Bonding Surface area and Bonding Mechanism-Two Important Factors fir the Understanding of Powder Comparability

Abstract

Two factors could be regarded as primary factors for the compactability of powders: the dominating bond mechanism and the surface area over which these bonds are active. Owing to considerable experimental difficulties, these factors have not been evaluated in any detail for pharmaceutical materials. Instead, more indirect, secondary factors are normally studied and used for correlations with tablet strength. Such secondary factors particle size, shape and surface texture. Also the importance of volume reduction mechanisms, i.e. elastic deformation, plastic deformation and particle fragmentation have been studied in detail.For the investigation of dominating bond mechanisms and estimation of the magnitude of the surface area of the solids involved in interparticulate attraction in compacts several pharmaceutical excipients representing both plastically deforming materials (sodium chloride, Avicel@ PH 101, Sta-Rx 1500@, and sodium 2143

Compression mechanics of granule beds: A combined finite/discrete element study

“…Since the size and shape of each particle are continually determined as an integral part of the solution procedure, this method has the potential to be very useful for studying the deformation and densification of individual particles, as has previously been done experimentally (Johansson and Alderborn, 1996;Johansson et al, 1998). Knowledge of the bonding surfaces between particles and the stresses/pressures that act at these surfaces, opens up the possibility to study the formation of coherent compacts in detail (Nyström et al, 1993). However, the FE/DE method generally requires quite extensive computational resources, and most studies [also recent ones, such as those by Procopio and Zavaliangos (2005) and by Choi and Gethin (2009)] have therefore been limited to two-dimensional systems.…”

Powder Compaction: Compression Properties of Cellulose Ethers

“…The high compactability of CE has been attributed to a relatively high propensity for plastic deformation and their anti-static behaviour during powder mixing (Ghori et al, 2014c;Timmins et al, 2014) which enables large surfaces to be in close proximity to each other and a large number of bonds, mainly intermolecular forces, to be established between the particles (Karehill et al, 1990;Nyström et al, 1993). Mechanical interlocking may also contribute to the mechanical strength (Karehill et al, 1990).…”

“…Different terms like compressibility, compactibility, and tabletability, have been used by authors to describe the same type of relationship. The root cause of this confusion is that three variables, pressure, tablet tensile strength and porosity, are not always studied simultaneously (Alderborn and Nyström, 1995;Nyström et al, 1993). Compressibility is the ability of a material to undergo a reduction in volume as a result of an applied pressure and is represented by a plot of tablet porosity against compression pressure; compactibility is the ability of a material to produce tablets with sufficient strength under the effect of densification and is represented by a plot of tablet tensile strength against tablet porosity; finally, tabletability is the capacity of a powder to be transformed into a tablet of specified strength under the effect of pressure and is represented by a plot of tablet tensile strength against compression pressure (Ghori, 2014a;Patel et al, 2006;Swarbrick, 2007).…”

Preparation and Evaluation of Orally Disintegrating Tablets Containing Vitamin E as a Model Fat-Soluble Drug

“…It is generally recognized that tablet strength decreases by decreasing the bonding surface area of the inter-particle. 22) Since powder VE is a fat-soluble drug, it was assumed that the increase of powder VE amount in a tablet might have led to the decrease of the bonding surface area of the inter-particle, which results in decrease in formation of solid bridging with PVP K-30 between D-mannitol particles in a tablet during drying process after wet powder tableting. This might have decreased the tensile strength and increased the friability.…”

“…In addition, it is also well known that tablet strength increases by increasing the bonding surface area of the inter-particle. 22) Therefore, it was assumed that hot storage conditions caused softening and migration of powder VE and caking occurred when the temperature was restored to room temperature, which resulted in increase in the bonding surface area of the inter-particle and tensile strength. On the other hand, with respect to VE-SD ODTs, oily VE was covered and maintained in gelatin by spray-drying.…”