Method Of Delignification Of Juncus Effusus Fibers And Preparation Of Its Thermal Infrared Stealth Material

Juncus effusus fibers（JEFs）feature a distinctive hollow,multi-pith structure and good physical chemical characteristics.It has been used for more than 1,000 years.It has been woven into household products such as straw mats and tatami mats,and has been presented as"national gifts"to foreign friends.However,on the one hand,the high lignin content of JEFs leads to poor flexibility,on the other hand,due to the few types of functional groups,its function is insufficient,which limits its further application.In the first part of the paper,aim at the problem that mechanical properties of JEFs need to be improved.Four different pre-treatments for delignification of JEFs,including sodium hydroxide solution（Na OH aq.）,sodium chlorite solution（Na Cl O₂aq.）,hydrogen peroxide solution（H₂O₂aq.）,and deep eutectic solvent（DES）,were used to comparatively study the effects of morphology,structure,and physical and chemical properties of the fiber before and after modification.The results are as follows:（1）The fiber treated with Na OH aq.exhibited the most obvious weight loss（30%）due to the obvious delignification effect,and the three-dimensional structure of the fiber was severely disrupted.However,the other three methods exhibited structure-preserving delignification processes,especially Na Cl O₂ aq,which selectively removed most of the lignin and hemicellulose,and the resulting modified fibers（CTFs）increase their tensile strength and specific surface area by 62.7%and 481.3%,respectively.（2）On the basis of delignification,oil absorption（HDTMS/CTFs）and strain sensor fiber materials（CNTs/CTFs）with excellent properties were prepared by siloxane modification and carbon nanotube loading,respectively.HDTMS/CTFs can maintain 78.6%efficiency after 10 cycles.CNTs/CTFs exhibit obvious pressure sensitivity and can be used to sensitively monitor human wrist,finger and other movements.In addition,CNTs/CTFs also have the phenomenon of humidity sensitivity,which has a certain application prospect in the field of intelligent wearable sensors.On the basis of the above work,the second part of the paper firstly filled silica aerogel inside CTFs to prepare Si O₂/CTFs,and then loaded polyethylene glycol（PEG）into Si O₂/CTFs by vacuum impregnation method to prepare phase change fiber materials（PEG/Si O₂/CTFs）.The morphology,structure,and physicochemical properties of the composites were characterized.The results showed that:（1）The SEM results show that Si O₂ can be well filled in CTFs due to its hollow and multi-pined structure,and at the same time CTFs endows Si O₂ with flexibility.（2）BET test showed that the specific surface area could reach 270.01 m²/g,37.8 times higher than that of CTFs.（3）The thermal conductivity test shows that the thermal insulation performance of Si O₂/CTFs is further improved,and the thermal conductivity is as low as 0.039 W/（m·K）,and the thermal insulation capacity is improved by 71.7%compared with that of CTFs.The maximum specific surface area is 270.01 m²/g,which is 37.8 times higher than that of CTFs.（4）After adding PEG to Si O₂/CTFs,due to the high porosity of Si O₂/CTFs,it is beneficial to load PEG,and the load rate of PEG is>90%.（5）The infrared thermal imaging test shows that the three-layer PEG/Si O₂/CTFs material exhibits similar thermal imaging images to the environment,indicating that PEG/Si O₂/CTFs has obvious infrared thermal stealth characteristics.