Green Preparation And Applications Of Palygorskite-based Plant Fiber Composite Aerogel

Aerogel materials have become the first choice of new materials in the field of building energy efficiency because of its low-density,low-thermal-conductivity,high-porosity,and unique nano-hole structures.At present,aerogel materials are mainly silicon-based aerogels,but their brittleness,high cost,and easy generation of dust limit its applications.In this study,a three-dimensional network structure of aerogels was constructed by natural one-dimensional nanomaterials-palygorskite,and aerogels were toughened and reinforced with plant fibers?wood fiber?.The environmentally friendly freeze-drying method was used to successfully prepare large-scale aerogel materials.Based on this process,its heat insulation and flame retardancy properties are investigated,and it was applied to humidity control through process adjustment.The main research contents and conclusions are as follows:?1?Preparation and Characterization of Pal/WF Composite AerogelsThe effects of freezing temperatures,raw material ratios,ethanol addition amounts,and preparation concentrations on the structure of Pal/WF composite aerogels were investigated by SEM.The results showed that Pal and WF could form a stable structure by hydrogen bonding without using any chemical cross-linking agent.The lower the temperature?-196??,the better the freezing effect.The most suitable ratio of Pal and WF was 4:1.The addition of organic reagents could greatly affect the freezing effect,but it was not that the larger the amount,the better.The 10%amount is the most suitable.The effect was best when the concentration was7wt%.Too high preparation concentration would cause the agglomeration of Pal,and the mechanical properties would be poor with too low concentration.?2?Research on Flame Retardant and Thermal Insulation Properties of Pal/WF Composite AerogelsThis chapter investigated the effect of the preparation concentration on the aerogel's thermal insulation and flame retardancy.The SEM photos proved that the higher the preparation concentration,the smaller the pore size of the aerogel.However,the thermal conductivity test shown that the lower the preparation concentration,the better the insulation?minimum 0.033W/m·K?.The reason was that the decrease in density leading to the reduction of solid-phase heat transfer.Conical calorimetry test shown that the Pal/WF composite aerogels were much lower than traditional insulation materials at high temperatures such as CO,CO₂and heat release.The LOI values were all more than 70%which indicated that this aerogel can hardly be ignited.The compressive strength of Pal/WF composite aerogels could reach 4.7 MPa,and the specific modulus can reach 65.27 MPa·cm³/g,which was enough to meet the requirements of practical use.?3?Preparation and Properties of Pal/WF Composite Aerogels with Intelligent Humidity ControlCalcium chloride?Ca Cl₂?is often used as a hygroscopic agent because of its deliquescent properties,but it is easy to turn water or agglomerate after water vapor absorption,making it is difficult to use repeatedly.In this part,Ca Cl₂was added during the preparation process to disperse it into the pores of the aerogel,so as to solve the problem of Ca Cl₂turned water and agglomerate.At the same time,the water vapor capacity of Pal/WF composite aerogels could be improved by this way.According to the static water vapor adsorption-desorption experimental analysis,it can be seen that with the increase of the amount of Ca Cl₂,the maximum water vapor absorption of the aerogel had significantly increased.However,when the added amount reached12%of the solid content,the effect of Ca Cl₂obvious reduced.Dynamic water vapor adsorption-desorption experiments shown that Pal/WF composite aerogels had a high water vapor response rate,and the water vapor adsorption could reach 30%of its own mass within 3hours.The dynamic cycle experiment shown that the Pal/WF composite aerogel humidity control material could be reused with almost no loss.