Polyacrylamide
Overview
 
Polyacrylamide is a polymer (-CH2CHCONH2-) formed from acrylamide
Acrylamide
Acrylamide is a chemical compound with the chemical formula C3H5NO. Its IUPAC name is prop-2-enamide. It is a white odourless crystalline solid, soluble in water, ethanol, ether, and chloroform. Acrylamide is incompatible with acids, bases, oxidizing agents, iron, and iron salts...

 subunits. It can be synthesized as a simple linear-chain structure or cross-link
Cross-link
Cross-links are bonds that link one polymer chain to another. They can be covalent bonds or ionic bonds. "Polymer chains" can refer to synthetic polymers or natural polymers . When the term "cross-linking" is used in the synthetic polymer science field, it usually refers to the use of...

ed, typically using N,N-methylenebisacrylamide. Polyacrylamide is not toxic. However, unpolymerized acrylamide, which is a neurotoxin
Neurotoxin
A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...

, can be present in very small amounts in the polymerized acrylamide, therefore it is recommended to handle it with caution.
Encyclopedia
Polyacrylamide is a polymer (-CH2CHCONH2-) formed from acrylamide
Acrylamide
Acrylamide is a chemical compound with the chemical formula C3H5NO. Its IUPAC name is prop-2-enamide. It is a white odourless crystalline solid, soluble in water, ethanol, ether, and chloroform. Acrylamide is incompatible with acids, bases, oxidizing agents, iron, and iron salts...

 subunits. It can be synthesized as a simple linear-chain structure or cross-link
Cross-link
Cross-links are bonds that link one polymer chain to another. They can be covalent bonds or ionic bonds. "Polymer chains" can refer to synthetic polymers or natural polymers . When the term "cross-linking" is used in the synthetic polymer science field, it usually refers to the use of...

ed, typically using N,N-methylenebisacrylamide. Polyacrylamide is not toxic. However, unpolymerized acrylamide, which is a neurotoxin
Neurotoxin
A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...

, can be present in very small amounts in the polymerized acrylamide, therefore it is recommended to handle it with caution. In the cross-linked form, the possibility of the monomer being present is reduced even further. It is highly water-absorbent, forming a soft gel
Gel
A gel is a solid, jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state...

 when hydrated, used in such applications as polyacrylamide gel electrophoresis
SDS-PAGE
SDS-PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis, describes a collection of related techniques widely used in biochemistry, forensics, genetics and molecular biology to separate proteins according to their electrophoretic mobility...

 and in manufacturing soft contact lens
Contact lens
A contact lens, or simply contact, is a lens placed on the eye. They are considered medical devices and can be worn to correct vision, for cosmetic or therapeutic reasons. In 2004, it was estimated that 125 million people use contact lenses worldwide, including 28 to 38 million in the United...

es. In the straight-chain form, it is also used as a thickener and suspending
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...

 agent. More recently, it has been used as a subdermal filler for aesthetic facial surgery (see Aquamid
Aquamid
Aquamid is a non-absorbable soft volume filler for aesthetic and reconstructive purposes. Aquamid is the trade name for a specific formulation of 97.5% water for injection and 2.5% cross-linked polyacrylamide. It is injected subcutaneously to correct wrinkles and folds or to add volume...

).

Uses of polyacrylamide

One of the largest uses for polyacrylamide is to flocculate
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...

 or coagulate solids in a liquid. This process applies to wastewater treatment
Industrial wastewater treatment
Industrial wastewater treatment covers the mechanisms and processes used to treat waters that have been contaminated in some way by anthropogenic industrial or commercial activities prior to its release into the environment or its re-use....

, and processes like paper making
Paper mill
A paper mill is a factory devoted to making paper from vegetable fibres such as wood pulp, old rags and other ingredients using a Fourdrinier machine or other type of paper machine.- History :...

