Nitrile rubber vulcanizate

Nandanan et al. [35] reported the utilization of linseed oil as an MFA in nitrile rubber vulcanizates. Linseed oil not only acted as a plasticizer but also as the fatty acid component of the activator in the NBR vulcanizates. Use of linseed oil gave appreciable increase in properties like tensile strength, tear resistance, etc. while the viscosity of the compound was marginally lower than that of the control compound (which used di-octyl phthalate as the plasticizer). The vulcanizates containing linseed oil also exhibited increased cure rate as well as reduced leachability compared to the control at a dosage of 2-5 phr. This loading was seen to replace 6 phr DOP and 2 phr stearic acid in conventional NBR vulcanizates thereby reducing compound costs. 

Anandhan, S., De, P.P., De, S.K., Swayajith, S., and Bhowmick, A.K., Thermorheological properties of thermoplastic elastomeric blends of nitrile rubber and poly(styrene-co-acrylonitrile) containing waste nitrile rubber vulcanizate powder, Kautsch. Gummi Kunst., 11, 2004. 

Nitrile rubber vulcanizates have a considerably higher electrical conductivity than do those of nonpolar elastomers and are, thus, not generally used in parts tbat require low electrical conductivities. 

Nigam V, Setua DK, Mathur GN (2001) Hybrid filler system for nitrile rubber vulcanizates. J Mater Sci 36 43... 

Elastomers, plastics, fabrics, wood and metals can be joined with themselves and with each other using nitrile rubber/epoxy resin blends cured with amines and/or acidic agents. Ethylene-propylene vulcanizates can also be joined using blends of carboxylated nitrile rubber, epoxy resin and a reactive metal filler (copper, nickel, cobalt). However, one of the largest areas of use of nitrile rubber modified epoxy systems is in the printed circuit board area [12]. 

The hydrogenation of unsaturated polymers and copolymers in the presence of a catalyst offers a potentially useful method for improving and optimizing the mechanical and chemical resistance properties of diene type polymers and copolymers. Several studies have been published describing results of physical and chemical testing of saturated diene polymers such as polybutadiene and nitrile-butadiene rubber (1-5). These reports indicate that one of the ways to overcome the weaknesses of diene polymers, especially nitrile-butadiene rubber vulcanizate, is by the hydrogenation of carbon-carbon double bonds without the transformation of other functional unsaturation such as nitrile or styrene. 

Santoprene PP dynamic vulcanizate with nitrile rubber AES... 

Carboxylated nitrile rubber (XNBR), a high-performance elastomer, is remarkable for providing vulcanizates that exhibit enhanced tensile strength, elastic modulus, hardness, and improved resistance to tear, abrasion, and the deleterious action of... 

S—EB—S (compounds) polyurethane/elastomer block copolymers polyester/elastomer block copolymers polyamide/elastomer block copolymers polyetherimide/polysiloxane block copolymers polypropylene/EPDM or EPR blends polypropylene/EPDM dynamic vulcanizates polypropylene/butyl rubber dynamic vulcanizates polypropylene/natural rubber dynamic vulcanizates polypropylene/nitrile rubber dynamic vulcanizates PVC/ nitrile rubber blends... 

Fillers in Rubber. Carbon black and calcium silicate are able to reinforce rubber. For example, the tensile strength of an SBR vulcanizate can be raised from 350 to 3500 Ib/in. by compounding with 50% of its weight of carbon black (54). The activity of the carbon black depends on particle size and shape, porosity, and number of active sites, which are less than 5% of the total surface. Elastomers of a polar nature, such as chloroprene or nitrile rubber, will interact more strongly with filler surfaces having dipoles, such as -OH and -CCX)H groups or chlorine atoms. 

HCV heat-curable vulcanizate H-NBR hydrogenated nitrile rubber... 

The surface modification of the ground rubber tire (GRT) powder was found to be suitable for enhancement of its adhesion to nitrile rubber (NBR) vulcanizates (Zhang et al., 2009c). By use of the atmospheric pressure dielectric barrier discharge, the hydrophobic surface of the powder transformed to a hydrophilic one as shown by the water contact angle, ATR-FTIR, and X-ray photoelectron spectroscopic (XPS) studies. After atmospheric plasma treatment, the improvement in the tensile strength and tear strength was observed for the modified tire powder-filled NBR vulcanizates. The latter was attributed to the enhanced interfacial interaction between modified GRT and NBR matrix. 

