Surface nanomodification of cotton fiber for flame retardant application.

This paper presents efficient surface modification methodology to increase fire resistance properties of cotton by radio frequency (RF) plasma-induced graft copolymerization of vinyl phosphate ester as nanometer residue structure onto cotton surface. Methacryloyloxyethyl diphenyl phosphate (MEDP) monomer was synthesized and grafted onto the surface of cotton fabric by argon RF plasma at ambient temperature. Under optimum RF power (30 W), amounts of MEDP and N,N methylenebisacrylamide cross linking agent were varied to obtain optimum graft copolymerization conditions. Untreated and treated cotton were characterized by attenuated total reflectance infrared (ATR-IR) spectroscopy to investigate their functional group characteristics. This showed a strong covalent attachment between the surface of cotton and flame retardant material as the carbonyl functionality of the MEDP was clearly observed in the spectra. Scanning electron microscopic (SEM) analysis also showed grafted material as nanometer residue on cotton surface. Thermogravimetric analysis (TGA) revealed that the decomposition of phosphorus compound which occurs at lower temperature than the cotton itself resulted in the formation of char which covers cotton surface. This protects the fabric surface from further burning, therefore, higher amounts of remaining materials were observed as char in all cases. Furthermore, limiting oxygen index (LOI) had increased from 19 in untreated to 28 in grafted cotton. Detailed analysis on structural and thermal properties as well as surface grafting efficiency are presented.