Preparation and characterization of polyamide 6 fibre based on a phosphorus-containing flame retardant

Intrinsically flame retardant polyamide 6 (FRPA6) was synthesized by melt polycondensation of caprolactam and 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl]-10-phosphaphenanthrene-10-oxide (DDP). Following this, FRPA6 fibres were prepared by melt spinning. The chemical structure, thermal stability, mechanical and combustion properties of FRPA6 were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, differential scanning calorimetry, thermogravimetric analysis, tensile measurements, vertical burning measurements, limiting oxygen index (LOI) measurements, cone calorimetry and scanning electron microscopy. The thermal stability of FRPA6 decreased to a certain extent, but the amount of residual char was improved. FRPA6 containing 5 wt% DDP could achieve a V-0 rating with an LOI value of 33.7%. The spinnability of FRPA6 fibres was good and the tenacity at break reached 3.0 cN dtex^-1 which met the requirements of textiles. The flame retardancy of FRPA6 fibres was definitely improved and the LOI value of FRPA6-5 fabric could reach 28.4%, thereby showing good prospect in applications.