Quiescent crystallization kinetics and morphology of i-PP resins for injection molding. II. Nonisothermal crystallization as a function of molecular weight

The quiescent nonisothermal crystallization kinetics of polypropylene resins was studied as a function of their molecular weight, Mw. Differential scanning calorimetry and polarized light optical microscopy were used to follow this kinetics. It was observed that a modified Hoffman and Lauritzen equation could describe with accuracy their nonisothermal behavior. Also it was found that the polypropylene nonisothermal growth rates, Gn, were similar to their corresponding isothermal rates, G, and also decreased with the increase in Mw. The use of a prior isothermal nucleation procedure allowed to obtain data at higher temperatures and to compare these data at higher cooling rates than the ones found in the literature. The morphology of all the samples revealed a fine and radial spherulitic texture.