The adhesion of film coatings to tablet surfaces—a problem of stress distribution

Nondimensional Scaling Laws for Controlling Pharmaceutical Spray Uniformity: Understanding and Scale-Up

“…These phenomena in turn influence the physical characteristics of the film coat. Their relation to spray operating parameters is evident from the following studies: Kim et al4 and Rowe and Forse,5 who reported that incidences of logo infilling (“bridging”) increased as coating liquid supply rate increased. Twitchell,1 Twitchell et al,6 and Reiland and Eber,7 who found that increasing the atomizing air pressure or decreasing the gun‐to‐target distance resulted in a smoother film coat. Twitchell,1 who noted that a decrease in gun‐to‐target distance decreased film surface roughness. Ruotsalainen et al,8 who determined that film surface roughness increased with an increase in liquid supply rate. Fisher and Rowe9 and Rowe,10 who observed that film‐to‐tablet adhesion decreased as liquid viscosity increased. …”

“…Fisher and Rowe9 and Rowe,10 who observed that film‐to‐tablet adhesion decreased as liquid viscosity increased.…”

Spatially resolved characteristics of pharmaceutical sprays

“…Not often explored are the roles that the spray and its characteristics play on film coat quality. Studies that do relate film coat quality to spray characteristics are: Kim et al1 and Rowe and Forse,2 who reported that incidences of logo infilling (bridging) increased as liquid supply rate increased. Twitchell,3 Twitchell et al,4 and Reiland and Eber,5 who found that increasing the atomizing air pressure or decreasing the gun‐to‐target distance resulted in a smoother film coat. Twitchell,3 who noted that a decrease in gun‐to‐target distance decreased film surface roughness. Ruotsalainen et al,6 who determined that film surface roughness increased with an increase in liquid supply rate. Fisher and Rowe7 and Rowe,8 who observed that film‐to‐tablet adhesion decreased as liquid viscosity increased. Twitchell3 and Rowe and Forse,9 who found that increasing the local spray mass flux at the tablet bed, achieved by increasing the liquid supply rate or changing the spray pattern from elliptical to circular, decreased the incidence of film splitting. …”

“…Fisher and Rowe7 and Rowe,8 who observed that film‐to‐tablet adhesion decreased as liquid viscosity increased.…”

Pharmaceutical Applications of Plasticized Polymers

“…The interfacial bonding between the tablet surface and polymer coating is made primarily with hydrogen bonds, to a lesser extent with dipoledipole and dipole-induced dipole interactions. The addition of plasticizing agents to coating formulations generally decreases the internal stress in the film by decreasing both the elastic modulus and the glass transition temperature of the film coating (Johnson  Hathaway, 1991;Rowe, 1981Rowe, , 1992). …”