Estudo do efeito do tratamento térmico e da radiação gama sobre o Poli(Tereftalato de Etileno) (PET)

Abstract

Poly (Ethylene Terephthalate), popularly known as PET, is a thermoplastic polymer that has a partially aliphatic structure, i.e. open and closed carbon chains; and aromatic, these chains composed of benzene rings. This semi crystalline material is one of the most commercially important materials in the polyester family. Currently, PET is used both in packaging manufacturing and in the replacement of steel, aluminum and glass in automotive vehicles, thus contributing to a vehicle’s weight reduction. In addition, this type of compound is used in the manufacture of tiles, bricks, insulation boards, among others. In this work, we chose to analyze PET from soda bottle packaging, because it is a cheap, versatile, rigid material, has thermal stability and light stability, and after its use as packaging it has found numerous applications. The research was developed in order to study the effects of heat treatment and gamma irradiation that could contribute to a possible degradation and influence the behavior of this type of material that is annually discarded in abundance in nature. Some samples were subjected to heat treatments ranging from 200 to 265 o C over a 30 minute period while others were subjected to gamma irradiation at doses ranging from 1kGy to 100kGy, and then were analyzed by vibrational spectroscopy (Fourier Transform Infrared Spectroscopy and Raman Spectroscopy) and X-ray Diffraction. In addition to these techniques, the FT-IR and Raman spectra were simulated to predict the behavior of the Poly (Ethylene Terephthalate) structure, to identify similar bands between the two cases and the possible functional groups or bonds present in the simulated spectra trying to explain the mechanism of their formation. The analyzes employed in this experiment were very important, because through them, it was possible to identify some functional groups belonging to Poly (Ethylene Terephthalate), the crystalline structure, the crystalline planes present in the PET structure and the functional groups that are responsible for the presence of the polyethylene terephthalate crystalline phase in the material, phase changes were also observed in PET samples that were exposed to heat treatment. Through these results, it becomes possible to explain that the phase increase can influence the transformation of the amorphous phase into crystalline phase, allowing a more rigid material.