A novel green phosphorus-containing flame retardant finishing on polysaccharide-modified polyamide 66 fabric for improving hydrophilicity and durability

Rising concerns about the toxic effects and environmental issues associated with various fireproof treatments on textiles have led to a demand for "green" materials. Chitosan (CS) is an amino polysaccharide green, recyclable, and non-toxic highly biocompatible biopolymer that consists of multiple hydroxyl groups and has a wide range of applications, including as a flame retardant additive. In this study, an eco-friendly bio-based formaldehyde-free flame retardant containing a higher level of phosphorus and nitrogen in phytic acid ammonia (PAA) was synthesized to amplify the most plentiful green chitosan (CS)-modified polyamide 66 (PA66) fabric surface through a simple pad-dry-cure technique for the improvement of durable flame retardancy with hydrophilicity. The findings revealed that each UV-grafted CS fabric could entirely stop the melt-dripping tendency during the vertical burning (UL-94) test and reached a V-1 rating. Meanwhile, limiting oxygen index (LOI) testing showed a rapid increase from 18.5 % to 24 % for the PA66 control and the PAA-treated (i.e., PA66-g-5CS-PAA) fabric samples, respectively. Moreover, compared to the PA66 control sample, a dramatic decrease in the peak heat release rate (PHRR), fire growth rate (FGR), and total heat release (THR) by approximately over 52 %, 0.63 %, and 19.7 %, respectively, was observed for the PA66-g-5CS-PAA fabric sample. Additionally, this arrangement of PAA catalyzed the charring of grafted CS and acted as a condensed phase flame retardant, resulting in a significant improvement in char yield% in both air and N2 atmospheres for the PA66-g-5CS-PAA fabric sample in TGA. In addition, only the lower grafting ratio of CS with PAA-treated fabric sample (i.e., PA66-g-2CS-PAA) could encourage it to gain its lowest water contact angle of 00, as well as impersonating a positive effect in improving the flame retardant coating durability in washing and sustaining even after 10 home laundering cycles. This phenomenon suggests that an actual hydrophilic and durable flame retardant finishing procedure for polyamide 66 fabrics might be applied with the novel, plentiful, sustainable, and environmentally friendly bio-based green PAA ingredient.