Synthesis and application of new macromolecular hindered phenol antioxidants of polyamide 6

Abstract The two macromolecular antioxidants, P(3,5‐di‐tert‐butyl‐4‐hydroxy cinnamic acid‐alt‐N‐phenylmaleimide) (PCN) and P(3‐butene‐1‐yl‐3,5‐di‐tert‐butyl −4‐hydroxyphenyl propionate‐alt‐N‐phenylmaleimide) (PPN) were designed and synthesized via free radical copolymerization. The structures of the resulting PCN and PPN antioxidants were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy (1H NMR), and gel permeation chromatography. In addition, the effect of the two macromolecular antioxidants on the thermal oxidation aging resistance of polyamide 6 (PA6) was studied. According to the analysis of differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, dynamic viscosity, and the mechanical property of PA6 and its blends, these two types of macromolecular antioxidants protected the molecular chain of PA6 from breaking, protected the crystallization of PA6 and maintained the stability of PA6 crystal form, improved the activation energy of thermal degradation and thermal stability of PA6, enhanced the strength and elasticity of PA6 and maintained the mechanical properties of PA6 during aging to a certain extent.