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Alkenylsuccinic Anhydrides
Alkenyl succinic anhydrides (ASA) are modified five-membered succinic anhydrides bearing a branched iso-alkenyl chain (C14 to C22). They are colorless, and usually viscous liquids. They are widely used, especially in surface sizing of paper, paperboard, and cardboard, as well as in the hydrophobicization of cellulose fibers. Products treated with it show reduced penetration of aqueous media, such as inks or drinks (like milk or fruit juices). In terms of their mode of action, the anhydride is proposed to react with the hydroxyl groups on the cellulose, forming an ester. The alkenyl side-chain modifies the surface properties of the paper product. The application is similar to that for alkyl ketene dimers. In the United States alkenylsuccinic anhydrides are the preferred paper sizing agents, whereas in Europe, alkyl ketene dimers (AKDs) predominate. History The reaction of maleic anhydride (MAN) with aliphatic monounsaturated ''n''- and ''iso''-alkenes was described as early as 19 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ASA Struktur
ASA as an abbreviation or initialism may refer to: Biology and medicine * Accessible surface area of a biomolecule, accessible to a solvent * Acetylsalicylic acid, aspirin * Advanced surface ablation, refractive eye surgery * Anterior spinal artery, the blood vessel which supplies the anterior portion of the spinal cord * Antisperm antibodies, antibodies against sperm antigens * Argininosuccinic aciduria, a disorder of the urea cycle * ASA physical status classification system, rating of patients undergoing anesthesia Education and research * African Studies Association of the United Kingdom * African Studies Association * Alandica Shipping Academy, Åland Islands, Finland * Albany Students' Association, at Massey University, Auckland, New Zealand * Alexander-Smith Academy, in Houston, Texas * Alpha Sigma Alpha, U.S. national sorority * American Society for Aesthetics, philosophical organization * American Student Assistance, national non-profit organization * Amer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polycation
Polyelectrolytes are polymers whose repeating units bear an electrolyte group. Polycations and polyanions are polyelectrolytes. These groups dissociate in aqueous solutions (water), making the polymers charged. Polyelectrolyte properties are thus similar to both electrolytes ( salts) and polymers (high molecular weight compounds) and are sometimes called polysalts. Like salts, their solutions are electrically conductive. Like polymers, their solutions are often viscous. Charged molecular chains, commonly present in soft matter systems, play a fundamental role in determining structure, stability and the interactions of various molecular assemblies. Theoretical approaches to describing their statistical properties differ profoundly from those of their electrically neutral counterparts, while technological and industrial fields exploit their unique properties. Many biological molecules are polyelectrolytes. For instance, polypeptides, glycosaminoglycans, and DNA are polyelect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isobutene
Isobutylene (or 2-methylpropene) is a hydrocarbon with the chemical formula . It is a four-carbon branched alkene (olefin), one of the four isomers of butylene. It is a colorless flammable gas, and is of considerable industrial value. Production Polymer and chemical grade isobutylene is typically obtained by dehydrating tertiary butyl alcohol (TBA) or catalytic dehydrogenation of isobutane (Catofin or similar processes).. Gasoline additives methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE), respectively, are produced by reacting methanol or ethanol with isobutylene contained in butene streams from olefin steam crackers or refineries, or with isobutylene from dehydrated TBA. Isobutylene is not isolated from the olefin or refinery butene stream before the reaction, as separating the ethers from the remaining butenes is simpler. Isobutylene can also be produced in high purities by "back-cracking" MTBE or ETBE at high temperatures and then separating the isobutylene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aluminum Trichloride
Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms hexahydrate with the formula , containing six water molecules of hydration. Both are colourless crystals, but samples are often contaminated with iron(III) chloride, giving a yellow color. The anhydrous material is important commercially. It has a low melting and boiling point. It is mainly produced and consumed in the production of aluminium metal, but large amounts are also used in other areas of the chemical industry. The compound is often cited as a Lewis acid. It is an example of an inorganic compound that reversibly changes from a polymer to a monomer at mild temperature. Structure Anhydrous adopts three structures, depending on the temperature and the state (solid, liquid, gas). Solid has a sheet-like layered structure with cubic close-packed chloride ions. In this framework, the Al centres exhibit octahedral coordination geometry. In contrast, has a more ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Raffinate