. Most polyacrylamide is supplied in a liquid form. The liquid is subcategorized as solution and emulsion polymer.
Even though these products are often called 'polyacrylamide', many are actually copolymers of acrylamide
Acrylamide
Acrylamide is a chemical compound with the chemical formula C3H5NO. Its IUPAC name is prop-2-enamide. It is a white odourless crystalline solid, soluble in water, ethanol, ether, and chloroform. Acrylamide is incompatible with acids, bases, oxidizing agents, iron, and iron salts...

 and one or more other chemical species, such as an acrylic acid
Acrylic acid
Acrylic acid is an organic compound with the formula CH2=CHCO2H. It is the simplest unsaturated carboxylic acid, consisting of a vinyl group connected directly to a carboxylic acid terminus. This colorless liquid has a characteristic acrid or tart smell. It is miscible with water, alcohols,...

 or a salt thereof. The main consequence of this is to give the 'modified' polymer a particular ionic
Ionic potential
Ionic potential is the ratio of electric charge to the radius of an ion.As such, the proportion measures the charge density at the surface of the ion; usually the denser the charge, the stronger will be the bond that the ion forms....

 character.

Another common use of polyacrylamide and its derivatives is in subsurface applications such as Enhanced Oil Recovery. High viscosity aqueous solutions can be generated with low concentrations of polyacrylamide polymers, and these can be injected to improve the economics of conventional waterflooding.

It has also been advertised as a soil conditioner
Soil conditioner
A soil conditioner, also called a soil amendment, is a material added to soil to improve plant growth and health. A conditioner or a combination of conditioners corrects the soil's deficiencies in structure and-or nutrients.-Purpose:...

 called Krilium by Monsanto Company in the 1950s and today "MP", which is stated to be a "unique formulation of PAM (water-soluble polyacrylamide)". It is often used for horticultural and agricultural use under trade names such as Broadleaf P4, Swell-Gel and so on. The anionic form of cross-linked polyacrylamide is frequently used as a soil conditioner on farm land and construction sites for erosion control
Erosion control
Erosion control is the practice of preventing or controlling wind or water erosion in agriculture, land development and construction. Effective erosion controls are important techniques in preventing water pollution and soil loss.-Introduction:...

, in order to protect the water quality
Water quality
Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which...

 of nearby rivers and streams.

The polymer is also used to make Gro-Beast toys, which expand when placed in water, as the Test Tube Aliens
Test Tube Aliens
Test Tube Aliens are a series of toys that were invented by JKID Ltd and released by 4Kidz, Inc., a toy and juvenile products company based in Stamford, Connecticut.- Story :...

. Similarly, the absorbent properties of one of its copolymers can be utilized as an additive in body-powder.

The ionic form of polyacrylamide has found an important role in the potable water treatment industry
Water industry
The water industry provides drinking water and wastewater services to residential, commercial, and industrial sectors of the economy. The water industry includes manufacturers and suppliers of bottled water...

. Trivalent metal salts like ferric chloride and aluminium chloride
Aluminium chloride
Aluminium chloride is the main compound of aluminium and chlorine. It is white, but samples are often contaminated with iron trichloride, giving it a yellow colour. The solid has a low melting and boiling point. It is mainly produced and consumed in the production of aluminium metal, but large...

 are bridged by the long polymer chains of polyacrylamide. This results in significant enhancement of 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...

 rate. This allows water treatment
Water purification
Water purification is the process of removing undesirable chemicals, materials, and biological contaminants from contaminated water. The goal is to produce water fit for a specific purpose...

 plants to greatly improve the removal of total organic content (TOC) from raw water.

Polyacrylamide is often used in molecular biology applications as a medium for electrophoresis of proteins and nucleic acids in a technique known as PAGE
Page
-Position or occupation:* Page , a traditionally young male servant* Page * Page of Honour, a ceremonial position in the Royal Household of the Sovereign of the United Kingdom* A participant in any of the following programs:...

.

Soil Conditioner

The primary functions of Polyacrylamide Soil Conditioners are to increase soil tilth, aeration, and porosity and reduce compaction, dustiness and water run-off. Secondary functions are to increase plant vigor, color, appearance, rooting depth and emergence of seeds while decreasing water requirements, diseases, erosion and maintenance expenses.

Patent Number 4,797,145 filed in February 1986, by Garn A. Wallace and Arthur Wallace
Arthur Wallace
Arthur Wallace, born January 4, 1919 in Bear River City, Utah died on October 11, 2008 in Santa Monica, California at age 89, was a soil scientist.-Schooling:Wallace received a B.S. from Utah State University in 1943 and at Ph.D...

 of Wallace Laboratories LLC, then published Jan. 10, 1989 - "Method of Agricultural Soil Improvement". As stated from the patent documents, Improvement in the physical properties of soils is achieved by the applicaton of qwuecus mixtures of agricultural polyelectrolytes and polysaccharides to the soil. The combination of agricultural polyelectrolytes and polysaccharides results in greatly improving the physical properties of the soil while significantly reducing the quantity of agricultural polymers as compared to to methods of the prior art.

