In situ stabilization of polyamide 6 with reactive antioxidant

To minimize the physical loss of antioxidants, a novel reactive antioxidant (HP-Cl) was prepared and grafted onto the backbones of polyamide 6 (PA6) by the reactive extrusion with high grafting efficiency (PA6-g-HP). The structure and composition of HP-Cl and PA6-g-HP were characterized by FTIR, 1H NMR, and UV spectrum analysis. Both thermal degradation kinetics and migration kinetics of PA6-g-HP were studied by comparing with PA6/Irganox® 245. It was found that the difference in the mass loss between the two samples became greater with increasing temperature and time, and the sample of PA6-g-HP had a relatively low thermal oxidation degradation rate constant (K). The average values of the activation energy (E a) and frequency factor (A) of PA6-g-HP kept relatively stable and were much higher than that of PA6/Irganox® 245 during degradation process. The migration of antioxidants followed Fick’s second law, and the equilibrium migration concentration and the diffusivity value of PA6/Irganox® 245 were much higher than that of PA6-g-HP. The results confirmed that the sample of PA6-g-HP exhibited excellent thermal stability and anti-migration property by in situ stabilization with reactive antioxidant.