Polyurethane (PU) foams were protected by phosphorous and nitrogen-based molecular flame retardant hexamethoxycyclotriphosphazene c-[N=P(OMe)2]3 (HMCPT). This compound was synthesized, analyzed, and investigated with respect to its thermal behavior, compatibility, and efficiency as a flame retardant (FR) for PU foams. The decomposition of HMCPT starts at 186°C in air and under argon, as indicated by TG/DSC measurements. It was possible to introduce 5 per hundred parts polyol (phpp) of HMCPT into the PU foams. The mechanical and morphological characteristics of the protected foams-compression load deflection, tenacity, tensile elongation, air perviousness, and raw density-were investigated indicating that the FR has an impact on all of these properties. The flame retardancy was evaluated with the FM VSS 302 test, where an self-extinguishing classification was reached with 5phpp of HMCPT. Cone calorimeter measurements provide evidence for a flame poisoning mechanism

Summary The production of carbon fiber reinforced (CFR) anionic polyamide 6 (APA6) plates by thermoplastic resin transfer molding (T‐RTM) processing is highly sensitive to the presence of polymer additives such as flame retardants (FRs). However, APA6 is flammable, and therefore, it is mandatory to protect the polymer matrix, especially if the produced materials are intended for aerospace applications. Typically used FR for PA6 cannot be incorporated in the T‐RTM processes. With hexaphenoxycyclotriphosphazene, an incorporable and effective FR additive for CFR APA6 was discovered. Cone calorimetry measurements indicate a char formation‐based mechanism, and the flame retardancy was further confirmed with limiting oxygen index tests, classification by UL94 (V‐0), and FAR25 tests. The influence of this FR on the thermal (thermogravimetric analysis and differential scanning calorimetry) and mechanical behavior (flexural, compressive and ultimate tensile strength, and Charpy impact tests) on CFR APA6 produced via T‐RTM processing is evaluated and indicates no interaction with the APA6; it works as a passive filler. Copyright © 2016 John Wiley & Sons, Ltd.