School of Chemical Sciences, Mahatma Gandhi University , Priyadarshini Hills P.O, Kottayam, Kerala, India 686 560.
J Phys Chem B. 2013 Oct 17;117(41):12632-48. doi: 10.1021/jp4039489. Epub 2013 Oct 3.
The viscoelastic behavior and reinforcement mechanism of nano ZnO reinforced natural rubber (NR) nanocomposites were investigated in this study. Dynamic mechanical analysis was performed to investigate the nature of the constrained polymer region in NR-nano ZnO nanocomposites, and the constrained polymer region is responsible for the reinforcement mechanism. The viscoelastic and tensile properties of NR nanocomposites were investigated with respect to the effect of nanofiller loading. All the nanocomposites showed a significant increase in storage modulus in the glassy and rubbery regions, the shift of the tan δ peak to the higher temperature region, and the lowering of the tan δ peak intensity compared to neat NR. The enhancement in the modulus is related to the weight % of the added nano ZnO as well as the volume of the constrained rubber chains in the proximity of ZnO nanoparticles. The study of the constrained volume of the polymer indicates that the structure of the nanocomposite possesses a moderately strong interfacial interaction between rubber chains and ZnO nanoparticles. The type of rubber-nanofiller interaction strongly influences the amount and modulus of the constrained region and contributes to the enhancement in the storage modulus of the resulting nanocomposites. The volume fraction of the constrained region of the NR nanocomposites was found to have good linear correlation with the weight % of nano ZnO. It was also understood that there should exist an optimum cross-linking density for a certain nanofiller reinforced rubber system, as well as partial physical adsorption of macromolecular rubber chains on the nanofiller surface. An optimum nanofiller loading is necessary for moderately strong rubber-nanofiller interaction and hence for the enhancement in the mechanical properties of the NR nanocomposites. A core-shell morphology model and constrained polymer model have been proposed to explain the constrained polymer chains in the NR-nano ZnO nanocomposite system on the basis of these results.
本研究探讨了纳米氧化锌增强天然橡胶（NR）纳米复合材料的黏弹性行为和增强机制。通过动态力学分析研究了 NR-纳米 ZnO 纳米复合材料中受限聚合物区域的性质，而受限聚合物区域是增强机制的原因。考察了纳米填料含量对 NR 纳米复合材料的黏弹性和拉伸性能的影响。与纯 NR 相比，所有纳米复合材料在玻璃态和橡胶态区域的储能模量均显著增加，tan δ 峰向高温区域移动，tan δ 峰强度降低。模量的增强与添加的纳米 ZnO 的重量%以及靠近 ZnO 纳米粒子的受限橡胶链的体积有关。聚合物的受限体积研究表明，纳米复合材料的结构具有橡胶链和 ZnO 纳米粒子之间中等强度的界面相互作用。橡胶-纳米填料相互作用的类型强烈影响受限区域的数量和模量，并有助于增强所得纳米复合材料的储能模量。发现 NR 纳米复合材料的受限区域体积分数与纳米 ZnO 的重量%呈良好的线性相关。还了解到，对于一定的纳米填料增强橡胶体系，应该存在一个最佳的交联密度，以及高分子橡胶链在纳米填料表面的部分物理吸附。对于中等强度的橡胶-纳米填料相互作用以及因此对 NR 纳米复合材料的机械性能的增强，需要最佳的纳米填料负载。根据这些结果，提出了核壳形态模型和受限聚合物模型来解释 NR-纳米 ZnO 纳米复合材料系统中的受限聚合物链。
