纳米填料在并用橡胶中“偏析”行为的介电表征解析方法的构建

The performance of rubber material was determined by dispersion and aggregation state of nano-fillers in rubber blends to large degree. The heterogeneous dispersion of nano-fillers between the different rubbers in blends appeared, because of the huge difference between fillers and rubbers in the blends with different structures, that is “segregation”. Although the segregation behavior had been investigated, so far the effective method, which could be used to characterize segregation behavior, had not been established, and it was at the exploratory stage to understand the segregation mechanism, because of the complexity of this issue and the limitation of the characterization technique. It was very sensitive to detect filler-rubber interaction by means of dielectric relaxation spectrum, and the filler-rubber interaction intensity was closely related to the filler segregation state. Therefore, in this work, the segregation behavior of nano-fillers in rubber blends was quantitatively analysed by means of dielectric relaxation measurement, with the help of Debye equation, Maxwell-Wegner interfacial polarization theory and so on, based on the different interaction between fillers and different rubbers. The function relationship was established between dielectric relaxation characteristic parameters and material structure, filler character and processing technology parameters. The segregation mechanism was made clear. The finite element analysis was used to make in-depth exploration for the above-mentioned relationships, and the correlation model database was established in order to realize the scientific description for the segregation behavior of nano-fillers in rubber blends.

纳米填料在并用橡胶中的分散及聚集状态是决定胶料性能的重要因素。由于填料与各胶种间的相互作用随橡胶分子链结构改变而有巨大差异，因此，出现纳米填料在并用橡胶各相间分布不均的现象，即“偏析”。尽管对偏析行为已有研究，但由于问题的复杂性及表征技术的局限性，至今尚未建立表征偏析行为的有效方法，对于偏析机理的认识还处于探索阶段。介电松弛谱对填料-橡胶相互作用的差异有极强的敏感性，而填料-橡胶相互作用又与填料的偏析状态密切相关。因此，本项目拟抓住填料与并用胶中不同橡胶相间相互作用强度的差异，通过介电松弛表征手段，借助Debye方程、Maxwell-Wegner界面极化理论等定量解析纳米填料在并用橡胶中的偏析行为。建立介电松弛特性参数与材料结构、填料性质、加工工艺等参数间的函数关系，弄清偏析现象的产生机理。采用有限元分析法对前述关系进行深入探讨，建立相关模型数据库，实现对并用胶中填料偏析规律的科学描述。

本工作按照项目申请书和计划书所列任务，严格围绕项目中心内容，综合采用介电松弛、DMA、FTIR、TEM等多种方法，从改变并用橡胶的结构、填料种类、加工工艺三个方面对多个填充并用橡胶体系进行了详细研究，取得了如下成果：其中，采用红外光谱、DMA、介电松弛谱等考察了白炭黑在NR/SBR并用混炼胶中的偏析行为。结果发现在NR/SBR并用胶中，白炭黑向NR相偏移，且该现象与两胶种的并用比无关。可分别采用介电松弛损耗因子和弛豫时间定量和定性判断白炭黑在该体系中的偏析行为。对白炭黑填充NR/NBR体系研究发现，白炭黑的偏析行为受橡胶并用比的影响，可采用介电松弛弛豫时间定性判断。采用TEM、DMA、拉伸应力-应变关系和介电松弛等针对炭黑及碳纳米管填充NR/NBR并用体系中填料偏析行为进行研究发现，炭黑和碳纳米管均易偏析于NBR相中，可采用介电松弛低频直流电导率定性判断填料的偏析行为。通过考察加料顺序以及硫化工艺对炭黑在NR/NBR并用胶中偏析行为的影响，发现介电松弛参数中的低频电导率与之具有定性关系。而对于白炭黑分别填充NR/SBR和NR/NBR等体系，则尚未发现介电松弛特征参数与填料偏析行为的定量定性关系。综上所述，对于白炭黑填充NR/NBR混炼胶中根据H-N函数所得的介电松弛时间和填料偏析行为之间的关系，以及通过改变加料顺序考察的炭黑填充NR/NBR并用硫化胶的电导率与填料偏析行为的关系均只能定性。因此，尚未得到足够的定量参数进行有限元模型的建立。