The present work aimed at assessing the pharmaceutical tableting properties of some
Egyptian kaolin samples belong to the Abu Zenima kaolin deposits (estimated at 120 million
tons). Four representative samples were selected based on kaolinite richness and their structural
order-disorder degree, and after purification, they were dried at 70 ºC and heated from room
temperature up to 400 ºC (10 ºC/min). Mineralogy, micromorphology, microtexture, granulometry,
porosimetry, moisture content, bulk and tapped density, direct and indirect flowability, and tableting
characteristics are studied. Results indicated that purified kaolin samples were made up of 95–99%
kaolinite, <3% illite, 1% quartz and 1% anatase. The powder showed mesoporous character (pore
diameters from 2 to 38 nm and total pore volume from 0.064 to 0.136 cm3/g) with dominance of fine
nanosized particles (<1 um–10 nm). The powder flow characteristics of both the ordered (Hinckley
Index HI > 0.7, crystallite size D001 > 30 nm) and disordered (HI < 0.7, D001 < 30 nm) kaolinite-rich
samples have been improved (Hausner ratio between 1.24 and 1.09) as their densities were influenced
by thermal treatment (with some observed changes in the kaolinite XRD reflection profiles) and
by moisture content (variable between 2.98% and 5.82%). The obtained tablets exhibited hardness
between 33 and 44 N only from the dehydrated powders at 400 ºC, with elastic recovery (ER) between
21.74% and 25.61%, ejection stress (ES) between 7.85 and 11.45 MPa and tensile fracture stress (TFS)
between 1.85 and 2.32 MPa, which are strongly correlated with crystallinity (HI) and flowability (HR)
parameters. These findings on quality indicators showed the promising pharmaceutical tabletability
of the studied Egyptian kaolin powders and the optimization factors for their manufacturability
and compactability.This work has been funded by the Egyptian Cultural Affairs and Missions Sector (Plan 2013–2014),
Ministry of Higher Education, in collaboration with the Group CTS-946 (Junta de Andalucía) and MINECO project
CGL2016-80833-R (Spain), and the grant funded by Erasmus+ KA1 mobility program 2016/2017