Flame retardant effectiveness of nanodispersed organophosphorus-derivative in polyamide 6 textile filament yarns

The halogen-free flame retardant (FR) polyamide 6 (PA6) composite textile filament yarns fabricated via melt-compounding have never achieved effective flame retardancy. The main reason for that is related to the agglomeration of FR additives due to their poor compatibility with PA6 polymer chains. The formed FR agglomerates substantially reduce the flame retardant effectiveness, disable continuous melt-spinning process due to clogging of the filters and spinnerets, and significantly impair fibre tensile properties. Therefore, the goal of this study was to investigate how lowering of the FR additive size to the nanoscopic level affects melt-spinning process and flame retardancy of the nanocomposite PA6 filament yarns. To this aim, we established a new scalable approach for the production of new-generation PA6/FR nanocomposite filament yarns with uniformly distributed nano-dispersed halogen-free FR. So, instead of mixing FR additive with PA6 melt, we rather chose a step back, i.e. mixing of FR additive with ε-caprolactam melt and performing the in situ polymerization.