Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials, Beijing 100029, PR China.
Phys Chem Chem Phys. 2011 Jan 14;13(2):518-29. doi: 10.1039/c0cp00297f. Epub 2010 Nov 5.
By employing an idealized model of a polymer network and filler, we have investigated the stress-strain behavior by tuning the filler loading and polymer-filler interaction in a broad range. The simulated results indicate that there actually exists an optimal filler volume fraction (between 23% and 32%) for elastomer reinforcement with attractive polymer-filler interaction. To realize this reinforcement, the rubber-filler interaction should be slightly stronger than the rubber-rubber interaction, while excessive chemical couplings are harmful to mechanical properties. Meanwhile, our simulated results qualitatively reproduce the experimental data of Bokobza. By introducing enough chemical coupling between the rubber and the filler, an upturn in the modulus at large deformation is observed in the Mooney-Rivlin plot, attributed to the limited chain extensibility at large deformation. Particularly, the filler dispersion state in the polymer networks is also characterized in detail. It is the first demonstration via simulation that the reinforcement mechanism stems from the nanoparticle-induced chain alignment and orientation, as well as the limited extensibility of chain bridges formed between neighboring nanoparticles at large deformation. The former is influenced by the filler amount, filler size and filler-rubber interaction, and the latter becomes more obvious by strengthening the physical and chemical interactions between the rubber and the filler. Remarkably, the reason for no obvious reinforcing effect in filled glassy or semi-crystalline matrices is also demonstrated. It is expected that this preliminary study of nanoparticle-induced mechanical reinforcement will provide a solid basis for further insightful investigation of polymer reinforcement.
通过采用聚合物网络和填料的理想化模型，我们通过在较宽范围内调整填料负载和聚合物-填料相互作用来研究应力-应变行为。模拟结果表明，对于具有吸引力的聚合物-填料相互作用的弹性体增强，实际上存在一个最佳的填料体积分数（在 23%到 32%之间）。为了实现这种增强，橡胶-填料相互作用应该略强于橡胶-橡胶相互作用，而过多的化学偶联对机械性能有害。同时，我们的模拟结果定性地再现了 Bokobza 的实验数据。通过在橡胶和填料之间引入足够的化学偶联，在 Mooney-Rivlin 图中观察到大变形时模量的上升，这归因于大变形时链的有限延伸性。特别是，聚合物网络中的填料分散状态也得到了详细的描述。这是首次通过模拟证明，增强机制源于纳米颗粒诱导的链排列和取向，以及大变形时相邻纳米颗粒之间形成的链桥的有限可扩展性。前者受填料量、填料尺寸和填料-橡胶相互作用的影响，后者通过增强橡胶和填料之间的物理和化学相互作用而变得更加明显。值得注意的是，还证明了在填充的玻璃态或半晶态基体中没有明显增强效果的原因。预计这项关于纳米颗粒诱导机械增强的初步研究将为进一步深入研究聚合物增强提供坚实的基础。
