Following is a list of common material categories based on flow properties and other characteristics*
Adhesive: An adhesive material sticks to everything, making it one of the most challenging materials to feed; a good example is color pigments, which are notorious for adhering to all types of surfaces.
Aeratable: An aeratable (or floodable) material, such as glass microspheres, flour, or phenolic resin typically has a low angle of repose (angle at which material slides down) and behaves like a fluid when aerated. This can cause it to flood in an uncontrolled flow from an equipment discharge.
Cohesive: A cohesive material typically has a high angle of repose (angle at which material slides down) and tends to pack or clumps like a snowball rather than flow easily. Examples include very fine powders and powders containing fat (like a cake mix) or moisture.
Fibrous: A fibrous material such as wood flour or biomass fibers contains long particles that tend to interlock and form masses that stop or slow flow.
Free-Flowing: A free-flowing material, like plastics pellets, flows easily by gravity without help from flow aids or specially designed equipment.
Friable: A friable material, such as wax beads, pasta products, or flake adhesives, has particles that are easily broken, so it requires gentle handling to avoid reducing the particle size, changed the particle shape, or causing the material to flow at an inconsistent rate.
Hydroscopic: A hydroscopic material, such as sugar, salt, or cellulose fibers, readily wicks up moisture that can cause it to clump. Leaving this material in equipment overnight can cause it to harden into a rock-hard lump by morning.
Meltable at low temperatures: A material with a low melting temperature tends to break down, melt, or caramelize when subjected to excess friction or energy.
Pressure sensitive: A pressure sensitive material, such as wax beads, is prone to packing, especially under a larger head load.
For help in choosing the best bag filler for your specific application, complete and submit a Packaging Solutions Worksheet .
* Source: Todd Messmer, Schenck AccuRate, Choosing a feeder: It’s all about your material, Power & Bulk Engineering, December, 2013. To see compete article, click here.