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Properties and Degradation of Nitrile Rubber
Published in Nicholas P. Cheremisinoff, Elastomer Technology Handbook, 2020
Susmita Bhattacharjee, Anil K. Bhowmick, Bhola Nath Avasthi
The principal driving force behind the development of hydrogenated NBR is the increasing performance demanded of elastomers by the automative and oil drilling industries. The conventional oil resistant rubbers such as NBR, chloroprene rubber, and chlorinated polyethylene are reaching their performance limits. Fluoroelastomers, which are the possible substituents in these applications, are highly expensive and possess processing difficulties. Hence, hydrogenated NBR has been developed to bridge the price-performance gap between general purpose oil resistance rubbers and fluoroelastomers. The double bonds present in the diene part of NBR makes it less resistant to heat and ozone. The selective hydrogenation of olefinic unsaturation in NBR upgrades the product performance in many of its traditional applications. The development HNBR is a great success in improving almost all the major drawbacks of nitrile rubber as well as in widening its range of applications.40-48
Organometallic and Inorganic–Organic Polymers
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
Other inorganic and metal-containing polymers have been formed using the addition approach. These include polyphosphazenes, polyphosphonitriles, and poly(sulfur nitride). Phosphonitrilic polymers (11.50) have been known for many years, but since they lacked resistance to water, they were not of interest as commercial polymers. However, when the pendant chlorine groups are replaced by fluorine atoms, amino, alkoxy, or phenoxy groups, these polymers are more resistant to hydrolysis. Allcock and coworkers have pioneered these efforts. Phosphonitrile fluoroelastomers are useful throughout a temperature range of −56°C to 180°C. Phosphazenes are produced by the thermal cleavage of a cyclic trimer obtained from the reaction of phosphorus pentachloride and ammonium chloride.
Trends in Polymer Applications
Published in Manas Chanda, Plastics Technology Handbook, 2017
Fluoroelastomers, which include elastomeric fluorocarbons, are family of carbon- or silicon-based polymers containing significant amount of fluorine. Fluoroelastomer products are a family of specialty materials valued for their elastic behavior under comparatively harsh conditions involving a broad thermal range and/or aggressive environments. Unique features and benefits afforded by specific fluoroelastomers have led to their diverse industrial applications as in seals, linings, tubing, hose, belting, fabrics, caulks, adhesives, laminated, and vibration absorbers, for service in harsh chemical and thermal conditions. Sound knowledge of all types of candidate materials is fundamental to making the right choice.
Development of an Apparatus for Testing of High-Temperature Static Seals
Published in Tribology Transactions, 2021
Abdolkarim Sheikhansari, Jonathan Knapton, Diego Benito, Ben Shaw, Ehsan Alborzi, Simon Blakey
Static seals are used in applications where the sealing surfaces are not subject to relative movement, although there might be a very slight degree of thermal expansion or separation by fluid pressure (1). In the piston arrangement, the seal is squeezed on the inner and outer surfaces and in the face seal arrangement the axis of the seal is normal to the sealing surfaces; that is, the sealing walls squeeze the seal on the top and bottom surfaces. In the latter design, the seals can be pressurized internally or externally. The face seals involved in internally pressurized applications are pushed toward the outer wall of the gland, whereas they are pushed toward the inner wall of the gland in externally pressurized arrangements. Static seals are made of different materials, including fluorocarbon (e.g., fluoroelastomer, perfluoroelastomer, and polytetrafluoroethylene) and metal (e.g., stainless steel, copper, and Inconel). They are also manufactured in several configurations such as solid, hollow tube, C-section, spring-energized, etc. Selection of the static seal type depends on a wide range of parameters; for example, temperature and pressure ranges, operating environment, fluids to be sealed, material of the sealing surfaces, safety and life expectancy, assembly methods, and testing criteria.
Driveline Lubricant Impacts on Dynamic Seal Test Life
Published in Tribology Transactions, 2018
Hongmei Zhao, Jiatong Chai, Xiaoming Lin, Wei Wang, Jeanne Petko, Valerie Woodward, Monica Ford
Compared with the large number of publications on engine oil–seal compatibility, there is a more limited number of publications on driveline lubricant–seal research. Jeon and Kim (1) investigated the impact of low-viscosity oils on engine seal friction and confirmed that using lower viscosity engine oils resulted in reduced frictional loss at the engine seal. Molitor (4) evaluated the performance and failure mode of silicone (VMQ) and fluoroelastomer (FKM) engine crankshaft seals at elevated temperature and recommended FKM over VMQ seals for crankshaft applications. Kurono, et al. (5) investigated the effects of engine oil additives on the properties of FKM seals and found that dithiocarbamate friction modifiers had a hardening effect on FKMs. Masuda, et al. (6) investigated FKM seals collected from field service and found that a loss of interference was the dominant failure mode of FKM seals in real-world service. Shuster (7) developed an accelerated laboratory testing method that mimicked two seal failure modes in field service of off-highway vehicles: (1) abrasive seal lip wear and (2) degradation of the seal due to inefficient lubricity and shaft wear.
Latest trends for structural steel protection by using intumescent fire protective coatings: a review
Published in Surface Engineering, 2020
Muhammad Yasir, Faiz Ahmad, Puteri Sri Melor Megat Yusoff, Sami Ullah, Maude Jimenez
Fluoropolymers contain (C-F) bond. They were used as additives in epoxy-based coatings in Ding et al. (2014) [96]. FKM (copolymer of vinylidene fluoride-hexafluoropropylene) fluoroelastomer was used and its thermal behaviour was studied. Zinc borate (ZB) and ethylene vinyl acetate copolymer were used as fillers, whereas epoxy resin, ethylene-acrylic acid copolymer and ketone–aldehyde resin were used as binders. ZB and ketone-aldehyde were showing the best fire resistance properties as compared to others. It was also found that the initial decomposition temperature of the FKM was optimised, which improved the char structure and resistance to oxidation.