Preparation And Characterization Of Bamboo-plastic Electromagnetic Shielding Composites With Three-dimensional Conductive Network Structure

In recent years,with the rapid progress of electronic information technology,the electromagnetic radiation problem also gradually received wide attention from all sectors of society.To solve the electromagnetic radiation of various harms,the bamboo fiber was coated with Ni-Fe-P ternary alloy to obtain excellent electrical conductivity.And then the coated bamboo fiber was used as dispersing phase,HDPE was used as continuous phase,and the bamboo-plastic electromagnetic shielding composite(BPSC)was prepared by hot pressing.Based on the control variable method,the optimal plating parameters for electroless plating of Ni-Fe-P on bamboo flakes and bamboo fibers were obtained.And for the first time,the coating quality of bamboo wall with different structures was studied.The results show that due to the differences in the physiological structure of the three structures,the wettability of the surfaces of the different structures is different,which leads to a large difference in the quality of the coatings between the three structures.In addition,the formation of the three-dimensional conductive network in BPSC,as well as the conductivity,magnetic permeability and electromagnetic shielding properties of BPSC were systematically studied.The results showed that the bamboo fibers overlapped with each other to form a perfect three-dimensional conductive network,which endowed the composites with excellent conductivity,magnetic conductivity and electromagnetic shielding.Among them,the shielding efficiency value(SE)of BPSC can reach 82d B(0.1MHz-2GHz),which reached the classification standard of high electromagnetic shielding materials.The research and preparation of bamboo-plastic electromagnetic shielding materials provide a new method for the preparation of high efficiency,low cost and degradable electromagnetic shielding materials.The specific results of the study are as follows:(1)The optimum plating parameters for electroless ni-fe-p plating on bamboo chip are:Ni SO₄·6H₂O 40g/L,(NH₄)₂Fe(SO₄)₂·6H₂O 10g/L,Na H₂PO₂·H₂O 30g/L,KNa C₄H₄O₆·4H₂O50g/L,(NH₄)₂SO₄ 30g/L,p H=9,temperature=90?.Under the optimal plating parameter,a dense,uniform metal alloy coating with crystal structure can be obtained.The deposition of the coating endows bamboo with good electrical conductivity,magnetic conductivity and electromagnetic shielding performance.Thereinto,the electromagnetic shielding efficiency(SE)of plated bamboo and was higher than 55 d B(0.1 MHz-2.0 GHz),meeting the electromagnetic shielding material standard.Due to the porosity of bamboo,the Ni-Fe-P alloy coating is not simply deposited on the surface of bamboo,but penetrates into the interior of bamboo through the pores on the surface,which is conducive to enhancing the interface between the coating and bamboo.In addition,due to the difference in physiological structure,the wettability of the surface of bamboo outer skin,bamboo inner skin,and bamboo pulp is different,which leads to large differences in the coating quality(surface resistivity,coating adhesion,etc.)among the three structures.(2)The bamboo fiber was electroless plated on the basis of the optimal Ni-Fe-P parameters.It was found that the load amount of BF in the bath had significant influence on the grain size,color,element content and conductivity of the metal coating.When the load amount of BF is5 g/L,the best conductivity of coated BF is 3.62×10^-2?·cm.The metalized bamboo fiber was filled into the HDPE matrix,and the plated BFs overlapped with each other in the matrix to construct rich conductive paths,forming a three-dimensional conductive network that can effectively reflect,scatter and absorb electromagnetic radiation,imparting BPSC efficient conductivity and electromagnetic shielding.The best SE value could be 82 d B(0.1 MHz-2.0GHz),meeting the high electromagnetic shielding material standard.The study found that the SE of BPSCs did not increase with the increase of filler,because when the filler content reached a certain level,a complete 3D conductive network was formed inside the matrix material,reaching the saturation of electromagnetic conduction.(3)The performance stability of BPSC in harsh environments such as simulated seawater and simulated acid rain was further studied,and the damage mechanism of the material was analyzed.The research results show that,the simulated seawater and the simulated acid rain materials have undergone different degrees of discoloration,and the surface of the simulated seawater-treated materials also got some rust.Both the simulated seawater and acid rain treatments have a greater impact on the electromagnetic shielding effectiveness of the material,among which the SE value of seawater treated samples decreased from 80 d B to 32d B,which changes from high magnetic shielding material to medium electromagnetic shielding material,but it can still reach the target value of 30 d B for commercial applications.While that of acid rain treated samples decreased from 80 d B to 29 d B,which changes from high electromagnetic shielding material to low electromagnetic shielding material.In addition,the lattice constants of the simulated seawater treated BPSC increased due to the doping of Na⁺and Cl^-,resulting in the increase of the thermal stability of the material.The thermal stability of the simulated acid rain treated materials tends to deteriorate due to the corrosion of metal coating on bamboo fibers.Due to the degradation of the two-phase interface combination,the tensile strength,bending strength and impact strength of the simulated seawater treatment materials were reduced by 10.2%,26.4%and 17.7%,respectively.After simulated acid rain treatment,the tensile strength,bending strength and impact strength of the materials were reduced by 23.1%,28.9%and 27.2%,respectively.