Organic Functionalization Of Mesoporous Silica And Study On Combustion Properties Of Flame-Retarded Epoxy Composites

Based on the research of flame-retardant epoxy resin,organic molecules containing phosphrous and nitrogen elements have been grafted and/or wrapped onto mesoporous silica to synthesize functionalized mesoporous silica by molecular design method.Functionalized mesoporous silica hybrids with the flame-retardant properties of catalytic carbonization and smoke suppression have been incorporated to prepare efficient flame retardant epoxy composites via solvent blending method.The influence of mesoporous silica functionalized by hyperbranched polyphosphate acrylate on the thermal degradation,thermal stability and combustion behavior of epoxy composites was investigated,and the flame-retardant mechanism was explored via the analysis of gaseous and condensed phase.The research work of the graduation thesis was elaborated as follows:1.Thiol-functionalized mesoporous silica(SH-mSiO2)was synthesized between tetraethoxysilane and(3-mercaptopropyl)-trimethoxysilane by the co-condensation method,and then ene-terminated hyperbranched polyphosphate acrylate(HPPA)molecules were chemically grafted onto SH-mSiO2 to prepare HPPA-SH-mSiO2 hybrids by thiol-ene reaction.The HPPA-SH-mSiO2 hybrids were added to prepare epoxy composites.During combustion,the addition of HPPA-SH-mSiO2 hybrids can increase charring amount,compactness and graphitic degree of char residues,thus improving thermal stability and flame retardance,and suppressing toxic smoke.2.Aminated mesoporous silica(NH2-mSiO2)was synthesized between tetramethoxysilane and(3-aminopropyl)trimethoxysilane by the co-condensation method.Then NH2-mSiO2 was repeatedly reacted with hexamethylenediamine and hexachlorocyclotriphosphazene to prepare mesoporous silica grafted with hyperbranched cyclotriphosphazene polymers.Functionalized mesoporous silica hybrids containing phosphrous and nitrogen elements have been incorporated to prepare epoxy composites with excellent flame retardance and smoke suppression.Based on the analysis of char residues,the addition of functionalized mesoporous silica results in charring amount,compactness and graphitic degree of char residues,contributing to inhibiting the release of combustible gas and permeation of combustion heat and oxygen.3.Phosphonate functionalised mesoporous silica(Si02-P03-)was synthesized between tetraethoxysilane and 3-trihydroxysilylpropyl methylphosphonate by the co-condensation method.Then chitosan and sodium tripolyphosphate were wrapped onto mesoporous silica to prepare intumescent mesoporous silica hybrids containing acid source,charring agent and blowing agent.The effect of intumescent mesoporous silica hybrids on thermal degradation,flame retardant properties and smoke hazards of epoxy composites was studied by thermogravimetric analysis,cone calorimeter and TG-IR coupling technology.Based on the analysis of gaseous and condensed phase,the flame-retardant mechanism of epoxy composites was probably explained.