Study On The Synthesis Of Reactive Phosphorous Polyborosiloxane And Its Effect On Polymethacrylimide

With the development of polymethacrylimide(PMI)foam in aerospace,rail transit and so on,the requirement for its performance is getting higher and higher.PMI foam has great obturator structure and thermodynamic properties,but it burns easily which limits its further development.The goal of this study is to synthesize an environmentally friendly and efficient reactive flame retardant containing phosphorus,silicon and boron,and apply it to PMI foam in order to obtain modified PMI foam with good flame retardancy and stable thermodynamic properties.Firstly,the amino-terminated phosphorous polyborosiloxane(N-PBSi)was prepared by the designed synthesis route,and its thermal decomposition behavior was explored.At the same time,the synthesis route of N-PBSi was optimized by changing the ratio of retardants and reaction time.When the ratio of retardants was 1:1.33:3 and the reaction time was 6 h,the N-PBSi can obtain the best comprehensive performance.Then,the N-PBSi was applied to PMI copolymer for the flame retardant modification.The feasibility of chemical grafting about the N-PBSi and PMI monomer was confirmed by structure characterization,and the flame retardancy of modified PMI copolymer with different N-PBSi content was explored.When N-PBSi was 15 wt.%,the modified PMI can reach V-0level of UL94,and the LOI value can reach 27%,showing great flame retardancy.Moreover,the flame retardant mechanism of N-PBSi in PMI copolymer was explored.Finally,N-PBSi was used for the modification of PMI foam.The introduction of N-PBSi can improved the density of modified PMI foam,and the cell diameter of the modified foam obviously decreased.The change of density and cell structure of modified PMI foam has a great influence on its mechanical properties.With the introduction of N-PBSi,the tensile properties of modified PMI foam changed from strong and tough to rigid and brittle,and the compressive properties increased significantly.When the N-PBSi content was 20 wt.%,the LOI value of modified PMI foam increased from the initial 20.6% to 22%.The heat release rate and smoke generation rate also decreased significantly,indicating that the introduction of N-PBSi has the effect of smoke suppression and flame retardancy.In addition,the flame retardant mechanism of N-PBSi in PMI foam was also analyzed.