Valorization of disposable polylactide (PLA) cups by rotational molding technology: The influence of pre-processing grinding and thermal treatment

This study presents the structure-property relationship of rotationally molded products made of waste-based polylactide (PLA) pre-processed with different procedures. While the use of recycled petrochemical thermoplastics, such as polyethylene, is a current industrial practice, there is no evidence of recycled, biodegradable polymers as a source of material for manufacturing the rotomolded parts. The main problem is the difficulty in grinding low-melting material with a high ability to degrade during the milling process into a powder, which is essential from the point of view of rotational molding. The work describes three types of polylactide pre-treatment from post-consumer disposable cups for applying powders and micropellet as a material for manufacturing rotationally molded purposes. The applied pre-treatments are annealing disposable cups for 24 h at 100 °C and melt processing by extrusion of previously shredded cups. As part of the conducted research, the influence of initial recrystallization of the polymeric material and the impact of additional melt processing on the geometric features of the charge materials and the degree of their degradation was assessed. Complete structural characteristics of particle-shaped materials (powders and micropellets) evaluated using spectroscopic and calorimetric methods (FTIR and DSC) were related to the structure of the final products assessed by the 3D computed tomography (CT) method and resulting mechanical properties. Based on the conducted analyses, the risks and potential paths of development of the technology of shaping rotomolded products with low porosity (void volume 0.53%) and favorable mechanical properties (tensile strength of 48 MPa), made of recycled, biodegradable polyesters, were shown. •The first attempt to recycle PLA waste in rotomolding has been made.•Disposable PLA cups were successfully processed into rotationally molded products.•Thermal treatment and melt extrusion pre-processing were used to improve PLA milling ability.•PLA preprocessing limit the porosity of rotomolded parts and reduce the degradation rate during processing.