Estudo da degradação da PCL e de blendas PS/PCL.

Abstract

This work aimed to study and understand the different degradation mechanisms of PS, PCL and PS / PCL and PS / PCL / SEBS blends. There are many factors and types of degradation to be studied, but for this research the photodegradation and the biodegradation were studied. These types of degradation have been chosen because they are considered to be the most common occurrences in polymers. In general, the material in use is always exposed to radiation and, when discarded, is deposited in dumps or landfills. Thus, polystyrene/poly(ɛ-caprolactone)(75/25%) and polystyrene/poly(ɛ-caprolactone) /copolymer(PS/PCL/SEBSMA)(70/25/5%) blends were prepared in a double extruder corrotational thread and then the specimens were injection molded. Neat PS and PCL were also processed under the same conditions for comparison. After the molding, the samples were subjected to the photodegradation tests where only the influence of the radiant light was investigated (in an accelerated aging chamber with UV-B light for times of 1 up 9 weeks) and the biodegradation in soil prepared according to ASTM G-160-03, for a maximum period of 90 days. Regarding torque rheometry we observed the evidence of reactions between PCL and SEBSMA. According the mechanical tensile test, the results obtained after photodegradation indicated a change in the behavior of PCL with the irradiation that was previously a ductile polymer and then became brittle and much more rigid. The Infrared Region Spectroscopy (FTIR) test changes were observed in the carbonyl peak. They can be attributed to the greater presence of groups, as well as possible changes in their location within the polymer chain. PCL and PS showed signs of surface degradation and according Scanning Electron Microscopy (SEM), the change in PCL and blends morphology was verified by means of the Optical Microscopy (OM) images. The results obtained after the biodegradation test indicated that PCL was more susceptible to attack by microorganisms, presenting changes in mechanical properties and morphology. The visual appearance of PCL samples presented a rough, brittle and altered staining surface. The PS and its blends did not show significant changes indicating that the test did not act effectively in the biodegradation of these systems.