1.3 General Terms

Glossary of Terms in Powder & Bulk Technology

Written by Lyn Bates – edited by mhd on 18. Sep. 2022

C/M/R substances Materials	Classified as category 1 or 2 carcinogens, mutagens or toxic to reproduction. (Related to points 29, 30 and 31 pf Annex 1 of Directive 76/769/EEC. (A Consolidated, 100 page, list of materials is given ).
coagulant	An agent causing coagulation./td>
colloid	A state of matter comprising a system with two or more phases, in which one phase exists as discrete particles of the order of 100 to 100,000 nanometers densely permeating a continuous phase. Physical characteristics related to the enormous surface area of the bulk tend to dominate the behaviour of such materials.
compression index	The slope of the linear portion of the pressure-void ratio curve on a semi-log plot.
compressive stress	A normal stress that tends to shorten the body to which it is applied, in the direction in which it acts. In solids, the effect is termed compaction.
consolidation	The reduction in volume of a bulk particulate mass resulting from the effect of gravity over time, or of a compacting stress. It is useful to consider consolidation as a state, rather than a process of volume reduction, which is better distinguished by the term ‘compaction’.
creep	A slow, plastic deformation under stress lower than the failure stress.
critical density	The unit weight of a unit volume of a granular material that will deform in a specific state of stress without change of volume. Below this value of density the bulk will gain strength when subjected to deformation, i.e. it is under-consolidated, and above which it will loose strength when deformed, an over-consolidated condition. Critical density reflects the condition of a material in instantaneous equilibrium during gravity flow.
deliquescent	The ability to absorb moisture from the atmosphere, to the extent that the product dissolves in the absorbed fluid.
dilatant suspension	A material that increases in shear strength with the rate of shear.
dilatation	A conditions of expanded particulate structure that may be brought about by such as agitation, aeration or shear. The opposite of compaction.
disintergrant	Materials incorporated within compacts of dry powders or granules to promote separation to the primary particles, on addition to a liquid.
elastic limit	Point on the stress-strain curve beyond which deformation will not fully recover on the removal of stress.
elastic state of equilibrium	State of stress within a stressed mass when the internal resistance to permanent deformation is not fully mobilised.
elastic strain energy	Potential energy stored within a strained solid equal to the work done in deforming the solid from its unstrained condition, less any energy dissipated by inelastic deformation.
elasto-plastic	A deformation that will partially recover on relaxation of the applied stress
emulsion	A dispersion of immiscible liquids.
entrainment pattern	The flow velocity contours that are generated over the cross section of the interface from a hopper outlet by a feeder used to discharge the container.
equivalent surface level	The level that the contents of a hopper would reach if the material were evenly spread across the surface.
failure	A state of dis-equilibrium brought about by stresses exceeding the elastic limit of deformation of a powder compact. (See shear failure, yield).

Page 2 of 7