Because nitrile rubbers are polar elastomers, their vulcanizates are very resistant to swelling in hot oil, gasoline, grease, and other nonpolar substances. The resistance to swelling in nonpolar oils, solvents, and so on, is improved greatly with increasing nitrile content. Here we see the need for compromises increasing nitrile content improves oil resistance but reduces elasticity and set resistance and most severely reduces low-temperature flexibility. Plasticizers are very necessary to surmount this problem. 

Thermoplastic Vulcanizate (TPV). TPVs are generally classified as f-TPV and p-TPV, wherein the prefixes indicate fully and partially vulcanized, respectively. Compounds of f-TPVs are typically made with EPDM and PP. In few special TPV compounds, EPDM is replaced by nitrile rubber, and natural rubber as well. The industry benchmark is TPV compounds, and they are sold under the trade name of Santoprene and marketed by Advanced Elastomer Systems (AES) Ltd. Mitsui is also dominant in the TPV based interior skins market in Europe. Seventy-five to 90 percent of TPV compounds are fully cross-linked with EPDM and are priced at approximately 1.80/lb. Two to 10 percent are par-... 

Advanced Elastomer Systems Santoprene thermoplastic vulcanizate is composed of polypropylene and finely dispersed, highly vulcanized EPDM rubber. Geolast t TPV is composed of polypropylene and nitrile rubber, and the company s Trefsin is a dynamically vulcanized composition of polypropylene plus butyl rubber. 

Thermoplastic vulcanizates (TPVs) are composed of a vulcanized rabber component, such as EPDM, nitrile rubber, and butyl rubber in a thermoplastic olelinic matrix. TPVs have a continuous thermoplastic phase and a discontinuous vulcanized rubber phase. The most common TPV polymer systan is PP/EPDM rubber however, a number of other polymer systems have been commercially developed. These include PP/NBR, PP/butyl and PP/halobutyl, PP/NR, and PP/EVA/EPDM. Producers include Advanced Elastomers Systems (Santoprene, Geolast, and Trefsin). The highly rubberlike properties of TPV have enabled than to perform as engineered thermoplastic rubbers. In numerous application areas they have directly replaced premium-performance thermoset rubber compounds. Prominent among these are dananding automotive applications, electrical insulation and connectors, compression seals, appliance parts, medical devices, and food and beverage contact applications. 

Even though vulcanized EPDM has some oil resistance, in contrast to unvulcanized EPDM which has virtually none, a rubber with inherent oil resistance should be even better. For this reason, more polar rubbers have replaced EPDM in applications where oil resistance is critical. Dynamic vulcanizates of nitrile rubber with polypropylene are the most important example. Commercial grades are somewhat harder than EPDM equivalents (between 70 on the Shore A scale to 40 on the Shore D scale) and are also more dense (about 1.0-1.1 specific gravity) (26,49). 

Evrard et al. [195] evaluated powdered polyamides of different types as sani-reinfoicing fillers in carboxylated nitrile rubber. They evaluated the filler vulcanizates for tensile properties, tear strength, coefficient of friction, filler matrix adhesion, and swelling in various fluids. 

Although oil- and radiation-resistant vulcanized nitrile rubbers have excellent resistance to high temperatures, cross-linking may be accompanied by a splitting reaction and, therefore, the mechanical properties are not always as good as those of conventional vulcanizates. 

Ruororubbers and silicones are the best materials to make seals resistant to extreme temperature conditions. Viton, a fluororubber marketed by M/S Du Pont USA, can operate at 200°C in contact with oils and lubricants. Polysulfide rubbers have low compression set, but exhibit excellent fuel resistance. For improved compression set, it is admixed with relatively cheap conventional nitrile rubbers. The fluorine-containing rubbers, such as fluororubber, possess outstanding resistance to heat, fuels and hydraulic fluids coupled with extremely good aging characteristics. The reversible physical effects with respect to the ultimate tensile strength of this rubber vulcanizate is a noteworthy phenomenon since this is not associated with the deterioration of the rubber itself. Fluororubber is resistant to most fluids used in the aircraft industiy, such as synthetic, ester type lubricants, aromatic and aliphatic hydrocarbons, and water. 

The more serious cause of deterioration in rubbers is its reaction with atmospheric oxygen. This is possible because rubber is a diene polymer and some, such as natural rubber, EPDM, SBR, nitrile rubber, and butyl rubber, have olefinic double bonds in their structure. Much research work is being done on the oxidative degradation of unvulcanized rubbers, but this is not relevant to the resistance of vulcanized rubbers in storage or in service as their aging behaviors differ widely. Unvulcanized rubber compound has to be vulcanized in order to produce usable products. The nature of the cross-link produced varies considerably, and this can affect the balance of chemical and particularly of physical properties of the vulcanizates. 

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