Effect of composition and molecular weight on the crystallization behavior of blends of iPP and a metallocenic ethylene/1-octene copolymer

摘要

Blends covering the entire range of compositions of a metallocenic ethylene/1-octene copolymer and two conventional isotactic poly(propylene)s (iPPs) of different molecular weight have been prepared, analyzing (by differential scanning calorimetry and X-ray diffraction) the effect of composition and molecular weight on the crystallization behavior. It was found that those blends, rich in the iPP component show a behavior practically coincident with the weighted addition of the two components. On the contrary, significant deviations were found for the blends where the ethylene copolymer is the major component. These deviations are considerably more important in the case of the blends with iPP of higher molecular weight. In such a case, the blend with a 25% by weight of iPP presents a normalized crystallinity degree of only 0.20, in comparison with the value of 0.57 exhibited by the pure iPP. After annealing at 120degreesC for 1 minutes, and cooling back to room temperature, that blend increases its crystallinity degree up to only 0.40. [References: 27]