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Polyphenyl Ether
Phenyl ether polymers are a class of polymers that contain a phenoxy or a thiophenoxy group as the repeating group in ether linkages. Commercial phenyl ether polymers belong to two chemical classes: polyphenyl ethers (PPEs) and polyphenylene oxides (PPOs). The phenoxy groups in the former class of polymers do not contain any substituents whereas those in the latter class contain 2 to 4 alkyl groups on the phenyl ring. The structure of an oxygen-containing PPE is provided in Figure 1 and that of a 2, 6-xylenol derived PPO is shown in Figure 2. Either class can have the oxygen atoms attached at various positions around the rings. Structure and synthesis The proper name for a phenyl ether polymer is poly(phenyl ether) or polyphenyl polyether, but the name polyphenyl ether is widely accepted. Polyphenyl ethers (PPEs) are obtained by repeated application of the Ullmann Ether Synthesis: reaction of an alkali-metal phenate with a halogenated benzene catalyzed by copper. PPE ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyphenyl Ether
Phenyl ether polymers are a class of polymers that contain a phenoxy or a thiophenoxy group as the repeating group in ether linkages. Commercial phenyl ether polymers belong to two chemical classes: polyphenyl ethers (PPEs) and polyphenylene oxides (PPOs). The phenoxy groups in the former class of polymers do not contain any substituents whereas those in the latter class contain 2 to 4 alkyl groups on the phenyl ring. The structure of an oxygen-containing PPE is provided in Figure 1 and that of a 2, 6-xylenol derived PPO is shown in Figure 2. Either class can have the oxygen atoms attached at various positions around the rings. Structure and synthesis The proper name for a phenyl ether polymer is poly(phenyl ether) or polyphenyl polyether, but the name polyphenyl ether is widely accepted. Polyphenyl ethers (PPEs) are obtained by repeated application of the Ullmann Ether Synthesis: reaction of an alkali-metal phenate with a halogenated benzene catalyzed by copper. PPE ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ionizing Radiation
Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel up to 99% of the speed of light, and the electromagnetic waves are on the high-energy portion of the electromagnetic spectrum. Gamma rays, X-rays, and the higher energy ultraviolet part of the electromagnetic spectrum are ionizing radiation, whereas the lower energy ultraviolet, visible light, nearly all types of laser light, infrared, microwaves, and radio waves are non-ionizing radiation. The boundary between ionizing and non-ionizing radiation in the ultraviolet area is not sharply defined, as different molecules and atoms ionize at different energies. The energy of ionizing radiation starts between 10 electronvolts (eV) and 33 eV. Typical ionizing subatomic particles include alpha particles, beta particles, and neutrons. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plastics
Plastics are a wide range of synthetic polymers, synthetic or semi-synthetic materials that use polymers as a main ingredient. Their Plasticity (physics), plasticity makes it possible for plastics to be Injection moulding, moulded, Extrusion, extruded or Compression molding, pressed into solid objects of various shapes. This adaptability, plus a wide range of other properties, such as being lightweight, durable, flexible, and inexpensive to produce, has led to its widespread use. Plastics typically are made through human industrial systems. Most modern plastics are derived from petrochemical, fossil fuel-based chemicals like natural gas or petroleum; however, recent industrial methods use variants made from renewable materials, such as corn or cotton derivatives. 9.2 billion tonnes of plastic are estimated to have been made between 1950 and 2017. More than half this plastic has been produced since 2004. In 2020, 400 million tonnes of plastic were produced. If global trends on pl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SABIC
Saudi Basic Industries Corporation ( ar, الشركة السعودية للصناعات الأساسية), known as SABIC ( ar, سابك), is a Saudi chemical manufacturing company. 70% of SABIC's shares are owned by Saudi Aramco. It is active in petrochemicals, chemicals, industrial polymers, fertilizers, and metals. It is the second largest public company in the Middle East and Saudi Arabia as listed in Tadawul. In 2017, SABIC was ranked fourth in the world among chemical companies by Fortune Global 500. By the end of 2018 SABIC was the world's 281st-largest corporation. In 2014, the company had sales revenues of $50.4 billion, profits of $6.7 billion and assets standing at $90.4 billion. It also has been recognized as the world's second most valuable brand in the chemicals industry by Brand Finance in 2021. History SABIC was founded in 1976 by royal decree to convert oil by-products into useful chemicals, polymers, and fertilizers. The first chairman of the company was Ghaz ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid with a distinctive, unpleasant fish-like smell. Pyridine is colorless, but older or impure samples can appear yellow, due to the formation of extended, unsaturated polymeric chains, which show significant electrical conductivity. The pyridine ring occurs in many important compounds, including agrochemicals, pharmaceuticals, and vitamins. Historically, pyridine was produced from coal tar. As of 2016, it is synthesized on the scale of about 20,000 tons per year worldwide. Properties Physical properties The molecular electric dipole moment is 2.2 debyes. Pyridine is diamagnetic and has a diamagnetic susceptibility of −48.7 × 10−6 cm3·mol−1. The standard enthalpy of formation is 100.2 kJ·mol−1 in the liquid phase ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cuprous Bromide
Copper(I) bromide is the chemical compound with the formula CuBr. This diamagnetic solid adopts a polymeric structure akin to that for zinc sulfide. The compound is widely used in the synthesis of organic compounds and as a lasing medium in copper bromide lasers. Preparation, basic properties, structure The compound is white, although samples are often colored due to the presence of copper(II) impurities. The copper(I) ion also oxidizes easily in air. It is commonly prepared by the reduction of cupric salts with sulfite in the presence of bromide.This report gives a procedure for generating CuBr: For example, the reduction of copper(II) bromide with sulfite yields copper(I) bromide and hydrogen bromide: :2 CuBr2 + H2O + → 2 CuBr + + 2 HBr CuBr is insoluble in most solvents due to its polymeric structure, which features four-coordinated, tetrahedral Cu centers interconnected by bromide ligands (ZnS structure). Upon treatment with Lewis bases, CuBr converts to mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fretting
