COMPACTION AND MEASUREMENT OF TABLETS IN LIQUIDS WITH DIFFERENT DIELECTRIC-CONSTANTS FOR DETERMINATION OF BONDING MECHANISMS - EVALUATION OF THE CONCEPT

In order to study bonding mechanisms in tablets, liquids with increasi ng dielectric constants have been used to filter out weak long range d istance forces. The aim of this study was to further critically evalua te this concept. Tablets of sodium chloride, sodium bicarbonate, Avice l(R), Emcompress(R), lactose and sucrose were compacted in media with dielectric constants from 1 to 24 and the remaining tensile strength o f tablets compacted in liquid was calculated. With increasing dielectr ic constant a continuos decrease in tensile strength was obtained and at a dielectric constant above approximately 10-15, a plateau level wa s reached for all materials except for Avicel(R). This level was assum ed to reflect the proportion of solid bridges in the compact and the v alues were consistent with previous data reported from our laboratory. The results also showed that by compacting particles suspended in a l iquid a more effective reduction of long range distance forces was obt ained, than if tablets were compacted in air followed by a soaking pro cess in liquid. Compaction in liquids may be unsuitable for some mater ials due to swelling or changes in volume reduction behaviour. Neverth eless, the method appears to be favourable for studying bonding mechan isms, especially for tablets with a low porosity.