Plasticizers are additives that increase the
plasticityor fluidityof the material to which they are added, these include plastics, cement, concrete, wallboard and clay bodies. Although the same compounds are often used for both plastics and concretes, the desired effect is slightly different.
concretesoften the mix before it hardens, increasing its workability or reducing water, and are usually not intended to affect the properties of the final product after it hardens.
wallboardincreases fluidity of the mix, allowing lower use of water and thus reducing energy to dry the board.
The plasticizers for
plasticssoften the final product increasing its flexibility.
Plasticizers for concrete production
Superplasticizers or high range water reducers or dispersants are chemical admixtures [cite web
last = Cement Admixture Association
title=CAA | Publications
accessdate=2008-04-02] that can be added to
concretemixtures to improve workability. Strength of concrete is inversely proportional to the amount of water added or water-cement (w/c) ratio. In order to produce stronger concrete, less water is added, which makes the concrete mixture very unworkable and difficult to mix, necessitating the use of plasticizers, water reducers, superplasticizers or dispersants.
Superplasticizers are also often used when
pozzolanic ashis added to concrete to improve strength. This method of mix proportioning is especially popular when producing high-strength concrete and fiber-reinforced concrete.
Adding 1-2% superplasticizer per unit weight of cement is usually sufficient. However, note that most commercially available superplasticizers come dissolved in water, so the extra water added has to be accounted for in mix proportioning. Adding an excessive amount of superplasticizer will result in excessive
segregationof concrete and is not advisable. Some studies also show that too much superplasticizer will result in a retarding effect.
Plasticizers are commonly manufactured from
lignosulfonates, a by-product from the paperindustry. High Range Superplasticizers have generally been manufactured from sulfonated naphthalenecondensate or sulfonated melamineformaldehyde, although new-generation products based on polycarboxylic ethers are now available. Traditional lignosulfonate-based plasticisers, naphthaleneand melaminesulfonate-based superplasticisers disperse the flocculated cement particles through a mechanism of electrostatic repulsion (see colloid). In normal plasticisers, the active substances are adsorbed on to the cement particles, giving them a negative charge, which leads to repulsion between particles. Lignin, naphthaleneand melaminesulfonate superplasticisers are organic polymers. The long molecules wrap themselves around the cement particles, giving them a highly negative charge so that they repel each other.
Polycarboxylate ethers (PCE) or just polycarboxylate (PC), the new generation of superplasticisers, are not only chemically different from the older sulfonated melamine and naphthalene-based products, but their action mechanism is also different, giving cement dispersion by steric stabilisation, instead of electrostatic repulsion. This form of dispersion is more powerful in its effect and gives improved workability retention to the cementitious mix. Furthermore, the chemical structure of PCE allows for a greater degree of chemical modification than the older-generation products, offering a range of performance that can be tailored to meet specific needs.
In ancient times, the Romans used
bloodas a superplasticizer for their concrete mixes. Fact|date=March 2007
Plasticisers can be obtained from a local concrete manufacturer.
Household washing up liquid may also be used as a simple plasticizer.
Plasticizers for gypsum wallboard production
Superplasticizers or dispersants, are chemical additives that can be added to
wallboardmixtures to improve workability. In order to reduce the energy in drying wallboard, less water is added, which makes the gypsum mixture very unworkable and difficult to mix, necessitating the use of plasticizers, water reducers or dispersants.
Adding about two pounds per thousand square feet of 1/2 inch wallboard (15 g/m² of wallboard) of dispersant is usually sufficient. Some studies also show that too much of lignosulfonate dispersant could result in a set-retarding effect. Data showed that amorphous crystal formations occurred that detracted from the mechanical needle-like crystal interaction in the core, preventing a stronger core. The sugars, chelating agents in lignosulfonates such as aldonic acids and extractive compounds are mainly responsible for set retardation.
