Study On The Preparation And Electromagnetic Shielding Properties Of Poly(vinylidene Fluoride)Nanocomposites

Electromagnetic shielding materials are mainly used to reflect or absorb electromagnetic waves,which can eliminate damage and interference to human bodies,electronic components and the environment.In practical applications,with the increasing requirements of light,thin,wide and strong.Compared to metal-based electromagnetic shielding materials,carbon materials,including carbon black,carbon fiber,carbon nanotubes,graphene have low density,high flexibility,high conductivity,easy forming process and controllable and adjustable electromagnetic shielding performance.However,compared to magnetic ferrite materials,carbon materials are not magnetic and their impedance matching performance is poor.A large part of the electromagnetic shielding performance is derived from the reflection loss,which leads to secondary pollution.Therefore,there is still much room for improvement in the electromagnetic shielding performance of carbon materials.How to improve the electromagnetic shielding material dominated by absorption loss.By using poly?vinylidene fluoride?as the matrix,magnetic Fe₃O₄ nanoparticles and carbon materials?CNTs and GNPs?as fillers,we prepared electromagnetic shielding composite films and foamed materials with synergistic effect of magnetic loss and dielectric loss.1.Flexible Poly?vinylidene fluoride??PVDF?/Fe₃O₄/CNTs films were prepared through the solution processing and compression molding method.The electrical conductivities and the electromagnetic interference?EMI?shielding properties of these composites were gradually increased with the increasing of CNTs content,as well as the film thickness.Total shielding of the PVDF/Fe₃O₄-8CNTs composites increased from 14.1 to 32.7 dB,while the film thickness was increased from 0.5 to 1.1 mm,respectively.Due to the synergetic effect of Fe₃O₄ nanoparticles and CNTs,the final EMI shielding of the composites could be mainly attributed to the absorption process.Moreover,the fabricated films possess higher thermal conductivities,which can dissipate heat generated by electromagnetic waves.These functional films have the potential usage in making high-efficiency EMI shielding devices with rapid heat dissipation.2.The conductive network formed by the special OD-2D?Fe₃O₄-GNPs?structure through the addition of two-dimensional conductive fillers?GNPs?not only has the synergistic effect of magnetic loss and dielectric loss,but also the special 2D GNPs could cause multiple reflection loss.They make the PVDF/Fe304/GNPs film have higher conductivity,electromagnetic shielding performance and thermal conductivity compared to?PVDF?/Fe₃O₄/CNTs film under the same concentration and thickness.The content of Fe₃O₄ nanoparticles is 5 wt%.With the increase of GNPs content and film thickness,the total shielding of PVDF/Fe₃O₄/8GNPs composites increases from 16.2dB to 35.6dB,with the film thickness increases from 0.5mm to 1.1mm.3.The lightweight PVDF/Fe₃O₄/CNTs nanocomposite foamed material was successfully prepared by supercritical CO₂ foaming method,and the obtained nanocomposite foamed material was found to have good electrical conductivity and excellent electromagnetic shielding performance.At the same time,It can also form a stronger electromagnetic shielding nanocomposite foaming material with the main of absorption loss.The results show that the presence of micropores can effectively improve the electrical conductivity of nanocomposites.In addition,the loss of electromagnetic waves inside nanocomposite foams The mechanism is mainly based on absorption loss.This section presents a simple,effective,inexpensive and environmentally friendly method for the preparation of lightweight,highly conductive poly?vinylidene fluoride?nanocomposites with excellent electromagnetic shielding properties for a wide range of applications in electronic devices.,automotive industry and packaging materials.