Preparation Of Hydrophobic Al₂O₃ And SiO₂ Modified Cellulose Aerogels And Their Application In Thermal Insulation Textiles

Porous thermal insulation materials can effectively block the transfer of heat,which mainly uses a large number of pores inside the material to slow down the rate of heat conduction and heat convection to achieve the purpose of heat insulation.Aerogel has the characteristics of low density,high porosity and low thermal conductivity,and is a good thermal insulation material.Cellulose aerogels have many advantages such as green environmental protection,wide source of raw materials,and renewable,but their thermal stability performance is poor.In this project,cellulose microfibers are instructively modified to improve the thermal stability and thermal insulation performance of aerogels,hydrophobic modification of aerogels,and then the modified aerogels are combined with fabrics to obtain aerogel composite fabrics with good thermal insulation performance.This study will provide some ideas for the application of cellulose aerogels on fabrics for thermal insulation.The research content of this paper is divided into the following three aspects:（1）Aluminum chloride hexahydrate（Al Cl₃·6H₂O）and ethyl orthosilicate（TEOS）were selected to inorganic modify cellulose microfibers to obtain modified cellulose aerogels.The effect of Al Cl₃·6H₂O and TEOS mass percentage concentration on the thermal insulation performance of aerogels was explored,and the optimal modification ratios of Al Cl₃·6H₂O and TEOS were obtained after analyzing the micromorphology,chemical composition and thermal insulation performance of aerogels.（2）Perfluorohexylethyltrimethoxysilane（PFOTMS）and 3-aminopropyltrimethoxysilane（KH540）were used for hydrophobic modification of inorganically modified aerogels.The effects of the ratio of modified monomers and the total amount of hydrophobic modifier on the hydrophobic properties of aerogels were explored,and the chemical composition,micromorphology,specific surface area,thermal conductivity and thermal insulation properties of aerogels were analyzed.（3）The hydrophobic treated Al₂O₃ and Si O₂ modified cellulose hydrogels were combined with cotton and polyester fabrics by casting to obtain aerogel composite fabrics.The effects of aerogel layer thickness and different substrates on the thermal insulation performance and consumption performance of aerogel composite fabrics were explored.The results showed that:（1）After modifying aerogels with Al Cl₃·6H₂O,the initial decomposition temperature of aerogels increased from 215°C to 264°C,and the thermal conductivity was 0.03041 W/（m·K）.After TEOS modification,the thermal decomposition temperature of aerogel was increased to 253°C,and the thermal conductivity was 0.02984 W/（m·K）.The optimal modification ratio was 6%Al Cl₃·6H₂O and 8%TEOS,the initial decomposition temperature of the aerogel was262°C,and the thermal conductivity was 0.03003 W/（m·K）.（2）The optimal hydrophobic modification ratio was:in 100 m L of 2 wt%CMF suspension,1 m L each of PFOTMS and KH540,6 g Al Cl₃·6H₂O,8 g TEOS,the resulting aerogel had good hydrophobic performance,and the water contact angle was 141.5°.Hydrophobic modification did not affect the thermal insulation and other properties of aerogels.（3）The thicker the aerogel layer,the better the thermal insulation performance of the aerogel composite fabric,but too thick will lead to a decrease in the air permeability of the composite fabric,when the thickness of the aerogel layer is 6 mm,the thermal insulation and taking performance of the aerogel composite fabric are better;The thermal insulation performance of different base cloth aerogel composite fabrics has been greatly improved compared with the original fabric,and the performance is mainly affected by the performance of the original fabric.