In the production of hot NBR, emulsifier (soap), 2-propenenitrile (acrylonitrile), various butadiene monomers (including 1,3-butadiene, 1,2-butadiene), radical generating activators, and a catalyst are added to polymerization vessels. Within the vessel, water serves as the reaction medium. The tanks are heated to 30°C-40°C to facilitate the polymerization reaction and to promote branch formation in the polymer. Because several monomers capable of propagation the reaction are involved in the production of nitrile rubber, the composition of ...

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Nitrile rubber, Nitrile rubber - Production Process, Nitrile rubber - Environmental Concerns, Nitrile rubber - Misc

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Although formaldehyde is a gas at room temperature, it is readily soluble in water, and it is most commonly sold as a 37% solution in water called by trade names such as formalin or formol. In water, formaldehyde polymerizes, and formalin actually contains very little formaldehyde in the form of H2CO monomer. Usually, these solutions contain a few percent methanol to limit the extent of polymerization. Formaldehyde exhibits most of the general chemical properties of the aldehydes, except that is generally more ...

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Formaldehyde, Formaldehyde - Properties, Formaldehyde - Production, Formaldehyde - Uses, Formaldehyde - Health effects

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Microtubules are polymers of α- and β-tubulin dimers. The tubulin dimers polymerize end to end in protofilaments. The protofilaments then bundle in a hollow cylindrical filaments. Typically, the protofilaments arrange themselves in an imperfect helix with one turn of the helix containing 13 tubulin dimers each from a different protofilament. The image above illustrates a small section of microtubule, a few αβ dimers in length. Another important feature of microtubule structure is polarity. Tubulin polymerizes end to end with the Π...

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Microtubule, Microtubule - Structure, Microtubule - Organization within Cells, Microtubule - Nucleation and growth, Microtubule - Dynamic instability, Microtubule - Use in medicine, Microtubule - Motor proteins, Microtubule - Microtubules and theory of consciousness

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Plastic wrap was first made from PVC, which remains the most common material, but non-PVC alternatives are now being sold because of concerns about the transfer of plasticizers from PVC into food. It is also problematic to achieve full polymerization of the material, which can contain remains of vinyl chloride. PVC is still used because of its permeability to water vapor and oxygen, which makes it suitable for preserving meat. Saran ...

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Plastic wrap, Plastic wrap - Materials used, Plastic wrap - Reference

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Above 400 °C (which is quite low for a hydrocarbon), the pyrolysis of acetylene will start. The main products are the dimer vinylacetylene (C4H4) and benzene. At temperatures above 900 °C, the main product will be soot. Polymerization with Ziegler-Natta catalysts produces polyacetylene films. ...

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Acetylene, Acetylene - Preparation, Acetylene - Properties, Acetylene - Safety and handling, Acetylene - Reactions, Acetylene - Uses

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Amber is heterogeneous in composition, but consists of several resinous bodies more or less soluble in alcohol, ether and chloroform, associated with an insoluble bituminous substance. Amber is a macromolecule by free radical polymerization of several precursors in the labdane family, communic acid, cummunol and biformene [1]. Labdanes are tetrameric terpenes (C20H32) and trienes which means that the organic skeleton has three alkene grou ...

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Amber, Amber - History, Amber - Composition, Amber - Amber in Geology, Amber - Amber inclusions, Amber - Locations and utilization, Amber - Varieties

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The smallest fullerene in which no two pentagons share an edge (which is destabilizing — see pentalene) is C60 (buckminsterfullerene), and this is also the most common. The structure of C60 is that of a truncated icosahedron, which resembles a round soccer ball of the type made of hexagons and pentagons, with a carbon atom at the corners of each hexagon and a bond along each edge. A polymerized single-walled nanotubule (P-SWNT) is a substance composed of polymerized fullerenes in which carbon atoms from on ...

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Fullerene, Fullerene - Naming, Fullerene - Buckminsterfullerene, Fullerene - Prediction and discovery, Fullerene - Properties, Fullerene - Possible dangers, Fullerene - Fullerene extract mixture C60/C70 solubility, Fullerene - Diffraction of fullerene, Fullerene - Notes, Fullerene - Mathematics of Fullerenes, Fullerene - Media

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The smallest fullerene in which no two pentagons share an edge (which is destabilizing — see pentalene) is C60 (buckminsterfullerene), and this is also the most common. The structure of C60 is that of a truncated icosahedron, which resembles a round soccer ball of the type made of hexagons and pentagons, with a carbon atom at the corners of each hexagon and a bond along each edge. A polymerized single-walled nanotubule (P-SWNT) is a substance composed of polymerized fullerenes in which carbon atoms from on ...

