Interparticle forces in binary and ternary ordered powder mixes.

An ultracentrifuge technique, previously described by Staniforth et al (1981), has been used to study the adhesion profiles of several binary and ternary ordered powder mixes of pharmaceutical interest. The adhesion profile of an ordered mix provides information about the proportion of drug powder adhering with different forces of attraction to the carrier excipient particle surface. The excipient particle size is shown to affect adhesion between the components of a binary ordered mix-recrystallized lactose formed more stable ordered mixes with drug powder when the carrier particle size was increased. Changes in the adhesion profile of each binary system on adding three different fine-powder excipients to form a ternary ordered mix are also examined. The physical properties of carrier particles and the charge interactions of a third powder component with previously formed binary ordered mixes, are found to influence the physical stability of ternary ordered mixes.

Compactibility of granules prepared by a novel method of granulation and their dissolution.

Increasing particle size during prolonged grinding by a ballmill has been used as a novel means of producing a pharmaceutical granulation. The compactibility properties of granules of sodium chloride and of paracetamol produced by this method have been elucidated and compared with those produced by conventional granulation techniques. Force-displacement diagrams and double compactions were used to measure the net energy input on tableting. When compared with conventional granulation methods, the agglomerative phase of comminution (APOC) method produced mechanically stronger tablets with a higher dissolution rate than those compacted from granules made by a conventional wet granulation method irrespective of the compaction energy used. Tablet tensile strength is related to the elasticity and yield strength of the substance used. It is suggested that binderless tablets may be prepared using this method, thus simplifying tablet formulation and enhancing stability. A possible mechanism for the increased dissolution rate is the increased internal surfaces area of the granules produced by the prolonged grinding method.

Powder homogenization using a hammer mill.

Hammer mill applicability in the comixing milling operation is discussed with reference to a 1:1000 microfine salicylic acid-sucrose binary system. The hammer mill would not serve as a mixing machine under most circumstances because of the low holdup capacity. Grinding of pure materials was preferable to mixture grinding since active ingredients could be lost during the milling operation. Remixing was always necessary following comminution of the mixture in the hammer mill. Grinding followed by remixing considerably enhanced mixture homogeneity. A large size range was produced by comminution, which resulted in the segregation of ordered units such that the final mixture could be described as a randomized ordered mixture.