Surface modification of LDPE with PE-PEO graft copolymer

Films of LDPE containing 1-10 wt % of various polymeric additives were prep ared by different techniques. Three poly(ethylene-graft-ethylene oxide)s sy nthesized by grafting poly(ethylene-co-acrylic acid) with poly(ethylene oxi de) monomethyl ether (MPEO), and two pure MPEOs having molecular weights 75 0 and 2000 were used as additives. The additives were mixed with LDPE both by blending in a common solvent and by melt mixing. The blends were then so lvent cast from xylene onto glass Petri dishes or compression molded betwee n glass plates. The film surfaces were studied by water contact angle measu rements and by X-ray photoelectron spectroscopy (XPS), and melting points a nd heats of melting were recorded by differential scanning calorimetry (DSC ). The blends had a two-phase morphology, with enrichment of the graft copo lymers at the glass-polymer interface, as shown by contact angle values and XPS spectra. Large differences in the interface accumulation between the d ifferent film samples were observed. Films prepared by compression molding of solution-mixed blends exhibited much lower surface accumulation of graft copolymer at the glass-polymer interface than did the solvent east or melt -mixed/compression-molded samples. (C) 2000 John Wiley & Sons, Inc.