Poly (lactic acid) (PLA) is a biodegradable and high-cost polymer which is nevertheless replacing the use of commodities in applications like packaging films, and is widely discarded in the environment. In this work, PLA was homogenized in a K-Mixer with different proportions of thermoplastic starch (TPS), a material with lower cost, and these mixtures were reinforced with natural cotton fibers, seeking to increase the tensile strength without compromising biodegradation. To evaluate the degradation behavior of PLA-TPS-cotton composites, tests were performed to measure the contact angle as well as the effect of hydrolysis and degradation in simulated soil. All the materials showed peak mass retention when removed from the water at 28 days and from the simulated soil at 14 days. The results showed that varying the content of TPS (0, 3 and 5%) caused increased water absorption and rate of degradation, but the fiber content (0, 10 and 20%) can distinguish the influence observed by incorporation of starch. The samples immersed in water presented retention values near those of the PLA matrix itself only for the ratio between fiber and TPS of 2:1 in mass percentage, showing the increased stability of the composite in contact with water.

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Poly(lactic acid) (PLA) is a biodegradable, brittle, and high-cost polymer, which can be applied over structural components and green packaging. In this study, we reinforced PLA with natural cotton (10 wt %) and thermoplastic starch (TPS; 3 wt %) to obtain a biodegradable and lower cost composite. TPS was incorporated in three distinct ways: it was blended, coated, and blended and coated. In this study, we investigated the compatibilization of TPS in the improvement of matrix-reinforcement adhesion and increase in the tensile behavior without a compromise in biodegradation. The samples were investigated with thermal analysis, dynamic mechanical thermal analysis, tensile testing, scanning electron microscopy, confocal laser scanning microscopy, and hydrolytic degradation. The results show that the coupling effect was more pronounced in the PLA TPS -cotton TPS (hybrid system with PLA and cotton) hybrid system. This formulation presented a higher glass-transition temperature, thermal stability, storage modulus, wettability, and ductility. The TPS addition improved the adhesion between the matrix and starched cotton fiber and retarded abiotic biodegradation. These properties will allow for green applications.

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