Synthesis And Application Of A Novel Modified Intumescent Flame Retardant Based On Chitosan

As a functional material,flame retardant is widely used in high molecular polymers to improve its flame retardancy.Although the traditional flame retardant can achieve a good flame retardant effect to a certain extent,it will release a large amount of toxic and harmful gases during the combustion process,which seriously polluted the environment and damaged people's health.With the progress and development of society,people's awareness of environmental protection has gradually increased.The development of halogen-free,low-toxic,low-smoke,environment-friendly and flame-retardant flame retardants has become the current research direction.Intumescent flame retardants(IFR)has become a research hotspot,since most of the current IFRs are mainly composed of small molecules,there are problems such as easy precipitation,large dosage and high cost.Therefore,the functional polymer intumescent flame retardant material with low research and development cost,green environmental protection and high flame retardant efficiency has important scientific research value and realistic significance.Polysaccharide natural polymers are widely found in nature,which are cheap,green,non-polluting,biodegradable and not easy to migrate.Therefore,it has been studied by most of researches for many years.In this paper,two different intumescent flame retardants were synthesized by using natural polymer chitosan as carbon source which were characterized by Fourier transform infrared spectroscopy(FTIR),nuclear magnetic resonance(¹H-NMR and ³¹P-NMR),X-ray diffraction(XRD),thermos-gravimetric analysis(TGA)and scanning electron microscopy(SEM).Then,the combustion performance was investigated by limiting oxygen index(LOI),vertical burning test(UL-94),cone calorimeter,thermos-gravimetric analysis(TGA)and thermos-gravimetric-infrared(TG-IR).The mechanical properties test was used to investigate the effect of flame retardant addition on the mechanical properties of epoxy resin,the morphology of residual carbon was measured by SEM.The main work of the dissertation is as follows:(1)A new type of intumescent flame retardant material(CEMP)was synthesized by reaction of chitosan,phosphorus pentoxide and melamine.The optimal reaction conditions of each modification step were investigated by orthogonal experiment.The structure of the target product was characterized indicating that CEMP was prepared,and the thermal stability was significantly higher than that of unmodified chitosan.(2)The flame retardant CEMP and the synergist organic montmorillonite(OMMT)were added to the EP,the effects of different amount of flame retardants on the combustion performance of EP were investigated by LOI,UL-94,cone calorimetry.The experimental results showed that when the dosage of CEMP and OMMT was 15%and 3%,the limiting oxygen index of EP was 30.6%,the vertical burning grade was V-0,the residual carbon ratio is 22.2%.the heat release rate(HRR)and smoke release rate(SPR)were significantly lower than pure EP,and the total smoke release(TSP)and total heat release(THR)were 5.0 m² and 35.1 MJ·m^-2 respectively.It can be seen the obvious expansion of the carbon layer after combustion.(3)The target product CEUP was formed by ACS and urea,which was explored its structure and solubility properties.Then CEUP and OMMT were applied to the epoxy resin to investigate its combustion performance.The experimental results indicated that when 3%OMMT and 15%CEUP were added,LOI was 34.8%,and the combustion grade of V-0 was obtained.The HRR and SPR were significantly lower than pure EP,and the THR and TSP were 30.4 MJ·m^-2 and 4.3 m² respectively.A large volume of expanded carbon layer appeared after combustion indicating that OMMT and CEMP had good synergistic flame retardant effect.