Degradation of Reinforced and Unreinforced Waste Polyamides During Mechanical Recycling

The paper discusses the degradation of waste polyamides during mechanical recycling from the automotive sector. Two different polyamides were investigated: glass fibre reinforced and unreinforced. Raw materials were reprocessed twenty times and the changes in their properties were investigated as a function of reprocessing number. Considerable differences were found in relation to the specimen properties between reinforced and unreinforced waste materials. For example, the tensile strengths of reinforced and unreinforced polyamide 6.6 wastes were 84.2 and 165.2 MPa, respectively, which dropped to 38.0 and 97.0 MPa after the twentieth reprocessing cycle. Specimens from the reprocessing procedure have been investigated by Fourier transformed infrared spectroscopy in the spectral range of 400–4000 cm-1. Due to mechanical stress between the rotating screw and plasticising cylinder, the reinforcements broke. The average length of the glass fibre was decreased as a function of the reusing cycle number from 1890 to 580 μm.