基于Stokes法则构建电阻渐变聚合物基电磁屏蔽功能材料

As a new research topic, resistance gradient electromagnetic shielding materials attracted more attentions in recent years, and the electrically conductive polymeric composites with homogeneous distribution have been found to be difficult to improve their electrically conductive performance and mechanical performance simultaneously. In this project, the concept of functionally gradient materials (FGM) is introduced to prepare the resistance gradient polymeric electromagnetic shielding composites; a suspension casting method based on the Stokes' law is employed. The influence of main factors on the sedimentation velocity of the filler particles will be investigated scientifically and the relations between the sedimentation velocity of particles in the polymer solution and the key influencing factors are expect to be understood. Due to the effects of the concentration and the shape of the particles and the viscosity of polymer solution varying with time, a modification on the Stokes' law is required in order to match the needs of polymeric suspension. A method of preparing polymeric gradient materials based on the principle of gravity settling will be developed. The polymeric resistance gradient electromagnetic shielding materials with the functions of low reflection and high absorption of the electromagnetic wave will be designed and prepared. Prospectively, the contradiction between the electrically conductive performance and mechanical performance of the electrically conductive polymeric composites with homogeneous distribution can be resolved successfully. Furthermore, the mechanism of gradient formation, the principle of electromagnetic shielding of the materials will be given as a reasonable interpretation according to the experimental results. The relations between the composition, structure and the shielding effectiveness of the resistance gradient material will be understood. A scientific basis for the relative research area is expected to be developed.

电阻渐变材料是电磁屏蔽材料研究中的新课题，而导电性能和力学性能不能兼顾也是长期存在于宏观均质复合型导电聚合物材料研究中的一个难题。本项目将"梯度功能化"的理念引入到传统的聚合物基导电复合材料研究中，运用Stokes法则，采用悬浮液流延法，通过控制影响导电粒子在聚合物溶液中沉降速度的关键因素，使其在材料厚度方向上形成连续的梯度分布而使复合材料呈现电阻渐变特征，并具备低反射、高吸收电磁波之功能。项目拟通过对Stokes方程的修正，明确粒子沉降速度与主要影响因素间的关系，揭示固体粒子在粘度变化的聚合物溶液中迁移的基本规律，建立利用重力沉降原理制备聚合物基梯度功能材料的方法，进行低反射、高吸收聚合物基电磁屏蔽材料的设计与制备，解决均质聚合物基导电复合材料在电磁屏蔽领域应用中的突出问题，对其梯度形成机制、电磁屏蔽机理等进行合理解析，明确材料组成、结构与屏蔽效能之间的关系，为相关材料的研究奠定基础。

本项目通过理论模拟与实验验证，对Stokes方程进行了修正，拓展了Stokes法则在非牛顿流体介质以及多粒子体系中的应用，建立了利用重力沉降原理制备聚合物基梯度功能材料的方法。在此基础上，成功制备出一系列电阻渐变的聚合物基电磁屏蔽梯度功能材料，证明了该方法的普适性。对所制备材料结构和性能表征的结果表明，电阻渐变的聚合物基电磁屏蔽梯度功能材料，不仅电磁屏蔽性能优越，而且很好地保持了材料的力学性能，解决了长期存在于复合型导电高分子材料中导电性能和力学性能不能兼顾的问题，为今后在该领域的深入探索奠定了研究基础。并且，梯度导电材料所表现出的不对称特征与性能为其应用提供了多重选择性。