Powder Properties and Mixing

The extent to which air spaces exist between particles in a powder. It's a measure of how much air is present in a powder sample.

The most loosely packed state of a powder, achieved by simply pouring it into a measuring cylinder without any vibration or disturbance.

The densest packing state achieved by applying pressure or tapping the measuring cylinder to allow the particles to settle.

Relates to the packing arrangement of particles in a powder. It describes how tightly the particles fit together. Cubical packing is looser, while rhombohedral packing is denser.

The densest arrangement of particles, where the particles are tightly packed together, leaving minimal air space between them. Rhombohedral packing is an example.

The density of a single particle, considering its volume and weight, ignoring any internal pores or capillaries.

The density of the entire powder sample, taking into account the volume of the air spaces between the particles.

The density of the material itself, excluding any air spaces or internal pores.

A measure of how easily a powder flows, calculated as the angle between the surface of a heap of powder and the horizontal plane.

A type of powder flow where particles move independently and evenly through an opening, resulting in predictable and consistent flow.

Refers to elongated particles with a length-to-width ratio greater than 1.7.

The density of a powder when it is packed as loosely as possible, typically measured by pouring it into a graduated cylinder without any tapping or vibration.

The density of a powder after it has been packed as tightly as possible, typically achieved by tapping or vibrating the container to allow the particles to compact.

The measured density of a powder when packed into a container and tapped until no further volume change occurs. Typically, this refers to the 'maximum bulk density' which is achieved when the powder is tapped repeatedly until a constant volume is reached.

The ratio of the difference between tapped density and bulk density to the tapped density, expressed as a percentage. It's a measure of how much a powder can be compacted.

The ratio of tapped density to bulk density. It's a measure of how easily a powder flows.

A substance added to a powder to improve its flowability. Often used to reduce friction between particles and thus allow the powder to flow more easily.

The difference between the tapped density and the bulk density of a powder. It's a direct indication of how much the powder can be compressed.

A type of mixer where the mixing vessel is fixed, but an internal impeller moves around particles, shifting groups from one location to another within the powder bulk.

A mixer known for high energy input, featuring blades rotating at high speeds (2000-3000 rpm) in a static vessel. Often used to break down aggregates after other mixing processes.

A mixing process involving subjecting powder to very high shear forces, usually employed after convective or tumbling mixing. This process effectively breaks down aggregates and improves homogeneity.

A type of mixer using a rotating impeller shaped like a 'U' to effectively move particles and blend powders.

This kind of mixer features a rotating vessel, but the powder itself doesn't fall back into the mix. Instead, it uses the rotating movement to mix the powder.

A type of powder mixing where no liquid is added, aiming to mix powders without altering their properties.

Powder mixing that involves adding a liquid binder to the powder mixture, often resulting in granules.

A preliminary mixing step for powder mixtures containing less than 5% of the active ingredient, often followed by further processing.

The final mixing step after the initial mixing, where external phases like lubricants or glidants are added to the mixture.

A type of mixing equipment that uses rotating vessels to tumble powders, causing them to mix by rolling over each other.

The process of moving powder from one location to another, often from a hopper to a processing machine.

The method of achieving homogeneous distribution of different powder components in a mixture by bringing particles of each component into close proximity.

A mixing technique where a powder is suspended in a flowing gas stream, resulting in increased particle mobility, turbulence, and efficient mixing.

The ratio of powder volume to the total volume of the mixing vessel, important for efficient mixing and preventing overfilling.

A mixing mechanism where individual particles move randomly within the powder system, often referred to as 'micromixing'.

A mixing mechanism where groups of particles are transferred through the powder system, often referred to as 'macromixing'.

A mixing mechanism where layers of particles slide past each other, creating 'slip planes'.

The tendency for particles of different sizes, shapes, or densities to separate during mixing, resulting in an uneven mixture.

The process of ensuring that the mixed powder remains homogeneous during further handling and processing, preventing segregation and maintaining a consistent mixture.