Study on polypropylene-polyethylene-based copolymer solidification

In the present work, nonisothermal crystallization is analyzed. Concretely, we study the solidification process of polypropylene-polyethylene-based co polymers by means of differential scanning calorimetry (DSC). Several sampl es with different additives are subjected to artificial aging processes. Th e calculation of the specific surface energy, sigma, is in good accordance with the results reported in the references. The artificial aging is respon sible for a slight increase of sigma values (i.e., increase of 1.6 kJ . m(- 2) for sample A and 0.3 kJ . m(-2) for sample B). On the other hand, the si gma value of sample B is considerably lower than that of samples A, C, and D (i.e., 17.3 kJ . m(-2) for sample B versus an average value of 23.0 kJ . m(-2) for the other samples). Microstructure analysis was performed by scan ning electronic microscopy (SEM). As shown from the analysis, aging only af fects superficial zones because no changes in the morphology of the central zone were detected in the different samples. Sample B shows a different be havior; it was less resistant to fracture. From DSC and SEM measurements, w e can state the additive influence on the original sample behavior as well as on the solidification process of polypropylene-polyethylene-based copoly mers. (C) 2000 John Wiley & Sons, Inc.