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Synthetic Resins
Synthetic resins are industrially produced resins, typically viscous substances that convert into rigid polymers by the process of curing. In order to undergo curing, resins typically contain reactive end groups, such as acrylates or epoxides. Some synthetic resins have properties similar to natural plant resins, but many do not. Synthetic resins are of several classes. Some are manufactured by esterification of organic compounds. Some are thermosetting plastics in which the term "resin" is loosely applied to the reactant(s), the product, or both. "Resin" may be applied to one of two monomers in a copolymer, the other being called a "hardener", as in epoxy resins. For thermosetting plastics that require only one monomer, the monomer compound is the "resin". For example, liquid methyl methacrylate is often called the "resin" or "casting resin" while in the liquid state, before it polymerizes and "sets". After setting, the resulting poly(methyl methacrylate) (PMMA) is often rename ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyurethane
Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic chemistry, organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane is produced from a wide range of starting materials. This chemical variety produces polyurethanes with different chemical structures leading to many List of polyurethane applications, different applications. These include rigid and flexible foams, varnishes and coatings, adhesives, Potting (electronics), electrical potting compounds, and fibers such as spandex and Polyurethane laminate, PUL. Foams are the largest application accounting for 67% of all polyurethane produced in 2016. A polyurethane is typically produced by reacting an isocyanate with a polyol. Since a polyurethane contains two types of monomers, which polymerize one after the other, they are classed as Copolymer#Alternating copolymers, alternating copolymers. Both the isocy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bis-GMA
Bis-GMA (bisphenol A-glycidyl methacrylate) is a resin commonly used in dental composite, dental sealants. and dental cement. It is the diester derived from methacrylic acid and the bisphenol A diglycidyl ether. Bearing two polymerizable groups, it is prone to form a crosslinked polymer that is used in dental restorations. For dental work, highly viscous bis-GMA is mixed with aluminosilicate particles, crushed quartz and other related acrylates; changes to component ratios lead to different physical properties in the end product. Bis-GMA was incorporated into composite dental resins in 1962 by Rafael Bowen. Until matrix development work in the early 2000s, bis-GMA and related methacrylate monomers were the only options for organic matrix composition. Safety Concerns have been raised about the potential for bis-GMA to break down into or be contaminated with the related compound bisphenol A. However, no negative health effects of bis-GMA use in dental resins have been found. Co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unsaturated Polyester Resin
Polyester resins are synthetic resins formed by the reaction of dibasic organic acids and polyhydric alcohols. Maleic anhydride is a commonly used raw material with diacid functionality in unsaturated polyester resins. Unsaturated polyester resins are used in sheet moulding compound, bulk moulding compound and the toner of laser printers. Wall panels fabricated from polyester resins reinforced with fiberglassso-called fiberglass reinforced plastic (FRP)are typically used in restaurants, kitchens, restrooms and other areas that require washable low-maintenance walls. They are also used extensively in cured-in-place pipe applications. Departments of Transportation in the USA also specify them for use as overlays on roads and bridges. In this application they are known AS Polyester Concrete Overlays (PCO). These are usually based on isophthalic acid and cut with styrene at high levelsusually up to 50%. Polyesters are also used in anchor bolt adhesives though epoxy based materials are a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solvent Impregnated Resin
Solvent impregnated resins (SIRs) are commercially available (macro)porous resins impregnated with a solvent/an extractant. In this approach, a liquid extractant is contained within the pores of (adsorption) particles. Usually, the extractant is an organic liquid. Its purpose is to extract one or more dissolved components from a surrounding aqueous environment. The basic principle combines adsorption, chromatography and liquid-liquid extraction. History The principle of Solvent Impregnated Resins was first shown in 1971 by Abraham Warshawsky. This first venture was aimed at the extraction of metals. Ever since then, SIRs have been mainly used for Extractive metallurgy, metal extraction, be it heavy metals or specifically Toxic metals, radioactive metals. Much research on SIRs has been done by J.L Cortina and e.g. N. Kabay, K. Jerabek or J. Serarols. However, lately investigations also go towards using SIRs for the separation of natural compounds, and even for separation of biotechnol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypolipidemic Agent
Lipid-lowering agents, also sometimes referred to as hypolipidemic agents, cholesterol-lowering drugs, or antihyperlipidemic agents are a diverse group of pharmaceuticals that are used to lower the level of lipids and lipoproteins such as cholesterol, in the blood (hyperlipidemia). The American Heart Association recommends the descriptor 'lipid lowering agent' be used for this class of drugs rather than the term 'hypolipidemic'. Classes The several classes of lipid lowering drugs may differ in both their impact on the cholesterol profile and adverse effects. For example, some may lower low density lipoprotein (LDL) levels more so than others, while others may preferentially increase high density lipoprotein (HDL). Clinically, the choice of an agent depends on the patient's cholesterol profilecardiovascular risk and the liver and kidney functions of the patient, evaluated against the balancing of risks and benefits of the medications. In the United States, this is guided by the ev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bile Acid Sequestrant
