Evaluating the Recyclability and Restabilization of Laboratory Plastics Consumables: Impact of Autoclaving and Mechanical Recycling on Polypropylene

Abstract

Laboratory environments generate substantial amounts of plastic waste primarily consisting of single-use polypropylene (PP) consumables such as pipette tips or test tubes. In this study, the recyclability of such materials is investigated with a focus on the influence of autoclaving and mechanical recycling. Further, restabilization strategies are evaluated for these materials. Virgin PP pipette tips and post-consumer laboratory PP recyclate consisting of low melt viscosity PP are subjected to multiple extrusion cycles to simulate mechanical recycling. Autoclaving at 121 °C and elevated pressure for 20 min does not adversely affect the material's melt flow, tensile properties, or oxidative stability. This shows that decontamination by autoclaving does not impair recyclability. In contrast, reprocessing of the regenerate simulated through repeated extrusion causes pronounced aging particularly in post-consumer laboratory PP. To counteract these effects, different stabilizer formulations are tested including a bio-based system containing an alditol and α-tocopherol. This formulation provides superior oxidative stability, consistent melt viscosity, and retention of mechanical properties compared to industrial reference stabilizer formulations. The results demonstrate that autoclaved laboratory PP can be successfully recycled utilizing a suitable stabilization strategy. This enables a sustainable reuse of laboratory plastics in a second life cycle through effective recycling processes.