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

• Published in: Journal of applied polymer science Vol. 138; no. 40
• Main Authors: Jiang, Siyuan, Liu, Yufei, Zou, Xiaoyu, He, Min, Zhang, Kai, Xu, Guomin, Qin, Shuhao
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 20.10.2021; Wiley Subscription Services, Inc
• Subjects: Antioxidants; Cinnamic acid; Copolymerization; Crystallization; Differential scanning calorimetry; Dynamic mechanical analysis; Fourier transforms; Free radical polymerization; Free radicals; hindered phenol antioxidants; Infrared spectroscopy; Liquid chromatography; macromolecular; Materials science; Mechanical properties; Molecular chains; NMR; NMR spectroscopy; Nuclear magnetic resonance; Oxidation resistance; polyamide 6; Polyamide resins; Polymers; Spectrum analysis; Thermal degradation; thermal oxygen aging; Thermal resistance; Thermal stability; Thermogravimetric analysis
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.51184

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. Phenolic hydroxyl, a free radical trap on macromolecular antioxidant PCN and PPN, reacts with peroxy radical or alkoxy radical generated by PA6 amide group due to thermal oxidative aging, which is consumed to form a stable compound, so that the reaction that free radical takes hydrogen to break the molecular chain can not continue, thus protecting the polymer chain from such free radicals and delaying the thermal oxidative aging of nylon.