The bile acid sequestrants are a group of resins used to bind certain components of bile in the gastrointestinal tract. They disrupt the enterohepatic circulation of bile acids by combining with bile constituents and preventing their reabsorption from the gut. In general, they are classified as hypolipidemic agents, although they may be used for purposes other than lowering cholesterol. They are used in the treatment of chronic diarrhea due to bile acid malabsorption. Mechanism Bile acid sequestrants are polymeric compounds that serve as ion-exchange resins. Bile acid sequestrants exchange anions such as chloride ions for bile acids. By doing so, they bind bile acids and sequester them from the enterohepatic circulation. The liver then produces more bile acids to replace those that have been lost. Because the body uses cholesterol to make bile acids, this reduces the level of LDL cholesterol circulating in the blood. Bile acid sequestrants are large polymeric structures, and they ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Melamine Resin
Melamine resin or melamine formaldehyde (also shortened to melamine) is a resin with melamine rings terminated with multiple hydroxyl groups derived from formaldehyde. This thermosetting plastic material is made from melamine and formaldehyde. In its butylated form, it is dissolved in ''n''-butanol and xylene. It is then used to cross-link with alkyd, epoxy, acrylic, and polyester resins, used in surface coatings. There are many types, varying from very slow to very fast curing. Curing Melamine-formaldehyde can be cured by heating, which induces dehydration and crosslinking. The crosslinking can be carried out to a limited degree to give resins. Either the melamine-formaldehyde resins or melamine-formaldehyde "monomer" can be cured by treatment with any of several polyols. Applications Construction material The principal use of melamine resin is as the main constituent of high-pressure laminates, such as Formica and Arborite, and of laminate flooring. Melamine-resin ti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AT-10 Resin
The 3M6 ''Shmel'' (russian: 3М6 «Шмель»; en, bumblebee) is an MCLOS wire-guided Anti-tank missile of the Soviet Union. Its GRAU designation is "3M6" and its NATO reporting name is AT-1 Snapper. Too large to be manportable, it was typically deployed from specialised vehicles or helicopters. The missile was intended to supplement traditional anti-tank weapons, like the 100 mm anti-tank gun whose accuracy beyond 1,500 m is poor. The missile's accuracy in contrast remained high as far as its maximum range of 2,000 m. However, the system's bulk, slow speed and poor combat accuracy drove development of later SACLOS systems, like the AT-5 Spandrel. Development The 3M6 ''Shmel'' was based on the western ATGMs of the time, such as the Nord Aviation SS.10; however, it is considerably larger. It was developed by the Special Mortar Design Bureau (SKB Gladkostvolnoi Artillery) in Kolomna, who were also responsible for the AT-3 Sagger. Development of the missile proceeded rapi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Reaction
Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, Mechanistic Organic Photochemistry, photochemical reactions and organic redox reaction, redox reactions. In organic synthesis, organic reactions are used in the construction of new organic molecules. The production of many man-made chemicals such as drugs, plastics, food additives, fabrics depend on organic reactions. The oldest organic reactions are combustion of organic fuels and saponification of fats to make soap. Modern organic chemistry starts with the Wöhler synthesis in 1828. In the history of the Nobel Prize in Chemistry awards have been given for the invention of specific organic reactions such as the Grignard reaction in 1912, the Diels-Alder reaction in 1950, the Wittig reaction in 1979 and olefin metathesis in 2005. Classifications Organic c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catalysis
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quickly, very small amounts of catalyst often suffice; mixing, surface area, and temperature are important factors in reaction rate. Catalysts generally react with one or more reactants to form intermediates that subsequently give the final reaction product, in the process of regenerating the catalyst. Catalysis may be classified as either homogeneous, whose components are dispersed in the same phase (usually gaseous or liquid) as the reactant, or heterogeneous, whose components are not in the same phase. Enzymes and other biocatalysts are often considered as a third category. Catalysis is ubiquitous in chemical industry of all kinds. Estimates are that 90% of all commercially produced chemical products involve catalysts at some s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Water Purification
Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids, and gases from water. The goal is to produce water that is fit for specific purposes. Most water is purified and disinfected for human consumption (drinking water), but water purification may also be carried out for a variety of other purposes, including medical, pharmacological, chemical, and industrial applications. The history of water purification includes a wide variety of methods. The methods used include physical processes such as filtration, sedimentation, and distillation; biological processes such as slow sand filters or biologically active carbon; chemical processes such as flocculation and chlorination; and the use of electromagnetic radiation such as ultraviolet light. Water purification can reduce the concentration of particulate matter including suspended particles, parasites, bacteria, algae, viruses, and fungi as well as reduce the concentration of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
