Preparation And Properties Of Micron Grade Hydrophobic Silica Aerogel Microspheres For Fabric Heat Insulation Coating Finishing

Heat insulation coating can effectively block heat,reduce the use of temperature control equipment,which can help the development of energy conservation society.SiO₂aerogel is an ideal new heat insulation material with light weight,high porosity and low thermal conductivity.However,the poor hydrophobicity of SiO₂ aerogel will cause the collapse of pore structure during preparation as the capillary force between its solid-liquid interphase,as well as the enter of finishing liquid during finishing process,finally effect the heat insulation of the coated fabric.What’s mroe,the SiO₂ aerogel obtained by the traditional sol-gel method is mostly massive and can not be directly applied to the finishing of fabric coating.Therefore,it is necessary to prepare the SiO₂ aerogel with hydrophobic property,and further reduce their size,in order to meet its application in fabric heat insulation finishing.In this study,hydrophobic methyl methoxy-silane compounds were used as silicon source precursor,sol-gel method was combined with emulsion pelletizing technology,for the preparation of hydrophobic SiO₂ aerogel microspheres which are suitable for cotton fabric heat insulation coating finishing.The contents and results are as follows:Part 1:Preparation of SiO₂ aerogel microspheres based on methyl trimethoxy-silane（MTMS）and their application in fabric heat insulation coating.The precursor MTMS was dispersed in deionized water by dodecyl trimethyl ammonium bromide（DTAB）as emulsifier.Then,they were were hydrolyzed to silanol by acetic acid as catalyst.After that,ammonia solution was added to catalyzed the condensation of silanol,and the dispersing liquid was quickly transferred into n-hexane to form water-in-oil emulsion with Span-80 as emulsifier.After a certain time of condensation,SiO₂ aerogel microspheres based on MTMS were prepared by aging and atmospheric drying.The effects of the amount of emulsifier,catalyst and aging time on the morphology and thermal conductivity of SiO₂ aerogel microspheres were investigated,the thermal conductivity of SiO₂ aerogel microspheres were tested,and the peoperty of SiO₂ aerogel microspheres coated cotton fabrics was studied.The results show that,the single precursor SiO₂ aerogel microspheres prepared with 10.0 mL of MTMS,0.10 g of DTAB,0.100 mL of acetic acid,1.2 mL of ammonia,0.80 g of Span-80 and aging for 3 h are mesoporous microspheres with diameter as about 5μm.They presented regular morphology and uniform size,the thermal conductivity is 0.0465 W/（m·K）,the water contact angle is 142°.When the heating temperature is 40℃,the temperature difference between front and back of their finished cotton fabric can reach 3.2℃.Part 2:Preparation of SiO₂ aerogel microspheres based on MTMS and dimethyldimethoxy-silane（DMDMS）,and their application in fabric heat insulation coating.In order to improve the hydrophobicity of the prepared SiO₂ aerogel microspheres,MTMS and DMDMS were used as co-precursors with cetyltrimethyl ammonium bromide（CTAB）as emulsifier.The influences of the ratio of MTMS/DMDMS volume,dosage of emulsifiers and catalysts,aging time on the morphology and thermal conductivity of SiO₂ aerogel microspheres were investigated,and the aerogel microspheres were applied to finish the thermal insulation coating of cotton fabrics.The results show that,the SiO₂ aerogel microspheres prepared with 8.0 mL of MTMS,2.0 mL of DMDMS,0.20 g of CTAB,0.200 mL of acetic acid,2.0 mL of ammonia,0.80 g of Span-80 and aging for 3 h also have mesoporous structure,and with regular morphology and uniform dispersion.Their particle size reduced to about 1μm,thermal conductivity reduced to 0.044 W/（m·K）,and the water contact angle increased to153°,which reaching the superhydrophobic level.When the heating temperature is 40℃,the maximum temperature difference between the front and back of their finished cotton fabric increases to 3.9℃.In conclusion,SiO₂ aerogel microspheres suitable for fabric heat insulation coating finishing can be prepared using hydrophobic MTMS as silicon source precursor,combined with sol-gel method and emulsion pellet formation technology.With the introduction of the second precursor DMDMS,the particle size of the prepared SiO₂aerogel microspheres decreases and the hydrophobicity increases,better finishing effect of fabric heat insulation coating can be obtained.The development of this project realizes the preparation of hydrophobic SiO₂ aerogel microspheres and their application in the finishing of fabric heat insulation coating,which can provide certain technical reference for the production and application of heat insulation coating fabric.