Abstract
This paper aims to develop a novel method, i.e., sol-gel combined with layer-by-layer assembly technology, to impart flame retardancy on polyacrylonitrile (PAN) fabrics. Silica-sol was synthesized via the sol-gel process and acted as cationic solution, and phytic acid (PA) was used as the anionic medium. Flame-retardant-treated PAN fabric (FR-PAN) could achieve excellent flame retardancy with 10 bilayer (10BL) coating through layer-by-layer assembly. The structure of the fabrics was characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The thermal stability and flame retardancy were evaluated by thermogravimetric (TG) analysis, cone calorimetry (CC) and limiting oxygen index (LOI). The LOI value of the coated fabric was up to 33.2 vol % and the char residue at 800 °C also increased to 57 wt %. Cone calorimetry tests revealed that, compared to the control fabric, the peak of heat release rate (PHRR) and total heat release (THR) of FR-PAN decreased by 66% and 73%, respectively. These results indicated that sol-gel combined with layer-by-layer assembly technique could impart PAN fabric with satisfactory flame-retardant properties, showing an efficient flame retardant strategy for PAN fabric.
Highlights
Polyacrylonitrile (PAN) fibers, one of the most important synthetic fibers, occupy a unique position in textile applications thanks to their good warmth retention and profound resistance to light, radiation, mildew, etc
The adsorption peaks of stretching vibrations at 2242 cm−1 (C≡N), 1732 cm−1 (C=O of ester group), 1446 cm−1 (C-H bending in CH2 ) and 1245 cm−1 (C-N bending) are clearly observed, which are the characteristic peaks of the copolymerized PAN fibers of acrylonitrile and vinyl acetate
The results demonstrate that the silica-sol and phytic acid (PA) have been successfully coated on the surface of PAN fabric by using layer-by-layer assembly technology
Summary
Polyacrylonitrile (PAN) fibers, one of the most important synthetic fibers, occupy a unique position in textile applications thanks to their good warmth retention and profound resistance to light, radiation, mildew, etc. PAN fibers have a very low limiting oxygen index (LOI). PAN fibers or fabrics are easy to ignite and burn vigorously and release dense smoke once they are ignited. Some flame-retardant methods have been developed for improving the flame retardancy of acrylonitrile copolymer, PAN fibers or PAN fabrics. Blending [4,5], copolymerization [6,7], finishing [2] and chemical modification [8,9,10] are the common techniques to obtain flame retardant PAN fibers or fabrics. Nanotechnological approaches have attempted to impart flame retardancy to different fabrics comprising a variety of fibre types, such as layer-by-layer assembly technique, sol-gel process, and plasma deposition [11], etc
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