Study of compatibilization of HDPE-PET blends by adding grafted or statistical copolymers

The reactive compatibilization of blends of HDPE-PET [high-density polyethy lene-poly(ethylene terephthalate)] was:investigated in this study. The comp atibilizers used were two grafted copolymers prepared by reactive extrusion containing 1.20-2.30 wt % GMA such as HDPE-g-GMA and one statistical copol ymer containing 1 wt % GMA such as Lotader AX8920. HDPE was successfully fu nctionalized using a melt free-radical grafting technique. Grafting was ini tiated in two ways: adding an initiator in the polymer-monomer mixture or a ctivation by ozone of polymer. Ozonization of HDPE by the introduction of a peroxide lead to a better grafting yield and to better grafting efficiency of the samples. The effects of the three compatibilizers were evaluated by studying the morphology and the thermal and mechanical properties of HDPE- PET (70/30 wt %) blends. Significant improvements were observed, especially in morphology, elongation at break, and Charpy impact strength of the comp atibilized blends. A more pronounced compatibilizing effect was obtained wi th the statistical copolymer, for which the elongation at break and the imp act strength were increased by 100%, while the uncompatibilized blends show ed a 60% decrease in the Young's modulus and the strength at break. We also were able to show that the grafting yield increase of 1.20-2.30 wt % of GM A did not affect the properties of the blends because the grafted copolymer s possess very similar chemical structures. However, compatibilization of b lends with grafted copolymers is an interesting method, particularly for re cycled blends, because the synthesis of these compatibilizers is easy and c heap in comparison to statistical copolymer. (C) 2001 John Wiley & Sons, In c. J Appl Polym Sci 81: 2377-2386, 2001.