| In recent years,fire accidents caused by textiles in the world have been increased.The methods of reducing the loss of people’s lives and property by flame retardant finishing of fabrics have drawn worldwide attention.Considering the defects of traditional flame-retardant finishing such as not environmentally friendly and not durable,the green and efficient click chemistry can be expected to be applied on flame retardant finishing which can offer the durability by covalent bonding between fibers and flame retardant agent.Thus,the thesis was devoted to proposing a flame retardant finishing on cotton fabric by thiol-ene click chemistry and giving semi-durable or even durable flame retardant properties.We believe this method will provide a facile and efficient idea for the modification of cotton fabrics under mild conditions.In this paper,the phosphorus-nitrogen flame retardant dimethyl-[1,3,5-(3,5-triacryloylhexahydro)triazinyl]-3-oxopropylphosphonate(DHTP)was firstly synthesized by triacryloylhexahydro-1,3,5-triazine(TAHT)and dimethylphosphite(DP)was separated and purified by silica gel column chromatography eluting with 10:1 ethyl acetate and methanol.The structure of the product was characterized successfully by FTIR,1HNMR and 13 CNMR.In the first part of finishing process,3-mercaptopropyltriethoxysilane(MPTES)was grafted to cotton fiber surface by one-step of hydrolytic and condensation at room temperature,and then the alkenyl-containing flame retardant DHTP and thiol-containing cotton fabric was reacted via thiol-ene click chemistry with the catalysis of TCEP.The results demonstrated the carbon residue increased from 13.0% to 34.6% and the limiting oxygen index also improved from 18.3% to 25.5%.However,after 30 times of soaping,the LOI value dropped to 21.7%,so the durability needs to be further enhanced.Therefore,we further optimized the pretreatment.When using two-step method of hydrolysis at room temperature and condensation at high temperature,the obvious mercapto peak appeared in Raman analysis and the atomic percentage of S and Si from the silane coupling agent was significantly increased on the surface of cotton fabric.Moreover,after flame retardant finishing with the catalysis of TCEP,the thermal stability and flame retardant properties of cotton were improved.Compared with the one-step part,the carbon residue increased from 34.6% to 43.2% and the LOI value increased from 25.5% to 26.0%.After 30 cycles of soaping,the LOI value of the flame retardant cotton was 22.3%.The results showed that the surface of the cotton fabric contained more mercapto groups after the optimized pretreatment,and so was more DHTP grafted,leading to the improved flame retardant durability.Finally,the method of flame retardant finishing was optimized.Under the UV radiation,light initiator DMPA was added to initiate the click chemical reaction.The thermal stability and flame retardant properties have been further improved.The carbon residue increased from 43.2% to 45.2% and the LOI increased from 26.0% to 26.7%.After 30 cycles of soaping,the LOI value was 24.2%,indicating the durability was also obviously improved.When 8 wt% DHTP was used,the LOI value of flame retardant cotton was 27.2% which reached the standard of nonflammable,and maintained at 25.1% after 30 cycles of soaping.The results showed that the thiol-ene click chemistry initiated by photoinitiator is faster and more efficient than by catalyst.As for the wearing performance of textiles,breaking strength,whiteness and stiffness test was carried out to explore the impact of application after treatment.The results showed that the finishing process did not result in obvious loss of breaking strength whiteness and stiffness. |
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