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Relationship between surface area coverage of flow-aids and flowability of cohesive particles
Powder Technology ( IF 5.2 ) Pub Date : 2017-12-01 , DOI: 10.1016/j.powtec.2017.09.013
Fabio Fulchini , Umair Zafar , Colin Hare , Mojtaba Ghadiri , Hossam Tantawy , Hossein Ahmadian , Massimo Poletto

Poor and inconsistent flow of cohesive powders is a major issue in powder processing. A common solution is to coat the surfaces of the cohesive particles with finer particles, referred to as flow-aids. Such particles adhere to sticky surfaces and act as spacers preventing them from contacting each other and thus reducing the inter-particle forces and bulk powder cohesion. A question which naturally arises is how much flow-aid is needed to enhance the flowability to an optimum level. This work aims to establish a relationship between the degree of Surface Area Coverage (SAC) of flow-aids and the flowability, the latter as determined by a quasi-static shear cell method, as well as the angle of repose test and the FT4 powder rheometer. Glass beads of 90–150 μm sieve cut are made cohesive by silanising their surfaces with a commercial chemical reagent, Sigmacote® and are used as host particles. Two types of zeolite particles are used as flow aids. The mass fraction of the flow aids required to achieve a theoretical SAC of 1, 5, 10, 20, 50 and 100% is first estimated and then the host particles are coated in a pan mixer. The SAC is measured by Scanning Electron Microscopy, coupled with image analysis, and found to correlate well with the estimated value. The optimum surface coverage is found to be when SAC is 10–20%, as this provides the greatest flowability. An increase in SAC beyond this range leads to a gradual reduction in flowability.

中文翻译:

助流剂的表面积覆盖率与粘性颗粒的流动性之间的关系

粘性粉末的流动性差且不一致是粉末加工中的一个主要问题。一种常见的解决方案是用更细的颗粒(称为助流剂)涂覆粘性颗粒的表面。这些颗粒粘附在粘性表面上并充当隔离物,防止它们相互接触,从而降低颗粒间力和散装粉末内聚力。一个自然出现的问题是需要多少助流剂才能将流动性提高到最佳水平。这项工作旨在建立助流剂的表面积覆盖度 (SAC) 与流动性之间的关系,后者由准静态剪切电池法确定,以及休止角测试和 FT4 粉末流变仪。筛分 90-150 微米的玻璃珠通过用商业化学试剂硅烷化其表面而变得有凝聚力,Sigmacote® 和用作宿主颗粒。两种类型的沸石颗粒用作流动助剂。首先估计达到 1、5、10、20、50 和 100% 的理论 SAC 所需的助流剂的质量分数,然后在盘式混合器中涂覆主体颗粒。SAC 是通过扫描电子显微镜测量的,结合图像分析,发现与估计值有很好的相关性。发现最佳表面覆盖率是在 SAC 为 10-20% 时,因为这提供了最大的流动性。超出此范围的 SAC 增加会导致流动性逐渐降低。首先估计 50% 和 100%,然后在盘式混合器中涂覆主体颗粒。SAC 是通过扫描电子显微镜测量的,结合图像分析,发现与估计值有很好的相关性。发现最佳表面覆盖率是在 SAC 为 10-20% 时,因为这提供了最大的流动性。超出此范围的 SAC 增加会导致流动性逐渐降低。首先估计 50% 和 100%,然后在盘式混合器中涂覆主体颗粒。SAC 是通过扫描电子显微镜测量的,结合图像分析,发现与估计值相关性很好。发现最佳表面覆盖率是在 SAC 为 10-20% 时,因为这提供了最大的流动性。超出此范围的 SAC 增加会导致流动性逐渐降低。
更新日期:2017-12-01
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