Nitrile elastomer

Highly saturated nitrile elastomers (HSN) have become available. These mbbers are prepared by (nearly complete) hydrogenation of the nitrile mbber copolymer. The resulting product has better heat and oxidation resistance than conventional nitrile mbber but still retains some double bonds for vulcanization. Trade names for HSN are Zetpol (Nippon Zeon), Therbar (Bayer), and Tormac (Polysar). HSN has been used, and is being developed, for oil field chemical, automotive, power station, aerospace, military, and industrial appHcations (66). 

Y. Kubo, K. Hashimoto, and N. Watanabe, "Stmcture and Properties of Highly Saturated Nitrile Elastomers," paper presented at theH.CA. 

K. Hashimoto and co-workers, "Highly Saturated Nitrile Elastomer, A Review," paper presented at theH.CA. Energy Rjibber Group, Dallas, Tex., Jan. 19,1989. 

Hydroformylation of nitrile rubber is another chemical modification that can incorporate a reactive aldehyde group into the diene part and further open up new synthetic routes to the formation of novel nitrile elastomers with a saturated backbone containing carboxyl or hydroxyl functionalities. 

ACRYLONITRILE. [CAS 107-13-1], Today over 90% of the approximately 4,000.000 metric tons of acrylonitrile (also called aciylic acid nitrile, propylene nitrile, vinyl cyanide, and propenoic acid nitrile) produced worldwide each year use the Soldo-developed ammoxidation process. Acrylonitrile is among the top 50 chemicals producedin the United States as aresult of the tremendous growth m its use as a starting material for a wide range of chemical and polymer products. Acrylic fibers remain the largest use of acrylonitrile other significant uses are in resins and nitrile elastomers and as an intermediate in the production of adiponitnle and acrylamide. 

Acrylonitrile resembles VC, a carcinogen, in structure. It is a flammable, explosive liquid (b.p. 77 C, V.P. 80 mm at 20°C). AN is a component of acrylic and modacrylic fibers produced by copolymerization with other monomers, e.g., with methyl acrylate, Me-methacrylate, vinyl acetate, VC and VDC. Other major uses of AN include copolymerizations with butadiene and styrene to produce ABS polymers, and with styrene to yield SAN resins which are used in the manufacture of plastics. Nitrile elastomers and latexes are also made with AN, as are a number of other chemicals, e.g. acrylamide and adiponitrile. Acrylonitrile is also used as a fumigant. 

ACRN is used to make acrylic fibers, acrylonitrile-butadiene-styrene (ABS), and styrene-acrylonitrile (SAN). Worldwide acrylic fiber accounts for over half of total demand while ABS and SAN consume about 30% of output. Smaller applications include nitrile rubber copolymers (4%), adiponitrile (ADN) and acrylamide. Acrylic fibers are used in carpets and clothing while ABS and SAN resins are used in pipes and fittings, automobiles, furniture, and packaging276. In the United States the ACRN uses are distributed differently 38% is used in ADN, 22% in ABS and SAN, 17% in acrylic fibers, 11% in acrylamide, 3% in nitrile elastomers, and 9% in miscellaneous, which includes polymers, polyols, barrier resins and carbon fibers277. 

Compared to the carboxylated nitrile elastomer additives, the use of thermoplastics has primarily been focused on the aerospace industry. On a cost per pound basis, the two-phase nitrile additives offer the best combination of property improvement without negative impact. The thermoplastic additives, however, may offer better high-temperature performance, but they are more difficult to formulate and to process as adhesives. As a result, the cost of these adhesives is generally much higher than that of other toughened epoxy mechanisms. 

Epoxy-nitrile adhesives have also been developed for the purpose of toughening conventional epoxy adhesives. These early adhesives were made from homogeneous blends of nitrile elastomer and epoxy resin. They are not similar to the modern-day CTBN toughened epoxy adhesive where the nitrile phase consists of discrete particles. An advantage of the... 

Use Plasticizer for nitrile elastomers and reactive diluents for epoxy. 

The presence of a higher aromatic content In the gasoline resulted In Increased swell and hence Increased deterioration of tensile properties of elastomers exposed to the gasoline and Its mixtures. Addition of benzene to Increase the aromatic content resulted In slightly more detrimental effects on nitrile elastomers than the addition of toluene. The data on all elastomers can be explained In terms of the solubility parameter concept. 

Figure I. Elongation, tensile strength, and volume change of nitrile elastomer after exposure to ethanol/gasoline compositions. Key o, Indolene HO-III and , spiked Indolene HO-III.

Here again is a formulation compromise between the brittle, high-temperature characteristics of the phenolic resin and the rubbery, low-temperature performance of the elastomer. Note also that the other ingredients are the type of material combination that is normally associated with nitrile elastomer vulcanization. 

Humes. [Hules Mexicanos] Nitrile elastomer or NBR/PVC blends used for molded parts, mech. goods subjected to oils and fuels, wire and cable jackets, soles, hoses. 

Contact Adhesive - An adhesive that will adhere to itself on contact. When applied to both adherends, it forms a bond after drying, without sustained pressure on the adherends. Composed of neoprene or, less commonly, nitrile elastomers. See also Pressure-Sensitive Adhesive. 

