Water-Soluble Cyclophosphazenes as Durable Flame-Retardant Finishes for Nylon/Cotton Blend Fabrics

Abstract

Nylon-cotton textile blends (Nyco) are known to be challenging substrates regarding their flame-retardant functionalization and its durability. In this study, two different water-soluble flame retardants based on cyclophosphazene together with glycerol (GlyCPZ) and thioglycerol (ThioGlyCPZ) were synthesized enabling a waterborne finishing for Nyco. An extensive investigation of the flame-retardant performance and mechanism as well as the washing fastness was conducted. Thermogravimetric analysis (TGA) indicated changed degradation mechanisms for treated samples, which resulted in a reduced heat release capacity in microscale combustion calorimetry (MCC) measurements and an increased char yield. As a consequence, the limiting oxygen index (LOI) was enhanced from 20% for pure Nyco to 23% and 27.5% for GlyCPZ and ThioGlyCPZ, respectively. Also, the standardized flammability test according to ISO 15025 was passed. In addition, self-extinguishing characteristics were observed even after 10 washing cycles at 80 °C confirming the durability of the finishing. Sulfur was found to be gas phase active, as recombined sulfur compounds were identified in pyrolysis gas chromatography mass spectrometry (Py-GC/MS). Phosphorus was mainly active in the condensed phase, which was verified by analyses of digested burned textile samples using inductively coupled optical emission spectroscopy (ICP-OES).

Flame-retardant finishing of cotton fabrics using DOPO functionalized alkoxy- and amido alkoxysilane

“…Hence, a chemical immobilization of the FR on the textile surface is required, which can be achieved using different approaches including UV-curable FRs (Mayer-Gall et al 2015), sol-gel technique (Wang et al 2016;Kanat and Eren 2019;Zhang et al 2020b) and crosslinking reaction between ammonium phosphate groups and cellulose using dicyandiamide as catalyst (Gu et al 2021;Chen et al 2022). Recently, a new methodology has been reported on the formation of physical networks via in-situ crosslinking reaction to produce a durable (Nazir et al 2021) or semi-durable (Zilke et al 2022) flame-retardant finishing. The utilization of DOPO-based silans and their application via pad-dry-cure procedure has previously been demonstrated for cotton (Hu et al 2011), polyester (Wang et al 2011), silk (Liu et al 2018), and polyamide (Šehić et al 2016;Kundu et al 2020a) textiles.…”