Graphene Oxide's Reduction of Hydrolytic Degradation in Polyamide-11

Graphene oxide (GO) was incorporated into polyamide-11 (PA11) via in-situ polymerization. The GO-PA11 nano-composite had elevated resistance to hydrolytic degradation. At a loading of 1 mg/g, GO to PA11, the accelerated aging equilibrium molecular weight of GO-PA11 was higher (33 and 34 kDa at 100 and 120 °C, respectively) compared to neat PA11 (23 and 24 kDa at 100 and 120 °C, respectively). Neat PA11 had hydrolysis rate constants (k_H) of 2.8 and 12 (×10^-2 day^-1) when aged at 100 and 120 °C, respectively, and re-polymerization rate constants (k_P) of 5.0 and 23 (×10^-5 day^-1), respectively. The higher equilibrium molecular weight for GO-PA11 loaded at 1 mg/g was the result of a decreased k_H, 1.8 and 4.5 (×10^-2 day^-1), and an increased k_P, 10 and 17 (×10^-5 day^-1) compared with neat PA11 at 100 and 120 °C, respectively. The decreased rate of degradation and resulting 40 % increased equilibrium molecular weight of GO-PA11 was attributed to the highly asymmetric planar GO nano-sheets that inhibited the molecular mobility of water and the polymer chain. The crystallinity of the polymer matrix was similarly affected by a reduction in chain mobility during annealing due to the GO nanoparticles' chemistry and highly asymmetric nano-planar sheet structure.