Sustainable plastic composites by polylactic acid-starch blends and bleached kraft hardwood fibers

The growing environmental consciousness of society has led to the development of sustainable products. Because of its noticeable tensile properties, polylactic acid (PLA) has been widely studied as a replacement for non-degradable and renewable polymers. However, the PLA by itself has a high rigidity that is increased when fibers are incorporated as reinforcement. In this sense, the present work aims to study the feasibility of obtaining compounds with high properties while maintaining a lower stiffness. For this purpose, a mixed PLA-PTA (thermoplastic starch-based polymer) matrix was chosen. The use of PTA to increase the compostability of the material caused the tensile strength decrease of 37.3%, the Young's modulus reduction of 34.9% and the strain decrease of 12.6% compared to PLA matrix when 30% PTA was added. Therefore, blends were reinforced with bleached kraft hardwood fibers (BKHF) to improve their mechanical performance. In the case of the blend with 20% PTA reinforced with 30% BKHF, 51.32 MPa tensile strength (35.4% of increase), 5.54 GPa Young's modulus (112.3% of increment) and a strain of 4% (23.5% of gain). Thermal, morphological and macro-mechanical properties of blends were investigated. It was found that the tensile properties and the interphase of the two components were fairly good in comparison with the literature. The study has allowed us to conclude through a preliminary LCA that it is possible to obtain materials with the same properties of PP with a 33.6% reduction in the carbon footprint. Thus, BKHF reinforced biocomposites are postulated as a real alternative to replace non-renewable ones.