| Abstract: | The recycling of poly (ethylene terephthalate) (PET), mainly from bottles, has been considered the most promising alternative to reduce municipal solid waste in Brazil. Stabilization processes of this polymer during recycling aim to maintain and improve its physicochemical properties and enhance its applicability. Several classes of additives may be used for PET stabilization, such as antioxidants, metal deactivator or anti-hydrolysis. However, there are no studies in literature about the synergistic or antagonistic effect of the individual or combined use of these additives for the stabilization of PET. The present investigation uses Design of Experiments (DoE) to analyze the effects of the variables that influence the stabilization of post-consumer PET. The variables were humidity and three different classes of additives represented by antioxidants (Irganox 1010® and Irganox B561®), a metal deactivator (Irganox MD1024®) and an anti-hydrolysis (Stabaxol KE7646®), known as polycarbodiimide. Taking intrinsic viscosity into consideration, the post-consumer PET flakes were processed with different additive contents in order to understand both the individual and combined effects that influence stabilization and generate the response surfaces. The results showed that the samples stabilized with polycarbodiimide had an effective increase in intrinsic viscosity. In addition, samples stabilized with antioxidants had lower contribution and the metal deactivator had no effect on the stabilization of recycled PET. Our findings indicate that the hydrolysis overlaps the thermo-oxidative degradation effects and is the main form of PET degradation in the course of recycling. Moreover, besides being marketed as an anti-hydrolysis, results suggest polycarbodiimide is an effective chain extender. Finally, this study sheds some light on the influence of the main additives and variables that influence the degradation and stabilization of PET. The increase in PET intrinsic viscosity promotes its physicochemical properties and allows the recycled polymer to be used in broader market segments. |
