Preparation And Combustion Performance Study Of Glass Fiber Reinforced Silica Aerogel Composites Based On Co-precursor Method

The demand for modern energy and the problem of energy shortage is increasing day by day.Modern buildings consume a lot of energy.Building energy conservation has become a hot spot of current concern,and it is also an important part of energy conservation and emission reduction.Silica aerogel is a typical nanoporous material composed of about 95%air and 5%SiO2.It has low density(0.03-0.5 g/cm3),high specific surface area(>1000 m2/g),low thermal conductivity(<0.015 W/(m-K))and many other excellent properties.It has broad application prospects in the field of thermal insulation.In this paper,glass fiber reinforced silica aerogel composites were synthesized using methltrimethoxysilane(MTMS)and water glass co-precursor by freeze drying method.Freeze-drying method avoids the problem of skeleton shrinkage and structural collapse by sublimation to avoid capillary forces.MTMS provides direct surface modification of methyl groups,eliminating the need for repeated solvent exchange and surface modification in conventional preparation process.Based on the prepared composite materials,the pyrolysis behavior and combustion performance were studied.The main research work in this paper includes:The effects of the molar ratio of MTMS/water glass on the properties of aerogel materials were investigated.The amount of MTMS affected the growth rate and size of the primary particles,which influenced the morphology and properties of the aerogel.Therefore,the amount of MTMS can be adjusted to regulate the performance of aerogel,so as to obtain the molar ratio when the performance is the best.The obtained composite has excellent properties with high specific surface area(870.9 m2/g),high thermal stability(560?)and low thermal conductivity(0.0248 W/(m·K))when the X=1.In the glass fiber reinforced silica aerogel composites,there is physical connection between glass and aerogel particles without chemical bond.Silica aerogel matrix adhered to the glass fibers tightly.The introduction of the glass fiber does not affect the three-dimensional nanoporous structure of the aerogel.It can also be seen from the uniaxial compression test and three-point bending test that the composites have significant mechanical strength and flexibility.They can withstand large compression stress and bending stress without material damage.When the molar ratio is 1,the elastic modulus and flexural modulus of the material can reach 1.4 MPa and 1.2 MPa respectively,which can meet the requirements of mechanical properties of building insulation and pipe insulation.The pyrolysis behavior and combustion properties of the composites were investigated.TG-DSC analysis and cone calorimeter test of glass fiber reinforced SiO2 aerogel composites were carried out to simulate the pyrolysis behavior and combustion behavior of materials in fire.The Combustion experiment confirms that the aerogel reinforced with non-combustible glass fiber is combustible and verifies that the organic groups introduced on the surface of the aerogel are the cause of its flammability.When the molar ratio is 1,the composite has a thermal stability temperature of 560?,which can meet the application requirements of thermali nsulation.In the cone calorimeter test,when the heat flux is 55 kW/m2,compared G5 ith G1,the THR of sample G5 is decreased by 84..%,the pHRR is decreased by 2.5%,and the time to reach the peak of heat release is delayed by 126 s.This ndicates that the fire hazard of glass fiber reinforced SiO2 aerogel composites ncreases with increasing MTMS.Taking the THR of the sample G5 as a baseline,we lot the THR as a function of the molar ratio and fit it to obtain a linear equation of HR and molar ratio:QTHR?3.6X.As the molar ratio increases,the total heat elease increases linearly.This can provide a reference for estimating the total heat elease in practical applications.