A study of particle adhesion for cohesive powders using a novel mechanical surface energy tester

Abstract

Powder cohesiveness has a strong correlation with particle adhesion, which is studied using a novel mechanical surface energy tester and a method to measure Bond numbers of the powders. The mechanical surface energy tester measures particle adhesion by detaching particles adhered to a substrate surface. When the substrate is dropped from a set of heights and stopped against a stopper, the particles are subject to a detached force, which in principle is equivalent to the particle adhesion force between the detached particles and the substrate. The detached particles are collected for further particle size analysis. The Bond number of the powders is calculated as a ratio of adhesion to gravity with the particle physical properties measured such as solid density and full-size distribution.In this study, particle adhesion forces for a wide range of sample powders were selected and investigated with powder tabletted substrates (same as the test powders), including Calcium Carbonate, Lactose, Microcrystalline Cellulose, Paracetamol, Ibuprofen and Titanium Dioxide for a wide range of material properties. Influences of substrate materials on the measurements are studied between the powder tabletted substrates and other standardised materials such as mild steel, glass, stainless steel and TIVAR. The study shows that the substrate material has little influence on the measurements of particle adhesion within a maximum variation of about 2.5%. This allows using different substrates for the measurement of Bond numbers. The adhesion forces measured are also compared to those calculated by other established methods, and some correlations have been found.