The Material Tensile Strength of Convex-faced Aspirin Tablets

Abstract

The material tensile strength of a range of convex-faced tablets, compacted under controlled conditions at pressures of 40 and 320 MPa from a size fraction of acetylsalicylic acid, has been assessed. The calculation of the tensile strength σ_t, from observed fracture loads obtained in diametral compression testing, is based on the equation derived by Pitt et al (1988), namely: where P is the fracture load, D is the tablet diameter, t is the overall tablet thickness and W is the central cylinder thickness. The strength of a tablet of a given shape compacted at 320 MPa was between two and four times greater than that of a similar tablet compacted at 40 MPa. For the thicker tablets (W/D ≥0·2) the material tensile strength was practically independent of shape. For the thinner tablets (W/D = 0·1) the material tensile strength varied considerably with face-curvature, showing a maximum for each of the two compaction pressures at a D/R value of 0·67.