Crystallization studies of propylene copolymer fractions

The aim of this work was to study the effect of comonomer content and tacticity on the crystallization behavior of propylene copolymer fractions. Initially two random copolymers of propylene and ethylene with similar molecular weight, but different ethylene (comonomer) content, were fractionated successively in a soxhlet apparatus with solvents of increasing solvent power. These fractions varied in comonomer content and tacticity. The thermal properties from DSC, the morphologial studies from light microscopy, polymorphism from WAXD and the linear growth rates from hot stage microscope were determined. The comonomer content had a significant effect on the thermal, structural and morphological properties of the copolymer. The total impurity content of the copolymers was determined by calculating the defects caused by the effects of tacticity and comonomer. The equilibrium thermodynamic properties of these fractions were determined using different extrapolation techniques. The total defect content obeyed the Flory's total exclusion model. The effect of comonomer content on the regimes of crystallization for these fractions was also evaluated.