Modification of Propylene-ethylene Copolymers by Reactive Extrusion

R.A. DIONISI; M.D. FAILLA; M.A. VILLAR; L.M. QUINZANI; E.M. VALLÉS

MACROMOLECULAR SYMPOSIA

WILEY

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

1022-1360

The rheological properties of commercial propylene-ethylene copolymers were modified by reactive extrusion. A dialkyl peroxide was used as initiator of the controlled degradation reaction of the starting polymers. The experiments were carried out in a twin screw extruder at different peroxide concentrations, temperatures, and screw speeds. Gel permeation chromatography was used to estimate the molecular weight distribution of the original and modified copolymers. It has been observed that the estimated molecular weight of the copolymers tends to decrease with the increase in peroxide concentration at all extrusion conditions studied. The linear viscoelastic properties of all the polymers were evaluated at different temperatures and frequencies in a rotational rheometer. Both the viscous and the elastic properties decrease with augmenting peroxide concentration. The Theological behavior of the materials is strongly affected by the global ethylene content of the copolymers. The scanning electron microscopy study did not reveal a significant difference between the morphology of the unmodified and the modified blends for a given composition of the original copolymers. In all the cases the microstructure is composed of a finely dispersed phase of ethylene-propylene copolymer within a continuous polypropylene phase.