Low range water reducing dispersants are commonly manufactured from
lignosulfonates, a by-product from the paperindustry. High range superplasticizers (dispersants} have generally been manufactured from sulfonated naphthalene condensate, although new generation products based on polycarboxylic ethers are now available. Traditional lignosulfonate and naphthalenesulfonate based superplasticisers disperse the flocculated gypsum particles through a mechanism of electrostatic repulsion (see colloid). In normal plasticisers, the active substances are adsorbed on to the gypsum particles, giving them a negative charge, which leads to repulsion between particles. Lignin and naphthalene sulfonate plasticizers are organic polymers. The long molecules wrap themselves around the gypsum particles, giving them a highly negative charge so that they repel each other.
Plasticizers for plastics
Plasticizers for plastics are additive, most commonly
phthalates, that give hard plastics like PVC the desired flexibility and durability. They are often based on esters of polycarboxylic acids with linear or branched aliphatic alcohols of moderate chain length. Plasticizers work by embedding themselves between the chains of polymers, spacing them apart (increasing of the "free volume"), and thus significantly lowering the glass transitiontemperature for the plastic and making it softer. For plastics such as PVC, the more plasticiser added, the lower its "cold flex temperature" will be. This means that it will be more flexible, though its strength and hardness will decrease as a result of it. Some plasticizers evaporate and tend to concentrate in an enclosed space; the " new car smell" is caused mostly by plasticizers evaporating from the car interior.
Dicarboxylic/tricarboxylic ester-based plasticizers
Phthalate-based plasticizers are used in situations where good resistance to water and oils is required. Some common phthalate plasticizers are:
Bis(2-ethylhexyl) phthalate(DEHP), used in construction materials, and medical devices,
Diisononyl phthalate(DINP), found in garden hoses, shoes, toys, and building materials
Bis(n-butyl)phthalate(DnBP, DBP), used for cellulose plastics, food wraps, adhesives, perfumes and also in cosmetics - about a third of nail polishes, glosses, enamels and hardeners contain it, together with some shampoos, sunscreens, skin emollients, and insect repellents
Butyl benzyl phthalate(BBzP) is found in vinyl tiles, traffic cones, food conveyor belts, artificial leather and plastic foams
Diisodecyl phthalate(DIDP), used for insulation of wires and cables, car undercoating, shoes, carpets, pool liners
Di-n-octyl phthalate(DOP or DnOP), used in flooring materials, carpets, notebook covers, and high explosives, such as Semtex. Together with DEHP it was the most common plasticizers, but now is suspected of causing cancer
Diisooctyl phthalate(DIOP), all-purpose plasticizer for polyvinyl chloride, polyvinyl acetate, rubbers, cellulose plastics and polyurethane.
Di-n-hexyl phthalate, used in flooring materials, tool handles and automobile parts
Trimellitates are used in automobile interiors and other applications where resistance to high temperature is required. They have extremely low volatility.
Adipate-based plasticizers are used for low-temperature or resistance to ultravioletlight. Some examples are:
N-ethyl toluene sulfonamide(o/p ETSA), ortho and para isomers
N-(2-hydroxypropyl) benzene sulfonamide(HP BSA)
N-(n-butyl) benzene sulfonamide(BBSA-NBBS)
Triethylene glycol dihexanoate(3G6, 3GH)
Tetraethylene glycol diheptanoate(4G7)
Some other chemicals working as plasticizers are
nitrobenzene, carbon disulfideand β-naphthyl salicylate. Plasticizers, such as DEHP and DOA, were found to be carcinogens and endocrine disruptors.
Safer plasticizers with better
biodegradabilityand less biochemical effects are being developed. Some such plasticizers are:
Acetylated monoglycerides; these can be used as food additives
citrates, used in food packagings, medical products, cosmetics and children toys
Acetyl triethyl citrate(ATEC), higher boiling point and lower volatility than TEC
Acetyl tributyl citrate(ATBC), compatible with PVC and vinyl chloride copolymers
Trioctyl citrate(TOC), also used for gums and controlled release medicines
Acetyl trioctyl citrate(ATOC), also used for printing ink
Trihexyl citrate(THC), compatible with PVC, also used for controlled release medicines
Acetyl trihexyl citrate(ATHC), compatible with PVC
Butyryl trihexyl citrate(BTHC, trihexyl "o"-butyryl citrate), compatible with PVC
Trimethyl citrate(TMC), compatible with PVC
alkyl sulphonic acid phenyl ester(ASE), compatible with PVC , vinyl chloride copolymers, TPU, NBR etc.
