Adhesion of polymeric films to pharmaceutical solids

The two major forces influencing polymer adhesion include the strength of the interfacial bonds between the polymeric film and the surface of the solid and the internal stresses within the film coating. While good adhesion between the polymer and the substrate is desirable for pharmaceutical products, the small size of the dosage form and the non-uniform surface roughness have created difficulties in assessing polymer adhesion. In this review, the experimental devices and procedures used to quantitate polymer adhesion are addressed. The affects of the physical and chemical properties of the substrate, including surface roughness and tablet hydrophobicity, on adhesion of a polymer to either tablets or capsules are discussed. The influence of the plasticizers, pigments, and solvents in film coating formulations on polymer adhesion, and the effects of aging of the coated solids on adhesion of polymers to tablets and capsules are also discussed.