Acrylonitrile-butadiene rubber temperature

In the past chemical cure linings have been employed on a wide scale. These linings, usually based on natural rubber or acrylonitrile-butadiene rubber consist of a standard lining compound with a chemical activator such as dibenzylamine incorporated in the formulation. Prior to the application of the lining to the substrate, the individual sheets of rubber are dipped or brush coated with carbon disulphide or a solution of a xanthogen disulphide in a solvent. The carbon disulphide or xanthogen disulphide permeates the rubber and combines with the dibenzylamine to form an ultra-fast dithiocar-bamate accelerator in situ, and thus the rubber rapidly vulcanises at ambient temperature. 

In more recent years, lining compounds have been developed that vulcanise at ambient temperatures. Most polymers can be used for such compounds, although most materials are based on natural rubber, acrylonitrile-butadiene rubber and polychloroprene. These compounds contain accelerators which usually give rise to a material which has a delay in the onset of vulcanisation with a subsequent rapid rise in cross-link formation to give full vulcanisation in 6 to 8 weeks. Such materials, unless to be used within a few days of manufacture, are refrigerated to arrest the sel f-vulcanisation. 

Polychloroprene and acrylonitrile-butadiene rubber compounds have satisfactory chemical resistance but, except for phosphoric acid, are not suitable for mineral acids at higher concentrations. However, they have good resistance to oils, acrylonitrile-butadiene rubber being the better, and so are often used in oil-contaminated aqueous environments. Generally, abrasion resistance is only fair. Normal maximum working temperature is about 100°C. Acrylonitrile-butadiene rubber ebonites are sometimes used especially where solvent contamination occurs, but are normally very brittle and so should be used with care. 

The glass transition temperatures of polyacrylonitrile at +90°C and of polybutadiene at -90°C differ considerably therefore, with an increasing amount of acrylonitrile in the polymer, the Tg temperature of NBR rises together with its brittleness temperature. The comonomer ratio is the single most important recipe variable for the production of acrylonitrile-butadiene rubbers. 

Solid-state 13C NMR has been used to identify elastomers in binary blends of chloroprene (CR) and NR, CR and CSM, NR and CSM, and SBR and acrylonitrile-butadiene rubber (NBR). The type of NBR can be determined by identifying the sequences of acrylonitrile and butadiene. The tertiary blend of NR/SBR/BR was also studied [49]. High-temperature 13C solid-state NMR identified ethylene-propylene diene terpolymer (EPDM) and fluoro and nitrile rubbers [50]. 

JSR Corp. Acrylonitrile butadiene rubber (NBR) Acrylonitrile and butadiene Emulsion process. NBR has hirji oil resistance, processed at low temperature 3 1994... 

Adimoll DO is a low-temperature-resistant plasticizer suitable for a large number of polymers, e.g. polyvinyl chloride (PVC), acrylonitrile-butadiene rubber (NBR), styrenebutadiene rubber (SBR) and polyvinyl acetate (PVAC). Commonly used in plastic wraps for food storage. 

Figure 15.10 Effect of aciylonitrile content upon low-temperature stiffening temperature (curve A) and swelling in mineral oil (curve B) of acrylonitrile-butadiene rubber vulcanizates (BP Chemicals (UK) [19].)...

Figure 15.9 Effeci of acrylonitrile content upon rdxwnd resilience at normal ambient temperature for aciylonitrile-butadiene rubber vulcanizates (Hofmann [6]). Compound (parts by mass) acrylonitrile-butadiene rubber KK) plasticizer 5 stearic add % zinc oxide S HAF carbon black 40 sulfur 1.5 -cydohexyl-2-benzibia l sulfenamide 0.8...

Spadaro et al. - polymerized methyl methacrylate (MMA) monomers in the presence of acrylonitrile-butadiene rubber by y-irradiation at a temperature of 70°C. For pure MMA, a total dose of 4 kGy is enough to complete polymerization and further irradiation (6.3 kGy) leads to a degradation of PMMA macromolecules. On the contrary, for PMMA/ABN blends, a higher dose... 

Before reviewing in detail the fundamental aspects of elastomer blends, it would be appropriate to first review the basic principles of polymer science. Polymers fall into three basic classes plastics, fibers, and elastomers. Elastomers are generally unsaturated (though can be saturated as in the case of ethylene-propylene copolymers or polyisobutylene) and operate above their glass transition temperature (Tg). The International Institute of Synthetic Rubber Producers has prepared a list of abbreviations for all elastomers [3], For example, BR denotes polybutadiene, IRis synthetic polyisoprene, and NBR is acrylonitrile-butadiene rubber (Table 4.1). There are also several definitions that merit discussion. The glass transition temperature (Tg) defines the temperature at which an elastomer undergoes a transition from a rubbery to a glassy state at the molecular level. This transition is due to a cessation of molecular motion as temperature drops. An increase in the Tg, also known as the second-order transition temperature, leads to an increase in compound hysteretic properties, and in tires to an improvement in tire traction... 

Zhang, J., Wang, L., Zhao, Y. Impoving performance of low-temperature hydrogenated acrylonitrile butadiene rubber nanocomposites by using nano-clays. Mater. Des. 50, 322-331 (2013)... 

