Nitrile rubber

Nitrile rubber known as NBR, Buna-N, acrylonitrile butadiene rubber, is a synthetic rubber copolymer of acrylonitrile and butadiene. Trade names include Perbunan, Nipol and Europrene. Nitrile butadiene rubber is a family of unsaturated copolymers of 2-propenenitrile and various butadiene monomers. Although its physical and chemical properties vary depending on the polymer’s composition of nitrile, this form of synthetic rubber is unusual in being resistant to oil and other chemicals, it is used in the automotive and aeronautical industry to make fuel and oil handling hoses, seals and self-sealing fuel tanks, since ordinary rubbers cannot be used. It is used in the nuclear industry to make protective gloves. NBR's ability to withstand a range of temperatures from −40 to 108 °C makes it an ideal material for aeronautical applications. Nitrile butadiene is used to create moulded goods, adhesives, sponges, expanded foams, floor mats, its resilience makes NBR a useful material for disposable lab and examination gloves.

Nitrile rubber is more resistant than natural rubber to oils and acids, has superior strength, but has inferior flexibility. Nitrile gloves are therefore more puncture-resistant than natural rubber gloves if the latter are degraded by exposure to chemicals or ozone. Nitrile rubber is less to cause an allergic reaction than natural rubber. Nitrile rubber is resistant to aliphatic hydrocarbons. Nitrile, like natural rubber, can be attacked by ozone, ketones and aldehydes. Emulsifier, 2-propenenitrile, various butadiene monomers, radical generating activators, a catalyst are added to polymerization vessels in the production of hot NBR. Water serves as the reaction medium within the vessel; the tanks are heated to 30–40 °C to facilitate the polymerization reaction and to promote branch formation in the polymer. Because several monomers capable of propagating the reaction are involved in the production of nitrile rubber the composition of each polymer can vary. One repeating unit found throughout the entire polymer may not exist.

For this reason there is no IUPAC name for the general polymer. The reaction for one possible portion of the polymer is shown below: 1,3-butadiene + 1,3-butadiene + 2-propenenitrile + 1,3-butadiene + 1,2-butadiene → nitrile butadiene rubberMonomers are permitted to react for 5 to 12 hours. Polymerization is allowed to proceed to ~70% conversion before a “shortstop” agent is added to react with the remaining free radicals. Once the resultant latex has “shortstopped”, the unreacted monomers are removed through a steam in a slurry stripper. Recovery of unreacted monomers is close to 100%. After monomer recovery, latex is sent through a series of filters to remove unwanted solids and sent to the blending tanks where it is stabilized with an antioxidant; the yielded polymer latex is coagulated using calcium nitrate, aluminium sulfate, other coagulating agents in an aluminium tank. The coagulated substance is washed and dried into crumb rubber; the process for the production of cold NBR is similar to that of hot NBR.

Polymerization tanks are heated to 5–15 °C instead of 30–40 °C. Under lower temperature conditions, less branching will form on polymers; the raw material is yellow, though it can be red tinted, depending on the manufacturer. Its elongation at break is ≥ 300% and possesses a tensile strength of ≥ 10 N/mm2. NBR has good resistance to mineral oils, vegetable oils, benzene/petrol, ordinary diluted acids and alkalines. An important factor in the properties of NBR is the ratio of acrylonitrile groups to butadiene groups in the polymer backbone, referred to as the ACN content; the lower the ACN content, the lower the glass transition temperature. Most applications requiring both solvent resistance and low temperature flexibility require an ACN content of 33%; the uses of nitrile rubber include disposable non-latex gloves, automotive transmission belts, hoses, O-rings, oil seals, V belts, synthetic leather, printer's form rollers, as cable jacketing. Unlike polymers meant for ingestion, where small inconsistencies in chemical composition/structure can have a pronounced effect on the body, the general properties of NBR are not altered by minor structural/compositional differences.

The production process. The necessary apparatus is easy to obtain. For these reasons, the substance is produced in poorer countries where labor is cheap. Among the highest producers of NBR are mainland Taiwan. In January 2008, the European Commission imposed fines totaling €34,230,000 on the Bayer and Zeon groups for fixing prices for nitrile butadiene rubber, in violation of the EU ban on cartels and restrictive business practices. Nitric acid penetrates nitrile gloves in a few minutes. Hydrogenated nitrile butadiene rubber (HNBR

Port Victoria P.V.5

The Port Victoria P. V.5 was a British single-engined floatplane fighter aircraft of the First World War. A single example was built and flown at the Royal Naval Air Service's Port Victoria Marine Experimental Aircraft Depot on the Isle of Grain in 1917. Despite demonstrating good manoeuvrability and handling, no production followed, with the Royal Naval Air Service instead using landplanes for the fighter role. In 1916, the Air Department of the British Admiralty issued a requirement for a single-seater fighter floatplane; the specification demanded a speed of 85 kn at 6,500 ft, an endurance of four hours and an armament of a single machine gun and two 65 lb bombs. The use of a 150 hp Smith Static radial engine as powerplant was requested; the Port Victoria Marine Experimental Aircraft Depot prepared two designs to meet the requirement. One, the Port Victoria P. V.5, was a development of its earlier P. V.2 sesquiplane, while the P. V.5A differed in having a more conventional biplane wing. Both the P.

