Mujtaba A, Keller M, Ilisch S, Radusch H-J, Beiner M, Thurn-Albrecht T, Saalwächter K
Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06099 Halle (Saale), Germany.
Zentrum für Ingenieurwissenschaften, Martin-Luther-Universität Halle-Wittenberg, 06099 Halle (Saale), Germany.
ACS Macro Lett. 2014 May 20;3(5):481-485. doi: 10.1021/mz500192r. Epub 2014 May 8.
Immobilized polymer fractions have been claimed to be of pivotal importance for the large mechanical reinforcement observed in nanoparticle-filled elastomers but remained elusive in actual application-relevant materials. We here isolate the additive filler network contribution to the storage modulus of industrial styrene-butadiene rubber (SBR) nanocomposites filled with silica at different frequencies and temperatures and demonstrate that it is viscoelastic in nature. We further quantify the amount of immobilized polymer using solid-state NMR and establish a correlation with the mechanical reinforcement, identifying a direct, strongly nonlinear dependence on the immobilized polymer fraction. The observation of a temperature-independent filler percolation threshold suggests that immobilized polymer fractions may not necessarily form contiguous layers around the filler particles but could only reside in highly confined regions between closely packed filler particles, where they dominate the bending modulus of aggregated particles.
固定化聚合物组分被认为对于在纳米颗粒填充的弹性体中观察到的大的机械增强至关重要，但在实际应用相关材料中仍然难以捉摸。我们在此分离出添加剂填料网络对不同频率和温度下填充二氧化硅的工业丁苯橡胶（SBR）纳米复合材料储能模量的贡献，并证明其本质上是粘弹性的。我们进一步使用固态核磁共振定量固定化聚合物的量，并建立与机械增强的相关性，确定对固定化聚合物组分的直接、强烈非线性依赖性。与温度无关的填料渗流阈值的观察表明，固定化聚合物组分不一定在填料颗粒周围形成连续层，而可能仅存在于紧密堆积的填料颗粒之间的高度受限区域，在这些区域中它们主导聚集颗粒的弯曲模量。
