Mechanical properties of poly(ethylene terephthalate) modified with functionalized polymers

This study examined the effect of blending poly(ethylene terephthalate) (PE T) with 5% of a functionalized polymer. The blends were characterized by pa rticle size and size distribution, unnotched tensile behavior, toughness, a nd notch sensitivity. The improved properties of blends that incorporated a functionalized elastomer were consistent with in situ formation of a graft copolymer by reaction with PET end groups. Triblock copolymers were examin ed that had styrene end blocks and an ethylene/ butylene midblock (SEBS) wi th grafted maleic anhydride. The present study extended previous investigat ions that focused on level of grafting to examine the effects of component molecular weight and PET hydroxyl-to-carboxyl end-group ratio. Increasing t he molecular weight of the SEES and decreasing the hydroxyl-to-carboxyl rat io of the PET increased the effectiveness of the SEES. In addition, a mix o f an unfunctionalized SEES with a functionalized SEES was more effective th an a single SEES with the same total anhydride content. The same elastomers were the most effective for modifying a lower molecular weight PET (intrin sic viscosity 0.73) and a higher molecular weight PET (intrinsic viscosity 0.95). Some functionalized polypropylenes included in the study did not enh ance the properties of PET. (C) 1999 John Wiley & Sons, Inc.