Thermal Insulation Materials:Silica Composite And A Novel Polymeric Ionic Liquid

Thermal insulation materials are widely used in building decoration,industrial production,aerospace,and so on.From the nature of materials,it includes inorganic and organic thermal insulation materials.The most potentially used inorganic thermal insulation material is silica aerogel;our group recently proposed a continuous pressurized carbonation method combined with supercritical drying for synthesis of high quality silica aerogel powders.However,the powder silica aerogel is hardly used in many application cases;therefore,this work tries to prepare silica composite to solve the problem.On the other hand,the organic thermal insulation material possesses obvious disadvantages,such as,relatively high thermal conductivity and poor heat stability;therefore,this work proposes and studies polymeric ionic liquid as a new type of organic thermal insulation material.Different silica composites were synthesized with aluminum tri-sec-butoxide(ASB)and polyvinyl alcohol(PVA)as the additives.The sensitive factors on the thermal conductivity of the prepared silica-alumina composite materials were the concentration of sodium silicate and molar ratio of ASB to silica.Results showed that when the concentration of sodium silicate was 0.5 mol·L-1 and the molar ratio was 0.2,the lowest thermal conductivity of 0.044 W·m-1·K-1 measured at room temperature was obtained.For the prepared silica-PVA composite,the key factor on the thermal conductivity was the mass fraction of PVA.When 50.8 wt%PVA was used,the lowest thermal conductivity of 0.034 W·m-1·K-1 measured at room temperature was obtained.A novel polymeric ionic liquid(PIL;quaternary phosphonium salt)as the organic thermal insulation material was proposed and synthesized.Results showed that when the hexafluorophosphate ion was used with the monomer concentration of 1 mol·L-1 under polymerization of 1h at 85 ?,The PIL had a low thermal conductivity of 0.092 W·m-1·K-1 measured at 40 ? and a high glass-transition temperature of 210.1? and a high melting point of 421.6?.Moreover,after appropriate foaming,the thermal conductivity could be reduced to 0.034 W·m-1·K-1.