Aramid fibres offer high strength, temperature and chemical resistance, light weight and ageing qualities and para-amid fibres are inherently self-extinguishing. They are being increasingly used in a range of high-tech applications, resulting in a recycling challenge for recycling of the fibres.
In this paper, end-of-life para-aramid fibres were washed, then reacted to add phosphorus (by soaking in phosphoric acid for four minutes), dried, washed and finally dried again. The resulting phosphorus para-aramid material was tested as a flame retardant in thermoplastic polyurethane (TPU), at 0.25 – 1% dosing of phosphorus para-amid and at 1% non-phosphorus para-aramid. Phosphorus para-aramid at 1% reduced Peak Heat Release Rate of TPU by nearly 50% and improved char structure, and was more effective than non-phosphorus para-amid. The authors conclude that phosphorus-modified recycled para-amid fibres are an “environmentally friendly” flame retardant enabling reuse of waste para-amid fibres.
“A recycled environmental friendly flame retardant by modifying para-aramid fiber with phosphorus acid for thermoplastic polyurethane elastomer”, X. Chen et al. J. Hazardous Materials 2017 http://dx.doi.org/doi:10.1016/j.jhazmat.2017.02.011