Introduction
From an economical point of view, the recycling process is the best way to reduce wastes of poly(ethylene terephthalate) (PET) [1] and, therefore, many technologies have been developed for performing this type of processes. The first effort in the world for recycling PET bottles was in 1977 [2]; but in the following decades, scientific studies were performed to analyze the properties of recycled PET wastes using extrusion processes. Several methods have been reported to obtain recycled recipients and bottles from PET, but in general PET wastes have been traditionally used for energy recovery [3-5]. Actually, the recycled PET is used in the synthesis of special plastic composite materials [6] and to reinforce concrete [7,8]. For example, Torres et al. [9] performed a comparative study of the thermal and mechanical properties of bottles made from waste and virgin PET. These authors have obtained elongation values of 200 % for virgin PET and values 10 % smaller for recycled PET. These results were attributed to the crystallinity differences. Oromiehie and Mamizadeh [10] used three different methods for recycling PET bottles, where virgin PET, recycled PET and mixtures of both PET types, with and without polypropylene