环氧树脂/碳纳米复合材料的微孔发泡及其结构对电磁屏蔽效能的影响机制

The project aims to preparing the lightweight, high-performance thermosetting microcellular electromagnetic shielding composites by controlling the relationship between the epoxy resin crosslinking networks structures and microcellular foaming, constructing the conductive network and the magnetic network in the epoxy resin carbon microcellular composites and exploring the effect of its structure on the electromagnetic shielding effectiveness. In this project, we would first prepare the cured and cross-linked epoxy resin which could meet the needs of gas transfer and microcellular foaming by controlling the curing degree, the molecular weight between crosslinking points and the viscoelasticity; the magnetic loss of composites would be improved by the in-situ growth of Fe3O4 on the surface of high aspect ratio carbon nanoparticles, and then the problem of the homogeneous dispersion and directional arrangement of the high content magnetic carbon nanoparticles in the epoxy matrix would be solved by the introduction technology of the solvent-free nanofluids and the external magnetic field, respectively. The viscoelastic epoxy wall is subjected to biaxial stretching and uniaxial compression to promote the redistribute of magnetic carbon nanoparticles to build conductive and magnetic networks in the supercritical CO2 microcellular foaming process, and the electromagnetic shielding effectiveness of the epoxy resin carbon microcellular composites would be substantially improved by the absorption loss and multiple reflections loss of the synergistic mechanism of the microcellular structure and the conductive network. This project would reveal the law between the cross-linking network of epoxy resin and microcellular foaming, and explore the effect of its structure on the electromagnetic shielding effectiveness to provide theoretical and experimental basis to prepare a new class of electromagnetic shielding composites.

围绕环氧树脂交联网络结构与微孔发泡的关系、环氧树脂/碳纳米微孔复合材料导电导磁网络的构筑以及微孔结构对电磁屏蔽效能的影响，以获取优异电磁屏蔽效能的轻质热固性微孔复合材料为目标。拟通过调控环氧树脂固化度、交联点之间分子量和粘弹性，使固化后环氧树脂交联网络满足气体传质与微孔发泡的需求；基于高长径比碳纳米材料表面原位生长Fe3O4提高复合材料的磁损耗；利用无溶剂纳米流体和外加磁场技术解决高含量磁性碳纳米材料在环氧树脂中的均匀分散及定向排列；利用超临界CO2微孔发泡过程中泡壁承受双轴拉伸和单轴压缩作用促使磁性碳纳米材料构筑导电导磁通道，借助于导电导磁通道以及微孔结构对于电磁波的吸收损耗和多重反射损耗的协同作用，提高环氧树脂/磁性碳纳米微孔复合材料的电磁屏蔽效能。揭示环氧树脂交联网络结构与微孔发泡的规律，探索微孔复合材料的结构对电磁屏蔽效能的影响机制，为电磁屏蔽新材料的研究提供理论基础和实验依据。

针对环氧树脂难以通过超临界流体实现微孔发泡，碳系纳米材料易团聚、含量低、功能单一，以及环氧树脂/碳系纳米复合材料难以实现轻质高效电磁屏蔽等难题。本项目围绕环氧树脂交联网络结构与微孔发泡的关系、环氧树脂/碳纳米微孔复合材料导电导磁网络的构筑及其微孔结构对电磁屏蔽效能的影响，以获取轻质、优异电磁屏蔽效能的热固性微孔复合材料为目标。通过调控环氧树脂交联网络结构、碳纳米材料与其它导电/磁性纳米材料复合、不同碳纳米材料之间的协同分散、无溶剂纳米流体和碳系气凝胶的制备等策略，利用超临界CO2发泡制备得到不同结构的环氧树脂/碳纳米微孔复合材料，并对微孔复合材料相态结构和泡孔结构与电磁屏蔽效能之间的构-效关系进行了深入系统的研究。研究发现：单一固化环氧树脂的交联点之间平均分子量（Mc）大于2000g/mol时可以制备微孔结构泡沫；添加液体端羧基丁腈橡胶（CTBN）、超支化环氧树脂（E102）以及硅烷偶联剂-聚醚胺共聚物（KM）均能有效调控环氧树脂交联网络结构，大幅度提高环氧树脂的微孔发泡能力；不同种类的纳米材料（MWCNT、CNF、ZrP、rGO、NCB、AgNS）之间相互作用有利于实现其在环氧树脂中的高效分散；无溶剂碳系纳米流体（f-MWCNT、f-NCB、f-rGO）可实现其在环氧树脂中的均匀分散并作为异相成核剂降低平均泡孔尺寸、增大泡孔密度，提高复合材料的电磁屏蔽性能，但纳米填料含量有限且表面有机基团限制了其导电性能发挥，微孔复合材料电磁屏蔽效能最大在30dB左右。为了进一步提升微孔复合材料电磁屏蔽效能，采用碳系气凝胶（rGO、rGO/Fe3O4、rGO/Ni-chains、rGO/SCF）预先构筑高导电、导磁网络，再引入环氧树脂并经后固化、SC-CO2发泡制备得到了高电磁屏蔽效能、力学性能突出的轻质微孔复合材料。如添加67.85 wt% rGO-SCF的m-E51/rGO-SCF微孔复合材料，具有低密度（1.14g/cm3）、高电导率（2365S/m）、优异的电磁屏蔽效能（95.5dB）以及高的压缩强度（243MPa）。所得到的微孔复合材料均表现为以吸收为主的电磁屏蔽机理。本项目揭示了环氧树脂交联网络结构与微孔发泡的规律，建立了环氧树脂/碳纳米微孔复合材料的结构对电磁屏蔽效能的影响机制，为轻质电磁屏蔽复合材料的设计与应用提供了理论研究基础与实验依据。