Transformando dejetos de PET em materiais de importância tecnológica

Abstract

The poly(ethylene)terephthalate (PET) is a thermoplastic polymer produced from terephthalic acid and ethyleneglycol This polymer has a high mechanical and chemical resistance, gas impermeability, low density and a low cost of production. Due to these properties, PET is one of the most widely used materials in industry, mainly to manufacture soft-drink bottles, and has become one of the major post-consumer plastic waste. Recycling PET wasting has been increasingly demanded by both ecological and technological reasons. The most common ways to dealing with PET disposal problems are incinerating and chemical recycling. However, most of the recycled PET is used for the manufacture of products of low commercial value. This work presents detailed studies of the hydrolysis process of PET in acid, basic and neutral medium, including the use of the obtained materials as adsorbents. Initially a carefully study of the hydrolysis process was carried out aiming to understand the process and to produce materials that could be uses as ion-exchange resins. The obtained materials were characterized by hydrolysis degree (loss of mass), presence of acid groups (titration), infrared spectroscopy, thermal analysis (TG/DTG, DSC and TMA) and X-ray diffraction. Considering the remarkable differences observed between the materials it was possible to propose that the acid hydrolysis occurs through a different mechanism as compared with the basic and neutral counterparts. The second part of this work presents some preliminary results obtained by the use of the materials as adsorbents. The superficial area of the materials was determined by BET and the adsorption properties were tested using the following ions: methylene blue, cadmium, cooper, zinc, iron and chromium. The results show that some of the materials obtained from acid hydrolysis have cation-adsortion capacity, though it is lower than the commercially available ion-exchange resins. These preliminary results indicate that the materials obtained from partially hydrolyzed PET may be used as adsorbents. Neverthless, more investment in this field is needed to improve the ion-exchange capacity.