INVESTIGATION OF THE COHESION BEHAVIOR OF POWDERS AND THEIR ADHESION TO A CARRIER BY AN ELECTRONIC TENSIOMETER

A modified electronic tensiometer was used to measure cohesive forces of powders and their adhesiveness to sorbitol instant as a coarse carr ier. The method is based on the determination of the force which is re quired to pull off a watch glass coated with white petrolatum as an ad hesive material from a powder bed. The following parameters were studi ed: type of powder, particle size and admixture of 1% colloidal silico n dioxide. The powders investigated were: pyridoxine hydrochloride, et ilefrine hydrochloride, riboflavine and propranolol hydrochloride. The results show differences between powders in cohesiveness. Cohesivenes s increases first with decreasing particle size and drops to a low val ue when agglomeration of the powder takes place. The addition of 1% co lloidal silicon dioxide lowers the cohesiveness with the exception of propranolol which forms after jet milling very stable agglomerates and supersaturated interactive mixtures. The formation of interactive and supersaturated interactive mixtures could be explained by the force m easurements.