In this paper, we present the development of a novel processing technology to tackle hard-to-recycle plastic packaging waste contaminated with food residues. The proof-of-concept (POC) technology can effectively separate food residual amounts from plastic waste materials to a level acceptable for further re-use or recycling of the plastic packaging. To assess this technology, we have conducted spectroscopic, thermal, and calorimetric characterizations of the obtained fractions, such as cleaned mixed plastics (CMP), food waste with mixed plastics (FWMP), and a mixture of microplastics (MP). The analyses were carried out with the aid of Fourier-Transform Infrared spectroscopy (FT-IR), Thermo-Gravimetric Analysis (TGA), Microcone Combustion Calorimetry (MCC), and 'bomb' calorimetry. The highest ratio of CMP to FWMP and the lowest amount of MP were obtained utilizing 700 rpm blade rotational speed and 15 s residence time of contaminated plastics in a cutting mill chamber. The plastics were freed from food contamination by 93-97%, which highlights a strong potential of the POC as a solution for 'dry-cleaning' of similar wastes on a larger scale. The main components of the CMP fraction were low-density polyethylene (LDPE), polypropylene (PP), and polyethylene terephthalate (PET), which are recyclable plastics. The knowledge and understanding of thermal degradation behaviours and calorimetric attributes of separated fractions, determined in this study, are essential in informing the industrial players using pyrolysis as a technique for recycling plastics.
Keywords: microplastics; plastic packaging; plastic recycling; polymer degradation; pyrolysis.