Study On The Interfacial Bonding And Paper Properties Of Aramid Fiber/NFC/Nano-TiO₂ Paper Based Composite

M-aramid paper based composite are made of m-aramid chopped fiber and fibrid（or pulps）by using modern papermaking wet forming technology and then prepared by the other subsequent processing.M-aramid fiber,due to its high molecular orientation and crystallinity,exhibits high specific strength,specific modulus,dielectric performance,excellent heat resistance,great chemical stability and low density,etc,the products of m-aramid are also rich and varied,including high temperature insulation materials,lightweight honeycomb structure materials,high performance electronic materials,etc.Excellent performance products have a wide range of applications in modern high technology and industry fields including electricity,aerospace,defense and military,rail transportation,etc.However,the mechanical strength and electrical performance of m-aramid paper was limited by poor interfacial bonding between choppped fiber and fibrid due to chemically inert surface of choppped fiber with skin core structure.In addition,the long-term use of the products could cause aging phenomenon,its also seriously affects the life of m-aramid paper.Generally,nanofibers cellulose and nano-TiO₂,because of its excellent properties of the enhanced effect and heat resistance,are widely applied in reinforcing the performance of composite materials.In this paper,NFC and nano-TiO₂ are introduced into m-aramid paper based composite to improve the strength and insulation properties of m-aramid paper.Firstly,through comparative analysis on the difference of apparent morphology and morphological parameters between m-aramid chopped fiber and fibrid,their had an influence on the structure of m-aramid paper.It showed that the poor strength of m-aramid paper was mainly determined by physical interlace through chopped fiber and fibrid.It caused inferior interfacial bonding strength.The m-aramid chopped fiber was modified by phosphoric acid solution in order to increase its surface activity and roughness.The m-aramid fiber/NFC paper composite was prepared by adding different ratios of NFC and the properties of m-aramid fiber/NFC paper based composite were investigated.The results showed that the tensile index,tear index,internal bonding strength and TEA of m-aramid fiber/NFC paper reached a maximum value of 22.44 N·m·g^-1,13.33mN·m²·g^-1,138.22 J·m^-2 and 29.71/J·m^-2 with 20wt% NFC,respectively.It could be found that enhanced mechanical properties of aramid fiber /NFC paper were derived from the strong hydrogen bonding interaction between m-aramid fiber and NFC by FT-IR.The SEM figures showed that NFC thin film structure just like the “spider web” or “silk” could become the pivotal bonding bridge and filling agent between m-aramid chopped and fibrid,which could improve interficail adhesion strength of m-aramid paper greatly.Secondly,nano-TiO₂ was modified by KH-550 to obtain uniformly dispersed nanoparticles.The three-dimensional network of NFC was used as a carrier to disperse and load nano-TiO₂.The dispersion stability and homogeneity of the NFC/nano-TiO₂ were studied by spectrophotometer.The results show that NFC plays an important role in dispersing nano-TiO₂ because of its special three-dimensional network structure and surface active groups.FT-IR proved that NFC/nano-TiO₂ was assembled into dense organic-inorganic hybrid nano-materials by hydrogen bonding interaction.Then the effects of NFC/nano-TiO₂ organic-inorganic hybrid nano-materials on the mechanical properties,stress-strain,dielectric strength and anti-aging properties of m-aramid paper were studied.The results showed that the tensile index,fracture stress and dielectric strength of the composite paper reached a maximum value of 16.42N·m·g^-1,6.991 MPa and 9.81kV·mm-1 with the ratio of m-aramid fiber/NFC/nano-TiO₂ was 8.7:0.5:0.8,respectively.Also the m-aramid fiber/NFC/nano-TiO₂ paper obtained a strong anti-aging properties.Finally,the enhancement mechanism of NFC/nano-TiO₂ was discussed,which was mainly divided into two aspects: on the one hand,the organic-inorganic interface phase has been formed between NFC and nano-TiO₂,and the activity of interfacial layer was increased.On the other hand,the surface roughness of NFC loaded with nano-TiO₂ were increased from 53 nm to 101.1nmgreatly.The enhanced mechanical properties of m-aramid fiber/NFC/nano-TiO₂ paper based composite was increased due to the meshing strength of interface between m-aramid fiber and NFC/nano-TiO₂ was improved.Thereby the comprehensive performance of m-aramid fiber/NFC/nano-TiO₂ paper based composite was improved greatly.