High-density polyethylene modified by polydimethylsiloxane

High-density polyethylene (HDPE) was modified by the grafting of polydimeth ylsiloxane (PDMS) through a free-radical process, in a melt-mixer chamber, using dicumyl peroxide (DCP) as an initiator. The influence of PDMS (0.2-0. 8 mol %) and peroxide (0.03-0.08 mol %) concentrations on the grafting, fin al torque, and melt flow rate (MFR) of copolymers were investigated using f actorial planning. Fourier transform infrared spectroscopy (FTIR), differen tial scanning calorimetry (DSC), gel permeation chromatography (GPC), MFR, and rheometry were used to characterize the copolymers obtained. Surface pl ots showed that higher degrees of grafted PDMS and higher final torques wer e obtained with increase in the PDMS amount at low DCP levels and with incr ease in the DCP amount at low PDMS levels. The peaks of fusion and crystall ization of the copolymers showed no significant changes with respect to HDP E. Data of MFR and GPC suggested that crosslinking reactions and/or chain e xtension occurred concomitant with the grafting reactions. Copolymers with high grafting degrees showed high MFR and low dynamic shear viscosities in comparison with low grafting degree copolymers, which is probably due to th e migration of the PDMS-containing copolymers on the surface. (C) 2001 John Wiley & Sons, Inc.