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English英语译成Chinese汉语: The Many Faces of Neoprene General field: 科学 Detailed field: 化学；化学/化工
原文文本 - English英语 The Many Faces of Neoprene
Diving suits, gaskets, hoses, life rafts, iPad covers, and giant balloons destined for Macy’s Thanksgiving Day parade. What do they have in common? All are made of neoprene! Not only does this synthetic rubber have myriad uses, but it also holds a place of honor in history for having ushered in the age of modern plastics.
Neoprene was first synthesized in 1930 by DuPont chemist
Wallace Carothers, who would later achieve worldwide fame as the inventor of nylon. It was born out of the need to find a substitute for natural rubber, an item that by the first decade of the twentieth century was becoming nearly as indispensable as coal or iron. The automobile industry and the military were particularly reliant on rubber, but the natural substance, an exudates of the rubber tree, was often in short supply and reacted too readily with oxygen, meaning that it did not age well.
Attempts to synthesize rubber trace back to 1860, when
English chemist Charles H. Greville Williams successfully
degraded natural rubber to its basic building block, a simple compound called isoprene. This germinated an idea: why not take some isoprene and “reverse engineer” it into rubber? It turns out that isoprene can be readily isolated from the mixture of compounds that form when petroleum is heated, a process known as cracking. But converting isoprene into rubber proved to be a formidable task. Failure followed failure until the World War I rolled around and a British blockade forced the German
hand.
As early as 1910, German chemists had experimented with
producing rubber from methyl isoprene, a close relative of isoprene. Although its properties were less than ideal, Germany’s desperate need for rubber to sustain the war effort pressed methyl rubber into service. The search for a better product continued until the 1930s, when Dupont chemists, led by Wallace Carothers, came up with neoprene, the first truly useful synthetic rubber. But that discovery would not have come about were it not for the pioneering work of Father Julius Nieuwland, a Roman Catholic priest who had taken up a post as a professor
of chemistry and botany at Notre Dame University.
As a graduate student, Nieuwland had become fascinated
with acetylene, a gas he would end up investigating for the rest of his career. At one point, he reacted acetylene with a copper catalyst to produce a yellowish oil, identified as divinylacetylene. Much to his surprise, when left to stand, the oil thickened into a jelly and then into a hard resin. The reaction wasn’t readily reproducible and Father Nieuwland began to work at fine-tuning the process. In 1923, he hit pay dirt by reacting
his divinylacetylene with sulphur dichloride to produce a substance with elastic properties. To Nieuwland, this was of great theoretical interest and merited a presentation at the American Chemical Society’s meeting in Rochester, ny. As chance would have it, Dr. Elmer Bolton, who headed a DuPont project to make synthetic rubber, happened to attend Nieuwland’s talk and immediately became interested in using divinyl acetylene as a starting material. The company struck an agreement with Father Nieuwland for the use of his catalyst and DuPont chemists began to produce a variety of rubbery materials, none of which were satisfactory.
Then, in 1930, the brilliant Carothers, years before his epic discovery of nylon, was asked to look into the problem. He suggested trying starting materials closely related to divinyl acetylene The breakthrough came with Carothers’ idea of using hydrogen chloride to try to link molecules of monovinyl acetylene together. Arnold Collins, one of Carothers’ assistants, worked on this reaction and found that monovinyl acetylene reacted with hydrogen chloride to produce a new liquid that was christened “chloroprene.” To Collins’ glee, upon standing, the liquid solidified into a rubbery substance that bounced when dropped on the lab bench. As Carothers would explain, the small molecules of chloroprene had linked together to form polychloroprene. DuPont originally named its new rubber “DuPrene” but later renamed it “neoprene,” a more generic term since the company only made the raw material, not any finished product. The synthesis of neoprene was destined to become a milestone in the development of polymers.
Neoprene had greater tensile strength than natural rubber and better resistance to oxygen, chemicals and abrasion. By the time the U.S. entered World War II, neoprene was being produced on a large scale at DuPont’s plant in Louisville, Kentucky, eventually resulting in the city being nicknamed “Rubbertown.” During the war, Japanese forces managed to cut off the U.S.’s natural rubber supplies from Malaysia, but thanks to the availability of neoprene, the effect of the embargo was greatly reduced.
