealing temperature.