Direct Evidence for the Role of Surface Free Energy

4 Direct Evidence for the Role of Surface Free Energy 

Direct evidence for the role of surface free energy in determine tablet tensile strength is limited. Two studies, however, have been performed that suggest a role of smface free energy in determining tablet tensile strength. Tablet porosity was not carefully controlled or recorded in these studies so further confirmation is likely to be desirable. 

El Gindy and Samara [27] measured the tensile strength of tablets composed of aspirin, indomethadn, magnesium stearate, potassium chloride and sodium chloride. The selection of materials used in this study allows 

For tablets to be commercially successful empirical experience suggests that tablets should have, at minimum, tensile strengths of 1-2 MPa with porosities of 10-20%. These properties ensure adequate strength for shipping and handling as well as appropriate dissolution times. 

Polymeric materials that adsorb water may show modified adhesion characteristics with the adsorption of water. The study by Sun [24] suggests that adsorption of water beyond 1 monolayer reduces adhesion between microcrystalline cellulose particles. Hydration of such polymers, of course, also alters the mechanical properties of a material. 

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