Preparation And Properties Of Polyimide Aerogel/Aramid Composite Heat Insulation Material

In order to meet the life safety of workers and firefighters in extreme thermal environment.In order to increase the comfort of thermal protective clothing and reduce the risk of heat stress reaction of the protected personnel.Higher performance requirements are put forward for heat insulation materials of thermal protective suits.Aerogel materials have attracted much attention due to their special internal three-dimensional network crosslinking structure and outstanding properties such as ultra-low density,ultra-high porosity,ultra-high surface area and ultra-low thermal conductivity(as low as 0.015 W/(m·k)).It has been widely studied and applied in the field of lightweight and efficient heat insulation materials.In this paper,polyimide(PI)aerogel as the matrix material,with Arlene felt as the reinforcement material,using freeze-drying and soft processing method to prepare flexible PI aerogel/Arlene composite insulation material.The mechanical properties,heat insulation,flame retardancy and softness of aerogel composites were studied.It provides reference for the application of aerogel material in thermal protective clothing field.In order to explore the forming and preparation technology of polyimide aerogel.In this paper,the effect of temperature on pore size distribution and heat insulation performance of polyimide aerogel was investigated.The pore size distribution,heat insulation,compression,thermal stability and flame retardancy of aerogel were also studied by the solid content of precursor PAAs solution.Scanning electron microscopy and thermal conductivity tests were carried out.The influence of freezing temperature-15? and liquid nitrogen environment(-196?)on the pore size and thermal insulation performance of aerogel was investigated.Scanning electron microscopy,compression experiment,thermogravimetric analysis,thermal conductivity test and vertical combustion experiment were carried out.The effect of solid content of different PAAs solutions on the structure and properties of PI aerogel was studied.It is found that PAAs can be completely dissolved when the solid content is less than 4%.And in the range of 1%?4%,with the increase of PAAs solid content,the smaller the pore diameter of PI aerogel,the better the mechanical properties,so the thermal conductivity becomes lower.PI aerogel,made of 4% PAAs solvent,has the lowest thermal conductivity of 0.0309 W/ K and the best flame retardant performance.PI aerogel/aramid fiber composite was further developed by freeze-drying method under the condition of optimizing the preparation process of PI aerogel.The effects of mass fraction of PI aerogel on microstructure,mechanical properties,thermal properties,thermal insulation properties and flame retardant properties of PI aerogel/Arlene fiber composites were studied.The results show that the increase of mass fraction of PI aerogel has a positive effect on the mechanical,thermal stability,heat insulation and flame retardant properties of PI aerogel/Arlene fiber composites.However,too much PI aerogel will lead to larger material thickness and worse wear resistance.The PI aerogel/aramid fiber composite with 30% PI aerogel mass fraction has relatively better mechanical properties.The tensile strength is 8 Mpa,the top breaking strength can reach 299 N,and it also has good heat insulation performance.The thermal conductivity is reduced to 0.0341 W/m K at room temperature,and it has excellent flame retardant performance.The length of carbonization damage in vertical combustion experiment is only 1.5 cm.At the same time,in order to improve the comfort of PI aerogel/aramid fiber composite when it is used as heat insulation material,the softener finishing method is used to soften the material.The influence of different concentration of softener on the softness,mechanical properties,thermal insulation,thermal stability and flame retardancy of PI aerogel/aramid fiber composites was investigated.The results showed that the internal structure of PI aerogel/aramid fiber composite was looser than before after finishing with softener.When the concentration of softener is 15%,the softness of PI aerogel/Arlene fiber composite is the best,and the crease recovery Angle is 127.7°.The mechanical properties,thermal stability,heat insulation and flame retardancy decrease with the increase of softener concentration.It was found that the thermal conductivity of PI aerogel/Arlene fiber composites treated with 5% softener was 0.046 W/(m·k).The length of combustion damage is 3.9 cm,which has good comprehensive performance.