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A dispersant or a dispersing agent or a plasticizer is either a non-surface active polymer or a surface-active substance added to a suspension, usually a colloid, to improve the separation of particles and to prevent settling or clumping. Dispersants consist normally of one or more surfactants, but may also be gases.

Contents

Applications

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Automotive

Dispersing agents are added to lubricating oils used in automotive engines to prevent the accumulation of varnishlike deposits on the cylinder walls and to gasoline to prevent the buildup of gummyish residues.

Bio-Dispersing

Dispersants can be used to prevent formation of biofouling or biofilms in industrial processes. It is also possible to disperse bacterial slime and increase the efficiency of biocides.

Concrete

Dispersants/plasticizer are used in the concrete mix (sand, stone, cement and water) to lower the use of water and still keeping the same slump (flow) property. This make the concrete stronger and more impervious to water penetration.[1]

Detergents

Dispersing agents are the principal applications of detergents for which the liquid bath is water. Detergents also are used as emulsifiers in many applications.

Gypsum Wallboard

A dispersant/plasticizer is added to the gypsum wallboard slurry to reduce the amount of water used, while maintaining the same slump as the slurry without dispersant. The lower water usage allows lower energy use to dry the wallboard.[2]

Oil Drilling

Dispersants in oil drilling are chemical that aids in breaking up solids or liquids as fine particles or droplets into another medium. This term is often applied incorrectly to clay deflocculants. Clay dispersants are various sodium phosphates and sodium carbonates aided by heat, mechanical shearing and time. Powdered polymers are dispersed by precoating the particles with a type of glycol to prevent formation of "fish-eye" globules. For dispersing (emulsification) of oil into water (or water into oils), surfactants selected on the basis of hydrophile-lipophile balance (HLB) number can be used. For foam drilling fluids, synthetic detergents and soaps are used, along with polymers, to disperse foam bubbles into the air or gas.

Oil spill

Dispersants can be used to dissipate oil slicks.

When used appropriately, dispersants can be an effective method of response to an oil spill[3]. They may rapidly remove large amounts of certain oil types from the sea surface by transferring it into the sea water. Wave energy will cause the oil slick to break up into small oil droplets that are rapidly diluted and subsequently biodegraded by micro-organisms occurring naturally in the marine environment. They can also delay the formation of persistent water-in-oil emulsions.

A dispersant was used in an attempt to clean up the Exxon Valdez oil spill[4] though their use was discontinued as there was not enough wave action to mix the dispersant with the oil in the water.

Process industry

In the process industry dispersing agents or plasticizers are added to process liquids to prevent unwanted deposits 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 coatings are inherently unstable, and they must be stabilized against the flocculation that might occur.

See also

References

  1. ^ http://en.wikipedia.org/wiki/Plasticizer
  2. ^ http://en.wikipedia.org/wiki/Plasticizer
  3. ^ http://www.itopf.com/spill-response/clean-up-and-response/dispersants/
  4. ^ ITOPF - Spill Response - Dispersants

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