Effect of moisture on tensile strength of bulk solids. II. Fine particle-size materials with varying inherent coherence

Influence of relative humidity on the adhesive properties of a model interactive system

The influence of relative humidity on the adhesive properties of model drug-carrier interactive systems was investigated using the centrifuge method. The degree of adhesion was quantified by determining the S50 from the adhesion profile. High ambient humidity (greater than 40% r.h.) decreased the degree of interaction of three sulphonamide powders with model hydroxypropyl methylcellulose phthalate-coated glass bead carriers during blending. All drug-carrier interactive systems displayed decreases in the degree of adhesion during storage. The extent and rate of the decreases increased with relative humidity and was interactive system-dependent. Preconditioning the powders to varying moisture contents produced contrasting results during blending, with one system showing a decrease in adhesion as the relative humidity increased, while the other's interactive capability increased. This increase was attributed to the enhancement of charging sites on the drug's powders surface by the adsorbed moisture.

Effects of paraffin coatings on the tensile strength of lactose

Measurements have been made of the tensile strength of lactose at different temperatures after coating it with up to 10(-4) mol of various paraffin hydrocarbons g-1 of powder. Providing the coating is in a liquified form, either as a result of the ambient temperature or because of the localized high pressure at the points of true contact between the particles, there is a correlation between the tensile strength of the powder and the thickness and viscosity of the coating layer.

The packing properties of moist bulk solids

The specific volumes of three bulk solids at moisture contents up to 50% w/w (dry basis) under various consolidating stresses have been shown to be dependent on the nature of the bulk solid. The values obtained can be related to the intraparticulate porosity and inherent cohesiveness of the dry materials. The influence of moisture on the packing properties and tensile strength of the three bulk solids is discussed in terms of the granulation process.