The Blow Test for measuring the stickiness of powders

摘要

Most powder stickiness tests measure a sticky point temperature characteristic for a powder at a particular water activity. However, most mechanisms for stickiness development involve fluid flow of viscous fluids or kinetic reactions, which are therefore, time dependant. This means that the sticky point is dependent on the method used to measure it. The blow tester was developed to measure the time dependent increase in stickiness of amorphous lactose held a set level above its glass transition point. It works by blowing a jet of air onto the powder at a fixed angle. The airflow rate is increased until a channel is blown into the powder. The blow tester has proved to be very sensitive in measuring when powders start sticking and in quantifying the stickiness increase with time. An attempt has been made to correlate the forces exerted by the blow tester on the individual powder particles to estimate the stickiness forces.