Study On Sol-gel And Chemical Flame Retardant Modification Of Polyacrylonitrile Fabric

Polyacrylonitrile(PAN)fibers play an important role in the textile fields among the main synthetic fibers.Compared with other synthetic fibers,PAN fiber has several excellent properties,such as light mass,good warmth retention,lasting compression elasticity,good performance of mildew resistance,and etc.However,PAN fiber belongs to an inflammable fiber with the limiting oxygen index(LOI)of only 17%.Thus PAN fabrics are also highly combustible,which brings enormous loss of people's lives and properties.Therefore,the development of flame retardant PAN fibers or fabrics has become an urgent need to prevent fires and minimize losses caused by fire.The first part of this paper aims to impart PAN fabric flame retardancy by sol-gel technique.Phytic acid(PA)and urea as phosphorus-nitrogen synergistic agent were added into the tetrathoxysilane(TEOS)sol to prepare the fire retardant coating system,then the modified sol was coated on polyacrylonitrile(PAN)fabric and gelated to obtain fire retardant PAN fabric.The structure,components,thermal properties of the resultant fabrics were characterized by Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),thermogravimetric(TG),differential scanning calorimetry(DSC)analysis,limited oxygen index(LOI)test,and microscale combustion calorimeter(MCC).And the surface morphology of fabrics was observed by scanning electron microscope(SEM).The results showed that the coated PAN fabric had an excellent thermal stability and flame retardancy.Particularly,when the fabrics was coated with phytic acid and urea containing silica sol,the coating almost covered the fibers completely,which could effectively hinder the spread of flame,the exchange of heat and oxygen between environment and fabrics.And it possessed the highest LOI value of 42.1%,showing excellent fire retardancy.The second part of this paper aims to invent a method to impart polyacrylonitrile(PAN)fabric durable flame retadancy.PAN fabric was modified with hydroxylamine hydrochloride(HA)to prepare amidoxime PAN fabric(A-PAN)followed by phosphorylation with phosphoric acid to obtain flame retardant PAN fabric(P-A-PAN).Thermogravimetric(TG)analysis,differential scanning calorimetry(DSC)and microscale combustion calorimetry(MCC)were used to analyze the thermal degradation process and flame retardant mechanisms.The structure of the fabrics was characterized by Fourier transform infrared spectroscopy(FTIR)and X-ray Photoelectron Spectroscopy(XPS).The surface morphology of fabrics was observed by scanning electron microscope(SEM).Moreover,the flame retardancy of fabrics before and after washing was evaluated by Limiting oxygen index(LOI).The results showed that the P-A-PAN possessed an excellent thermal stability with the highest LOI value of 34.1%and the highest char residue of 55.67%at 800?.Most importantly,the P-A-PAN possessed a wonderful flame retardant durability with a little decrease of LOI after 20 washing cycles.