Strong Synergistic Effects between Boron-Containing Compounds and Aluminum Diethylphosphinate for Enhanced Fire Safety and Mechanical Properties of Polyamide 6

Polyamide 6 (PA6) is an eminent engineering plastic renowned for its exceptional mechanical attributes, yet its flammability restricts its application scope. Aluminum diethylphosphinate (ADP) has exhibited an ability to significantly reduce the flammability of PA6, yet it is incapable of enhancing the char-forming capacity of PA6. More importantly, ADP causes serious damage to the mechanical properties of PA6. Here, a boron-containing polymer (PDBD) was prepared and added to PA6 together with ADP to prepare flame-retardant PA6 composites. Compared with PA6/13ADP, the PA6/10ADP/3PDBD sample with 3 wt % PDBD replacing the ADP not only can pass a UL-94 V-0 rating, but also, the peak of heat release rate (PHRR) and the total heat release (THR) were reduced by 35.6% and 16.5%, respectively. Simultaneously, the incorporation of PDBD significantly enhanced the char-forming potential of PA6, signifying a robust synergism between PDBD and ADP in catalyzing and facilitating the char-forming procedure of PA6. Significantly, compared to those of PA6/13ADP, the elongation at break and notch impact strengths of PA6/10ADP/3PDBD composites are notably increased by 174.3% and 45.8% due to the robust hydrogen bond between PDBD and PA6. These results illustrate that PDBD can effectively augment the charring propensity of PA6/ADP and mitigate the detrimental effects of ADP on the mechanical properties of PA6. Therefore, this work provides a simple and feasible method for preparing high-performance PA6 composites.