Stability

In dilute aqueous solution, such as is commonly used for Enhanced Oil Recovery
Enhanced oil recovery
Enhanced Oil Recovery is a generic term for techniques for increasing the amount of crude oil that can be extracted from an oil field...

 applications, polyacrylamide polymers are susceptible to chemical, thermal, and mechanical degradation. Chemical degradation occurs when the labile amine moiety hydrolyzes at elevated temperature or pH, resulting in the evolution of ammonia and a remaining carboxyl group. Thus, the degree of anionicity of the molecule increases. Thermal degradation of the vinyl backbone can occur through several possible radical mechanisms, including the autooxidation of small amounts of iron and reactions between oxygen and residual impurities from polymerization at elevated temperature. Mechanical degradation can also be an issue at the high shear rates experienced in the near-wellbore region.
However, cross-linked variants of polyacrylamide have shown greater resistance to all of these methods of degradation, and have proved much more stable.

Environmental effects

Concerns have been raised that polyacrylamide used in agriculture may contaminate food with the nerve toxin acrylamide
Acrylamide
Acrylamide is a chemical compound with the chemical formula C3H5NO. Its IUPAC name is prop-2-enamide. It is a white odourless crystalline solid, soluble in water, ethanol, ether, and chloroform. Acrylamide is incompatible with acids, bases, oxidizing agents, iron, and iron salts...

. While polyacrylamide itself is relatively non-toxic, it is known that commercially available polyacrylamide contains minute residual amounts of acrylamide remaining from its production, usually less than 0.05% w/w.

Additionally, there are concerns that polyacrylamide may de-polymerise to form acrylamide. In a study conducted in 2003 at the Central Science Laboratory
Central Science Laboratory
The Central Science Laboratory was an executive agency of the UK government department the Department for Environment, Food and Rural Affairs . It specialises in the sciences underpinning agriculture for sustainable crop production, environmental management and conservation and in food safety and...

 in Sand Hutton
Sand Hutton
Sand Hutton is a village and civil parish in the Ryedale district of North Yorkshire, England, about north-east of York.Part of the Department for Environment, Food and Rural Affairs's Food and Environment Research Agency is sited at Sand Hutton....

, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

, polyacrylamide was treated similarly as food during cooking. It was shown that these conditions do not cause polyacrylamide to de-polymerise significantly. California requires (current as of 2010) products containing acrylamide as an ingredient to be labeled with a statement that it is "a chemical known to the State of California to cause cancer."

In a study conducted in 1997 at Kansas State University
Kansas State University
Kansas State University, commonly shortened to K-State, is an institution of higher learning located in Manhattan, Kansas, in the United States...

, the effect of environmental conditions on polyacrylamide were tested, and it was shown that degradation of polyacrylamide under certain conditions does in fact cause the release of acrylamide. The experimental design of this study as well as its results and their interpretation have been questioned, and a 1999 study by the Nalco Chemical Company did not replicate the results.

See also

  • Aquamid
    Aquamid
    Aquamid is a non-absorbable soft volume filler for aesthetic and reconstructive purposes. Aquamid is the trade name for a specific formulation of 97.5% water for injection and 2.5% cross-linked polyacrylamide. It is injected subcutaneously to correct wrinkles and folds or to add volume...

  • Chitosan
    Chitosan
    Chitosan is a linear polysaccharide composed of randomly distributed β--linked D-glucosamine and N-acetyl-D-glucosamine...

  • Rhoca-Gil
    Rhoca-Gil
    Rhoca-Gil is a type of industrial sealant produced by Rhône-Poulenc, used in the construction of tunnels to block the passage of groundwater into the tunnel...

  • Sodium polyacrylate
    Sodium polyacrylate
    Sodium polyacrylate, also known as waterlock, is a polymer with the chemical formula [-CH2-CH-]n widely used in consumer products. It has the ability to absorb as much as 200 to 300 times its mass in water. Acrylate polymers generally are considered to possess an anionic charge...

    , a similar material

External links

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