Preparation And Properties Of Durable Flame Retardant Polyvinyl Alcohol

Polyvinyl alcohol(PVA)is a kind of water-soluble polymer widely used.It has excellent mechanical properties,good chemical resistance,biodegradability and nontoxic.It has been widely used in textile,medical,building materials,furniture,adhesives,packaging materials and many other fields.However,its flammability limits its further development,so it is of great significance to study its flame retardant modification.In order to improve the flame retardancy of polyvinyl alcohol,the first part of this paper used blending technology to prepare flame retardant polyvinyl alcohol.Firstly,the PVA was mixed with water-soluble ammonium polyphosphate(APP)to obtain the APP/PVA membrane,then the APP/PVA membrane was placed in calcium chloride solution for ion exchange with Ca2+,and then durable flame retardant polyvinyl alcohol membrane(FR-PVA)was obtained.The X-ray photoelectron spectroscopy(XPS),Fourier transform infrared spectroscopy(FTIR),Field emission scanning electron microscope(FE-SEM),Thermogravimetric analysis(TG),Differential scanning calorimetry(DSC),Thermogravimetric coupled with Fourier transform infrared spectrometry(TG-IR),Raman spectroscopy(Raman),Micro cone calorimetry(MCC)and Limiting oxygen index(LOI)were used to characterized the structural properties,thermal stability,flame retardant mechanism,combustion behavior and durability of the samples before and after flame retardant modification.The test results showed that the thermal stability of PVA was significantly improved after flame retardant modification,the carbon residue in nitrogen atmosphere was increased to 26.9%,and the heat release capacity during the combustion process was decreased by 71.5%.Meanwhile,it had excellent water washing resistance,after the 30 times of washing,the limiting oxygen index of FR-PVA could still maintain 29.0%.In the second part of this paper,firstly,phosphoric acid and urea were used to phosphorylate polyvinyl alcohol to obtain the phosphorylated PVA(P-PVA),and then diphenylmethane diisocyanate(MDI)was used to crosslink P-PVA to obtain durable flame retardant polyvinyl alcohol film(FR-PVA).The XPS,FTIR,FE-SEM,TG,TGIR,Raman,MCC and LOI were used to characterize the properties of the samples before and after flame retardant modification.The results showed that P and N flame retardant elements were successfully introduced into the flame retardant polyvinyl alcohol,the thermal stability of the PVA was significantly improved,and the carbon residue in nitrogen atmosphere was increased to 38.4%,At the same time,the heat release rate of FR-PVA was decreased by 72.0%.The flame retardant mechanism analysis showed that the FR-PVA played a role in both gas phase and condensed phase during combustion.