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EFFECT OF THE ADDITION OF POLYETHYLENE GRAFT-MALEIC ANHYDRIDE ON THE RHEOLOGICAL, MECHANICAL AND MORPHOLOGICAL PROPERTIES OF RECYCLED POLY (ETHYLENE TEREPHTALATE)

Maria Sönmez

Abstract

The use of recycled polyethylene terephthalate (PETr) in new value-added products is problematic because, during reprocessing in the melt, it undergoes a number of chemical, mechanical, thermal and oxidative degradations, which leads to decreased intrinsic viscosity / molecular mass and implicitly to poor mechanical and thermal properties. In the literature, numerous approaches have focused on obtaining polymer blends using PETr in combination with other thermoplastic polymers. Unfortunately, such mixtures are incompatible and require the addition of compatibilizing agents capable of improving the dispersion and implicitly the interface between the two polymers. In this paper, the effect of the addition of various quantities (10, 20, 30, 40 and 50%) of polyethylene grafted with maleic anhydride (PE-g-AM) on mechanical, thermal, morphological and rheological properties of PETr, was studied. Petr / x PE-g-AM blend were obtained on a Brabender mixer at 240°C and a speed of 30rpm for 2 min, and 110 rpm for 5 minutes. From the processed blends, test specimens were obtained, by the compression method in a mold with a length dimension of 80 mm, width - 10 mm and thickness - 4 mm. These specimens were used for flexural strength, flexural modulus, flexural strain, impact strength, Vicat softening point, and SEM. The results obtained show a different behavior between mixtures depending on the amount of PE-g-AM used. Flexural strength improves significantly with PETr for all PE-g-AM mixtures. The best flexural strength values were obtained for mixtures containing 10 or 40% PE-g-AM respectively. Flexural modulus decreases and flexural strain improves with increasing amounts of PE-g-AM. Analyzing the flexural stress versus strain graph, different behaviors are observed depending on the amount of PE-g-AM. At low PE-g-AM quantities (10, 20 and 30%) as well as PETr, the curvature linearity in the elastic zone is observed, indicating that the mixtures exhibit brittle behavior. At high volumes of 40 and 50% PE-g-AM, is noticed the variation from the linearity of the curves, with plastic deformation zones (characteristic of the ductile materials). Impact strength is significantly improved for blends containing high PE-g-AM (40-50%), relative to PETr, due to increased ductility of the mixture. The torsional versus time analysis, recorded during PETr's processing, shows that the torque value is low indicating that degradation processes occur (decrease in molecular weight, reflected in decreased intrinsic viscosity). However, higher torque values were obtained as the amount of PE-g-AM increased. The SEM images show very good compatibility between the phases, even at high amounts of PE-g-AM. The Vicat softening temperature, drops considerably relative to PETr, with the increase in PE-g-AM.

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DOI resolver: doi.org/10.5593/sgem2019/4.1/s18.086

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