A dispersant or a dispersing agent is a substance, typically a surfactant, that is added to a suspension of solid or liquid particles in a liquid (such as a colloid or emulsion) to improve the separation of the particles and to prevent their settling or clumping.
Dispersants are widely used to stabilize various industrial and artisanal products, such as , , and . The or , used to improve the workability of pastes like concrete and clay, are typically dispersants. The concept also largely overlaps with that of detergent, used to bring oily contamination into water suspension, and of emulsifier, used to create homogeneous mixtures of immiscible liquids like water and oil. Natural suspensions like milk and latex contain substances that act as dispersants.
Applications
Automotive
Automotive
Motor oil contain both detergents and dispersants. Metallic-based detergents prevent the accumulation of varnish like deposits on the cylinder walls. They also neutralize acids. Dispersants maintain contaminants in suspension.
Dispersants added to gasoline prevent the buildup of gummy residues.
Bio-dispersing
Dispersants are used to prevent formation of
biofouling or
in industrial processes. It is also possible to disperse
slime and increase the efficiency of
biocides.
Concrete and stucco
Dispersants are used as
or
in
concrete formulations to lower the use of water while retaining the needed slump (flow) property. A lower water content makes the concrete stronger and more impervious to water penetration.
[ Superplasticizers . Fhwa.dot.gov. Retrieved on 2010-10-27.]
Similarly, dispersants are used as plasticizers in the gypsum slurry during wallboard manufacture, to reduce the amount of water used. The lower water usage allows lower energy use to dry the wallboard.[ Gypsum wallboard, and method of making same - Patent 5879446. Freepatentsonline.com. Retrieved on 2010-10-27.]
Detergents
Dispersing is the principal goal in the use of
detergents, which the liquid bath is water (detergents also are used as
in some applications). Laundry detergents encase dirt and grime in miscelles, which naturally disperse.
Oil drilling
Dispersants in
oil drilling aid in breaking up
solids or
liquids as fine particles or
droplets into another medium. This term is often applied incorrectly to clay
. Clay dispersants prevent formation of "fish-eye" globules. For dispersing (emulsification) of
oil into
water (or water into oils),
selected on the basis of hydrophilic-lipophilic balance (HLB) number can be used. For foam drilling fluids, synthetic
and
are used, along with
, to disperse foam bubbles into the air or gas.
Oil spill
Dispersants can be used to dissipate
.
They may rapidly disperse large amounts of certain oil types from the
sea surface by transferring it into the
water column. They will cause the oil slick to break up and form water-soluble
that are rapidly
dilute. Then effectively spread throughout a larger volume of water than the surface from where the oil was dispersed. They can also delay the formation of persistent oil-in-water emulsions. However, laboratory experiments showed that dispersants increased toxic hydrocarbon levels in fish by a factor of up to 100 and may kill fish eggs.
Dispersant Corexit 9527 was for example used to disperse an oil slick in the Gulf of Mexico in 1979 (Ixtoc)
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Process industry
In the process industry dispersing agents are added to process liquids to prevent unwanted
Fouling by keeping them finely dispersed. They function in both aqueous and nonaqueous media.
Surface coating
In order to provide optimal performance, pigment particles must act independently of each other in the coating film and thus must remain well dispersed throughout manufacture, storage, application, and film formation. Unfortunately, colloidal dispersions such as the pigment dispersions in liquid
are inherently unstable, and they must be stabilized against the
flocculation that might occur.
See also
