Deutsches Institut für Kautschuktechnologie e V, Eupener Straße 33, D-30519 Hannover, Germany.
J Phys Condens Matter. 2011 Jan 26;23(3):035104. doi: 10.1088/0953-8984/23/3/035104. Epub 2010 Dec 16.
The combined effect of filler networking and reduced chain mobility close to the filler interface is analyzed based on investigations of the relaxation dynamics of a solution of styrene butadiene rubber filled with different loadings and types of nanostructured carbon blacks. Dynamic-mechanical and dielectric spectra are studied in a wide frequency and temperature range. By referring to a tunneling process of charge carriers over nanoscopic gaps between adjacent carbon black particles the gap distance is evaluated from the dielectric spectra. This distance corresponds to the length of glassy-like polymer bridges forming flexible bonds between adjacent filler particles of the filler network. It is found that the gap distance decreases with increasing filler loading and specific surface area which correlates with an increase of the apparent activation energy of the filler network evaluated from dynamic-mechanical data. Due to the thermal activation of glassy-like polymer bridges the time-temperature superposition principle is not fulfilled for filled elastomers and the introduction of vertical shift factors is necessary to obtain viscoelastic master curves. The change in the low frequency viscoelastic properties by the incorporation of fillers is shown to be related to the superimposed dynamics of the filler network governed by the viscoelastic response of the glassy-like polymer bridges. This effect is distinguished from the reduced chain mobility close to the filler surface which results in a broadening of the glass transition on the high temperature or low frequency side. The microstructure-based interpretation of viscoelastic data is supported by an analysis of the relaxation time spectra.
基于对不同填充量和类型的纳米结构炭黑填充苯乙烯-丁二烯橡胶溶液的松弛动力学的研究，分析了填料网络的综合效应以及靠近填料界面处链流动性的降低。在较宽的频率和温度范围内研究了动态力学和介电谱。通过参考载流子在相邻炭黑颗粒之间的纳米级间隙中的隧道过程，从介电谱评估了间隙距离。该距离对应于形成填充网络中相邻填料颗粒之间柔性键的玻璃状聚合物桥的长度。结果表明，随着填充量和比表面积的增加，间隙距离减小，这与从动态力学数据评估的填充网络表观活化能的增加有关。由于玻璃状聚合物桥的热活化，填充弹性体不满足时-温叠加原理，需要引入垂直移动因子才能获得粘弹性主曲线。通过加入填料，低频粘弹性性能的变化与由玻璃状聚合物桥的粘弹性响应控制的填充网络的叠加动力学有关。这种效应与靠近填料表面的链流动性降低区分开来，后者导致玻璃化转变在高温或低频侧变宽。粘弹性数据的基于微观结构的解释得到了松弛时间谱分析的支持。
