It is convenient to remark that several studies have reported that raw material flakes produced by the size reduction of PET waste should have certain minimum requirements in order to achieve a satisfactory PET recycling process [12- 15]. This is because there is a loss of molecular weight in PET extrusion process due to hydrolytic [16,17] and thermal- mechanical degradation during melting process [18]. Degradation also causes non uniformity in the flow of fused material generating negative effects in subsequent processes