PTFE or Telfron is a common commercial organic fluoropolymer which is obtained by the polymerization of tetrafluoroethylene. It was first synthesized by Roy Plunkett accidentally in New Jersey in 1938 (Plunkett, R. J., 1987). It gradually becomes as an important industrial material for its extraordinary properties of high corrosion resistance, good electrical insulation, good heat insulation and low frictional coefficient. Due to those properties it is widely used as seals in chemical processing sector, and tubing or piping for laboratory uses. The low frictional coefficient makes it as a good lubricant as well.
Property of Tetrafluoroethlyene
The PTFE is polymerised from the monomer TFE. The TFE is made up by 2 carbon atoms and 4 fluorine atoms. The atomic orbitals of the two carbon atoms undergo sp2 hybridization individually with the 2 fluorine atoms and overlap with each other to give out a planar structure. As fluorine is a very electronegative element, the TFE has very poor solubility in most solvent. The carbon-fluorine bonds are very stable in the compound, relatively, the pi bonding in the carbon-carbon double bond is weaker and more reactive. The high polarity presenting in the structure also contributes to the value of enthalpy change of polymerization of TFE is 41.12kcal per mole which is very exothermic (Gangal, S. V., 1989).
Principle of Polymerization
In general, the free radical polymerization is favored by TFE which can be divided into 3 steps, namely, initiation, propagation and termination.
1. Initiation:
The common free radical initiator is ammonium persulfate and disuccinic acid peroxide. (F.A. Bovey and F.H Winslow, 1979)
The free radicals are formed due to the deco...
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...tember 1952, http://www.freepatentsonline.com/2612484.html
George, Odian. Principles of Polymerization. McGraw Publishing, Canada, 1981, pp319-317 pp194-201
Kapeliouchko, Valery (Alessandria, IT), Marchese, Enrico (Asti, IT), “Fine powders of polytetrafluoroethylene”, U.S. Patent 6479591, November 2002, http://www.freepatentsonline.com/6479591.html
Morgan, Richard A. (Vienna, WV, US), “Directly polymerized low molecular weight granular polytetrafluoroethylene”, U.S. Patent 7176265, February 2007 , http://www.freepatentsonline.com/7176265.html
Plunkett, R. J., “The History of Polytetrafluoroethylene: Discovery and Development,” in: High
Performance Polymers: Their Origin and Development, Proceed. Symp. Hist. High Perf. Polymers at the ACS Meeting in New York, April 1986, (R. B. Seymour and G. S. Kirshenbaum, eds.), Elsevier, New York, 1987.
The gaseous free radical nitric oxide is an abundant intracellular messenger molecule that plays a central role in maintenance of health, and is heavily involved in signal transduction in various cells of the body [1]. This molecule acts as a mediator in the regulation of cardiac function as well as having an important role in regulating contractility of the heart and maintenance of vascular tone in the cardiovascular system. As one of the most significant individuals in our discovery of nitric oxide, Dr. Robert Furchgott pioneered our understanding of this molecule through his experiments on the vasorelaxant properties of acetylcholine and the subsequent proposal of the presence of the endothelium derived relaxing factor, which was later identified to be nitric oxide [7]. Given the observation that cardiovascular disorders are the number one cause of death in many nations around the world, research into the vasorelaxant properties seems particularly relevant in order to help combat rising rates of vascular hypertension and high blood pressure. In this paper, the properties of nitric oxide are discussed largely with respect to the cardiovascular system. This paper focuses on the synthesis and characteristics of nitric oxide, the mechanisms of action by which nitric oxide works and the regulation of nitric oxide in the body, and finally a short summary of Robert Furchgott’s contributions to the discovery of nitric oxide and its properties.
After an organism absorbs sulforaphane, it begins to help the organism's body in a number of ways. This molecule is an antioxidant, has anti-aging properties, detoxifies the human body, and most notably, is used in the treatment of cancer. In a UCLA clinical trial, doctors found that due to the work of sulforaphane and Phase II enzyme RNA, cellular oxidative stress went through major shutdown; this in turn lead to the disarmament of asthma. "Several studies have analyzed the biological and molecular mechanisms of the anti-cancer activity of synthetic R,S-sulforaphane, which is thought to be a result of its antioxidant properties and its ability to inhibit histone deacetylase enzymes" (Marc A. Riedl, Andrew Saxon, and David Diaz-Sanchez 2011, April 6). Moreover, it has been concluded that sulforaphane can help fight aging by stopping the oxidation of free radicals. Although free radicals will always be absorbed, sulforaphane is one known molecule that can deplete the amount present in humans. Sulforaphane
The rattling commencement of plastic was appointed by Aleksander Parkes He presented a material called Parkesine ,which was both named after him and an non- synthetic material derived from cellulose ,which when heated could be molded and wrought, and after cooling the substance sustain the shape it was primitively wrought into. As time advanced plastic had become more in demand and is now one of the most common materials of our time. In terms of quantity us humans are using twenty times more plastic today than fifty years ago.
