Modification of Propylene-Ethylene Copolymersby Reactive Extrusion

RODOLFO DIONISI; MARCELO DANIEL FAILLA; MARCELO VILLAR; LIDIA MARÍA QUINZANI; ENRIQUE M. VALLÉS

MACROMOLECULAR SYMPOSIA

WILEY

Lugar: New York; Año: 1998 vol. 128 p. 127 - 136

1022-1360

The rheological properties of commercial propylene-ethylenecopolymers were modified  by  reactive extrusion.  A dialkyl peroxide was used as initiator ofthe controlled degradation reaction of the starting polymers.  The experiments were carried out in a twinscrew extruder at different peroxide concentrations, temperatures, and screwspeeds.  Gel permeation chromato-graphywas used to estimate the molecular weight distribution of the original andmodified copolymers.  It has beenobserved that the estimated molecular weight of the copolymers tends todecrease with the increase in peroxide concentration at all extrusionconditions studied.  The linearviscoelastic properties of all the polymers were evaluated at differenttemperatures and frequencies in a rota-tional rheometer.  Both the viscous and the elastic propertiesdecrease with augmenting peroxide concentration.  The rheological behavior of the materials isstrongly affected by the global ethylene content of the copolymers.  The scanning electron microscopy study didnot reveal a significant difference between the morphology of the unmodifiedand the modified blends for a given composition of the originalcopolymers.  In all the cases themicrostructure is composed of a finely dispersed phase of ethylene-propylenecopolymer within a continuous poly-propylene phase.