Crystallization kinetics of binary mixtures of isotactic polypropylene and poly(iso-propylene-stat-1-hexene)

The crystallization behaviour of binary mixtures of an isotactic low molar mass polypropylene (Mw = 7000; Mw/Mn = 1.7) and a higher molar mass (Mw = 510 000; Mw/Mn = 2.2) random poly(propylene-co-1-hexene) with 1 mol.% of 1-hexene has been studied by differential scanning calorimetry, polarized light microscopy and wide angle X-ray scattering. The crystal structure of the homopolymer is unaffected by crystallization temperature whereas the copolymer showed lattice expansion after crystallization at the lower temperature and a unit cell similar to that of the homopolymer after crystallization at the higher temperatures. The blends showed unit cell parameters in between those of the constituents. The melting characteristics and the gradual change in the fold surface energy is obtained from the linear growth rate measurements indicate partial cocrystallization of the constituents.