Synergistic flame-retardant system enhances epoxy-polyamide coatings

A research group has developed an innovative flame-retardant system for epoxy-polyamide coatings, combining sodium polyacrylate-modified ammonium polyphosphate (SAPP) with scandia and yttria co-stabilised zirconia (ScYSZ). The objective was to achieve enhanced fire safety and thermal insulation properties.

With a formulation containing 19.4 wt% SAPP and 3.2 wt% ScYSZ, the coating achieved a limiting oxygen index (LOI) of 31.3 % and a UL-94 V-0 rating. Compared with pure epoxy resin, the total heat release (THR) was reduced by 61.3 % and total smoke production (TSP) by 67.8 %.

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High-quality char formation through synergy

Analyses revealed that the synergy of SAPP and ScYSZ promoted the development of a high-quality protective layer. Crosslinked structures and P–O–C aromatic bonds formed during combustion, creating an effective barrier against heat and oxygen. These findings highlight the potential of hybrid flame-retardant systems in coatings with improved thermal insulation and smoke suppression.

Source: Yuan, L. et al., Synergistic effects of sodium polyacrylate-loaded ammonium polyphosphate in combination with ScYSZ to enhance the flame retardancy and thermal insulation properties of epoxy-polyamide coatings. Prog. Org. Coat. 203, 109175 (2025).

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