Oil-resistent rubbers

Nitrile rubber (NBR) was first commercialized by I.G. Farbindustry, Germany, in 1937, under the trade name of Buna N. Its excellent balance of properties confers it an important position in the elastomer series. Nitrile rubber, a copolymer of butadiene and acrylonitrile, is widely used as an oil-resistant rubber. The acrylonitrile content decides the ultimate properties of the elastomer. In spite of possessing a favorable combination of physical properties, there has been a continuous demand to improve the aging resistance of NBR due to the tougher requirements of industrial and automotive applications. 

Uses Its largest uses are for polymeriztion to polybutadiene and copolymerization with styrene to make synthetic rubber (SBR) for tires and other rubber uses. Other uses include the preparation of chloroprene for oil-resistant rubber (neoprene) and hexamethylenediamine for the preparation of nylon. 

Copolymers of butadiene and acrylonitrile are soluble in aromatic or chiorinated hydrocarbons but insoiubie in aiiphatic hydrocarbons.Therefore they find use in oil-resistant rubber articles (hoses, sealings etc.)... 

Neoprene is the generic name for polychloroprene rubber. It has been produced commercially since 1931 and had rapid and wide acceptance because it is much superior to natural rubber for heat and oil resistance. Heat resistance is far better than NR, BR or SBR. but less than EPDM. When heated in the absence of air, neoprene withstands degradation better than other elastomers which are normally considered more heat resistant, and retains its properties fifteen times longer than in the presence of air. Compression set at higher temperature is better than natural rubber and 100°C is typically the test temperature rather than 70°C. Abrasion resistance is not as good as natural rubber but generally better than most heat resistant and oil resistant rubbers. This is also true for tear strength and flex resistance. 

GeoLas. [Advanced Elastomer Systems Monsanto] Thermo[dastic rubber high oil resistance rubber. 

The most important of the above products are the copolymers of vinylidene fluoride and hexafluoropropylene (VF2-HFP), as typified by the Du Pont product Viton A. The terpolymer of these two monmers together with tetrafluoroethylene (VF2-HFP-TFE) is also of importance (e.g., Du Pont product Viton B). This terpolymer is the best among oil-resistant rubbers in its resistance to heat aging, although its actual strengths are lower than for some other rubbers. The copolymers of vinylidene fluoride and chlorotrifluoroethylene (VF2-CTFE) are notable for their superior resistance to oxidizing acids such as fuming nitric acid. 

Krynac Oil Resistant Rubbers, Polysar, Sarnia, Canada... 

Features Heat and oil-resist, rubber with outstanding weatherability readily dissolved in soivs. useful over flexible substrates, giving good low-temp, flexibility... 

Features Heat and oil-resist, rubber with outstanding weatherability dissolvable in soivs. hard, glos surface over rigid substrates Properties Wh. chips odorless readily sol. in common soivs. sp.gr. 127 vise. 400 cps (25% in toluene) Vulcanizate props. tens. str. up to 24.2 MPa (carbon bIk. stocks) Shore hardness A 60-95 43% Cl 1.1% S Toxicology TSCA listed Hypan QT100 [Hymedix inti. Lipo]... 

Rubbers are further classified according to application as all-purpose rubbers, oil-resistant rubbers, and heat-stable rubbers. About half of rubber production is used to make tires and the other half is used for commercial rubber articles. 

A series of these rubbers possess polar groups consequently, the corresponding elastomers do not swell in oil. Polyurethane rubbers and polysulfide rubbers, as well as the already mentioned nitrile and chloroprene rubbers (Table 37-5), belong to the good oil-resisting rubbers. Moderate oil resistance with simultaneously improved heat resistance is shown by chlorosulfonated ethylene, acrylic, silicone, and fluorine rubbers. 

Oils of high paraffin content are particularly effective. Naphthenic-based oils, if used, require the use of special oil-resistant rubber belting on conveyors. Oils containing added amines are said to have enhanced dust-con-trol properties. 

As described in Section 1.1, the first commercial polymers, which were naturally occurring, were polyisoprenes (natural rubber and gutta-percha) and subsequently cellulose derivatives. From the early twentieth century, various totally synthetic polymers were introduced. Farbenfabrrken Bayer introduced bulk polymerized totally synthetic elastomers in 1910. Poly(dimethyl butadiene) synthetic rubber was produced commercially by Bayer in Leverkusen during World War I. The 1920s saw the commercial development of polystyrene (PS) and poly(vinyl chloride) (PVC). In 1934, the IG Farbenindustrie (a combine of Bayer, BASF, Floechst, and other firms) began to commercially manufacture butadiene-acrylonitrile copolymer (N BR) as an oil resistant rubber and in 1937 butadiene-styrene copolymer (SBR) intended for pneumatic tires. 

Neoprenes are the workhorse of the elastomer industry. They are classified as a moderately oil-resisting rubber with very good weather- and ozone-resisting properties. Other properties are closer to those of natural rubber than to styrene butadiene rubber (SBR). 

While the focus is on oil-resistant rubbers, there is also interest in materials that display enhanced heat resistance. 

A very wide range of copolymers has been prepared in which a diene, particularly 1,3-butadiene, is the principal comonomer. Only a very small number have achieved commercial significance but one, styrene-butadiene rubber (SBR) has become the world s leading rubber in terms of tonnage consumption. Another, acrylonitrile-butadiene rubber (nitrile rubber, NBR) has been an important oil resistant rubber for some 40 years. It is these two rubbers which form the main subject matter of this chapter which also includes brief notes on two lesser known copolymers, butadiene-vinyl pyridine and butadiene-vinyl isopropyl ketone polymers and on novel alternating copolymers. 

THE DEVELOPMENT OF OIL-RESISTANT RUBBERS WITH LOW BRITTLE POINT... 

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