Preparation And Properties Of Flame Retardant Polyvinyl Alcohol Composites

Polyvinyl alcohol（PVA）is a water-based polymer with hydroxyl group（-OH）,it has good film forming,mechanical properties and barrier properties,widely used in medicine,packaging and construction fields.However,The limiting oxygen index of polyvinyl alcohol is less than 20%,making it a flammable material.In order to solve the problem,this topic designs and synthesizes a series of environmental friendly flame retardants that can be used for PVA.By blending the flame retardants are mixed with PVA at different mass ratios,and the interaction between flame retardant and PVA was studied,the flame retardant performance,thermal stability and other properties were also investigated.This thesis is mainly divided into the following parts:（1）Ammonium polyphosphate（APP）and chitosan（CS）were added to polyvinyl alcohol（PVA）,and the polymer was crosslinked using boric acid（H₃BO₃）.In the PVA hydrogels,the negatively charged APP and positively charged CS formed a polyelectrolyte complex（PEC）through ionic interaction.Cone calorimetry and vertical burning tests（UL-94）indicated that the PVA composite aerogels have excellent flame retardancy;they could decrease the heat release rate,total heat release rate,and carbon dioxide（CO₂）generation.The flame-retardant PVA composite aerogel has a porous structure,which makes PVA aerogel flame retardant and heat insulation.The analysis shows that PVA/H₃BO₃ and PEC combustion in PVA aerogel form carbon together,which makes PVA aerogel have good flame retardant performance.（2）A phosphorus-silicon flame retardant poly(10-（2-diethoxylmethylsilane）-9-hydro-9-oxa-10-phosphorus-phenanthrene（DOPO-VTES）was synthesized by the addition reaction of9,10-dihydro-9-oxa-10-phosphorus-phenanthrene（DOPO）and vinyl silane（VTES）.The hydroxyl group in the molecular structure of phosphorus-silicon flame retardant reacts with the hydroxyl group on PVA,and the P-Si flame retardant DOPO-VTES is introduced into the PVA structure.When the DOPO-VTES dosage is 33 wt%and theα-zirconium phosphate dosage is 1.6 wt%,the flame retardant performance of PVA composite reaches UL-94 V-0level.Reduce the amount of smoke release,analysis of its flame retardant mechanism,DOPO-VTES combustion heat degradation into P-O chemical bond,phosphoric acid and Si O₂ generation,withα-zirconium phosphate further catalytic carbon,the generated dense carbon layer can isolate the heat and oxygen exchange,can play a good flame retardant role in condensed phase.（3）Melamine polyphosphate（MPP）was synthesized from melamine and phosphoric acid,which was added to polyvinyl alcohol.The results showed that there was hydrogen bond between MPP and PVA,which improved the mechanical strength of PVA.At the same time,MPP has excellent flame retardant performance,because MPP decomposition generates polyphosphates when heated,promotes the carbon formation of PVA and decomposes inert gas CO₂,which can reduce the concentration of combustible gas and oxygen to a certain extent and play the role of gas phase flame retardant.At the same time,1,3,5-triazine-2,4,6triamino acts as a nitrogen flame retardant,which plays a condensing phase flame retardant role.