Conditions recommended by the manufacturers for extrusion of elastomer are listed blend in Table 10.23. Articles made of NBRIPVC blends (Carloy , Geon/Hycar , Denka LCS, JSR NV, Krynac NV, Nipol , Oxyblend , Paracril OZO, Vynite ) can be manufactured by dispersing powdered nitrile elastomers in a continuous mixing operation, which enables them to be used directly in extrusion. Easy and smooth extrusion and calendering are usual. Plasticizers and stabilizers should be pre-dispersed in PVC otherwise they may swell the elastomer and cause formation of lumps. 

It is these solid carboxylic nitrile elastomers which began to show utility in the modification of epoxy resins. Processing needs for solid elastomer Inclusion, particularly in liquid epoxy resins, have not always been advantageous. Associated problems include gel, viscosity threshold limitations and achieving desired rubber levels in excess of 5-6 phr. Sometimes processing must be carried out in selected solvents, not always a desirable or tolerable step. 

In the mid-60 s carboxyl-terminated polybutadiene/acrylo-nitrile (CTBN) liquid polymers were introduced for the purpose of epoxy resin modification. These telechellc polymers are essentially macromolecular diacids. They offer processing ease (and therefore advantage) over the solid carboxylic nitrile elastomers. It is no surprise that the epoxy prepreg industry (adhesive and non-adhesive varieties) found the liquid and solid carboxylic nitrile elastomer species useful together in processing liquid and lower molecular weight solid epoxy resins where elastomer modification was needed. 

Later, in 1974, amine reactive versions of the liquid nitrile polymers (ATBN) were issued, thereby offering another way to introduce rubbery segments into a cured epoxy resin network. References are cited which provide detailed discussions of nitrile rubber, carboxylic nitrile rubber and both carboxyl- and amine-terminated nitrile liquid polymers (1-4). Table I illustrates CTBN and ATBN products structurally. Table II provides properties for typical solid carboxylic nitrile elastomers. 

Another chosen example stems from the perceived benefits of combining solid and liquid carboxylic nitrile elastomers in the same modification scheme. This is particularly useful when a degree of tack is required in the system. Table VIII exhibits one approach for preparing such an elastomer-modified solid DGEBA resin. In this instance a resin (epoxide equivalent weight of 650) was prepared by advancing two available liquid epoxy resin adducts — one utilizing a liquid nitrile, the other a solid nitrile elastomer. 

In each instance of nitrile elastomer modification - whether rubber is added to the epoxy portion or to the hardener portion -the level of rubber largely determines whether a toughened or a flexibilized epoxy results. The former is characterized by little loss in thermal/mechanical properties. The latter shows a dominant influence of the added rubber. 

Consequent to documentation surrounding methods of employing reactive nitrile elastomers to modify epoxy resins is a growing body of literature which serves to characterize and elucidate these systems. Such topics as morphology in the cured and uncured state, transitions from toughening to flexlbilization, viscoelastic effects, equilibrium physical properties and phase structure are available to the investigator (12-17). 

As previously mentioned in this chapter, carboxyl-reactive nitrile liquids appear to be the preferred modifiers for latent epoxy structural film adhesives. One of the major components used in formulating these adhesives is a solid epoxy resin of similar molecular weight (1000). This limited coatings study suggests that similar elastomer-modified epoxy resins are equally impressive in solution epoxy coatings. In addition. Table XI/Recipe 3 features a high impact coating modified with both liquid and solid carboxylated nitrile elastomers. 

The chemical literature reveals relatively new and varied interests for nitrile elastomer-modification of epoxy resins in diverse areas of coatings and primers. Desirable properties such as impact resistance, mandrel bend and adhesion improvement are attainable with little or no sacrifice in critical film properties. In some instances, it is documented that proper elastomer modification of select epoxy coatings will enhance corrosion and moisture resistance. This may relate to better film/substrate adhesion durability. The combined literature, journal and patent, has led to continuing study of nitrile elastomer modified epoxy coatings. 

Chem. Descrip. Carbor lated nitrile elastomer, nonstaining antioxidant CAS 9003-18-3... 

Synonyms Acrylonitrile/butadiene copolymer Acrylonitrile/butadiene rubber Acrylonitrile rubber 1,3-Butadiene, polymer with 2-propenenitrile NBR Nitrile/butadiene rubber Nitrile elastomer Nitrile rubber 2-Pro-penenitrile, polymer with 1,3-butadiene Classification Polymer... 

Nitric acid, sodium salt. See Sodium nitrate Nitrile/butadiene rubber Nitrile elastomer Nitrile rubber. See Butadi-ene/actylonitrile copolymer... 

Nitrile 10 D. See Decane nitrile Nitrile 12. See Lauryl nitrile Nitrile BG. See Tallow nitrile Nitrile/butadiene rubber. See Butadiene/acrylonitrile copolymer Nitrile C4. See Butyronitrile Nitrile elastomer Nitrile rubber. See Butadiene/acrylonitrile copolymer Nitrile rubber, hydrogenated. See Acrylonitrile-butadiene rubber, hydrogenated Nitriles, coco. See Coco nitrile Nitriles, tallow. See Tallow nitrile Nitriloacetic acid trisodium salt. See Trisodium NTA... 

Nipol Nitrile elastomers, NBR, AN = 21-51 % also liquids, powders, or crumbs Nippon Zeon Co., Ltd. 

Zetpol Hydrogenated, nitrile elastomer (HNBR), highly saturated for fuel and solvent resistance Nippon Zeon Co., Ltd. 

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