Preparation And Thermal Insulation Properties Of PAN Pre-oxidized Fiber Mat/SiO 2 Aerogel Composite

The energy shortage has become a major problem affecting human development.Human beings continue to seek the development of new energy sources but also pay more attention to energy conservation.The most direct and effective way of energy conservation is to further strengthen the development and utilization of thermal insulating materials,especially the high efficiency and reliability,simple process,low cost composites for thermal insulation has become the focus of the study.Therefore,the research of this paper involves PAN-based preoxidized fiber felt/silica aerogel thermal insulating composites.PAN-based preoxidized fiber is an intermediate product of carbon fiber,which was used in this research because of its good heat resistance,low thermal conductivity and low cost.Firstly,preoxidized fiber felt was prepared through needle punching process.Effects of needle-punching parameters including cycle,depth and frequence of needle-punching on thermal insulating performance under room temperature and moderate temperature were studied.The results showed that the structural parameters of the preoxidized fiber felts were affected by the needle-punching parameters,leading to the change of the thermal insulating performance.In addition,the linear relationship between the steady-state temperature difference and the usage temperature of preoxidized felt was presented.Through orthogonal experiment,the optimum preparation technology of preoxidized fiber felt with the best heat insulating performance was obtained.The best preparation technology is 2 needle-punching cycles,8mm needle-punching depth and a needle-punching frequency of 140 punchings/min.Silica aerogel particles whose dispersed medium are air were introduced by coating on the preoxidized felt.The effects of silica aerogel content on the thermal insulating properties of silica aerogel heat insulating blanket under room temperature and moderate temperature were studied.The results showed the thermal insulting property of silica aerogel heat insulating blanket under moderate temperature is better than that of preoxidized fiber felt.Addition of silica aerogel has a maximum point for heat insulating blanket under room temperature and moderate temperature.Moreover,linear relationship between steady-state temperature difference and usage temperature of heat insulation blanket was presented.In view of infrared radiation transmittance of silica aerogel under moderate temperature,compound silica aerogel coating heat insulating blankets were prepared by adding the infrared opacifier SiC into silica aerogel.The effects of the content ratio between silica aerogel and SiC on thermal insulating properties of compound silica aerogel coating heat insulating blankets at room temperature and moderate temperature were studied.The results showed that thermal conductivity of the compound coating blanket under room temperature increases with increasing of content of SiC,but at moderate temperature,the addition of SiC has a maximum point.Adding SiC within the maximum point can effectively suppress infrared radiation and enhance the heat insulating performance.In addition,a simple method calculated the thermal conductivity of thermal insulating material at moderate temperature was presented to elaborate the significance of linear relationship between steady-state temperature difference and usage temperature.