Pull-off force of coated fine powders under small consolidation

• Published in: Physical review. E, Statistical, nonlinear, and soft matter physics Statistical, nonlinear, and soft matter physics, 2009-04, Vol.79 (4 Pt 1), p.041305-041305, Article 041305
• Main Authors: Chen, Yuhua, Quintanilla, M A S, Yang, Jun, Valverde, Jose M, Dave, Rajesh N
• Format: Article
• Language: English
• ISSN: 1539-3755; 1550-2376
• DOI: 10.1103/physreve.79.041305

In this paper, a three-dimensional model taking into account the contact deformation and surface area coverage (SAC) of nanoadditives is proposed to predict the force required to separate two contacting particles (the pull-off force) under consolidation stress up to 10 KPa, for cornstarch, a Geldart group C powder, sparsely and densely dry-coated with nanosilica. The experimental pull-off force measurement is conducted in a Seville powder tester. Comparison of the predicted results with the experimental results indicates (1) that the pull-off force of sparsely coated cornstarch is larger than that of densely coated cornstarch due to the greater hardness and small particle radius of fumed silica; (2) there is not a continuous variation in the pull-off force with the coverage of silica; on the contrary, values of the pull-off force of sparsely coated samples are grouped in similar range, while the values of the pull-off force of densely coated samples are grouped in another range of lower values. (3) Within a range, the SAC does not have a big effect on the pull-off force for sparsely coated samples and only a slight effect for densely coated samples (4) the pull-off force increases with increasing consolidation force due to larger deformation in the contact area; (5) under consolidation stresses up to 10 KPa, the deformation of the cornstarch particles is not large enough to fully embed the nanosized silica.