Synthesis And Application Of Polymerized Phosphorus-Nitrogen Intumescent Flame Retardant

Intumescent flame retardants are well known for their unique swelling properties.They are halogen-free,low-smoke,low-toxic and non-corrosive.It is one of the halogen-free flame retardants currently developed by researchers.However,most of the intumescent flame retardants are small molecular compounds,which have the disadvantages of small molecular weight and poor thermal stability.In this paper,three aspects of research on the application of the synthesis of new polymeric intumescent flame retardants and cotton fabrics,acrylic fabrics and polypropylenes have been developed.(1)The intermediate ditrimethylolpropane bisphosphonyl chloride DTDC is synthesized by phosphoryl chlorination using ditrimethylolpropane and phosphorus oxychloride,and then DTDC is prepared by polymerization with thiourea and urea respectively.A novel polymeric intumescent flame retardant polybistrimethylolpropanephosphoryl thiourea PDTPT and polybistrimethylolpropanephosphoryl urea PDTPU are produced.The optimal synthesis process of the flame retardant was determined by single factor test.The yields of DTDC,PDTTT and PDTPU were 88.99 %,89.12 % and 92.41 %.It was verified by IR and 1H NMR that DTDC,PDTPT and PDTPU were successfully synthesized,and the molecular weight of PDTTP was 1781 and the degree of polymerization was 4 by gel chromatography GPC.Through thermal analysis and charcoal performance test,the thermal decomposition temperatures of the polymers PDTTP and PDTPU are 270 °C and 280 °C,the carbonation rates of polymer PDTPT and PDTPU at 600 ? were 48.86 % and 35.47 %,and the carbon layer formed was compact and complete,the expansion was obvious.(2)The flame retardants PDTPT and PDTPU were applied to cotton fabrics respectively.It was found that when the concentration of PDTPT reached 100 g/L,the flame-retardant effect of the flame-retardant cotton fabric reached B1,and the damaged carbon length was 13.0 cm;When the concentration is 400 g/L,the carbon length is only 7.0 cm.At this time,the limiting oxygen index is 27.0 %,and the flame-retardant effect of the flame-retardant cotton fabric after 10 times of washing can still reached B2,but the flame retardant PDTPT can cause yellowing of cotton fabrics.The color of the cotton fabric after flame retardant finishing by the flame retardant PDTPU did not change significantly,and when the concentration reached 100 g/L,the flame retardant effect reached B2,the damaged carbon length was 17.0 cm,and the concentration reached 400 g/L,the flame retardant effect reaches B1,the damaged carbon length is 7.5 cm,and the limit oxygen index LOI value reaches 26.8%.(3)The flame retardants PDTPT and PDTPU were applied to the acrylic fabrics respectively.It was found through experiments that the breaking strength of the acrylic fibers was improved,and when the concentration reached 100 g/L,the acrylic fabrics appeared self-extinguishing phenomenon after flame retardant finishing,when the flame retardant concentration is 400 g/L,the limiting oxygen index LOI values of the acrylic fabrics treated with the flame retardants PDTPT and PDTPU are 26.6% and 26.8%,and both reach the flame retardant fiber grade.The flame retardant polyacrylonitrile materials prepared by the flame retardants PDTPT and PDTPU were found to be uniformly distributed in the polyacrylonitrile material,and the flame retardant PDTPT and PDTPU had a mass fraction of 30% flame retardant polyacrylonitrile material.The char formation rate was 7.38 % and 6.60 % at 800 ?,respectively,while the polyacrylonitrile material was only 1.44 % at 800 ?,and the carbon formed by the two flame-retardant polyacrylonitrile materials at 600 ?.The layers are filled with small holes and play a good expansion foaming effect during the combustion process.Through the performance comparison between the thermal properties of the flame retardants PDTPT and PDTPU,the flame-retardant application of cotton fabrics and the flame-retardant applications in acrylic fabrics and polyacrylonitrile materials.It was found that the flame retardant PDTPT has a swelling property and a high temperature charring rate.The aspect is obviously superior to the flame retardant PDTPU,and the flame-retardant effect is also slightly better than the flame retardant PDTPU.It is confirmed that the synergistic effect of the three flame retardant elements containing nitrogen-phosphorus-sulfur is better than the nitrogen-phosphorus only resistance.The synergistic effect of the burning elements,especially in the high temperature resistance and char forming performance,has obvious advantages.However,it has been found through experiments that sulfur can turn the flame retardant into yellow,which in turn affects the fabric that is flame retarded by it.Therefore,in the application,it is necessary to comprehensively consider the performance of the flame retardant,in some fields where the whiteness of the fabric is high,try to choose some intumescent flame retardants without sulfur.