INFLUENCE OF PLASTICIZERS ON THE ADHESIVE PROPERTIES OF AN ACRYLIC RESIN COPOLYMER TO HYDROPHILIC AND HYDROPHOBIC TABLET COMPACTS

The influence of plasticizers in film coating formulations on the adhe sive properties of an acrylic resin copolymer was determined using the butt adhesion technique. Hydrophilic and hydrophobic plasticizing age nts were incorporated into aqueous dispersions of Eudragit(R) L 30 D-5 5 and coated onto hydrophilic and hydrophobic tablet compacts. Using d ata obtained from a Chatillon digital force gauge attached to a motori zed test stand, force-deflection profiles, similar to stress-strain cu rves generated in the tensile testing of free films, were constructed and the force of adhesion, elongation at adhesive failure, and adhesiv e toughness were determined. Plasticizer concentration and plasticizer type were found to influence the adhesive properties-of the acrylic p olymer. An increase in adhesive toughness was found when the concentra tion of triethyl citrate (TEC) in the coating formulation was increase d from 20 to 30%, which was attributed to an increase in the elasticit y of the film and a decrease in the internal stresses within the polym er. Films containing water soluble plasticizers were found to adhere m ore strongly to the tablet compacts than the water insoluble agents, d ue to more effective disruption of the intermolecular attractions betw een the polymer chains. Adhesion of the polymer to tablet compacts was found to be significantly influenced by the hydrophobicity of the tab let surface when the water soluble plasticizers were incorporated into the film coating, whereas no significant differences in the adhesive properties were found when the polymer was plasticized with water inso luble agents. Aging of the film-coated tablets resulted in a decrease in adhesive toughness, irrespective of the environmental storage condi tion. (C) 1997 Elsevier Science B.V.