Evaluation of recycling performance of neat poly(butylene succinate) and its composites with agro-industrial by-products

This study evaluates the processability and performance of virgin polybutylene succinate (PBSv) when blended with two recycled materials: recycled PBS (PBSr) and a recycled biocomposite (MIXr), consisting of PBS blended with 30 wt% brewery waste. Blends were produced with recycled contents from 2 wt% up to 40 wt%, and their rheological behavior, mechanical properties, and thermal stability were characterized using mixing torque analysis, rheometer (complex viscosity, storage and loss modulus), tensile testing, DSC, and TGA data. The addition of both recycled materials induced an increase in melt viscosity of PBSv at low concentrations, followed by a marked decrease in torque at higher recycled content, up to a ~50% reduction at 40 wt% for both PBSr and MIXr blends. Across all formulations, PBSv–PBSr blends maintained superior rheological and mechanical performance compared with PBSv–MIXr blends. Incorporation of even small amounts of MIXr (2 wt%) led to a drastic loss of ductility, reducing elongation at break from ~400% for PBSv to just 33%, over an order of magnitude decrease. In contrast, PBSv maintained its characteristic ductility up to 10 wt% PBSr. Consequently, MIXr can be incorporated up to 30 wt% when designing rigid, low-deformability second-life products, whereas PBSr can be used up to 10 wt% in ductile applications and up to 40 wt% in applications requiring rigidity. Thermal stability, assessed by DSC and TGA, decreased progressively with increasing recycled content.