Modification Of Ammonium Polyphosphate And Its Application In Flame Retardant PU-coated Fabrics

In this paper,the preparation of modified ammonium polyphosphate by different methods and its effect on the flame retardant properties of polyurethane（PU）were studied.Then,the flame retardant polyurethane slurry was applied to the fabric coating.In this paper,ammonium polyphosphate（APP）,tetraethoxysilane（TEOS）,vinyltriethoxysilane（VTES）,9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide（DOPO）and boric acid were used as raw materials to prepared four kinds of modified ammonium polyphosphate.The structure and thermal stability of the flame retardant were characterized by FTIR,SEM,EDS and TG,and the flame retardant PU composite was prepared.The flame retardant properties of PU composites were tested by limiting oxygen index（LOI）and vertical combustion（UL-94）,and the flame retardant mechanism of modified APP was discussed by TG,SEM and EDS.The main research work of this paper is as follows.（1）The phosphorus containing silane coupling agent DOPO-VTES was synthesized by DOPO and VTES.APP was directly modified by mechanical method.At the same time,polysiloxane modified APP and polyborosiloxane modified APP were prepared by DOPO-VTES and boric acid.SEM showed that the morphology of modified APP was different with different modification methods.The introduction of DOPO makes the modified APP an intumescent flame retardant which integrates acid source,carbon source and gas source.The thermal stability of the modified APP at high temperature is improved,and the flame retardancy is also improved compared with APP.The APP coated with polyborosiloxane has relatively good flame retardancy due to the existence of Si-O-B bond,which can promote the formation of a relatively smooth and dense carbon layer of the flame retardant PU composite.（2）The modified ammonium polyphosphate（VTSAPP）flame retardant was prepared by a sol-gel method that used tetraethoxysilane（TEOS）and vinyltriethoxysilane（VTES）as precursors.It was found that the water resistance and flame retardancy of VTSAPP were improved.The water contact angle of VTSAPP reached 138°and the solubility decreased from 0.205 g/ml H₂O to 0.0125 g/ml H₂O.The compatibility of VTSAPP with PU matrix was improved,and the amount of carbon residue increased significantly at high temperature.The flame retardant test results show that when the content of VTSAPP is 20wt%,the LOI of flame retardant PU composite is increased by 30.0%,and it has passed UL-94V-0.（3）Flame retardant PU-coated fabrics with different coating layers were prepared by coating the fabrics with flame retardant PU coating slurry prepared by VTSAPP.The results show that the flame retardant coating on the surface of single ply bonded fabric is discontinuous,and the VTSAPP particles are exposed.The coating is continuous and uniform when the fabric is double ply bonded.The flame retardant test results show that the LOI of the fabric with double-layer flame retardant coating is increased to 28.4%,which can pass the test of GB 17927.2-2011 fire source0 and fire source 1,and has the best flame retardant performance and ignition resistance.