Additives nitrile rubber

Figure 17 (69) shows the mechanical behavior of different synthetic elastomers. They were found to be generally less efficient than natural rubber in promoting polymerization because of reduced stress during mastication due to greater softening by monomer addition. Nitrile rubber crumbed with methyl methacrylate, styrene and acrylonitrile. 

Nitrile mbber finds broad application in industry because of its excellent resistance to oil and chemicals, its good flexibility at low temperatures, high abrasion and heat resistance (up to 120°C), and good mechanical properties. Nitrile mbber consists of butadiene—acrylonitrile copolymers with an acrylonitrile content ranging from 15 to 45% (see Elastomers, SYNTHETIC, NITRILE RUBBER). In addition to the traditional applications of nitrile mbber for hoses, gaskets, seals, and oil well equipment, new applications have emerged with the development of nitrile mbber blends with poly(vinyl chloride) (PVC). These blends combine the chemical resistance and low temperature flexibility characteristics of nitrile mbber with the stability and ozone resistance of PVC. This has greatly expanded the use of nitrile mbber in outdoor applications for hoses, belts, and cable jackets, where ozone resistance is necessary. 

Nitrile Rubber. Vulcanized mbber sheets of NBR and montmorillonite clay intercalated with Hycar ATBN, a butadiene acrylonitrile copolymer have been synthesized (36). These mbber hybrids show enhanced reinforcement (up to four times as large) relative to both carbon black-reinforced and pure NBR. Additionally, these hybrids are more easily processed than carbon black-filled mbbers. 

Because nitrile rubber is an unsaturated copolymer it is sensitive to oxidative attack and addition of an antioxidant is necessary. The most common practice is to add an emulsion or dispersion of antioxidant or stabilizer to the latex before coagulation. This is sometimes done batchwise to the latex in the blend tank, and sometimes is added continuously to the latex as it is pumped toward further processing. PhenoHc, amine, and organic phosphite materials are used. Examples are di-Z fZ-butylcatechol, octylated diphenylamine, and tris(nonylphenyl) phosphite [26523-78-4]. All are meant to protect the product from oxidation during drying at elevated temperature and during storage until final use. Most mbber processors add additional antioxidant to their compounds when the NBR is mixed with fillers and curatives in order to extend the life of the final mbber part. 

Flexibilized epoxy resins are important structural adhesives [69]. Liquid functionally terminated nitrile rubbers are excellent flexibilizing agents for epoxy resins. This liquid nitrile rubber can be reacted into the epoxy matrix if it contains carboxylated terminated functionalities or by adding an amine terminated rubber. The main effects produced by addition of liquid nitrile rubber in epoxy formulations is the increase in T-peel strength and in low-temperature lap shear strength, without reducing the elevated temperature lap shear. 

In addition to epoxy-phenolic adhesives three-part epoxy-phenolic-nitrile rubber systems are used in metal-metal edge joints and honeycomb constructions [208], These add toughness not available in most EP systems and improve peel strengths. When used on honeycomb, the NR-P is normally applied to the aluminum skin and the EP to the honeycomb for assembly. Service temperature limitations are those imposed by the NR-P part. 

There are several ways in which the impact properties of plastics can be improved if the material selected does not have sufficient impact strength. One method is by altering the composition of the material so that it is no longer a glassy plastic at the operating temperature of the product (Chapter 6). In the case of PVC this is done by the addition of an impact modifier which can be a compatible plastic such as an acrylic or a nitrile rubber. The addition of such a material lowers the glass transition temperature and the material becomes a rubbery viscoelastic plastic with much improved impact properties. This is one of the methods in which PVC materials are made to exhibit superior impact properties. 

Modified PAN fibres have been obtained from copolymers containing up to 15% or ISP units using the wet spinning process30. Some properties of modified fibres are presented in Table 1. For comparison are also given the properties of fibres obtained from copolymers additionally crosslinked with conventional crosslinking agents used in the vulcanization of nitrile rubbers. 

The ductility of GRT-polyethylene blends drastically decreases at ground rubber concentration in excess of 5%. The inclusion of hnely ground nitrile rubber from waste printing rollers into polyvinyl chloride (PVC) caused an increase in the impact properties of the thermoplastic matrix [76]. Addition of rubber powder that is physically modihed by ultrasonic treatment leads to PP-waste ethylene-propylene-diene monomer (EPDM) powder blends with improved morphology and mechanical properties [77]. 

Infrared spectroscopy is a major tool for polymer and rubber identification [11,12]. Infrared analysis usually suffices for identification of the plastic material provided absence of complications by interferences from heavy loadings of additives, such as pigments or fillers. As additives can impede the unambiguous assignment of a plastic, it is frequently necessary to separate the plastic from the additives. For example, heavily plasticised PVC may contain up to 60% of a plasticiser, which needs to be removed prior to attempted identification of the polymer. Also an ester plasticiser contained in a nitrile rubber may obscure identification of the polymer. Because typical rubber compounds only contain some 50% polymer direct FUR analysis rarely provides a definitive answer. It is usually necessary first... 

