基于多层结构设计的聚苯乙烯纳米复合材料构筑与阻燃、电磁屏蔽性能调控机制研究

polystyrene (PS) used in the fields of electron and electic appliance is required to possess good fire safety and anti-electromagnetic interference properties. However, at present, the polymeric material shows low efficiency in flame retardancy, smoke suppression and electromagnetic shielding. In order to solve these issues, according to our previous work, this research proposal aims at designing and synthesizing phosphorus- and nitrogen-containing highly effective flame-retardant polyelectrolytes endowed with anionic or cationic characteristics and multi-hydroxyl structure. In addition, conductive two-dimensional nanoadditives where their surfaces are filled with positive or negative charges are synthesized by adjusting size and surficial charge characteristics of flame retardants. Then, in order to achieve good dispersion of nanoadditives in PS matrix, as-synthesized flame-retardant multihydroxyl structured polyelectrolytes and conductive two-dimensional nanoadditives are layer-by layer assembled onto surface of PS sphere. Hot-pressed and molten processes are adopted to construct multi-structured PS nanocomposites with excellent performances, i.e., synergistic flame retardancy, smoke suppression and electromagnetic shielding. Here, the effects of sequence and layer number of self-assembly treatment, the element type, concentration and proportion of flame retardants, type and concentration of conductive two-dimensional nanoadditives and structure of nanocomposites on thermal degradation, flame retardancy, smoke suppression and electromagnetic shielding of as-prepared multilayer-structured PS nanocomposites are investigated. Furthermore, internal relationship among composition, structure and property of the multilayer-structured PS nanocomposites is studied. Finally, the mechanisms of properties control and properties improvements for multilayer-structured PS nanocomposites are proposed. The research proposal would provide a solid theoretical basis and experimental support for design and application of multifunctional polymer nanocomposites.

作为电子电器领域的聚苯乙烯（PS）材料要具备火安全性能和抗电磁干扰性能，然而目前其阻燃、抑烟减毒、电磁屏蔽效率低下。本项目利用尺寸控制、表面调控技术设计、合成具有阴阳离子特性的含磷、氮元素高效阻燃多羟基聚电解质和表面具有正负电性的导电二维纳米添加剂，然后为保证纳米添加剂在PS材料中的良好分散，将合成的阻燃多羟基聚电解质和导电二维纳米添加剂按组形式层层组装在PS微球表面，最后通过热压、熔结等方式构筑兼具阻燃、抑烟减毒、电磁屏蔽性能的协同增效多层结构PS纳米复合材料。研究阻燃元素含量及协同情况、导电二维纳米添加剂种类及含量、纳米复合材料结构、组装顺序、组装层数等因素对多层结构PS纳米复合材料热解、阻燃、抑烟减毒、电磁屏蔽性能的影响；研究纳米复合材料组成、结构、性能之间的内在关系，揭示多层结构PS纳米复合材料的性能调控、增强机理，为多功能聚合物纳米复合材料的设计与应用奠定坚实理论基础和实验依据。

本项目基本按照项目计划进行。针对聚苯乙烯（PS）阻燃、抑烟减毒、电磁屏蔽效率低下等缺点，将阻燃剂分子设计、纳米复合技术、协同效应原理相结合，通过改进层层自组装技术、球磨、热压等方法构筑一系列集阻燃、电磁屏蔽于一体的多层结构PS复合材料。研究结果表明：利用层层自组装技术在PS表面引入酸化多壁碳纳米管（aMWCNT）、石墨状氮化碳（g-C3N4）能够提高PS的热稳定性和阻燃性能。此外，二者的组装顺序会影响PS的阻燃性能；通过层层自组装技术将g-C3N4和氧化石墨烯（rGO）引入PS球表面，导致PS复合材料的阻燃性能和热稳定性显著提高；对于真空辅助抽滤-热压方法制备的PS纳米复合材料，含磷阻燃剂、aMWCNT以及rGO的添加降低了PS的可燃性，提高了其电磁屏蔽性能；通过球磨-热压法制备的PS复合材料，不仅使PS的阻燃效果更好，还简化了实验操作步骤，同时电磁屏蔽效能也获得了提高；导电纳米材料微胶囊化阻燃剂不仅能够提高其在聚合物中的分散性，而且显著提高材料的热稳定性、阻燃性能和电磁屏蔽效能。同时提出了相应的阻燃、抑烟减毒和电磁屏蔽机理：对于多层结构PS复合材料，由于双层膜结构，其在PS基体外部能够形成“曲折路径”阻碍热渗透和热解挥发分产物逸出，同时，一维、二维导电纳米添加剂在燃烧过程中能够催化成碳，形成致密网络结构，从而提高PS的稳定性和耐火性能。此外，导电二维纳米添加剂能够有效捕获•H和•OH，最终使燃烧终止，提高PS的阻燃、抑烟减毒性能。与此同时，导电二维纳米添加剂的引入，使本来绝缘的PS基体内部导电，形成一个连续导电网络，使外部电磁波在其内部衰减。同时，研究发现吸收电磁波在屏蔽机制中占主导地位。综上，这项研究工作为设计兼具阻燃性、抑烟减毒及电磁屏蔽性能的多层结构PS复合材料的制备奠定了理论依据和实验基础，同时也为静电自组装技术以及功能化阻燃剂设计合成提供了新思路。