Design And Preparation Of Hybrid Silica Aerogel And Its Application In Rigid Polyurethane Foam

Rigid polyurethane foam（RPUF）has many advantages such as light weight,high porosity,good heat insulation,and easy construction,which makes it an excellent insulation material with comprehensive performance.However,the limiting oxygen index（LOI）of pure RPUF was only about 17%,which causes high flammability.Meanwhile,RPUF burns rapidly,with the release of large amounts of smoke and toxic gases,which greatly endangers the safety of human life and property,and also does not meet the requirements of green environmental protection.Therefore,the improvement of RPUF flame retardant performance has been the subject of close attention of scientific researchers.In this paper,from the perspective of preparing phosphorus-containing and high-efficiency flame retardants,three different hybrid Si O₂ aerogels were designed and synthesized by using silica（Si O₂）aerogel with low thermal conductivity as a backbone and selectively accessing organic phosphorus-containing compounds and transition metal compounds,and added into RPUF matrix for flame retardation and smoke suppression.The main research work of this thesis is as follows:1.In order to improve the flame retardancy and thermal conductivity of RPUF materials,copper acetate and phosphorus containing silane coupling agent（APD）were respectively graft to the three-dimensional network structure of Si O₂ aerogels to prepare hybrid Si O₂ aerogels（m-SA）containing P/Cu/Si.The cone calorimetry（CC）test results showed that the peak heat release rate（PHRR）of RPUF/m-SA-5 decreased from 320.2k W/m² to 262.3 k W/m²,and the total smoke emission（TSP）decreased from 10.9 m² to8.9 m².Raman,TG-FTIR and SEM tests demonstrated the good denseness and high graphitization of RPUF/m-SA residual carbon,which has effectively improved the flame-retardant properties of RPUF composites.2.To further upgrade the flame-retardancy of RPUF materials,a green and efficient flame-retardant DA@（m-SA）was synthesized by coating m-SA with dopamine hydrochloride,phenylphosphoric acid（PPOA）,dicyandiamide（DCD）and ferric chloride hexahydrate（Fe Cl₃·6H₂O）.The thermogravimetric（TG）test results showed that with the addition of DA@（m-SA）,the initial decomposition temperature(T_-5%)and T_-50%of RPUF composites increased,and the carbon residue of RPUF/DA@（m-SA）increased to 30.3 wt%.CC test results showed that the PHRR and TSP of RPUF/DA@（m-SA）-15 decreased by 45.9%and 25.0%respectively.Raman test and TG-FTIR test showed that the graphitization degree of carbon residue for RPUF/DA@（m-SA）composite was greatly improved,and the content of volatile gas produced by decomposition was reduced.3.In order to further optimize the experimental scheme and improve the flame retardancy,phosphorus containing compound DDP was combined with ammonium polyphosphate（APP）to prepare phosphorus hybrid Si O₂ aerogel（P-SA）.LOI test showed that the LOI value of RPUF/P-SA-15 increased to 23.1%.The results of cone calorimetry（CC）showed that the addition of P-SA prolonged the time for the RPUF composite to reach the maximum heat release peak.It was confirmed by Raman and XPS tests that the residual carbon graphitization of RPUF/P-SA composites was enhanced and mainly played the role of cohesive phase flame retardant,and the flame-retardant performance was improved.