Two different polyamides with 30% glass fibres, based on terephthalic acid (PTA) or isophthalic acid (ITA), were tested for fire performance and other properties with a halogenated and a PIN FR solution. The ITA-based polyamide has a lower melting point, facilitating processing, but poorer mechanical and fire characteristics. The PIN FR Alpi (aluminium diethyl phosphinate) was loaded at 18% w/w. In the halogenated compound, brominated polystyrene and zinc borate were loaded at 21% + 7%. Both FR solutions enable to achieve UL94-V0 @ 0.75 mm, and reduce toxic gas (carbon monoxide, hydrogen cyanate) and smoke emissions. Peak heat release rate was lower with the halogenated FR but time to ignition was marginally shorter. The authors conclude that the PIN FR solution, at these loadings, offers higher flame retardancy efficiency.
“Halogen and halogen-free flame retarded biologically-based polyamide with markedly suppressed smoke and toxic gases releases”, T. Cai et al., Composites Part B 184 (2020) 107737, https://doi.org/10.1016/j.compositesb.2019.107737