Efeito do teor de TPS e mesocarpo de babaçu nas propriedades da blenda PBAT/TPS.

Abstract

This work aims to investigate the influence of the use of different processing temperatures on rheological, mechanical and biodegradation properties of PBAT/TPS blends and of a biocomposite based on one of these blends. Three PBAT/TPS blends (90:10, 80:20, 70:30) and a biocomposite based on babassu mesocarp/PBAT/TPS, (17:58:25), were prepared by melt blending on a torque rheometer at three different processing temperatures (150, 170, 190 °C). The samples for the tensile and biodegradation tests were obtained by hot pressing, the latter being later buried in simulated soil. The rheological characterization showed that higher processing temperatures reduced significantly the molecular weight of the blends and biocomposites, and that this reduction tended to increase with the amount of TPS in the blend. The mechanical properties of the PBAT hardly changed with processing temperature. In general, the mechanical properties of the blends tend to decrease with starch content and temperature. Optimium properties were achieved for the samples processed at 170 °C containing 20% starch and unoptimized properties for the blends and biocomposite systems processed at 190 °C, indicating that the temperature had a more significant effect on these properties than the amount of TPS. The addition of fibers led to a system with higher modulus and a lower strength and elongation at break than that of the corresponding blend at all processing temperatures investigated. Biodegradation tests revealed high degradation rates for the blends and biocomposites, this reduction being proportional to the amount of TPS in the systems. The blend with the highest fraction of thermoplastic starch presented a biodegradation rate equivalent to that of the biocomposite. PBAT did not show significant mass loss after being buried in soil for up to 12 weeks. Morphological analysis showed that after 6 weeks burial all blends and biocomposites displayed evidence of surface erosion. Differential scanning calorimetry analyzes showed that the increase in biodegradation exposure time led to a progressive increase in melting and crystallization temperatures and to a reduction in the crystallization rate of the blends and biocomposite systems.