Fretting refers to wear and sometimes corrosion damage of loaded surfaces in contact while they encounter small oscillatory movements tangential to the surface. Fretting is caused by adhesion of contact surface asperities, which are subsequently broken again by the small movement. This breaking causes wear debris to be formed. If the debris and/or surface subsequently undergo chemical reaction, i.e., mainly oxidation, the mechanism is termed fretting corrosion. Fretting degrades the surface, leading to increased surface roughness and micropits, which reduces the fatigue strength of the components. The amplitude of the relative sliding motion is often in the order of micrometers to millimeters, but can be as low as 3 nanometers. Typically fretting is encountered in shrink fits, bearing seats, bolted parts, splines, and dovetail connections. Materials Steel Fretting damage in steel can be identified by the presence of a pitted surface and fine 'red' iron oxide dust resembl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vacuum Pump
A vacuum pump is a device that draws gas molecules from a sealed volume in order to leave behind a partial vacuum. The job of a vacuum pump is to generate a relative vacuum within a capacity. The first vacuum pump was invented in 1650 by Otto von Guericke, and was preceded by the suction pump, which dates to antiquity. History Early pumps The predecessor to the vacuum pump was the suction pump. Dual-action suction pumps were found in the city of Pompeii. Arabic engineer Al-Jazari later described dual-action suction pumps as part of water-raising machines in the 13th century. He also said that a suction pump was used in siphons to discharge Greek fire. The suction pump later appeared in medieval Europe from the 15th century.Donald Routledge Hill (1996), ''A History of Engineering in Classical and Medieval Times'', Routledge, pp. 143 & 150-2Donald Routledge Hill, "Mechanical Engineering in the Medieval Near East", ''Scientific American'', May 1991, pp. 64-69 (cf. Donald Ro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffusion Pump
Diffusion pumps use a high speed jet of vapor to direct gas molecules in the pump throat down into the bottom of the pump and out the exhaust. They were the first type of high vacuum pumps operating in the regime of free molecular flow, where the movement of the gas molecules can be better understood as diffusion than by conventional fluid dynamics. Invented in 1915 by Wolfgang Gaede, he named it a ''diffusion pump'' since his design was based on the finding that gas cannot diffuse against the vapor stream, but will be carried with it to the exhaust. However, the principle of operation might be more precisely described as gas-jet pump, since diffusion plays a role also in other high vacuum pumps. In modern textbooks, the diffusion pump is categorized as a momentum transfer pump. The diffusion pump is widely used in both industrial and research applications. Most modern diffusion pumps use silicone oil or polyphenyl ethers as the working fluid. History In the late 19th century, mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perfluoropolyether
Perfluoropolyether (PFPE) is a type of liquid lubricant that has been used in the aerospace industry for over 30 years. The main properties of PFPE are being temperature resistant between and (depending on specific composites), having very low outgassing compared to other fluids (vapour pressure of ) and having a dielectric strength of around 15.7 MV/m. Perfluoropolyether consists of a polymer chain in which monomers consisting of perfluoro-alkyl groups are joined by ether linkages. The bonds between carbon and oxygen or fluorine are strong. The thermal and chemical stability of PFPE along with a vapor–liquid equilibrium of 230 °C when mixed with the right composites make it a suitable candidate for vapor phase soldering technologies. History It's been developed in early 1960s at request of USAF with a requirement to be non-reacting with liquid and gaseous oxygen (O2). Manufacture Perfluoropolyether can be synthesized from tetrafluoroethylene or hexafluoropropyl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isomerization
In chemistry, isomerization or isomerisation is the process in which a molecule, polyatomic ion or molecular fragment is transformed into an isomer with a different chemical structure. Enolization is an example of isomerization, as is tautomerization. When the isomerization occurs intramolecularly it may be called a rearrangement reaction. When the activation energy for the isomerization reaction is sufficiently small, both isomers will exist in a temperature-dependent equilibrium with each other. Many values of the standard free energy difference, \Delta G^\circ, have been calculated, with good agreement between observed and calculated data. Examples and applications Alkanes Skeletal isomerization occurs in the cracking process, used in the petrochemical industry. As well as reducing the average chain length, straight-chain hydrocarbons are converted to branched isomers in the process, as illustrated the following reaction of ''n''-butane to ''i''-butane. :\overset -> \o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isoteniscope
An Isoteniscope is a measuring device used to measure the vapor pressure of liquids. It consists of a submerged manometer Pressure measurement is the measurement of an applied force by a fluid (liquid or gas) on a surface. Pressure is typically measured in units of force per unit of surface area. Many techniques have been developed for the measurement of pressu ... and container holding the substance whose vapor pressure is being measured. The open end of the manometer is then connected to a pressure measuring device. A vacuum pump is used to adjust the pressure of the system and purify the sample. Various ASTM vapor pressure measurement standards use the isoteniscope. Dr. Bertrand of the Missouri University of Science and Technology offers an interactive animation of a lab procedure using the isoteniscope on his web page. References {{Reflist Pressure gauges ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
