To use all functions of this page, please activate cookies in your browser.
With an accout for my.chemeurope.com you can always see everything at a glance – and you can configure your own website and individual newsletter.
- My watch list
- My saved searches
- My saved topics
- My newsletter
Plasticizers for wallboard increases fluidity of the mix, allowing lower use of water and thus reducing energy to dry the board.
The plasticizers for plastics soften the final product increasing its flexibility.
Additional recommended knowledge
Plasticizers for concrete production
Superplasticizers or High Range Water Reducers or Dispersants, are chemical admixtures that can be added to concrete mixtures 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 ash is added to concrete to improve strength. This method of mix proportioning is especially popular when producing high strength concrete and fiber reinforced concrete.
Adding 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 segregation of 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 paper industry. High Range Superplasticizers have generally been manufactured from sulfonated naphthalene condensate (produced in the US by GEO Specialty Chemicals, Inc.) or sulfonated melamine formaldehyde, although new generation products based on polycarboxylic ethers are now available. Traditional lignosulfonate based plasticisers, naphthalene and melamine sulfonate 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, naphthalene and melamine sulfonate 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 blood as a superplasticizer for their concrete mixes.
Plasticisers can be obtained by your 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 wallboard mixtures 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 ~2 pounds/MSF (Thousand Square Feet of 1/2 inch wallboard) (14.7g/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.
Dispersants are commonly manufactured from lignosulfonates, a by-product from the paper industry. High Range Superplasticizers have generally been manufactured from sulfonated naphthalene condensate (produced in the US by GEO Specialty Chemicals, Inc.), although new generation products based on polycarboxylic ethers are now available. Traditional lignosulfonate and naphthalene sulfonate 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 cement 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 transition temperature 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
Safer plasticizers with better biodegradability and less biochemical effects are being developed. Some such plasticizers are:
Plasticizers for energetic materials
Due to the secondary alcohol groups, NG and BTTN have relatively low thermal stability. METN, DEGN, BDNPF and BDNPA have relatively low energies. NG and DEGN have relatively high vapor pressure. 
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Plasticizer". A list of authors is available in Wikipedia.|