Modificación Estructural del Polietiléntereftalato con Ácido Poliláctico. Síntesis de Polímeros Biodegradables

Abstract

Polyethylene terephthalate (PET) is a very important polymer, but this kind of synthetic polymer is resistant to biological degradation. For this reason there is an urgent need to develop renewable source based biopolymers able to degrade via a natural composting process. An interesting biodegradable polymer is poly(lactide acid) (PLA), which made primarily from renewable agricultural resources. Extrusion is widely used for processing thermoplastic polymer, and studies indicate that, under the high-shear and high-temperature conditions, polymers can undergo a variety of changes at the intra and intermolecular level. Therefore an extrusion process is a very attractive approach, for obtained polymeric blends. In this work, poly(ethylene terephthalate) (PET)-poly(lactide acid) (PLA) blends at different PLA contents (1, 2.5, 5 and 7.5 wt-%), are proposed. PET, PLA and their blends are obtained by extrusion method and characterized using DSC, XRD, SEM, AFM and mechanical tests. The glass transition temperatures (Tg) are ranging from TgPET (74.91 °C) to TgPLA (61.54 °C), as the PLA content increase: 73.12 °C, 69.04 °C, 65.91 °C and 62.11 °C, for 1, 2.5, 5 and 7.5 wt-%, respectively. From XRD, it can be observed that all the blends are missing the crystallite signals from PET and PLA, and only the amorphous character is detected. Spherical form agglomerates, immersed in an amorphous matrix, are detected by SEM; any different phases are not distinguishable, then, a selective solvent was used to dissolve PLA and determine the sites that this polymer occupies in the blend. The differences were observed by SEM and also by AFM. The 2.5 wt-% blend shows a high tensile strength (76-79%) and, was observed by the morphology of the fracture behavior of polymer is ductile.