TENSILE STRENGTH OF CIRCULAR FLAT AND CONVEX-FACED AVICEL PH102 TABLETS

Abstract

The mechanical properties of flat and convex-faced circular tablets made from a size fraction of microcrystalline cellulose (Avicel PH102), compacted under control conditions of pressures of 20 and 112 MPa have been assessed in term of tensile strength. The calculation of tensile strength (at), for flat-faced tablets was determined from the load (P) in diametral compression test as described by Fell & Newton ot = 2P/ (7tDt). The material tensile strength of convex-faced tablets calculated from the observed fraction loads obtained in diametral compression testing, based on the equation derived by Pitt et al at= 10P/ [TTD2 (2.84I/D - 0.126t/W+ 3.15W/D + 0.01)"1 ], where P is the fracture load, D is the tablet diameter, t is the overall tablet thickness and W is the central cylinder thickness. By comparing the tensile strength values of convex-faced tablets using porosity, tensile stress, and compaction pressure values, an optimum face-curvature in normal to unity range (D/R=0.67-1.0) and an optimum cylinder length of W/D=0.3, were found to be necessary for producing the overall strongest tablets. These optimum values varies with the formation pressure.