Plasticizers for energetic materials
Energetic materialcompositions, especially solid rocket propellants and smokeless powders for guns, often employ plasticizers to improve physical properties of the propellant binder or of the overall propellant, to provide a secondary fuel, and ideally, to improve specific energy yield (e.g. specific impulse, energy yield per gram or propellant, or similar indices) of the propellant. An energetic plasticizerimproves the physical properties of an energetic materialwhile also increasing its specific energy yield. Energetic plasticizersare usually preferred to non-energetic plasticizers, especially for solid rocket propellants. Energetic plasticizers reduce the required mass of propellant, enabling a rocket vehicle to carry more payload or reach higher velocities than would otherwise be the case. However, safety or cost considerations may demand that non-energetic plasticizers be used, even in rocket propellants. The solid rocket propellantused to fuel the Space Shuttle solid rocket boosteremploys a non-energetic plasticizer/binder/secondary fuel: HTPB. HTPBis a synthetic rubber.Here are some energetic plasticizers used in rocket propellants and smokeless powders:
Nitroglycerine(NG, aka "nitro", glyceryl trinitrate)
Trimethylolethane trinitrate(TMETN, aka Metriol trinitrate, METN)
Diethylene glycol dinitrate(DEGDN, less commonly DEGN)
2,2,2-Trinitroethyl 2-nitroxyethyl ether(TNEN)Due to the secondary alcoholgroups, NG and BTTN have relatively low thermal stability. TMETN, DEGDN, BDNPF and BDNPA have relatively low energies. NG and DEGN have relatively high vapor pressure. [http://www.freepatentsonline.com/4745208.html]
* [http://www.medscape.com/viewarticle/407990_17 Medscape: Alternative Materials for Flexible PVC and DEHP]
last = Kirby
first = Glen H.
coauthors = Jennifer A. Lewis
date = 2002
title = Rheological property evolution in concentrated cement-polyelectrolyte suspensions
journal = Journal of the American Ceramic Society
accessdate = 2008-03-27
volume = 85
issue = 12
pages = 2989–2994
doi = 10.1111/j.1151-2916.2002.tb00568.x
url = http://www.blackwell-synergy.com/doi/abs/10.1111/j.1151-2916.2002.tb00568.x
doi_brokendate = 2008-07-02
last = Lewis
first = Jennifer A.
coauthors = Hiro Matsuyama, Glen Kirby, Sherry Morissette, J. Francis Young
date = 2000
title = Polyelectrolyte effects on the rheological properties of concentrated cement suspensions
journal = Journal of the American Ceramic Society
volume = 83
issue = 8
pages = 1905–1913
accessdate = 2008-03-27
doi = 10.1111/j.1151-2916.2000.tb01489.x
url = http://www.blackwell-synergy.com/doi/abs/10.1111/j.1151-2916.2000.tb01489.x
doi_brokendate = 2008-07-02
* [http://www.plasticisers.org/ Plasticisers Information Centre]
* [http://www.pslc.ws/mactest/tg.htm Glass transition]
* [http://ecb.jrc.it/DOCUMENTS/Existing-Chemicals/RISK_ASSESSMENT/SUMMARY/didpsum041.pdf DIDP] , [http://ecb.jrc.it/DOCUMENTS/Existing-Chemicals/RISK_ASSESSMENT/SUMMARY/dinpsum046.pdf DINP] , and [http://ecb.jrc.it/DOCUMENTS/Existing-Chemicals/RISK_ASSESSMENT/SUMMARY/dibutylphthalatesum003.pdf DBP] - Risk Assessment Reports by the
European Chemicals Bureau(ECB).
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Look at other dictionaries:
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