Nanocomposites of recycled and of virgin polyamide 6.6 with cellulose nanofibers

The inherent properties of cellulose nanofibers (CNFs) make them an interesting and sustainable choice for reinforcing polymeric matrices intended for the automotive, electronic, construction, and packaging sectors. Effective recycling and reuse of polyamide 6.6 significantly reduce the environmental impact of automotive components throughout its entire life cycle. Nanocomposites of recycled polyamide 6.6 and CNF and of virgin polyamide 6.6 and CNF were processed through dissolution in a formic acid/water mixture followed by melt extrusion and injection molding. The results show that pure recycled polyamide exhibited a thermal degradation onset temperature 10 °C lower and a 9 % lower crystallinity compared to pure virgin polyamide. The method used for processing the nanocomposites resulted in homogeneous dispersion and good anchoring of CNF in both polymer matrices. The processing method and the presence of CNF reduce the thermal stability by up to 15 °C for recycled polyamide nanocomposites and up to 26 °C for virgin polyamide nanocomposites. The processing method did not significantly impair the elastic modulus and tensile strength of both recycled and virgin polyamides, showing a 3 % and 1 % reduction in tensile strength for recycled and virgin polyamides, respectively. The incorporation of 1 wt% and 2 wt% of CNF in virgin polyamide showed an increase in the elastic modulus of 16 % and 5 %, respectively, and a reduction in ductility. In summary, this work offers an alternative processing pathway for nanocomposites of recycled or virgin polyamide 6.6 with CNF; however, some improvements are still necessary to achieve the reinforcing effect of CNF on the mechanical strength of the matrices.