Antiozonant additives are employed with unsaturated rubbers such as natural rubber, nitrile rubber, styrene-butadiene rubber, etc., to minimise the atmospheric ozone degradation reaction. Common antiozonant types include the parapheny-lene diamines such as N-(l,3-dimethylbutyl)-AT-phenyl-p-phenylene diamine (6PPD) and N-isopropyl-N7 phenyl-p-phenylene diamine (IPPD). Both these antioxidants can be identified and quantified using GC- or LC-based techniques. 

Carbon black is widely used as a reinforcing agent for most synthetic elastomers. It is especially important for synthetic elastomers such as SBR, nitrile rubber (NBR), and BR that do not crystallize at high strains. Thus, non-carbon-filled SBR has a tensile strength of about 2 MPa and with addition of carbon black this increases to about 20 MPa. 

Cadmium oxide is used in storage battery electrodes. Its solution, mixed with sodium cyanide, is used in electroplating baths. Other uses are in PVC heat stabilizers as an additive to nitrile rubbers and plastics to improve heat resistance and in ceramic glazes and phosphors. 

An example of this type of a safer chemical is methacrylonitrile (1) compared with acrylonitrile (2) (Figure 1.1). Both compounds are a, 3-unsaturated aliphatic nitriles, and structurally very similar, but 2 causes cancer whereas 1 does not appear to do so. Among other applications, 2 is used in the production of acrylic and modacrylic fibers, elastomers, acrylonitrile-butadiene-styrene and styrene-acrylonitrile resins, nitrile rubbers, and gas barrier resins. In a study conducted by the US National Toxicology Program (NTP) in which 2 was administered orally to mice for 2 years, there was clear evidence that it caused cancer in the treated mice (in addition to causing other toxic effects), and is classified by the NTP as a probable human carcinogen [26]. 

Acrylonitrile is made from ethylene oxide by combining it with hydrogen cyanide and dehydrating the resultant cyanohydrin. Acrylonitrile is now used mostly for nitrile rubber. The new synthetic fibers Orion, Dynel, and Chemstrand will be large consumers of acrylonitrile. However, a large part of the expanded output of this derivative may come from the addition of hydrogen cyanide to acetylene. 

Pure polyvinyl chloride alone It a rigid plastic of high volume resistivity. Addition of monomeric liquid plasticizer makes It flexible but lowers volume resistivity seriously. This loss of volume resistivity was not prevented by pre-purification of commercial resin and plasticizer, though It could be worsened by addition of Ionic soluble Impurities. Volume resistivity was surprisingly Increased by heat aging. It was not improved by use of polymeric liquid plasticizers, nor even, surprisingly, by use of nitrile rubber as plasticizer. Flexlblllzatlon without serious loss of volume resistivity was best achieved by internal plasticization by copolymerization with 2-ethylhexyl acrylate. Further studies are needed to explain these observations and to optimize the use of Internal plasticization In this way. 

The mechanical degradation and production of macroradicals can also be performed by mastication of polymers brought into a rubbery state by admixture with monomer several monomer-polymer systems were examined (10, 11). This technique was for instance studied for the cold mastication of natural rubber or butadiene copolymers in the presence of a vinyl monomer (13, 31, 52). The polymerization of methyl methacrylate or styrene during the mastication of natural rubber has yielded copolymers which remain soluble up to complete polymerization vinyl acetate, which could not produce graft copolymers by the chain transfer technique, failed also in this mastication procedure. Block and graft copolymers were also prepared by cross-addition of the macroradicals generated by the cold milling and mastication of mixtures of various elastomers and polymers, such as natural rubber/polymethyl methacrylate (74), natural rubber/butadiene-styrene rubbers (76) and even phenol-formaldehyde resin/nitrile rubber (125). 

Small Quantities. Work in the fume hood. Wear eye protection, nitrile rubber gloves and laboratory coat. Place 6.0 g (7 mL, 0.107 mol) of acrolein in a 1 L, three-necked, round-bottom flask equipped with a thermometer, stirrer, and dropping funnel. Over a period of 10 minutes, add 50 mL of a solution of 63 g (0.4 mol) of potassium permanganate in 700 mL of water. If the purple color is not discharged, warm the mixture on steam bath until it becomes brown. Add the remainder of the permanganate solution at such a rate that the temperature does not exceed 45°C. When addition is complete, heat the mixture on the steam bath to 70-80°C, while stirring, for 1 hour. Cool the mixture to room temperature, and acidify to pH 1 with 3 M sulfuric acid (16 mL of concentrated acid cautiously added to 84 mL of cold water). Add solid sodium bisulfite, while stirring, until a colorless solution is produced. Wash the solution into the drain with water.7... 

