Water-Soluble Cyclophosphazenes as Durable Flame-Retardant Finishes for Nylon/Cotton Blend Fabrics
Olga Zilke, Wael Ali, Leonie Kamps, Tori Engels, Simon Schumacher, Dominic Danielsiek, Valbone Shabani, Alaa Salma, Dennis Plohl, Ruth Wallmeier, Klaus Opwis, Jochen S. Gutmann, Thomas Mayer‐Gall
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).