Toughened Recycled Plastic Composites with Waste Elastomer and Hemp for Sustainability

Abstract This research focuses on the development of toughened eco-friendly composites based on recycled polyethylene terephthalate (rPET). The properties of rPET reinforced with alkaline- and silane-treated hemp fibers (HFs) and waste-derived micronized ground tire rubber (MRP) are investigated following a series of processing stages. Comprehensive characterization is conducted using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The addition of MRP and fiber influences the compounding process, producing thermostable composites below 300 °C. DSC results indicate that the presence of MRP and increasing hemp fiber content enhance the rPET crystallization rate while reducing overall crystallinity, suggesting a nucleation effect from the dispersed phase. Rheological analysis demonstrates substantially increased storage moduli and complex viscosity for the reinforced composites. Mechanical testing reveals notable improvements in impact-absorbed energy, with an increase of up to 30% over the rPET upon incorporating poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) (EMAGMA) as a reactive compatibilizer in the rPET/MRP/HF composite. However, these improvements are accompanied by reductions in maximum tensile strength (MTS) and Young’s modulus (YM) of approximately 50−55% relative to neat rPET. These findings suggest that PET waste can be effectively transformed into easily extrudable thermoplastic materials with a balanced property profile by integrating 20 wt % MRP and 1 wt % alkaline-treated hemp fibers.