Small Quantities. Wear nitrile rubber gloves, laboratory coat, and eye protection. Work in the fume hood. Sodium hydroxide solution (60 mL of 2.5 M) is added to a 100-mL, three-necked, round-bottom flask equipped with a stirrer, dropping funnel, and thermometer. Benzenesulfonyl chloride (0.05 mol, 8.9 g, or 6.5 mL) is added dropwise. If the reaction is sluggish (no dissolution or rise in temperature) at first, heat the mixture on a steam bath to about 90°C. When the initially added benzenesulfonyl chloride has dissolved, add the remainder dropwise. After addition is complete, continue heating until a clear solution is obtained. Cool the mixture is cooled to room temperature, neutralize with 10% hydrochloric acid, and wash into the drain.5... 

Small Quantities. Wear nitrile rubber gloves, laboratory coat, and eye protection. In the fume hood, slowly and carefully add the cleaning solution (100 mL) to a container of water (about 1 1 dilution). Adjust pH to 1 by the addition of 3 M sulfuric acid or sodium carbonate. While stirring, slowly add solid sodium thiosulfate (about 13.5 g) until the solution becomes cloudy and blue colored. Neutralize the solution with sodium... 

Small Quantities. Wear nitrile rubber gloves eye protection large, heavy face shield and laboratory coat. Work in the fume hood behind a heavy body shield. Slowly add the dibutyl peroxide (1 g) to a solution of sodium iodide (2.5 g) in hydrochloric acid (1 mL) and glacial acetic acid (20 mL). Stir at room temperature for 24 hours. Neutralize the solution by the slow addition of sodium carbonate while stirring. Wash into the drain.6... 

Small Quantities. Wear nitrile rubber gloves, laboratory coat, and eye protection. Work in the fume hood. Small quantities of hexamethylphosphoramide can be hydrolyzed with concentrated hydrochloric acid under reflux for at least 5 hours. Add 215 mL of concentrated hydrochloric acid to a 500-mL, three-necked, round-bottom flask equipped with stirrer, heating mantle, water-cooled condenser, and dropping funnel. Over a period of about 30 minutes, add 50 mL (51.5 g, 0.3 mol) of the hexamethylphosphoramide through the dropping funnel while refluxing the reaction mixture. After addition is complete, reflux the mixture for at least 5 hours. Cool the contents of the flask, neutralize carefully with dilute sodium hydroxide or sodium carbonate, and wash the resultant mixture into the drain.6... 

Small Quantities. Wear nitrile rubber gloves, eye protection, laboratory coat, and respirator (or work in hood). The selenium salt is dissolved in water and the solution is neutralized by the addition of 1 M NaOH (prepared by dissolving 4 g of NaOH in 100 mL of water) or 1 M sulfuric acid (prepared by cautiously adding 5 mL of concentrated acid to 85 mL of cold water). A 1 M solution of sodium sulfide (prepared by dissolving 7.8 g of Na2S in 100 mL of water) is added to the selenium salt solution and the pH is again adjusted to neutral with 1 M sulfuric acid solution. The precipitate is separated by filtration or decantation. Wash, dry, and recycle or send for disposal in a secure landfill.1 ... 

Small Quantities or Solutions. Wear eye protection, laboratory coat, and nitrile rubber gloves. In the fume hood, add the sodium cyanide to a solution of 1% sodium hydroxide (about 50 mL/g of cyanide). Household bleach (about 70 mL/g of cyanide) is slowly added to the basic cyanide solution while stirring. When addition of the bleach is complete, the solution can be tested for the presence of cyanide using the Prussian blue test To 1 mL of the solution to be tested, add 2 drops of a freshly prepared 5% aqueous ferrous sulfate solution. Boil this mixture for at least 60 seconds, cool to room temperature, and then add 2 drops of 1% ferric chloride solution. The resulting mixture is made acid to litmus with 6 M hydrochloric acid (prepared by adding concentrated acid to an equal volume of cold water). If cyanide is present, a deep blue precipitate will form. (Concentrations of cyanide greater than 1 ppm can be detected.) If the test is positive, add more bleach to the cyanide solution, and repeat the test. Continue until no Prussian blue precipitate is formed. Wash the solution into the drain.4 6... 

Small Quantities. Wear nitrile rubber gloves, laboratory coat, a face shield, and goggles. Work in the fume hood. Dissolve the thallium salt in water. Add a 10% aqueous solution of sodium sulfide until no further precipitation occurs. Filter the precipitated thallium sulfide, dry, package, and send for disposal in a secure landfill site. Destroy excess sulfide in the filtrate by the addition of laundry bleach, neutralize the solution with 6 M hydrochloric acid (prepared by cautiously adding a volume of concentrated acid to an equal volume of cold water), and wash into the drain.4... 

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