CRYSTALLIZATION KINETICS OF METALLOCENE TYPE POLYPROPYLENES Influence of molecular weight and comparison with Ziegler-Natta type systems

M. J. GALANTE; L. MANDELKERN; R.G. ALAMO; A. LEHTINEN; R. PAUKKERI

JOURNAL OF THERMAL ANALYSIS

John Wiley & Sons Ltd

Año: 1996 vol. 47 p. 913 - 929

0368-4466

The crystallization kinetics from the melt of metallocene type isotactic poly(propylenes) havingthe same chain defect concentration and molecular weights ranging from 68480 to 288430have been studied by differential scanning calorimetry. The crystallization rates and the variationof the rates with crystallization temperature follow a pattern that is basically independent of molecularweight. This result contrasts with the molecular weight dependence on the crystallizationrate observed in linear polyethylene, random ethylene copolymers as well as other semierystallinesystems.Most significant is the fact that the metalloeene poly(propylenes) show apparently significantlyhigher o9 products than do the Ziegler type fractions of matched molecular weight anddefect eoneentration. This difference can be interpreted as the metallocene type crystallites havinghigher effect on surface interfaeial free energies than the Ziegler type, or can result from thetwo different chain types having different sequence propagation probabilities.