In chemical separation terminology, the raffinate (from French ''raffiner'', to refine) is a product which has had a component or components removed. The product having the removed materials is referred to as the extract. For example, in solvent extraction, the raffinate is the liquid stream which remains after solutes from the original liquid are removed through contact with an immiscible liquid. In metallurgy, raffinating refers to a process in which impurities are removed from liquid material. In pressure swing adsorption the raffinate refers to the gas which is not adsorbed during the high pressure stage. The species which is desorbed from the adsorbent at low pressure may be called the "extract" product. Types Raffinate-1 or C4R1 In naphtha cracking process, C4R1 refers to C4 residual obtained after separation of 1,3-butadiene from C4 raffinate stream and which, mainly consists of isobutylene 40~50 wt% and ''cis''- or ''trans''-2-butene 30~35 wt%. Normally C4R1 is a side pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dispersant
A dispersant or a dispersing agent is a substance, typically a surfactant, that is added to a suspension of solid or liquid particles in a liquid (such as a colloid or emulsion) to improve the separation of the particles and to prevent their settling or clumping. Dispersants are widely used to stabilize various industrial and artisanal products, such as paints, ferrofluids, and salad dressings. The plasticizers or superplasticizers, used to improve the workability of pastes like concrete and clay, are typically dispersants. The concept also largely overlaps with that of detergent, used to bring oily contamination into water suspension, and of emulsifier, used to create homogeneous mixtures of immiscible liquids like water and oil. Natural suspensions like milk and latex contain substances that act as dispersants. Applications Automotive Automotive engine oils contain both detergents and dispersants. Metallic-based detergents prevent the accumulation of varnish like deposits on t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ethyleneamines
Ethyleneamines are a class of amine compounds containing ethylene (-CH2CH2-) linkages between amine groups. These compounds are generally colorless, low-viscosity liquids with a fishy amine odor. They are primarily used as building block chemicals and in epoxy resin curing agent chemistry. Production There are two main routes for the production of ethyleneamines, the reaction between ethylene dichloride and ammonia, and the reductive amination of monethanolamine. World capacity of ethyleneamines for the year 2001 was estimated to be 385,000 tonnes/year, with the majority comprising the ethylene dichloride route. In the ethylene dichloride route, the initial product of this reaction is ethylenediamine. In the presence of excess ethylene dichloride, the initial ethyleneamine is extended by one ethylene unit. The terminal alkyl chloride reacts with ammonia to give the amine, and the polyamine chain can be extended further in this fashion. Addition of a polyamine to the initial react ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyisobutylene
Polyisobutene (polyisobutylene) is a class of organic polymers prepared by polymerization of isobutene. The polymers often have the formula Me3C H2CMe2sub>nX (Me = CH3, X = H, F). They are typically colorless gummy solids. Polymerization is typically initiated with a strong Brønsted or Lewis acid. The molecular weight (MW) of the resulting polymer determines the applications. Low MW polyisobutene, a mixture of oligomers with Mns of about 500, is used as plasticizers. Medium and high MW polyisobutenes, with Mn ≥ 20,000, are components of commercial adhesives.{{cite encyclopedia , author1=Kenneth S. Whiteley , author2=T. Geoffrey Heggs , author3=Hartmut Koch , author4=Ralph L. Mawer , author5=Wolfgang Immel , title=Polyolefins , encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry , year=2005 , publisher=Wiley-VCH , place=Weinheim , doi=10.1002/14356007.a21_487 See also *Butyl rubber *Polybutene Polybutene is an organic polymer made from a mixture of 1-butene, 2-bu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shear Stress
Shear stress, often denoted by (Greek: tau), is the component of stress coplanar with a material cross section. It arises from the shear force, the component of force vector parallel to the material cross section. ''Normal stress'', on the other hand, arises from the force vector component perpendicular to the material cross section on which it acts. General shear stress The formula to calculate average shear stress is force per unit area.: : \tau = , where: : = the shear stress; : = the force applied; : = the cross-sectional area of material with area parallel to the applied force vector. Other forms Wall shear stress Wall shear stress expresses the retarding force (per unit area) from a wall in the layers of a fluid flowing next to the wall. It is defined as: \tau_w:=\mu\left(\frac\right)_ Where \mu is the dynamic viscosity, u the flow velocity and y the distance from the wall. It is used, for example, in the description of arterial blood flow in which case which ther ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyacrylamide
Polyacrylamide (abbreviated as PAM) is a polymer with the formula (-CH2CHCONH2-). It has a linear-chain structure. PAM is highly water-absorbent, forming a soft gel when hydrated. In 2008, an estimated 750,000,000 kg were produced, mainly for water treatment and the paper and mineral industries. Physicochemical properties Polyacrylamide is a polyolefin. It can be viewed as polyethylene with amide substituents on alternating carbons. Unlike various nylons, polyacrylamide is not a polyamide because the amide groups are not in the polymer backbone. Owing to the presence of the amide (CONH2) groups, alternating carbon atoms in the backbone are stereogenic (colloquially: chiral). For this reason, polyacrylamide exists in atactic, syndiotactic, and isotactic forms, although this aspect is rarely discussed. The polymerization is initiated with radicals and is assumed to be stereorandom. Copolymers and modified polymers Linear polyacrylamide is a water-soluble polymer. Other p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
