Scientists from the National Institute of Chemistry and the Faculty of Natural Sciences and Engineering at the University of Ljubljana (NTF-UL) are developing functionalized ε-caprolactam ring with phosphorus flame retardant group, fibre-forming flame retardant polyamide 6 with covalently attached flame retardant side functionality, as well as the textile filaments. This represents a scientific and technological breakthrough in the development of advanced flame retardant polymers and melt-spun textile ibres.