V.5 and P. V.5A were nearing completion in late 1916, but the absence of their intended engines delayed testing. The Smith Static was an experimental ten-cylinder single-row radial engine developed by the American John W. Smith, which had attracted the attention of the Admiralty because of its light weight and promised low fuel and oil consumption, but proved to be a failure, with only a few engines completed; when it was realised at Grain that the Smith Static would not be forthcoming, a 150 hp Hispano-Suiza 8 V8 engine was obtained, it was decided to modify the P. V.5 to use it. Soon after, in January, overall control for the supply of aircraft was transferred to the Ministry of Munitions, who subjected the operations of Port Victoria to scrutiny, while work continued on the P. V.5, the P. V.5A was suspended. Work restarted on the P. V.5A, it flew in 1918 fitted with a 200 hp Hispano-Suiza, although no production followed. The P. V.5's wing bracing struts carried the aircraft's floats, forming a "W" shape when viewed from the front, with no bracing wires used, while a high-lift wing section, developed by the National Physical Laboratory and used on the Port Victoria P.

V.1 and P. V.2 was again employed. Armament was the specified single synchronised Vickers machine gun, with two 65 lb bombs carried internally; the Hispano-Suiza engine drove a two-bladed propeller. Flat-bottomed pontoon-type floats were fitted, which were angled outwards to divert spray away from the engine and propeller; the P. V.5, serial number N53, flew in July 1917, but capsized when it alighted at the end of its first flight when a float failed. The aircraft was manoeuvrable and pleasant to fly, with a good view from the cockpit, but performance failed to meet specifications, this being blamed by Port Victoria on the aircraft's propeller being poorly matched to the aircraft, the Hispano-Suiza engine being heavier than the Smith Static that the aircraft was designed for. No production followed, with the fighter requirements of the Royal Naval Air Service being met by landplanes such as the Sopwith Pup and Camel Data from British Aeroplanes 1914–18General characteristics Crew: 1 Length: 25 ft 6 in Upper wingspan: 32 ft Lower wingspan: 21 ft Height: 9 ft 9 in Wing area: 245 sq ft Empty weight: 1,788 lb Gross weight: 2,456 lb Fuel capacity: 36 imp gal Powerplant: 1 × Hispano-Suiza 8 water-cooled V8 engine, 150 hp Performance Maximum speed: 94.5 mph Service ceiling: 9,900 ft Time to altitude: 4 min 50 s to 2,000 ft 20 min 15 s to 6,500 ft Armament Guns: 1× 0.303 in Vickers machine gun Bombs: 2× 65 lb bombs "PV.5" Уголок Неба

Purdon, Texas

Purdon is an unincorporated community in Navarro County, United States. According to the Handbook of Texas, the community had an estimated population of 133 in 2000. Purdon is located at 31°56′57″N 96°37′00″W, along FM 55, three miles south of State Highway 31 in south central Navarro County. Purdon is situated 14 miles southwest of Corsicana; the earliest named settlement near what would become Purdon was a community called Belle Point. It was settled by Captain J. A. Harrison. In the early 1880s, the St. Louis Southwestern Railway was built two miles south of Belle Point and lots were soon platted around the rail stop; the new community was named Purdon. Credit for the name is given to a railroad man named Harris, attracted to a cashier where he brought supplies – Miss Ada Purdom. By an inadvertent spelling mistake at the general office, the town became Purdon. A post office was established in 1881. Purdon became a thriving community with most of the black land in the area used to raise cotton and other feed grains.

By 1896 80 people lived in the community. In 1912, a new two-story brick school was completed. According to 1920 Census figures, Purdon had a population of 346. With the coming of school buses in 1928, Belle Point and Silver City schools were consolidated with Purdon; the population began to decline, falling to 30 in 1930, 262 by 1940. The decline accelerated after World War II, when many residents left he area in search of greater job opportunities in larger cities. Purdon's school was consolidated with nearby Dawson in the fall of 1959; as of 1960, Purdon recorded 151 inhabitants, less than half of the population at its peak in 1920. During the remainder of the twentieth century, the population hovered around 133. Today, most residents travel to either Corsicana or Dawson for groceries, banking and employment. On October 14, 2014 the fake news site National Report reported that a family of five had contracted the Ebola virus; this was distributed through social media as fact. Although Purdon is unincorporated, it has a post office, with the ZIP code of 76679.

Public education in the community of Purdon is provided by the Dawson Independent School District. U. S. Geological Survey Geographic Names Information System: Purdon, Texas Purdon, Texas from the Handbook of Texas Online