Flame retardant finishing based on novel boron polymers

Abstract

Statistics about the fire injuries revealed that department fire is the major cause of fire incidents. Since the highly flammable cotton is one of the most common materials for home textiles, flame retardant treatment on cellulosic substrate is necessary to safeguard human lives and properties. Stringent legislations have been proposed to eliminate the application of halogenated flame retardants for a few decades. Recently, dominant flame retardants for textiles are phosphorus or phosphorous-nitrogen based. However, more voices are emerging on the potential toxic effects caused by the gas phase phosphorus radicals. Therefore, a new boron-nitrogen polymer (PEIPA) was synthesized to provide a green alternative for flame retardant finishing on cotton fabrics. An organic boron compound, phenylboronic acid (PA) was successfully bonded to the branched polyethylenimine (PEI), which was confirmed by proton nuclear magnetic resonance and Fourier transform infrared analysis. Identified by thermogravimetric analysis, the polymer with molar ratio 1:1 of ethylenimine (EI) : PA, denoted as PEIPA 1:1, presented the best thermal-oxidative stability. PEIPA 1:1 was easily applied on cotton fabric through a simple dipping method with high add-on percentage in acetone medium. The fabric with 33.8 wt% add-on got self-extinguishing ability. Scanning electron microscopy analysis on the char morphology of the treated fabrics revealed the intumescent flame retardant mechanism. Moreover, evolved gases analysis in thermogravimetric Fourier transform infrared spectroscopy revealed that the treated cotton has great reduction in flammable volatiles and total amount of gases. PEIPA 1:1 coating on cotton has certain sustainability in water and poor durability in detergent solution. Therefore, a novel crosslinked FR system (PEIPA 3:1 / NeoFR) was developed. The treated fabric got very high LOI value, i.e. 29.6, which showing excellent flame retardancy and significantly improved laundering durability. On the other hand, PEIPA 1:1 was also applied on a green thermoplastic polymer, Polylactic acid (PLA), for further exploration of the application of the novel flame retardant. Significant char promotion was observed on the PEIPA blended PLA after burning by direct gas flame. The present study provides a platform to investigate the less popular type flame retardant (i.e. organic boron-nitrogen based) on cotton, to learn more about flame retardant mechanisms of B-N containing compounds.