Fire retardance in polyamide-6. The effects of red phosphorus and radiation-induced cross-links

• Published in: Fire and materials 2001-09, Vol.25 (5), p.179-184
• Main Authors: Balabanovich, A.I., Levchik, G.F., Levchik, S.V., Schnabel, W.
• Format: Article
• Language: English
• Subjects: Applied sciences; Building technical equipments; Buildings; Buildings. Public works; Exact sciences and technology; Fire behavior of materials and structures; Fire protection; Materials; Plastics; polyamide-6; red phosphorus
• ISSN: 0308-0501; 1099-1018
• DOI: 10.1002/fam.768

Red phosphorus contained in non‐irradiated polyamide‐6 at concentrations up to 12.5 does not significantly improve the fire resistance of the polymer. It weakens the thermal stability of the polymer as reflected by a decrease in the onset temperature for mass loss from 407°C to 363°C, but causes char formation as indicated by mres=13 wt%, the non‐volatile residue at 600°C. Irradiation of polyamide‐6, loaded with red phosphorus, with 60Co‐γ‐rays generates intermolecular cross‐links resulting in an improved fire resistance. However, the absorbed dose necessary to achieve improvement is too high (>1 MGy) from a practical point of view. This inconvenience is overcome by applying triallyl cyanurate (TAC) as a cross‐linking promoter. Typically, polyamide‐6 containing 5 wt% TAC and 12.5 wt% red phosphorus exposed to a γ‐ray dose of 22 kGy yields a V‐0 rating (in the mode A UL 94 test) concurrently with a small increase in the onset temperature for mass loss and a drastic increase in the residue non‐volatile at 600°C. Copyright © 2002 John Wiley & Sons, Ltd.