| As a nano-porous material with controllable structure,SiO2 aerogel is characterized by low thermal conductivity,light weight,environmental protection and good stability.It is the solid material with the best thermal insulation performance in the world and has been widely applied in the field of thermal insulation.However,there are still some problems in the preparation of SiO2 aerogel:SiO2 aerogel is prepared by supercritical drying method,which has high equipment requirements and poor operability.SiO2 aerogel is prepared by atmospheric pressure drying method,which is highly operable.However,in the preparation process,the traditional solvent replacement process has the disadvantages of long time of solvent replacement and large consumption of organic solvent.In addition,the pore structure will be subjected to huge shrinkage pressure in the subsequent drying process,resulting in the pore structure being easily destroyed.Atmospheric pressure drying method is adopted for SiO2 aerogel in this project.In the process of preparation,the solvent replacement technology was optimized to improve the efficiency of the solvent replacement.Before the atmospheric pressure drying,the wet gel was modified on the surface for hydrophobicity to decrease the damage of pore structure of the SiO2 aerogel in the drying process.The self-made SiO2 aerogel was applied in thermal insulation coating of the fabric in order to obtain a thermal insulation coated fabric with excellent performance,it was aim of the project to provide a new way for the development of a new type of textile thermal insulation coated fabric.The contents and results of specific research were as follows:Part 1:Study on preparation and property of SiO2 aerogel.SiO2 aerogel was prepared by atmospheric pressure drying with ethyl orthosilicate(TEOS)as the precursor of silicon source.The effects of the molar ratio of TEOS,H2O and EtOH and the gel pH on the density and thermal conductivity of aerogel were studied,the preparation condition of SiO2 aerogel was optimized.The results showed that the optimal preparation technology condition of SiO2 aerogel was that the molar ratio of TEOS,H2O and EtOH was 1:5:8,and the gel pH was 6.In view of the disadvantages of long replacement cycle of solvent replacemen and large consumption of organic solvent,the effects of different technology of solvent replacement on the structure and properties of SiO2 aerogel were studied.The results showed that the recombination technology of suction filtration and multi-step solvent replacemen was optimal solvent replacement technology,the solvent can be replaced quickly in half an hour,and the consumption of organic solvent is also greatly reduced,the prepared SiO2 aerogel had better structure and performance.Trimethylchloros-ilane(TMCS)was used as a hydrophobic surface modifier,and the effects of surface modification on the structure and properties of SiO2 aerogel were studied.The results showed that the optimal molar ratio of TEOS and TMCS was 1:1,time of modification was 6h,the produced SiO2 aerogel had a very small density of 0.068g/cm3,a very high porosity of 96.90%and a minimum thermal conductivity of 0.0274w/(m·k).The structure and properties of aerogel were characterized by FTIR,SEM,automatic specific surface area and aperture analyzer,water contact angle tester,the results showed that SiO2 aerogel has typical nanoscale porous network structure,with an average pore diameter of 16.86nm,uniform pore distribution and good hydrophobicity.Part 2:Study on preparation and property of thermal insulation coated fabric with SiO2 aerogel.In order to deal with the adverse effects of extreme high temperatures on people's production and life in summer,the hydrophobic SiO2 aerogel material was used to prepare thermal insulation coated fabric,the influence of dispersion medium on dispersion of hydrophobic SiO2 aerogel was studied,the volume fraction of 50%ethanol solution was confirmed as dispersion medium.The thermal insulation coating finishing agent was prepared with waterborne polyurethane adhesive and hydrophobic SiO2 aerogel,and used to prepare hydrophobic SiO2 aerogel thermal insulation coated fabric.the effects of the amount of SiO2 aerogel and waterborne polyurethane on thermal insulation performance of coated fabrics were studied,the conditions of coating finishing process were optimized,and the thermal insulation performance of coated fabrics was tested,and compared with that of unmodified SiO2 aerogel coated fabrics.The results showed that when the content of hydrophobic SiO2 aerogel was 2.0%wt and that of waterborne polyurethane was 25%wt,the temperature difference between the front and the back of the coated fabric could reach 4.4? after 30min irradiation with the infrared heating lamp,which was 3.6? higher than that of the unmodified SiO2 aerogel coated fabric,the hydrophobic SiO2 aerogel coated fabric had better thermal insulation performance.The microstructure,hand feel,mechanical property,fabric thickness and gram weight of coated fabric were characterized and tested,the results showed that the surface of the coated fabric was attached with a large number of hydrophobic SiO2 aerogel particles,and hand feel of coated fabric was worse compared with that of the pure cotton fabric.The breaking strength and tearing strength of the coated fabric were increased and decreased compared with the pure cotton fabric respectively.After being coated with hydrophobic SiO2 aerogel,the thickness and gram weight of coated fabric were increased to 0.39mm and 32g/m2,respectively.Part 3:Study on preparation and property of composite thermal insulation coated fabrics.In order to explore the influence of composite thermal insulation functional materials on thermal insulation properties of coated fabrics.The composite thermal insulation coated fabric was prepared with the hydrophobic SiO2 aerogel and rutile TiO2 as the composite thermal insulation functional materials,and the waterborne polyurethane as the adhesive.The influence of mass ratio of SiO2 aerogel and TiO2 on thermal insulation performance of composite coated fabric was studied,the optimal mass ratio of SiO2 aerogel and TiO2 was determined to be 4:6,the temperature difference between the front and the back of the composite thermal insulation coated fabric could reach 7.4? after 30min irradiation with the infrared heating lamp,which improved 3.0? and 2.2? respectively compared with SiO2 aerogel thermal insulation coated fabric and TiO2 thermal insulation coated fabric,and the composite thermal insulation coated fabric had better thermal insulation performance.The microstructure,hand feel,mechanical property,fabric thickness and gram weight of composite coated fabric were characterized and tested.The results showed that the surface of the coated fabric was attached with the coating film with a sponge-like honeycomb structure,which was filled with a large number of holes,the composite thermal insulation coated fabric had a better handle than SiO2 aerogel thermal insulation coated fabric and TiO2 thermal insulation coated fabric,the breaking strength and tearing strength of composite thermal insulation coated fabric were close to that of SiO2 aerogel thermal insulation coated fabric and TiO2 thermal insulation coated fabric,the thickness and coating gram weight of composite thermal insulation coated fabric were 0.41mm and 45g·m-2,respectively,which was higher than that of SiO2 aerogel thermal insulation coated fabric,but close to that of TiO2 thermal insulation coating fabric.The results of the study showed that SiO2 aerogel was prepared successfully by atmospheric pressure drying,the recombination technology of suction filtration and multi-step solvent replacemen could greatly improve the efficiency of solvent replacement,before the atmospheric pressure drying,the surface modification of wet gel for hydrophobicity could decrease the damage of pore structure of the gel in the drying process,and improve the thermal insulation performance of SiO2 aerogel effectively.The SiO2 aerogel applied in thermal insulation coating of the fabric could give the coated fabric good thermal insulation performance.The thermal insulation coated fabric being prepared with SiO2 aerogel and TiO2 as composite heat insulation functional materials had better thermal insulation performance than that of coated fabrics prepared with SiO2 aerogel only. |
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