Influence of pigment concentration and particle size on adhesion of an acrylic resin copolymer to tablet compacts

The effects of the particle size and the concentration of pigments in aqueo us polymeric dispersions on the adhesive properties of cm acrylic resin cop olymer were investigated. Aqueous polymeric dispersions containing up to 20 % (v/v) pigment were coated onto hydrophilic and hydrophobic tablet compact s, and polymer adhesion was assessed using a novel butt adhesion technique. An inverse relationship was found between the particle size of the pigment present in the aqueous polymeric dispersion and film-tablet adhesion. As t he particle size of the pigment increased the adhesive strength of the poly mer to the tablet compact decreased. Increased concentrations of the opacif ying agent titanium dioxide in the acrylic dispersion resulted in stronger film-tablet adhesion. No clear relationship could be established between th e wettability of the tablet compact by the pigmented polymeric dispersion a nd the strength of film-tablet adhesion. The hydrophobicity of the tablet c ompact was found To affect the glass transition temperature of the polymeri c film to a greater extent than the particle size, morphology or concentrat ion of the pigment incorporated into the acrylic dispersion.