Abstract
This paper intends to evaluate the heat of fusion of isotactic polypropylene crystals in monoclinic form by thermal analysis and the method of x-ray diffraction. A whole polymer having viscosityaverage molecular weight _??_v=1.93×105 and three fractions (_??_v=1.47×105, 1.75×105 and 6.31×105, respectively), insoluble in boiling n-heptane, were moulded into 0.1mm thick film, and then, annealed at the temperature ranging from 120°C to 165°C by using the descending temperature method in similar manner as that described in the previous paper (K. Kamide, M. Sanada; Chem. High Polymers, Japan, 24, 662 (1967)). Heat of fusion ΔH, x-ray crystallinity Cx and density were measured on the slowly-cooled film after annealing. From the relationships among ΔH, Cx and density, ΔH=ca 33cal/g for crystals with Cx=100% was obtained irrespective of molecular weight and molecular weight distribution, respectively.
