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Cyanate Ester
In chemistry, cyanate esters are chemical substances in which the hydrogen atom of the phenolic OH group is substituted by a cyanide group (). The resulting product with a cyanate group is termed a cyanate ester. Cyanate esters based on a bisphenol or novolac derivative are used in the production of resins. Use in resins Cyanate esters can be cured and postcured by heating, either alone at elevated temperatures or at lower temperatures in presence of a suitable catalyst. The most common catalysts are transition metal complexes of cobalt, copper, manganese and zinc. The result is a thermoset material with a very high glass-transition temperature (Tg) of up to 400 °C, and a very low dielectric constant, providing excellent long term thermal stability at elevated end use temperatures, very good fire, smoke and toxicity performance and specific suitability for printed circuit boards installed in critical electrical devices. This is also due to its low moisture uptake. This p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spaceplane
A spaceplane is a vehicle that can fly and glide like an aircraft in Earth's atmosphere and maneuver like a spacecraft in outer space. To do so, spaceplanes must incorporate features of both aircraft and spacecraft. Orbital spaceplanes tend to be more similar to conventional spacecraft, while sub-orbital spaceplanes tend to be more similar to fixed-wing aircraft. All spaceplanes to date have been rocket-powered but then landed as unpowered gliders. Four types of spaceplanes have successfully launched to orbit, reentered Earth's atmosphere, and landed: the U.S. Space Shuttle, Russian Buran, U.S. X-37, and the Chinese CSSHQ. Another, Dream Chaser, is under development in the U.S. As of 2019 all past, current, and planned orbital vehicles launch vertically on a separate rocket. Orbital spaceflight takes place at high velocities, with orbital kinetic energies typically at least 50 times greater than suborbital trajectories. Consequently, heavy heat shielding is required ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyanates
Cyanate is an anion with the structural formula , usually written . It also refers to any salt containing it, such as ammonium cyanate. It is an isomer of the much less stable fulminate anion .William R. Martin and David W. Ball (2019): "Small organic fulminates as high energy materials. Fulminates of acetylene, ethylene, and allene". ''Journal of Energetic Materials'', volume 31, issue 7, pages 70-79. A cyanate ester is an organic compound containing the cyanate group. The cyanate ion is an ambidentate ligand, forming complexes with a metal ion in which either the nitrogen or oxygen atom may be the electron-pair donor. It can also act as a bridging ligand. Cyanate ion The three atoms in a cyanate ion lie on a straight line, giving the ion a linear structure. The electronic structure is described most simply as : :Ö̤−C≡N: with a single C−O bond and a triple C≡N bond. The infrared spectrum of a cyanate salt has a band at ca. 2096 cm−1; such a high frequen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BT-Epoxy
BT-Epoxy (where BT stands for bismaleimide triazine, its chemical components) is one of a number of thermoset resins used in printed circuit boards (PCBs). It is a mixture of epoxy resin, a common raw material for PCBs and BT resins. BT stands for Bismaleimide-Triazine resin. This is in turn a mixture of bismaleimide, which is also used as a raw material for PCBs and cyanate ester. Three cyano groups of the cyanate ester are trimerized to a triazine ring structure, hence the T in the name. In presence of a bismaleimide, the double bond of the maleimide group can copolymerize with the cyano groups to heterocyclic 6-membered aromatic ring structures with two nitrogen atoms (pyrimidines). The cure reaction occurs at temperatures up to 250 degrees C, and is catalyzed by strongly basic molecules like Dabco (diazabicyclooctane) and 4-DMAP (4-dimethylaminopyridin). Products with very high glass transition temperatures (Tg)- up to 300 degrees C - and very low dielectric constant can be o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bismaleimide
Maleimide is a chemical compound with the formula H2C2(CO)2NH (see diagram). This unsaturated imide is an important building block in organic synthesis. The name is a contraction of maleic acid and imide, the -C(O)NHC(O)- functional group. Maleimides also describes a ''class'' of derivatives of the parent maleimide where the N''H'' group is replaced with alkyl or aryl groups such as a methyl or phenyl, respectively. The substituent can also be a small molecule (such as biotin, a fluorescent dye, an oligosaccharide, or a nucleic acid), a reactive group, or a synthetic polymer such as polyethylene glycol. Human hemoglobin chemically modified with maleimide-polyethylene glycol is a blood substitute called MP4. Organic chemistry Maleimide and its derivatives are prepared from maleic anhydride by treatment with amines followed by dehydration. A special feature of the reactivity of maleimides is their susceptibility to additions across the double bond either by Michael additions or vi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allyl
In organic chemistry, an allyl group is a substituent with the structural formula , where R is the rest of the molecule. It consists of a methylene bridge () attached to a vinyl group (). The name is derived from the scientific name for garlic, . In 1844, Theodor Wertheim isolated an allyl derivative from garlic oil and named it "". The term allyl applies to many compounds related to , some of which are of practical or of everyday importance, for example, allyl chloride. Allylation is any chemical reaction that adds an allyl group to a substrate. Nomenclature A site adjacent to the unsaturated carbon atom is called the allylic position or allylic site. A group attached at this site is sometimes described as allylic. Thus, "has an allylic hydroxyl group". Allylic C−H bonds are about 15% weaker than the C−H bonds in ordinary sp3 carbon centers and are thus more reactive. Benzylic and allylic are related in terms of structure, bond strength, and reactivity. Other re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bisphenol E
