Effect of composition on transcrystallization with reorientation of polypropylene in drawn PET/PP blend

The crystallization behaviour of three blend compositions of poly(ethylene terephthalate)/polypropylene (PET/PP), namely 30/70, 50/50 and 70/30 wt.% was studied. The samples were heated up to temperature between the melting temperatures of the blend components and then cooled to 30 °C. X-ray pictures were taken at every stage and it was shown that a recrystallization with reorientation of the PP crystallites took place during the nonisothermal recrystallization. The PP crystallites in the PET/PP blend reorient with molecular axis tilted at aprox. 49° against the FA during the recrystallization. The amount of PP in the blend does not directly affect the process of trancrystallization with reorientation but has only a masking effect. Such reorientation was observed for all three blends. No reorientation occurs if the PET crystallites have been melted before the recrystallization, i.e., when oriented they induce the reorientation of the PP crystallites.