# Construction of a P/N/Zn Synergist for Enhancing the Fire Safety and Char Formation of PA6/Aluminum Diethylphosphinate Composites

## TL;DR

A new synergist improves fire safety and char formation in polyamide 6 composites used in electrical applications.

## Contribution

A novel P/N/Zn synergist is developed to enhance flame retardancy and char formation in PA6 composites.

## Key findings

- The synergist improved flame retardancy, achieving UL-94 V-0 rating and 30.7% limiting oxygen index.
- Peak heat release rate and smoke production rate decreased by 34.0% and 33.3%, respectively.
- The composite achieved a 750 °C glow-wire ignition temperature, suitable for high-safety electrical applications.

## Abstract

Polyamide 6 is an important engineering thermoplastic; however, its practical use is often constrained by its high flammability. Although aluminum diethylphosphinate is widely employed as a flame retardant for polyamide 6, its relatively slow char-forming kinetics hinders the attainment of the stringent 750 °C glow-wire ignition temperature required for electrical applications at moderate loadings. To address this limitation, a synergist was fabricated via the self-assembly of phytic acid, benzoguanamine, and ZnSO4·7H2O and subsequently incorporated to enhance the char-forming capability and flame retardancy of polyamide 6/aluminum diethylphosphinate composites. The results revealed that the synergist acted as an efficient charring promoter, improving flame retardancy. At a total loading of 15 wt%, the composite reached a UL-94 V-0 rating and high limiting oxygen index of 30.7%. Cone calorimetry data indicate that the peak heat release rate decreased by 34.0%, and the smoke production rate decreased by 33.3% compared with the polyamide 6/aluminum diethylphosphinate composites. Mechanistic analysis indicated that the synergist catalyzed the carbonization of the polyamide 6, enabling the formation of a dense thermally insulating char barrier in the condensed phase. Notably, the optimized formulation achieved a glow-wire ignition temperature of 750 °C, demonstrating its strong potential for high-safety electrical applications.