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Fullerene, Fullerene - Naming, Fullerene - Buckminsterfullerene, Fullerene - Prediction and discovery, Fullerene - Properties, Fullerene - Possible dangers, Fullerene - Fullerene extract mixture C60/C70 solubility, Fullerene - Diffraction of fullerene, Fullerene - Notes, Fullerene - Mathematics of fullerenes, Fullerene - Media

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Monosaccharides are carbohydrates in the form of simple sugars. Disaccharides are formed from two monosaccharides joined together. Monosaccharides and disaccharides are sweet, water soluble, and crystalline. Examples of monosaccharides include the hexoses (glucose, fructose, and galactose) and pentoses (ribose, deoxyribose). Examples of disaccharides include sucrose, maltose, and lactose. Polysaccharides are polymerized monosaccharides, complex unsweet carbohydrates. They are, generally, large and often have a complex, branched ...

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Biomolecule, Biomolecule - Types of biomolecules, Biomolecule - Nucleosides and nucleotides, Biomolecule - Saccharides, Biomolecule - Lipids, Biomolecule - Hormones, Biomolecule - Amino acids, Biomolecule - Protein structure, Biomolecule - Metalloproteins, Biomolecule - Vitamins

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Organic peroxides find numerous uses in various industries, as accelerators, activators, catalysts, cross-linking agents, curing and vulcanization agents, hardeners, initiators and promoters. Methyl ethyl ketone peroxide, benzoyl peroxide and to much smaller degree acetone peroxide are used as radical initiators for radical polymerization of some resins, eg. polyester and silicone, often encountered when making fiberglass. Methyl ethyl ketone peroxide can oxidize acetone to acetone peroxide, so mixing it with acetone is discouraged. P ...

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Organic peroxide, Organic peroxide - Occurrence and use, Organic peroxide - Safety

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Their bonding nature vastly differs from element to element and changes according to external criteria such as temperature, pressure and electric current. Titanium and coinage metal hydrides are polymeric. Other transitional metal hydrides are interstitial in nature. In these, molecules of hydrogen dissociate and hydrogen atoms settle in the octahedral or tetrahedral holes in the metal lattice called the interstitial sites. Interstitial hydrides often have non-stoichiometric nature. Hydrogen atoms trapped in the lattice can migrate th ...

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Hydride, Hydride - Ionic hydrides, Hydride - Covalent hydrides, Hydride - Interstitial hydrides of the Transitional metals, Hydride - Usage

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Kevlar is synthesized from the monomers 1,4-phenyl-diamine (para-phenylenediamine) and terephthaloyl chloride. The result is a polymeric aromatic amide (aramid) with alternating benzene rings and amide groups. When they are produced, these polymer strands are aligned randomly. To make Kevlar, they are dissolved and spun, causing the polymer chains to orient in the direction of the fiber. Kevlar has a high price at least partly because of the difficulties caused by the use of concentrated sulfuric acid in its manufacture. These harsh conditions are needed to keep the highly insoluble polymer in solution during ...

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Kevlar, Kevlar - Properties, Kevlar - Production

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Cucurbiturils are aminals and synthesized from urea 1 and a diketone (e.g., glyoxal 2) via a nucleophilic addition to give the intermediate glycoluril 3. This intermediate is condensed with formaldehyde to give hexamer cucurbit[6]uril above 110 degrees celcius. Ordinarily multifunctional monomers such as 5 would undergo a step-growth polymerization that would give a distrubuation of products, but due to favorable strain and an abundance of hydrogen bonding the hexamer is the only reaction product isolated after precipitation.^{See also:}

Cucurbituril, Cucurbituril - Synthesis, Cucurbituril - Host guest chemistry, Cucurbituril - Applications, Cucurbituril - Nomenclature, Cucurbituril - Related compounds, Cucurbituril - Systematic name

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Plasmin is produced in an inactive form, plasminogen, in the liver. Although plasminogen cannot cleave fibrin, it still has an affinity for it, and is incorporated into the clot when it is formed. Plasminogen contains secondary structure motifs known as kringles, which bind specifically to lysine and arginine residues on fibrin(ogen). When converted from plasminogen into plasmin it functions as a serine protease, cutting specifically C-terminal to these lys and arg residues. Fibrin monomers, when polymerized, form protofibrils. These ...

