Thermoforming of bio-based polylactic acid (PLA) sheets reinforced with cork powder

Cork polymer composites (CPC) are based on thermoplastic matrices, produced through extrusion process and usually processed by injection molding. The use of bio-based thermoplastics like polylactic acid (PLA) to produce CPC is a promising path to develop innovative and sustainable materials to replace fossil-based materials. CPC sheets based on PLA thermoplastic were produced and thermoformed. PLA was functionalized with maleic anhydride (MA) and MAgPLA was incorporated to produce CPC to improve the compatibility between cork and PLA. The graft degree was determined as 0,33 ± 0,02 % and the effectiveness of the functionalization was confirmed by Fourier Transform Infrared-Attenuated Total Reflection (FTIR-ATR). The viscoelastic behavior of PLA and CPC was studied. The forming temperature was determined to be 72°C. Strain and thickness variation were analyzed in the formed parts. The presence of cork and MAgPLA are suggested to prevent PLA polymer chains mobility and CPC present lower strain and thickness loss results. The color change and mechanical performance of PLA and CPC were analyzed before and after 28 days of accelerated weathering test. The color change is more intense for CPC than PLA due to cork lightening because of UV exposure. The mechanical performance of PLA is affected by the presence of cork. Tensile strength significantly decreases on PLA and CPC after weathering test while Young’s modulus is not significantly affected. After the thermoforming process, cork in CPC keeps its honeycomb closed cell structure. • Introduction of cork led to an increase on the T g of the CPC comparing with PLA. • Cork prevents PLA polymer chains mobility decreasing strain in thermoforming. • Cork becomes lighter due to UV light exposure impacting total color change of CPC. • CPC present decreased mechanical performance than neat PLA. • Cork alveolar structure is not damaged during thermoforming process.