Characterization of recycled polyamide 6: Effect of polypropylene and inorganic contaminants on mechanical properties

Recycled polyamide 6 (PA6) from post-industrial waste fibers (PIW) and post-consumer carpet waste (PCW) are characterized in this study. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) indicate the presence of polypropylene (PP) in PCW. Furthermore, measured ash content of PCW is ca. 6 wt.%, while PIW has only 0.5 wt.% inorganic content. X-ray fluorescence (XRF) and X-ray diffraction (XRD) show that inorganic contaminants of PCW and PIW are calcium carbonate (CaCO3) and titanium dioxide (TiO2), respectively. Due to higher inorganic filler content, PCW exhibits higher melt viscosity and higher storage modulus than that of PIW. PIW has 20% higher tensile strength than that of PCW. However, a drastic 70% drop is observed in vibration weld strength of PCW, which is attributed to its PP contamination. The negative effect of PP on the weld strength of recycled PA6 is also confirmed by measuring the mechanical properties of model compounds.