Preparation And Application Of Polymer Flame Retardant Containing DOPO Structure

In this paper,using DOPO as raw materials,a series of phosphorus-silicon flame retardants and nitrogen,phosphorus and silicon flame retardants containing DOPO structure were prepared and applied into PC/ABS and methyl vinyl silicone rubber.The effects of flame retardants with different structures on the compatibility and flame retardancy of the materials were studied,and the synergistic effect of multielement flame retardants was explored.The work is divided into the following parts.1.Preparation and application of phosphorus and silicon polymer flame retardant containing DOPO structureDOPO-VMDMS was prepared by the reaction of DOPO with methylphenyldimethoxy silane?VMDMS?through hydrolysis and dehydration polymerization,and then polymerized with D₄,D₄^Viand the blocking agent?MM?in the presence of alkali gel to obtain a phosphorus-silicon flame retardant containing DOPO structure FRSR.A best condition was obtained:The catalyst was alkali gel,the polymerization temperature was 90-110?,the reaction time was 2h,the dosage of the blocking agent was 0.1%of the total mass of the reaction system and the final yield was 83%.The structure and properties of the flame retardant were characterized by FTIR,NMR and GPC.The results showed that the copolymer had good thermal stability.The flame retardants FRSR were added to PC/ABS in different proportions.Thermal properties of flame retardant materials were analyzed by limiting oxygen index?LOI?,vertical combustion?UL-94?,thermogravimetric analysis?TGA?and SEM.The results showed that the addition of flame retardant FRSR can enhance the oxygen index and vertical combustion grade of PC/ABS alloy.It is found that the outer carbonaceous layer of flame retardanded PC/ABS is denser than that of PC/ABS,and the pore size of the inner carbon layer is much smaller than that of PC/ABS,which led the structure relatively dense.This carbon layer structure can prevent material heat transfer incombustion,and play the role of heat insulation.The results also showed that the addition of 20%flame retardant can significantly enhance the residual carbon content after PC/ABS combustion.In addition,SEM results showed that the compatibility of flame retardant FRSR in PC/ABS is not very good.The flame retardant FRSR(or FRSR and Al?OH?₃ complex)was added to the 110-type methyl vinyl silicone rubber in different proportions.The thermal stability of silicone rubber and flame retardant silicone rubber was analyzed by thermogravimetric analysis.The flame retardancy of flame retardanded silicone rubber was tested by limiting oxygen index?LOI?test and vertical combustion?UL94?.The results showed that the higher oxygen index of silicone rubber was increasd with Al?OH?₃ than the flame retardant FRSR under the same addition amount.When Al?OH?₃ or flame retardant FRSR is used alone,although the oxygen index of silicone rubber is improved,the UL-94 fire rating is still insufficient.Only when the ratio is 1:1,the flame retardant effect is the best,and when the addition of flame retardant is only 20%,UL-94 test can reach the V1 level.Thermogravimetric analysis?TGA?showed that the addition of 20%flame retardant?Al?OH?₃:flame retardant=1:1?resulted in higher carbon yield and slower Degradation rate.2.Preparation and application of nitrogen,phosphorus and silicon polymer flame retardant containing DOPO structureThe imine compound was prepared by using p-aminophenol and p-hydroxybenzaldehyde as raw materials,and then reacted with DOPO,followed by reaction with propargyl bromide or allyl bromide to get two compounds containing nitrogen and phosphorus.Finally,in the presence of karstedt catalyst,the hydrosilylation reaction between nitrogen-phosphorus compound and double-decker silsesquioxane was carried out to obtain two novel containing nitrogen,phosphorus and silicon polymer flame retardants containing DOPO structure?DDSQ-N-P-ene/DDSQ-N-P-yne?,and the reaction mechanism of silicon hydride addition was discussed.The polymers were characterized by¹HNMR,²⁹SiNMR and gel permeation chromatography.The spectra analysis data were consistent with the structure of the copolymer.Moreover,the thermal stability of polymers were also studied by thermogravimetric analysis?TGA?and the results indicated that the polymers have good thermal stability.Finally,the flame retardant was applied to PC/ABS,and 15 samples were designed and prepared.The effect of different components and different additions on the flame retardancy and compatibility of PC/ABS was studied.Thermogravimetric analysis?TGA?results showed that the higher carbon yield and slower degradation rate of nanocomposites can be achieved by increasing the content of DDSQ-N-P-yne?or ene?in PC/ABS.SEM results showed that the compatibility of the polymer DDSQ-N-P-yne in the PC/ABS alloy is better than that of the polymer DDSQ-N-P-ene in the PC/ABS alloy,which indicated the double bond acting a role in the material and making the material more compatible.The results of the limit oxygen index?LOI?,vertical combustion test?UL-94?and microcalorimetry showed that when the amount of DDSQ-N-P-yne?or ene?was 10wt%,the flame retardancy of PC/ABS composites improved significantly.HRR and THR of flame retardanded PC/ABS respectively decreased from 537.4 W/g to 270.5?344.6?W/g,24.7KJ/g to 23.2?23.6?KJ/g,and UL-94 grade can reach V-0?3.2 mm?.The UL94 combustion of the carbon layer through the SEM micrograph analysis shows that the surface of the carbon layer is a dense protective carbon layer,can prevent further combustion of polymers.All of these results show that the novel phospho-nitrogen-silicon copolymers with double silsesquioxane in the main chain not only exhibit excellent properties in PC/ABS alloys but also significantly enhance the flame retardancy.