Iron is a trace element, which is a group of minerals present in small quantities in the body. Other trace elements include copper, zinc, selenium, manganese and iodine. These minerals cannot be synthesized by the body and must therefore be supplied in the diet. Iron is the most common trace element in the human body; adult males have approximately 3.5 g iron in total, or 50 mg per kg body weight while females have about 2g total iron or 35 mg per kg bodyweight. Iron can exist in oxidation states from -2 to +6, but mainly exists in the ferrous (+2) and ferric (+3) states in biological systems. As iron has the ability to accept and donate electrons readily, it can interconvert between these two forms with ease. Thus, iron can participate in
Stiffness In terms of stiffness this additive is hard and stiff. This affects the polymers in a good way because it acts like a protective shield for the polymer to stop any polymer oxidation on the polymer.
2.2.1. The analysis for the ability of the antioxidant activity to prevent the occurred of hydroperoxide.
The Crystallinity of Kevlar Polymer strands, contributes to the unique strength and stiffness of the material. Kevlar is very similar to other common synthetic polymers, including Nylon, Teflon and Lycra. In all Polated to strength. Aromatic refers to the Carbon atoms attached in a ring, and Amides refers to a group of Carbon, Nitrogen and Hydrogen atoms. Kevlar fiber is therefore a “Polyaromatic amide”, as it has a high breaking strength.
The most common form of polyethylene is petroleum based or olefins based; as before mentioned polyethylene compounds have a wide commercial applicability and are made from non-renewable resources (Harding, Dennis, von Blottnitz, Harrison, & S.T.L., 2007). Its manufacturing processes are regarded as energy intensive and release significant amount of CO2 and heat into the atmosphere (Broderick, 2008). Next a little more detailed description of polyethylene’s production processes will be presented, with a focus on the way the material inputs are extracted and synthesized.
This causes the stabilization of the compound. Diethyl ether or Tetrahydrofuran (THF) are the two commonly used ethereal solvents. Diethyl ether is used over tetrahydrofuran due to cost and the ability to be easily removed from the solution (1). Use caution when opening diethyl ether and tetrahydrofuran containers because they have the ability to create hydroperoxides, which are dangerous because they are explosives.
To remove the impurity, the fluorene had to be recrystallized and purified. In an aside step, 15 mL of ethanol was heated until the solvent was boiling. Ethanol is the ideal solvent to crystallize fluorene, because it is polar. Though fluorene is nonpolar, fluorene is not too soluble or insoluble in ethanol. The decision for selecting this solvent came from past experimentations as well. At first, methanol would have been a good solvent for fluorene, but methanol evaporates very quickly. A greater amount of methanol would have been required to dissolve the impure fluorene, but a little amount of ethanol is only needed to dissolve the impure fluorene completely. Once the ethanol solvent was boiling, a small amount was added to the flask, just enough to cover the impure fluorene solids. That flask was then heated on a hot plate, and additional hot ethanol was added continuously until the fluorene completely dissolved (10). As soon as the solid dissolved, the flask was stoppered and placed into an ice-water bath (11). Crystallization happened almost
The synthesis of polymers starts with ethylene, (or ethene). Ethylene is obtained as a by-product of petrol refining from crude oil or by dehydration of ethanol. Ethylene molecules compose of two methylene units (CH2) linked together by a double carbon
The purpose of this experiment was to create a polymer by reacting a mixture of decanedioyl dichloride and dichloromethane with a mixture of water, 1,6-hexadiamine and sodium carbonate. Specifically, we created the polymer Nylon-6,10. Nylon-6,10 polymers are used in a vast majority of things we use in everyday life such as zippers, the bristles in brushes, and even car parts. This experiment was different from the industrial method of making nylon because that takes place at a much higher temperature. A polymer is a substance that has a structure made of similar or identical units bonded together. All polymerizations fall into two categories: step-growth and chain-growth (both of which we used to form our polymer). Step growth polymerization
Flocculants.info (Nov. 2013) "Polymers for Coagulation, Flocculation and Dewatering of Solids and Sludge" N.p., Accessed on 25th Nov. 2013 at .
Port Pirie is a town located between the Gulf of Spencer and the Flinders’ Ranges of South Australia. In 1889 a large lead smelter was built, and by 1934 it had become one of the biggest in the world. The smelter, now owned by Nyrstar, is linked to mines and other metal processer all over the world. (Port Pirie 2014) Recently, the smelter has been the subject of many health complaints and due to this Nyrastar has threatened to close the smelter down unless it receives government supports to upgrade the plant to be able to meet the EPA regulations.