Uses of neoprene were not restricted to the military effort. Father Nieuwland had a pair of heels made for his shoes as he traveled through Europe in 1934. When the soles wore out, he had the heels transferred to another pair. Since that time, neoprene has found numerous applications. It is one of the components of space suits, and its ability to be “foamed” has made wet suits possible. Foaming allows for bubbles of nitrogen gas to be incorporated into the material for insulation purposes. The softness of foamed neoprene makes it an ideal material for the protection of laptops, cell phones and iPads. Due to his vows of piety, Father Nieuwland never accepted any royalties for his invention. For DuPont, however, neoprene was a great success in many ways. The product sold very well, but perhaps even more importantly, it stimulated Carothers to delve into the chemistry of neoprene. It was clear that the novel material was a polymer, formed by linking the small molecules of chloroprene together. A series of classic papers by Carothers in the 1930s put polymer chemistry on a firm footing and resulted in his invention of polyesters and then, famously, nylon.
Father Nieuwland is also known for his discovery of the
chemical weapon Lewisite during his acetylene research.
Nicknamed “dew of death” on account of its terrible blistering effect, Lewisite was produced by the U.S. but never used in warfare. When the compound he had discovered was turned into a weapon, Nieuwland nearly gave up chemical research entirely. Good thing he didn’t, or today we might not have had neoprene or its descendants.
English英语译成Chinese汉语: ITC，International Trade Centre General field: 市场开发 Detailed field: 商务/商业（普通）
原文文本 - English英语
Developing countries and economies in transition have benefited from free access to these tools since 2008, thanks to support from ITC’s donors. Now users in developed countries will also have free access to these tools. While nearly all data have become freely accessible, the most recent monthly trade data at the very detailed product level, as well as company data and a few other analytical features, will remain free only to users in developing countries.
About 6,000 new users sign up to access ITC’s market analysis tools each month and ITC now has 320,000 users, of which 85% are in developing countries and 15% in developed countries.
This initiative of providing free trade-related data and tools to exporters and buyers in all countries is aimed at facilitating and improving transparency in international trade, leading to increased exports by small and medium-sized enterprises of developing countries and economies in transition.
English英语译成Chinese汉语: Safety Assessment for Silicone Quaternium-25 General field: 技术/工程设计 Detailed field: 材料（塑料、陶瓷等）
原文文本 - English英语 Safety Assessment for Silicone Quaternium-25
1. Toxicity information for Silicone Quaternium-25
Silicone quaternium-25 is a complex polymer which is formed by Epoxy siloxanes, Aminopolyether, and Tetramethylhexanediamine and its average molecular weight is around 11,000Da (Mn) and around 52000Da (Mw). Silicone quaternium-25 is planned to be formulated in rinse-off hair care products, such as shampoo and conditioner, at 5% at maximum. According to the polymer toxicological profiles and SFDA NCI registration guidance, following toxicological endpoints are required to be assessed to ensure the safety of this ingredient under the intended use condition as a cosmetic ingredient; Primary skin irritation, Eye irritation and Phototoxicity.
General understanding on toxicological profiles for polymers
WHO [1] reported in symposium “percutaneous absorption” that molecular weight is an important factor influencing percutaneous permeability of the chemicals. It has been proved that percutaneous permeability of the chemicals and the maximum permeance decrease exponentially as the molecular weight increases, the absorption of the chemicals with molecular weight >500Da via skin is relatively low.
I grew up in China, and earned Bachelor degree at an university there in chemical engineering. In 80's, I came to Canada for graduate studies, and obtained Master and PhD degrees at the University of Toronto, also in chemical engineering.
Later, I worked as post-doc in several universities in Canada and the US. In mid-90, I switched to industry/manufacturing as R&D engineer/chemist/manager in Canada/Singapore for more than 15 years.
I love translation, and I can provide you with satisfactory work. I can do translation in English<>simplified Chinese<>traditional Chinese. 1-905-604-0529, [email protected]
加入会员日期： Sep '13
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