Phumnok Ekaroek, Khongprom Parinya, Ratanawilai Sukritthira
Department of Chemical Engineering, Faculty of Engineering, Prince of Songkla University, Hat Yai 90112, Songkhla, Thailand.
Air Pollution and Health Effect Research Center, Prince of Songkla University, Hat Yai 90112, Songkhla, Thailand.
ACS Omega. 2022 Mar 1;7(10):8364-8376. doi: 10.1021/acsomega.1c05848. eCollection 2022 Mar 15.
A wet mixing process is proposed for filled rubber composites with a high silica loading to overcome the drawbacks of high energy consumption and workplace contamination of the conventional dry mixing process. Ball milling was adopted for preparing the silica dispersion because it has a simple structure, is easy to operate, and is a low-cost process that can be easily scaled up for industrial production. The response surface methodology was used to optimize the making of the silica dispersion. The optimum conditions for a well-dispersed silica suspension with the smallest silica particle size of 4.9 mm were an about 22% silica content and 62 h of ball milling. The effects of dry and wet mixing methods on the properties of silica-filled rubber composites were investigated in a broad range of silica levels from low to high loadings. The mixing method choice had little impact on the properties of rubber composites with low silica loadings. The silica-filled rubber demonstrated in this study, however, shows superior characteristics over the rubber composite prepared with conventional dry mixing, particularly with high silica loadings. When compared to silica-filled natural rubbers prepared by dry mixing (dry silica rubber, DSR), the wet mixing (for WSR) produced smaller silica aggregates with better dispersion. Due to the shorter heat history, the WSR exhibits superior curing characteristics such as a longer scorch time (2.2-3.3 min for WSR and 1.0-2.1 min for DSR) and curing time (4.1-4.5 min for WSR and 2.2-3.1 min for DSR). Additionally, the WSR has superior mechanical properties (hardness, modulus, tensile strength, and especially the elongation at break (420-680% for WSR and 360-620% DSR)) over the DSR. The rolling resistance of WSR is lower than that of DSR. However, the reversed trend on the wet skid resistance is observed.
为克服传统干混工艺能耗高和工作场所污染的缺点，提出了一种用于高白炭黑填充橡胶复合材料的湿混工艺。采用球磨法制备白炭黑分散体，因为其结构简单、易于操作，且成本低，易于扩大规模用于工业生产。采用响应面法优化白炭黑分散体的制备。制备具有4.9mm最小白炭黑粒径的良好分散白炭黑悬浮液的最佳条件是白炭黑含量约为22%，球磨62小时。在从低到高的广泛白炭黑含量范围内，研究了干混和湿混方法对白炭黑填充橡胶复合材料性能的影响。混合方法的选择对低白炭黑含量橡胶复合材料的性能影响很小。然而，本研究中展示的白炭黑填充橡胶比用传统干混制备的橡胶复合材料具有更优异的特性，特别是在高白炭黑含量时。与通过干混制备的白炭黑填充天然橡胶（干白炭黑橡胶，DSR）相比，湿混（用于WSR）产生的白炭黑聚集体更小，分散性更好。由于热历史较短，WSR表现出优异的硫化特性，如焦烧时间更长（WSR为2.2 - 3.3分钟，DSR为1.0 - 2.1分钟）和硫化时间更长（WSR为4.1 - 4.5分钟，DSR为2.2 - 3.1分钟）。此外，WSR比DSR具有更优异的机械性能（硬度、模量、拉伸强度，尤其是断裂伸长率（WSR为420 - 680%，DSR为360 - 620%））。WSR的滚动阻力低于DSR。然而，在湿滑阻力方面观察到相反的趋势。