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Fibrinolysis, Fibrinolysis - Physiology, Fibrinolysis - Measurement, Fibrinolysis - Role in disease, Fibrinolysis - Pharmacology, Fibrinolysis - Reference, Fibrinolysis - External link

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In 1863, a French chemist isolated a previously unknown hydrocarbon from the pyrolysis of amyl alcohol.[N] This hydrocarbon was identified as butadiene in 1886, after Henry Edward Armstrong isolated it from among the pyrolysis products of petroleum.[N] In 1910, the Russian chemist Sergei Lebedev polymerized butadiene, and obtained a material with rubber-like properties. This polymer was, however, too soft to replace natural rubber in ...

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13-Butadiene, 13-Butadiene - History, 13-Butadiene - Production, 13-Butadiene - From ethanol, 13-Butadiene - Uses, 13-Butadiene - Safety

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Most butadiene is polymerized to produce synthetic rubber. While polybutadiene itself is a very soft, almost liquid material, polymers prepared from mixtures of butadiene with styrene or acrylonitrile, such as ABS, are both tough and elastic. Styrene-butadiene rubber is the material most commonly used for the production of automobile tires. Smaller amounts of butadiene are used to make nylon via the intermediate adiponitrile, other synthetic rubber materials such as ch ...

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13-Butadiene, 13-Butadiene - History, 13-Butadiene - Production, 13-Butadiene - From ethanol, 13-Butadiene - Uses, 13-Butadiene - Safety

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The individual subunits of actin are known as globular actin (G-actin), while the filamentous polymer composed of G-actin subunits (a microfilament), is called F-actin. The microfilaments are the thinnest component of the cytoskeleton, measuring only 7 nm in diameter. Much like the microtubules, actin filaments are polar, with the plus (+) end elongating approximately 10 times faster than the minus (-) end. (Known as the treadmill effect). The process of actin polymerization, nucleation, starts with the association of three G-actin monomers ...

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Actin, Actin - Microfilaments assembly, Actin - Organization, Actin - Bundles, Actin - Networks, Actin - Genetics, Actin - History

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Biofilms are usually found on solid substrates submerged in or exposed to some aqueous solution, although they can form as floating mats on liquid surfaces. Given sufficient resources for growth, a biofilm will quickly grow to be macroscopic. Biofilms usually consist of many species of bacteria and archaea, each performing specialized metabolic functions. However, some organisms will form monospecies films under certain conditions. The biofilm is held together and protected by a matrix of excreted polymeric compounds. This matrix protects th ...

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Biofilm, Biofilm - Formation, Biofilm - Properties, Biofilm - Examples

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Many such problems can be solved by using a more elaborate monomer recycling process, in which a condensation polymer essentially undergoes the inverse of the polymerization reaction used to manufacture it. This yields the same mix of chemicals that formed the original polymer, which can be purified and used to synthesize new polymer chains of the same type. Du Pont opened a pilot plant of this type in Cape Fear to recycle PET by a process of me ...

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Plastic recycling, Plastic recycling - Obstacles, Plastic recycling - Alternative processes

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Rheology has important applications in engineering, geophysics and physiology. In particular, hemorheology, the study of blood flow, has an enormous medical significance. In geology, solid Earth materials that exhibit viscous flow over long time scales are known as rheids. In engineering, rheology has had its predominant application in the development and use of polymeric materials (plasticity theory has been similarly important for the design of metal forming processes, but in the engineering community is often not cons ...

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Rheology, Rheology - Terminology, Rheology - Scope, Rheology - Applications, Rheology - Elasticity viscosity solid- and liquid-like behaviour and plasticity

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MDI is an isocyanate compound. It is highly reactive, rapidly hydrolysed to form 4,4'-methylene dianiline (MDA), which with additional MDI reacts ot insoluble urea derivatives. Other MDI isomers include 2,2'-MDI and 2,4'-MDI, but these have no commodity size. Mixtures of all MDI monomers (often mainly 4,4'-MDI with minor amounts of 2,4-MDI) are known as Polymeric MDI. ...

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44'-MDI, 44'-MDI - History, 44'-MDI - Chemistry, 44'-MDI - Production, 44'-MDI - Uses, 44'-MDI - Safety

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