MODIFICATION OF PROPYLENE-ETHYLENE COPOLYMERS BY REACTIVE EXTRUSION

RODOLFO A. DIONISI; MARCELO D. FAILLA; MARCELO VILLAR; LIDIA M. QUINZANI; ENRIQUE M. VALLÉS

MACROMOLECULAR SYMPOSIA

WILEY

Lugar: New York; Año: 1998 vol. 129 p. 127 - 136

1022-1360

The rheological properties of commercial propylene-ethylenecopolymers were modified by reactive extrusion. A dialkyl peroxide was usedas initiator of the controlled degradation reaction of the starting polymers. Theexperiments were carried out in a twin screw extruder at different peroxideconcentrations, temperatures, and screw speeds. Gel permeation chromatographywas used to estimate the molecular weight distribution of the original andmodified copolymers. It has been observed that the estimated molecular weightof the copolymers tends to decrease with the increase in peroxide concentrationat all extrusion conditions studied. The linear viscoelastic properties of all thepolymers were evaluated at different temperatures and frequencies in a rotationalrheometer. Both the viscous and the elastic properties decrease withaugmenting peroxide concentration. The rheological behavior of the materials isstrongly affected by the global ethylene content of the copolymers. The scanningelectron microscopy study did not reveal a significant difference between themorphology of the unmodified and the modified blends for a given composition ofthe original copolymers. In all the cases the microstructure is composed of afinely dispersed phase of ethylene-propylene copolymer within a continuous polypropylenephase.