Swelling kinetics of HPMC tablets

Hydroxypropyl methylcellulose (HPMC) is a cellulosic polymer widely employed in tablets formulation. In contact with biological fluids, it undergoes a glassy-rubbery transition and drug release is strongly influenced by swelling. We study the kinetic parameters of a classical phenomenological model (Astarita and Sarti), which describes the velocity of a glassy-rubbery interface as a function of the local solvent concentration. One dimensional mass transport equations with moving boundaries are numerically solved by finite elements method (FEM) in order to fit Astarita-Sarti parameters k and n on experimental swelling fronts and concentration profiles taken from literature for HPMC K4 M, HPMC K15 M and HPMC K100 M.