Dispersant
Encyclopedia
A dispersant or a dispersing agent or a plasticizer
or a superplasticizer
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 surfactant
s, but may also be gas
es.
to prevent the buildup of gummyish residues.
or biofilm
s in industrial processes. It is also possible to disperse bacteria
l slime and increase the efficiency of biocides.
/superplasticizer
s 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 makes the concrete stronger and more impervious to water penetration
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, since less water is present in the wallboard
into water
(or water into oils), surfactant
s selected on the basis of Hydrophilic-lipophilic balance
(HLB) number can be used. For foam drilling fluids, synthetic detergent
s and soap
s are used, along with polymer
s, to disperse foam bubbles into the air or gas.
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 micelle
s that are rapidly diluted. The oil is 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.
A dispersant was used in an attempt to clean up the Exxon Valdez oil spill
though its use was discontinued as there was not enough wave action to mix the dispersant with the oil in the water. Dispersant Corexit
9500 is currently being used on the Deepwater Horizon oil spill
. Dispersant Corexit 9527 was used to disperse an oil slick in the Gulf of Mexico in 1979 (Ixtoc), used over one thousand square miles of sea.
s are added to process liquids to prevent unwanted deposits
by keeping them finely dispersed. They function in both aqueous and nonaqueous media.
s are inherently unstable, and they must be stabilized against the flocculation
that might occur.
Plasticizer
Plasticizers or dispersants are additives that increase the plasticity or fluidity of the material to which they are added; these include plastics, cement, concrete, wallboard, and clay. Although the same compounds are often used for both plastics and concretes the desired effects and results are...
or a superplasticizer
Superplasticizer
Superplasticizers, also known as high range water reducers, are chemicals used as admixtures where well-dispersed particle suspension are required. These polymers are used as dispersants to avoid particle aggregation, and to improve the flow characteristics of suspensions such as in concrete...
is either a non-surface active polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
or a surface-active substance
Surfactant
Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...
added to a suspension
Suspension (chemistry)
In chemistry, a suspension is a heterogeneous fluid containing solid particles that are sufficiently large for sedimentation. Usually they must be larger than 1 micrometer. The internal phase is dispersed throughout the external phase through mechanical agitation, with the use of certain...
, usually a colloid
Colloid
A colloid is a substance microscopically dispersed evenly throughout another substance.A colloidal system consists of two separate phases: a dispersed phase and a continuous phase . A colloidal system may be solid, liquid, or gaseous.Many familiar substances are colloids, as shown in the chart below...
, to improve the separation of particles and to prevent settling
Settling
Settling is the process by which particulates settle to the bottom of a liquid and form a sediment. Particles that experience a force, either due to gravity or due to centrifugal motion will tend to move in a uniform manner in the direction exerted by that force...
or clumping
Clumping
The terms clump, clumping may refer to:* an organic behavior, see Clumping ;* a software testing scenario, see Clumping and LURCH;...
. Dispersants consist normally of one or more surfactant
Surfactant
Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...
s, but may also be gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
es.
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 gasolineGasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...
to prevent the buildup of gummyish residues.
Bio-dispersing
Dispersants can be used to prevent formation of biofoulingBiofouling
Biofouling or biological fouling is the undesirable accumulation of microorganisms, plants, algae, or animals on wetted structures.-Impact:...
or biofilm
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...
s in industrial processes. It is also possible to disperse bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
l slime and increase the efficiency of biocides.
Concrete
Dispersants/plasticizerPlasticizer
Plasticizers or dispersants are additives that increase the plasticity or fluidity of the material to which they are added; these include plastics, cement, concrete, wallboard, and clay. Although the same compounds are often used for both plastics and concretes the desired effects and results are...
/superplasticizer
Superplasticizer
Superplasticizers, also known as high range water reducers, are chemicals used as admixtures where well-dispersed particle suspension are required. These polymers are used as dispersants to avoid particle aggregation, and to improve the flow characteristics of suspensions such as in concrete...
s are used in the concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
mix (sand, stone, cement and water) to lower the use of water and still keeping the same slump (flow) property. This makes the concrete stronger and more impervious to water penetration
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/plasticizerPlasticizer
Plasticizers or dispersants are additives that increase the plasticity or fluidity of the material to which they are added; these include plastics, cement, concrete, wallboard, and clay. Although the same compounds are often used for both plastics and concretes the desired effects and results are...
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, since less water is present in the wallboard
Oil drilling
Dispersants in oil drilling are chemicals that aid 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 prevent formation of "fish-eye" globules. For dispersing (emulsification) of oilOil
An oil is any substance that is liquid at ambient temperatures and does not mix with water but may mix with other oils and organic solvents. This general definition includes vegetable oils, volatile essential oils, petrochemical oils, and synthetic oils....
into water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
(or water into oils), surfactant
Surfactant
Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...
s selected on the basis of Hydrophilic-lipophilic balance
Hydrophilic-lipophilic balance
The Hydrophilic-lipophilic balance of a surfactant is a measure of the degree to which it is hydrophilic or lipophilic, determined by calculating values for the different regions of the molecule, as described by Griffin in 1949 and 1954...
