Alloying synergistic flame retardant effect improving fire resistance and mechanical properties of polyamide 6

Abstract The alloying synergistic flame retardant effect was studied by using polyetherimide (PEI) and aluminum diethylphosphinate (ADP) for polyamide 6 (PA6), which can endow PA6 composites with excellent mechanical properties and flame retardancy simultaneously. On the one hand, because the molecular structures of PEI and PA6 are similar, adding PEI with PA6 can form PEI‐PA6 alloy by the hydrogen bond effect and nice homogeneous phase, which can endow PA6 composites with excellent mechanical properties. On the other hand, the test results of flame retardancy show that 9ADP/10PEI‐PA6 composite can obtain higher LOI value (LOI = 31%), and excellent flame retardant rating (UL94 V‐0) with 9%ADP and 10%PEI. From the results of cone calorimetry test, the pk‐HRR and THR of 9ADP/10PEI‐PA6 are reduced by 24.4% and 24.7%, respectively, compared to PA6, and higher char residue rate was obtained, which shows that ADP combined with PEI‐PA6 alloying exerts an excellent flame retardant synergistic effect. Through the study of flame retardant mechanism found that ADP works together with PEI can effectively increase the quenching effect in the gas phase, promote thermal stability, and delay the decomposition process of PA6 matrix during the combustion process. Meanwhile, it also increases the char yield to exert a synergistic effect in the condensed phase by ADP/PEI‐PA6. The residual char rate reached 36.6%, higher than neat PA6 about 4.6 wt.%. Thus, the alloying flame retardant method using ADP/PEI‐PA6 can endow PA6 with better flame retardancy and more excellent mechanical properties. Importantly, it provides a new direction for developing high‐performance halogen‐free flame retardant materials.