Compact formation compression force

The TS of the compacted samples was determined by transverse compression with a custom-built tensile tester. Tensile failure was observed for all the rectangular compacts when compressed between flat-faced platens at a speed ranging between 0.006 and 0.016 mm/sec. Platen speed was adjusted between materials to maintain a time constant of 15 2 seconds to account for viscoelastic differences the constant is the time between the sample break point and when the measured force equals Fbreak/e in the force versus time profile, where the denominator is the mathematical e. Specially modified punch and die sets permitted the formation of square compacts with a centrally located hole (0.11 cm diameter) that acted as a stress concentrator during tensile testing. This capability permitted the determination of a compromised compact TS and thus facilitated an assessment of the defect sensitivity of each compacted material. At least two replicate determinations were performed for each mechanical testing procedure and mean values are reported. 

Some tablet presses are equipped with two sets of rollers a smaller roller located between the feed frame, and the main compression roller which allows a small degree of compression (e.g., precompression) to take place. Precompression can remove air from the powder bed in order to minimize tablet capping and lamination. Good com-pactibility of the powder blend is essential to tablet formation under the influence of compression forces and ensures that tablets will remain intact compact when the compression force is removed. 

Capping. (1) The formation of a weak region at the end of a pressed compact. In the region just below the top punch, the compact is subjected to a compressive force only, with no shear component die to interaction with the die walls. This region is consequently weak. This fault is also known as endcapping. 

Precompression and Main Compression Rollers. After die fill and scrape-off, the punches rotate to the precompression station where an initial force is applied to the compact. The tablet is frequently partially formed during the precompression stage. Subsequently, the upper and lower punches move together under the main compression rollers where the final tablet is formed. The main compression roller is usually larger than the precompression roller. However, latest advances suggest that similar sizes for precompression and main compression rollers with the ability to apply similar loads may result in optimal tablet formation. The compression rollers are made of premium tool steels and are surface hardened. 

The density of the material, at the point of the nip angle approaches its tapped density value and the material begins to undergo compression between the rolls. The material is then forced through the region of maximum pressure where it undergoes a rapid increase in the density resulting in the formation of the compacted mass. 

Slugg Comi ing/Roller )action Formation of powder plugs by compression. Dissolution is dependent on the duration and force of slugging/roller compaction. 

---