PART 2: The Influence of Solid Inclusions

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Abstract
Solids in the form of colour pigments are commonly added to tablet film coats for the purpose of identification. This work examines the effect of their addition on certain mechanical properties of the films. Films were cast from aqueous solutions of hydroxypropylmethylcellulose (HPMC) in which the solids had been dispersed. Titanium dioxide was added in concentrations of up to 40% in the dried film. Two grades (regular and high tinting) of the following aluminium lakes (Colorcon Limited) were also investigated: Brilliant Blue FCF, Erythrosine and Tartrazine. A tensile test was performed on the films using an Instron test machine. In general, the addition of solid particles reduced the tensile strength of the film, shortened the elongation at break and increased the elastic modulus, i.e. the films became more brittle. The influence of storage humidity on these properties is also reported. Changes in these fundamental properties are correlated with practical problems associated with the addition of solid particles to films. The way in which the presence of solids affects the desirable mechanical properties of tablet film coats is also discussed.