Study On Preparation And Properties Of Electromagnetic Shielding Wood

Nowadays,various electronic devices can be seen everywhere in people's daily life.With the popularity of electronic equipment,people's lives become convenient.However,electromagnetic pollution has become serious.Electromagnetic radiation has caused great interference and damage to people's normal work,life and health,and arised extensive attention.Electromagnetic shielding is an effective means to resist electromagnetic interference and reduce the harm from electromagnetic wave.Electromagnetic shielding has become the mainstream method to purify electromagnetic environment all over the world.The matrix of common electromagnetic shielding materials is mostly non-renewable and not easy to degrade.Therefore,it is an inevitable trend to use resource-rich,renewable and environmentally friendly materials as the matrix to prepare electromagnetic shielding materials in the future.Wood is a natural material rich in resources,renewable and degradable in nature.The wood and conductive fillers can be used to prepare the ultalight and renewable composite for electromagnetic shielding applicaions.At the same time,the wood is endowed with electromagnetic shielding function,and so as to the added value of wood is improved.In this work,the impregnation channel of wood was opened up.The electromagnetic shielding network was constructed and the structure of electromagnetic shielding wood was optimized.The main results achieved are as follows:(1)On the premise of ensuring the integrity of wood structure,the results show that the NaClO2 treatment is better than the deep eutectic solvent(DES)treatment.The results indicated that the optimal process conditions for NaClO2 treatment were temperature of 90?,treatment time of 5 h and NaClO2 dosage of 7 wt%.Under this condition,the porosity and total pore area of treated wood increased greatly which the porosity increased from 11.82%of the original wood to 32.83%,and the total pore area increased from 0.06 m2/g to 0.36 m2/g.By the characterization of chemical structure,crystal structure and morphology observation,it was found that the whole structure of wood was not destroyed and the crystal structure of cellulose did not change after NaClO2 treatment.Due to lignin,hemicellulose and other components have been removed,wood substrate is mainly composed of cellulose.(2)The preparation process and properties of pure polyaniline were investigated.Then based on the optimal process of pure polyaniline preparation,polyaniline was impregnated into wood by vacuum impregnation and in situ polymerization,so as to prepare polyaniline electromagnetic shielding wood,and its properties were tested and characterized.The experimental results showed that the optimal process conditions for preparation of pure polyaniline were molar ratio of ammonium persulfate to aniline monomer of 1.25:1,HCl concentration of 1 mol/L,polymerization temperature of 5? and monomer concentration of aniline of 0.2 mol/L.Raman detection of electromagnetic shielding wood of polyaniline indicates that polyaniline has been successfully introduced.Compared with original wood,polyaniline was more easily impregnated into the wood substrate prepared in this experiment.The optimum content of polyaniline in electromagnetic shielding wood is 30%,and the material has high conductivity and electromagnetic shielding efficiency,which reach 0.0605 S/cm and 10 dB,respectively.(3)The structure of polyaniline electromagnetic shielding wood was optimized.The AgNWs surface layer was introduced on the surface of polyaniline electromagnetic shielding wood.A sandwich structure with AgNWs layer as the surface and polyaniline wood electromagnetic shielding network as the center was constructed which enhanced the electromagnetic shielding performance of the material.In this work,the preparation process and properties of AgNWs were investigated and tested.Then the properties of AgNWs-polyaniline electromagnetic shielding wood were tested.The experimental results showed that the optimal process conditions for preparation of AgNWs were K27-32 to K88-96 ratio of 1:2,temperature of 150? and number of dips of 4.The structural analysis of the AgNWs shows that the AgNWs has been successfully prepared in the experiment and has high crystallinity.The AgNWs-polyaniline electromagnetic shielding wood has good electromagnetic shielding performance which was about 31 dB,which was about 21 dB higher than that of the previously prepared polyaniline electromagnetic shielding wood.The mechanical properties of AgNWs-polyaniline electromagnetic shielding wood are good which tensile strength reached about 8 MPa,and its mechanical properties are stronger than that of general cellulose-based electromagnetic shielding materials.