Development of new sustainable inorganic flame retardant additive system for polyamide 6,6 with improved performance

We report the effect of new sustainable inorganic phosphate glass (P‐glass) flame retardants for polyamide 6,6 (PA6,6). Three P‐glasses differing in chemical composition and glass transition temperature ( T g ) were prepared and their flame retardant effect on PA6,6 was studied by cone calorimetry, thermogravimetric analysis, and SEM‐EDX. The effect of high and intermediate T g P‐glasses on the thermal stability of PA6,6 was negligible as compared to that of the low T g P‐glass due to the hygroscopic nature of the latter. However, the char formation was independent of the P‐glass composition and was observed to increase by 30% in the presence of P‐glass. The low T g P‐glass composition (i.e., ILT‐1) was found to be a promising flame retardant for PA6,6 at a concentration of up to 15% by weight. Cone calorimetry data showed that the ILT‐1 decreased both the peak heat release rate and the total heat amount released from the PA6,6/ILT‐1 hybrids, resulting in an efficient formation of a glassy char layer. In contrast to the intermediate and high T g P‐glasses of this study, SEM‐EDX indicated that the ILT‐1 P‐glass was well dispersed in the PA6,6 matrix to yield a typical droplet‐in‐matrix phase morphology in the melt‐blended binary immiscible P‐glass/PA6,6 hybrids. POLYM. ENG. SCI., 55:1741–1748, 2015. © 2014 Society of Plastics Engineers