(HLB) number can be used. For foam drilling fluids, synthetic detergent
Detergent
A detergent is a surfactant or a mixture of surfactants with "cleaning properties in dilute solutions." In common usage, "detergent" refers to alkylbenzenesulfonates, a family of compounds that are similar to soap but are less affected by hard water...
s and soap
Soap
In chemistry, soap is a salt of a fatty acid.IUPAC. "" Compendium of Chemical Terminology, 2nd ed. . Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford . XML on-line corrected version: created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN...
s are used, along with polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
s, to disperse foam bubbles into the air or gas.
Oil spill
Dispersants can be used to dissipate oil slicks. They may rapidly disperseDispersion (chemistry)
A dispersion is a system in which particles are dispersed in a continuous phase of a different composition . See also emulsion. A dispersion is classified in a number of different ways, including how large the particles are in relation to the particles of the continuous phase, whether or not...
large amounts of certain oil types from the sea surface
Surface
In mathematics, specifically in topology, a surface is a two-dimensional topological manifold. The most familiar examples are those that arise as the boundaries of solid objects in ordinary three-dimensional Euclidean space R3 — for example, the surface of a ball...
by transferring it into the water column. They will cause the oil slick to break up and form water-soluble micelle
Micelle
A micelle is an aggregate of surfactant molecules dispersed in a liquid colloid. A typical micelle in aqueous solution forms an aggregate with the hydrophilic "head" regions in contact with surrounding solvent, sequestering the hydrophobic single tail regions in the micelle centre. This phase is...
s that are rapidly diluted. The oil is 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.
A dispersant was used in an attempt to clean up the Exxon Valdez oil spill
Exxon Valdez oil spill
The Exxon Valdez oil spill occurred in Prince William Sound, Alaska, on March 24, 1989, when the Exxon Valdez, an oil tanker bound for Long Beach, California, struck Prince William Sound's Bligh Reef and spilled of crude oil. It is considered to be one of the most devastating human-caused...
though its use was discontinued as there was not enough wave action to mix the dispersant with the oil in the water. Dispersant Corexit
Corexit
Corexit is a product line of solvents primarily used as a dispersant for breaking up oil slicks. It is produced by Nalco Holding Company which is associated with BP and Exxon. Corexit was the most-used dispersant in the Deepwater Horizon oil spill in the Gulf of Mexico, with COREXIT 9527 having...
9500 is currently being used on the Deepwater Horizon oil spill
Deepwater Horizon oil spill
The Deepwater Horizon oil spill is an oil spill in the Gulf of Mexico which flowed unabated for three months in 2010, and continues to leak fresh oil. It is the largest accidental marine oil spill in the history of the petroleum industry...
. Dispersant Corexit 9527 was used to disperse an oil slick in the Gulf of Mexico in 1979 (Ixtoc), used over one thousand square miles of sea.
Process industry
In the process industry dispersing agents or plasticizerPlasticizer
Plasticizers or dispersants are additives that increase the plasticity or fluidity of the material to which they are added; these include plastics, cement, concrete, wallboard, and clay. Although the same compounds are often used for both plastics and concretes the desired effects and results are...
s are added to process liquids to prevent unwanted deposits
Fouling
Fouling refers to the accumulation of unwanted material on solid surfaces, most often in an aquatic environment. The fouling material can consist of either living organisms or a non-living substance...
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 coatingCoating
Coating is a covering that is applied to the surface of an object, usually referred to as the substrate. In many cases coatings are applied to improve surface properties of the substrate, such as appearance, adhesion, wetability, corrosion resistance, wear resistance, and scratch resistance...
s are inherently unstable, and they must be stabilized against the flocculation
Flocculation
Flocculation, in the field of chemistry, is a process wherein colloids come out of suspension in the form of floc or flakes by the addition of a clarifying agent. The action differs from precipitation in that, prior to flocculation, colloids are merely suspended in a liquid and not actually...
that might occur.
See also
- PlasticizerPlasticizerPlasticizers or dispersants are additives that increase the plasticity or fluidity of the material to which they are added; these include plastics, cement, concrete, wallboard, and clay. Although the same compounds are often used for both plastics and concretes the desired effects and results are...
- Deflocculant
- DetergentDetergentA detergent is a surfactant or a mixture of surfactants with "cleaning properties in dilute solutions." In common usage, "detergent" refers to alkylbenzenesulfonates, a family of compounds that are similar to soap but are less affected by hard water...
- SurfactantSurfactantSurfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...
- SuperplasticizerSuperplasticizerSuperplasticizers, also known as high range water reducers, are chemicals used as admixtures where well-dispersed particle suspension are required. These polymers are used as dispersants to avoid particle aggregation, and to improve the flow characteristics of suspensions such as in concrete...
- SolubilizationSolubilizationSolubilization, according to an IUPAC definition, is a short form for micellar solubilization, a term used in colloidal and surface chemistry....