Preparation And Application Of Water-glass Based SiO₂ Aerogel/expanded Perlite Composite Insulation Material

SiO₂ aerogel is a new light nanometer material with lower thermal conductivity at room temperature than that in air.It is considered to be an ideal thermal insulation material in the field of building energy conservation,but its strength is very low and can not be used as insulation material alone.The expanded perlite is a kind of inorganic thermal insulation lightweight aggregate with light weight,high porosity and non-combustible property,but it is easy to absorb moisture and its thermal conductivity is larger than that of organic thermal insulation material.In this paper,the SiO₂ aerogel and expanded perlite are combined with each other,the SiO₂ aerogel/expanded perlite composite insulation material was prepared by combining the advantages of the two materials.Its properties and structure were tested and characterized,and its application was further explored in order to promote the development of building energy saving industry.The main contents of this paper are as follows:?1?Taking sodium silicate as silicon source,the effects of pH value,gel temperature,aging time,aging temperature and two modified processes?one-step replacement and multi-step replacement modification?on the properties of the prepared aerogels in sol gel process were studied.The structure is characterized by a series of characterization.The research shows that:When the pH value of sol is about 3.40 and the gel temperature is25?,the aerogel prepared by aging in water for 24 hours has good properties;In the one-step replacement process,when the amount of TMCS is 120%,V?TMCS??V?EtOH?=1?0.25,V?TMCS??V?Heptane?=1?1.5,the density of the prepared SiO₂aerogel is 0.1285 g·cm^-3,the porosity is 94.34%,and the thermal conductivity is 0.0238W/?m·k?;In the process of multistep replacement modification,When the amount of TMCS is 40%of the gel volume and V?TMCS??V?Heptane?=1?3,the density of the prepared SiO₂ aerogel is 0.1152 g·cm^-3,the porosity is 94.92%,and the thermal conductivity is 0.0230 W/?m·k?.?2?Based on the optimized conditions for preparing SiO₂ aerogels,the sol was adsorbed into the inner pore of expanded perlite,and the particle size,the amount of sol adsorption,the adsorption mode and the adsorption pressure were explored.Effect of adsorption time on properties of SiO₂ aerogel/expanded perlite composite insulation material,the prepared composite materials were tested by macro test and microstructural characterization.The results show that when the particle size of expanded perlite is in the range of 0.84².00 mm,SiO₂ sol was adsorbed by vacuum impregnation adsorption method,the adsorption pressure is-0.08 MPa,the adsorption time is 15 min,then through a series of treatments such as aging,hydrophobic modification,displacement washing,atmospheric pressure drying,etc.The bulk density of the SiO₂aerogel/expanded perlite composite insulation material was 109.26 kg·m^-3,the thermal conductivity of perlite is reduced from 0.0648 W/?m·k?to 0.0565 W/?m·k?,the decline was 12.81%,and the water absorption rate of perlite is reduced from 401.6%to 15.6%.The perlite has better hydrophobicity.?3?The composite perlite thermal insulation material prepared in the earlier period was used as aggregate,and water glass,polyvinyl alcohol and cement were used as binders respectively to prepare the thermal insulation board.The results showed that the thermal conductivity of the composite thermal insulation board was decreased.However,the compressive strength is obviously reduced.