Morphology and crystallization of isotactic polypropylene/poly(dicyclohexylitaconate) blends

The influence of the addition of poly(dicyclohexylitaconate), PDCHI, on the crystallization process of isotactic polypropylene and its morphology was studied as a function of PDCHI mol mass, blend composition, and sample preparation. In particular three fractions of PDCHI with different mol masses were used. Irrespective of mol mass and blend composition, the morphological and the calorimetric analyses indicate that the blend components are always immiscible. In fact, the blends are characterized by a non-homogeneous melt and on the DSC thermograms two glass transitions are always detected. Conversely the kinetics properties, related to the isothermal crystallization from the melt, are greatly dependent on PDCHI molecular mass. For a given crystallization temperature and composition, in the case of the iPP/ PDCHI(HM) blends containing the highest molecular mass PDCHI, the values of half time of crystallization, ?1/2, are lower than those relative to plain iPP, whereas for the blends with lower molecular mass PDCHI, the presence of PDCHI causes an increase in the ?1/2. It was found, moreover, that the spherulite growth rate does not depend on composition. The crystallization behavior of iPP rate in dependence on the PDCHI molecular mass was attributed to the influence of PDCHI on the nudeation rate of IPP spherulites.