The bisphenols () are a group of chemical compounds related to diphenylmethane. Most are based on two hydroxyphenyl functional groups linked by a methylene bridge. Exceptions include bisphenol S, P, and M. "Bisphenol" is a common name; the letter following denotes the variant, which depends on the additional substituents. Bisphenol A is the most popular representative of the group, often simply called "bisphenol".. List Health effects Bisphenols A (BPA), F (BPF) and S (BPS) have been shown to be endocrine disruptors. Due to its high production volumes, BPA has been characterised as a "pseudo-persistent" chemical, leading to its spreading and potential accumulation in a variety of environmental matrices, even though it has a fairly short half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bisphenol F
Bisphenol F (BPF; 4,4′-dihydroxydiphenylmethane) is an organic compound with the chemical formula . It is structurally related to bisphenol A (BPA), a popular precursor for forming plastics, as both belong to the category of molecules known as bisphenols, which feature two phenol groups connected via a linking group. In BPF, the two aromatic rings are linked by a methylene connecting group. In response to concern about the health effects of BPA, BPF is increasingly used as a substitute for BPA. Uses BPF is used in the manufacture of plastics and epoxy resins. It is used in the production of tank and pipe linings, industrial flooring, road and bridge deck toppings, structural adhesives, grouts, coatings and electrical varnishes. BPF is also utilized in liners, lacquers, adhesives, plastics, and the coating of drinks and food cans. BPF is found in dental materials, such as restorative materials, liners, adhesives, oral prosthetic devices and tissue substitutes. Biological effec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bisphenol A
Bisphenol A (BPA) is a chemical compound primarily used in the manufacturing of various plastics. It is a colourless solid which is soluble in most common organic solvents, but has very poor solubility in water. BPA is produced on an industrial scale by the condensation of phenol and acetone, and has a global production scale which is expected to reach 10 million tonnes in 2022. BPA's largest single application is as a co-monomer in the production of polycarbonates, which accounts for 65–70% of all BPA production. The manufacturing of epoxy resins and vinyl ester resins account for 25–30% of BPA use. The remaining 5% is used as a major component of several high-performance plastics, and as a minor additive in PVC, polyurethane, thermal paper, and several other materials. It is not a plasticizer, although it is often wrongly labelled as such. The health effects of BPA have been the subject of prolonged public and scientific debate. BPA is a xenoestrogen, exhibiting hormone ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Substituent
A substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. (In organic chemistry and biochemistry, the terms ''substituent'' and ''functional group'', as well as ''side chain'' and '' pendant group'', are used almost interchangeably to describe those branches from the parent structure, though certain distinctions are made in polymer chemistry. In polymers, side chains extend from the backbone structure. In proteins, side chains are attached to the alpha carbon atoms of the amino acid backbone.) The suffix ''-yl'' is used when naming organic compounds that contain a single bond replacing one hydrogen; ''-ylidene'' and ''-ylidyne'' are used with double bonds and triple bonds, respectively. In addition, when naming hydrocarbons that contain a substituent, positional numbers are used to indicate which carbon atom the substituent attaches to when such information is needed to distinguish between isomers. Su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermoset Polymer Matrix
A thermoset polymer matrix is a synthetic polymer reinforcement where polymers act as binder or matrix to secure in place incorporated particulates, fibres or other reinforcements. They were first developed for structural applications, such as glass-reinforced plastic radar domes on aircraft and graphite-epoxy payload bay doors on the Space Shuttle. They were first used after World War II, and continuing research has led to an increased range of thermoset resins, polymers or plastics, as well as engineering grade thermoplastics. They were all developed for use in the manufacture of polymer composites with enhanced and longer-term service capabilities. Thermoset polymer matrix technologies also find use in a wide diversity of non-structural industrial applications. The foremost types of thermosetting polymers used in structural composites are benzoxazine resins, bis-maleimide resins (BMI), cyanate ester resins, epoxy (epoxide) resins, phenolic (PF) resins, unsaturated polyester ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymer Network
In polymer chemistry, branching is the regular or irregular attachment of side chains to a polymer's backbone chain. It occurs by the replacement of a substituent (e.g. a hydrogen atom) on a monomer subunit by another covalently-bonded chain of that polymer; or, in the case of a graft copolymer, by a chain of another type. Branched polymers have more compact and symmetrical molecular conformations, and exhibit intra-heterogeneous dynamical behavior with respect to the unbranched polymers. In crosslinking rubber by vulcanization, short sulfur branches link polyisoprene chains (or a synthetic variant) into a multiple-branched thermosetting elastomer. Rubber can also be so completely vulcanized that it becomes a rigid solid, so hard it can be used as the bit in a smoking pipe. Polycarbonate chains can be crosslinked to form the hardest, most impact-resistant thermosetting plastic, used in safety glasses. Branching may result from the formation of carbon-carbon or various ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
