E. Okutgen et al., QUANTITATIVE ESTIMATION OF INTERNAL-STRESS DEVELOPMENT IN AQUEOUS HPMC TABLET FILM COATS, International journal of pharmaceutics, 119(2), 1995, pp. 193-202
Data have been produced on the parameters which influence the developm
ent of internal stresses within aqueous HPMC film coats plasticized wi
th glycerol in an attempt to calculate the magnitude of internal stres
s generation. Films have been prepared under conditions which equate t
o those experienced during film coating processes. The changes in mech
anical and thermal properties of fresh films formed at different table
t bed conditions have been studied during their ambient storage. The c
ontribution of internal stresses from three sources are calculated ind
ividually and a single equation is used to estimate the total internal
stress within a film. This equation considers the contribution made b
y the volumetric changes of the tablet core during ambient conditions
in addition to those caused by other well-established mechanisms. The
results of these calculations showed that the total internal stress is
influenced, not only by these volumetric changes, but also by the con
ditions in which the film coating process was performed. The possibili
ty of the film coating undergoing failure is also discussed.