A strategy toward improving flame retardancy and thermal oxidative stability of polyamide 6 based on cuprous diethylphosphinate

With the number of vehicles increases every year, the demand for flame retardant and thermal oxidative stabilized PA6 has also surged significantly. Therefore, it is crucial to improve the flame retardancy and thermal oxidative stability of PA6. In this regard, a novel dual-functional cuprous diethylphosphinate (CuDP) was successfully prepared through an ion exchange reaction and was used to prepare PA6 composites. the effects of CuDP on the flame retardancy and thermal oxidative stability of PA6 composites were studied in detail. In contrast with an LOI value of 22.6, pHRR of 911.3 kW·m-2, and THR of 109.2 MJ·m-2 for pure PA6, the addition of 15 wt% of CuDP upgrades the LOI value to 28.2 and reached UL-94 V-0 rating. Meanwhile, there was a 43.8%, 22.3% and 17.9% decrease in pHRR, THR and av-CO2Y, respectively. In addition, the flame retardant mechanism of CuDP was explored in detail, where CuDP can encourage PA6 to form a protective char layer in the condense phase and quench free radicals in the gas phase. Moreover, the incorporation of CuDP helped maintain the mechanical properties of PA6 composites during accelerated thermal oxidative aging experiments. This work presents a new approach for enhancing the flame retardancy and thermal oxidative stability of PA6 composites, which paves the way for its broader application.