Preparation Of Aramid Nanofibers And Research On The Properties Of Functionalized Materials

Aramid fiber has high modulus,high thermal stability and solvent resistance.Resin matrix composites made from aramid fiber have been widely used.In recent years,aramid nanofibers(ANFs)are a new type of polymer nanofiber materials,which have excellent properties of macro aramid fibers and large specific surface area.In this paper,ANFs were prepared by deprotonation method,and then the thermal conductive fillers were added to prepare the thermal conductive membrane materials with ANFs as the substrate by vacuum assisted flocculation method.(1)The prepared ANFs were dispersed in ethanol and water,and then the dispersion was filtered into a membrane by vacuum assisted flocculation method.The mechanical properties,thermal stability,contact angle,X-ray electron diffraction and surface morphology of ANFs membrane were studied.The surface morphology of ANFs membrane is smooth and dense.The analysis of cross-section morphology shows that the membrane prepared by vacuum assisted flocculation method has obvious layered structure,which provides the feasibility for the subsequent preparation of functional ANFs membrane.The ANFs membrane prepared by using water as proton donor has better mechanical properties and thermal stability.The mechanical properties of ANFs membrane can reach 186.01 MPa,the initial decomposition temperature is503 ℃,the contact angle of ANFs membrane prepared with water as proton donor is73 ℃,and the contact angle of ANFs membrane prepared with ethanol as proton donor is 40.8 ℃.This is mainly due to more polar groups on the surface of ethanol,which leads to better hydrophilicity.(2)The suspensions of ANFs and Nano-BN were prepared by ultrasonic assisted blending method,and then ANF/Nano-BN composite films were prepared by vacuum assisted flocculation method and hot pressing.Scanning electron microscope(SEM)and transmission electron microscope(TEM)were used to observe the changes of Nano-BN before and after modification.At the same time,SEM was used to observe the cross section and microstructure of the composite film.It was found that ANFs and Nano-BN were closely combined,indicating that there was a strong force between ANFs and Nano-BN.At the same time,ANF/Nano-BN composite membrane has high mechanical properties.Due to the existence of thermal conductive material Nano-BN,Nano-BN is distributed in ANFs matrix to form a thermal conductive network,which improves the thermal conductivity of ANFs membrane.(3)On the basis of the previous research,the interfacial thermal resistance is the key factor affecting the thermal conductivity.The deposition of silver nanoparticles on the surface of Nano-BN can reduce the interfacial thermal resistance of the material.Nano-BN@Ag was dispersed in deionized water and compounded with ANFs by ultrasound,and ANF/Nano-BN@Ag composite membrane was prepared by vacuum assisted flocculation.Silver particles were successfully deposited on the surface of Nano-BN by TEM and X-ray electron diffraction analysis,and the size distribution of silver particles was measured at 28.4 ～ 34.1 nm.Silver particles loaded on Nano-BN can reduce the interface thermal resistance of the material,and further improve the thermal conductivity of the composite film on the basis of ANF/Nano-BN composite film.