The tensile strength of lactose powder coated with fatty acids

Tensile strength and compression of coated pharmaceutical powders

A study has been made of the tensile strength and compression of loosely packed beds of lactose, sodium chloride and calcium phosphate powders after they had been coated with small amounts of stearic acid, polyethylene glycols and polyvinylpyrrolidones. The properties of the systems were measured over a range of temperatures. Only when the coatings were continuous and durable did they produce reductions in both tensile strength and resistance to compression. Marked changes occurred in tensile strength at temperatures 20 ° — 40 °C below the conventional melting points of the coatings. The tensile strength results have been expressed in terms of the range and magnitude of the interparticle forces which depend on the surface free energy of the coated powders and on the Brinell hardness of the coating materials employed.

A consideration of the range and strength of interparticle forces in coated lactose powder

A study has been made of the range and strength of interparticle forces in lactose powder coated with increasing concentrations of paraffins at different temperatures. Marked changes occurred in these forces as the paraffin content was altered and the temperature increased from -10 degrees to +50 degrees C. The strength and range of interparticle forces depended on the mechanical properties of the coating materials and the surface free energy of the coated powders.

The plasto-elasticity and compressibility of coated powders and the tensile strengths of their tablets

A study has been made of the effects produced on the tensile strength, brittle fracture index (BFI), 'plasto-elasticity' ratio, ER/PC, and yield pressure (1/KH derived from Heckel plots) of sodium salicylate and calcium carbonate as a result of coating their particles with increasing amounts of silicones and polysorbates before subjecting them to compression to form tablets. The coatings act as lubricants reducing bond formation due to plastic deformation of particles. They caused a reduction in the tensile strengths and yield pressures of the tablets but increased their BFI values and their ER/PC ratios. Tablets of calcium carbonate tended to cap or laminate when their BFI value was greater than 0.7 and their ER/PC ratio was greater than 7. Sodium salicylate whose BFI values were all less than 0.7 produced satisfactory tablets when their ER/PC ratio was less than 10 but tended to cap or laminate when it was greater than 10.

Tensile strength and compression of coated pharmaceutical powders: tablets

A study has been made of the tensile strength and compression during tableting of lactose, sodium chloride and calcium phosphate powders after they had been coated with small amounts of stearic acid, polyethylene glycols and polyvinylpyrrolidones. The properties of the systems were measured over a range of temperatures. The tensile strength and the compression behaviour depended not only on the amount and type of the coating material but also on the homologous temperature of processing. The changes in tensile strength have been explained in terms of changes in interparticle separation, changes in interparticle forces and the formation of welded bonds by the coatings. The compression results have been analysed in terms of the Heckel and the Cooper & Eaton equations.

Effects of paraffin coatings on the shearing properties of lactose

An annular shear cell has been employed to measure the shearing properties of lactose powder coated with up to 10(-4) mol g-1 of powder of a series of paraffin hydrocarbons. The angle of internal friction, delta, of the coated powders was independent of their packing density. The shearing properties of the powders depended on the concentration, the viscosity and thickness of the coating material.

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.