The Swiss company, WW Fischer, offers PTFE (Teflon PTFE or Hostaflon), PBT (Celanex, Crastin, Ultradur or Valox) or PEEK (Victrex) insulator material options in its 405 series of cylindrical connectors according to the requirements of working temperature and other criteria. PEEK is an expensive polymer which tends to be employed when other materials fail to meet the specification requirements of the application. Other Fischer connector types use polyamide-imide (Torlon) or POM (Celcon, Delrin or Hostaform). Elastomeric seals used by Fischer in conjunction with their connectors are made from acrylonitrile-butadiene rubber (NBR N BUNA) or to MIL-P-25732, fluoroelastomer (FPM VITON), polychloroprene elastomer (CR Neoprene), ethylene-propylene diene elastomer (EPDM) and styrene-ethylene-butadiene-styrene thermoplastic elastomer (TPE-S or TPE-O) where each compound is followed by its trade name. Fischer s Swiss competitor, Lemo, manufactures a similar range of connectors including the Redel types which have a plastic body. 

FIG. 19-2. Coefficient of friction for acrylonitrile-butadiene rubber sliding on wavy glass, plotted against logarithm of velocity times shift factor ar reduced to 20 C. Temperature dependence of ar corresponds to equation 40 of Chapter 11 with 7, 30 C. Points identify 13 different temperatures from —15 (at right) to 85 C (at left). (Grosch. )... 

LTG-HNBR Low-temperature-grade hydrogenated acrylonitrile butadiene rubber... 

With the increased usage of 120°C cured, rubber modified epoxy structural adhesives for aluminum airframes, certain service problems have been observed which have been attributed to environmental factors. The problems associated with the combined effects of sustained load, elevated temperature and high humidity upon the aluminum substrate, corrosion inhibiting primers, and the structural epoxy adhesive matrix are discussed. A particular type adhesive matrix, based on acrylonitrile/butadiene rubber modified bisphenol type epoxy systems is discussed in detail, and important advances in the preparation of more moisture resistant aluminum (oxide) surfaces are reviewed. 

It appears that the glass transition temperature of an amorphous polymer is an important characteristic. Grosch obtained the isothermal friction-speed curves of four different rubber compounds on a glass countersurface. The rubber compounds used were styrene-butadiene, aery Ionitrile butadiene, butyl and isomerized natural rubber. The curves were all reduced to 20 C, making use of the W.L.F. transform. The peak values of friction were found to occur at different speeds. In this series, acrylonitrile butadiene rubber has the highest Tg. It attains its peak value of friction at the lowest of the four speeds. At the other extreme, isomerized natural rubber having a low Tg, attains its peak friction at the highest of the four speeds. The other two compounds lie between the extremes in the expected order. 

Blends of polyvinyl chloride (PVC) with acrylonitrile butadiene rubber (NBR) have been used for many years as masterbatches in the rubber industry. Typically the PVC and NBR blend is fluxed at elevated temperatures to achieve optimal properties. Vulcanization curatives can be added to this blend. 

The major factors affecting low-temperature brittleness and flexibility are the level and type of plasticizer. Compounds for low-temperature service most often use blends of standard with special-purpose low-temperatuie plasticizers (e.g., di-2-ethyUiexyl adipate (DOA)). Plasticization typically decreases chemical, solvent, and oil resistance. This can be countered by use of polymeric plasticizers, with attendant increase in cost and typical loss of processing ease, or by means of blends and alloys with highly oil-resistant polymers such as acrylonitrile-butadiene rubber (NBR). 

Nitrile rubbers, copolymers of butadiene and acrylonitrile, are used for resistance to swelling by mineral oils and fuels enhanced by formulations with a high acrylonitrile/butadiene ratio. They have poor resilience and low-temperature properties. However, these rubbers should not be used with ketones, phenols or aromatic hydrocarbons [66-69]. 

FIGURE 13.2 Calculated relation between the solubility parameter and glass transition temperature (Jg) for a variety of ethylene-propylene copolymers (EPMs) grafted with polar monomers the window for rubbers with an oil resistance similar to or better than hydrogenated acrylonitrile-butadiene copolymer (NBR) (20 wt% acrylonitrile) is also shown. 

The generic term applied to all elastomers resulting from the copolymerisation of butadiene and acrylonitrile. Nitrile rubbers are available with different butadiene/acrylonitrile ratios ranging from 18% to 50%, a high acrylonitrile content giving rubbers excellent oil resistance, a lower acrylonitrile content giving improved low-temperature flexibility. 

Polycarbonate is blended with a number of polymers including PET, PBT, acrylonitrile-butadiene-styrene terpolymer (ABS) rubber, and styrene-maleic anhydride (SMA) copolymer. The blends have lower costs compared to polycarbonate and, in addition, show some property improvement. PET and PBT impart better chemical resistance and processability, ABS imparts improved processability, and SMA imparts better retention of properties on aging at high temperature. Poly(phenylene oxide) blended with high-impact polystyrene (HIPS) (polybutadiene-gra/f-polystyrene) has improved toughness and processability. The impact strength of polyamides is improved by blending with an ethylene copolymer or ABS rubber. 

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