WATER-VAPOR DIFFUSION IN MODEL TABLET SYSTEMS .2. EXPERIMENTS WITH LACTOSE ANHYDROUS BASED TABLETS

Investigations were conducted to study water vapor diffusion in lactos e-based compacts of increasing compositional complexity, using a previ ously described diffusion apparatus. Diffusion parameters were found t o be a function of a pore structure for a particular system. The pore structure was influenced by tablet composition and degree of densifica tion. Results from mercury intrusion porosimetry suggest that a large percentage of the pore volume had pore diameters in which the diffusio n process was transitional between viscous (ordinary) diffusion and fr ee-molecular (Knudsen) diffusion. The diffusion process was modeled us ing Percolation Theory. Resulting estimates of percolation threshold ( phi(c),) and coordination number (z) suggested that the pore network i n lactose compacts was highly connected.