Modified nitrile rubber

At one time butadiene-acrylonitrile copolymers (nitrile rubbers) were the most important impact modifiers. Today they have been largely replaced by acrylonitrile-butadiene-styrene (ABS) graft terpolymers, methacrylate-buta-diene-styrene (MBS) terpolymers, chlorinated polyethylene, EVA-PVC graft polymers and some poly acrylates. 

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]. 

Polymers can be modified by the introduction of ionic groups [I]. The ionic polymers, also called ionomers, offer great potential in a variety of applications. Ionic rubbers are mostly prepared by metal ion neutralization of acid functionalized rubbers, such as carboxylated styrene-butadiene rubber, carboxylated polybutadiene rubber, and carboxylated nitrile rubber 12-5]. Ionic rubbers under ambient conditions show moderate to high tensile and tear strength and high elongation. The ionic crosslinks are thermolabile and, thus, the materials can be processed just as thermoplastics are processed [6]. 

Although, the heat resistance of NBR is directly related to the increase in acrylonitrile content (ACN) of the elastomer, the presence of double bond in the polymer backbone makes it susceptible to heat, ozone, and light. Therefore, several strategies have been adopted to modify the nitrile rubber by physical and chemical methods in order to improve its properties and degradation behavior. The physical modification involves the mechanical blending of NBR with other polymers or chemical ingredients to achieve the desired set of properties. The chemical modifications, on the other hand, include chemical reactions, which impart structural changes in the polymer chain. 

The liquid nitrile rubbers are generally used as nonvolatile and nonextractable plasticizers. They also function as binders and modifiers for epoxy resins. Their moderate heat resistance limits their ability to meet industrial requirements. Hence, attempts have been made to improve their thermal and oxidative resistance by saturating the polymer backbone. 

Characterization and understanding of the microstructure become important after hydrogenation and hydroformylation of the nitrile rubber since the amount and distribution of the residual double bonds influence the properties of modified rubber. The conventional analytical tools have been used to characterize the elastomers. Spectroscopy is the most useful technique for determination of the degree of hydrogenation in nitrile rubber. 

Coran and Patel [74] investigated the reactive com-patibilization of PP-NBR and HDPE-NBR blends using phenolic modified polyolefin, maleic anhydride modified polyolefin, and amine terminated nitrile rubber as reactive components. Dynamic vulcanization was also inves-... 

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. 

NBROC4 = nitrile rubber with 19% acrylonitrile + 4 phr octadecyl amine modified MMT, 19NBRN4 = nitrile rubber... 

Researchers at Goodyear 121 have successfully exploited route 1 above to produce antioxidant-modified SBR and NBR for example, Chemlgum HR 665, is a commercial grade of nitrile rubber containing a... 

Butyl rubber is not compatible with natural rubber, SBR, nitrile rubber or with any other elastomer having an appreciable degree of unsaturation modified butyls (chlorobutyl and bromobutyl) are compatible with such elastomers and used as liners in tubeless tyres to improve air retention. 

Copolymers of styrene, especially with acrylonitrile, also attained increasing importance both in the unmodified form (30) and modified with rubber as ABS copolymers. The first products of this kind were blends of nitrile rubber and SAN (31). However, these only had mediocre mechanical properties because the interfacial compatibility was insufficient. The breakthrough came when nitrile rubber was replaced by a polybutadiene rubber which was grafted in emulsion with styrene and acrylonitrile... 

Moisture acts as a debonding agent through one of or a combination of the following mechanisms 1) attack of the metallic surface to form a weak, hydrated oxide interface, 2) moisture assisted chemical bond breakdown, or 3) attack of the adhesive. (2 ) A primary drawback to good durability of metal/adhesive bonds in wet environments is the ever present substrate surface oxide. Under normal circumstances, the oxide layer can be altered, but not entirely removed. Since both metal oxides and water are relatively polar, water will preferentially adsorb onto the oxide surface, and so create a weak boundary layer at the adhesive/metal interface. For the purposes of this work, the detrimental effects of moisture upon the adhesive itself will be neglected. The nitrile rubber modified adhesive used here contains few hydrolyzable ester linkages and therefore will be considered to remain essentially stable. 

In essence, the durability of metal/adhesive joints is governed primarily by the combination of substrate, surface preparation, environmental exposure and choice of adhesive. As stated earlier, the choice of the two-part nitrile rubber modified epoxy system (Hughes Chem - PPG) was a fixed variable, meeting the requirement of initial joint strength and cure cycle and was not, at this time, examined as a reason for joint failure. Durability, as influenced by substrate, surface preparation, and environmental exposure were examined in this study using results obtained from accelerated exposure of single lap shear adhesive joints. 

Butadiene is used primarily in the production of synthetic rubbers, including styrene-butadiene rubber (SBR), polybutadiene nibber (BR), styrene-butadiene latex (SBL), chloroprene rubber (CR) and nitrile rubber (NR). Important plastics containing butadiene as a monomeric component are shock-resistant polystyrene, a two-phase system consisting of polystyrene and polybutadiene ABS polymers consisting of acrylonitrile, butadiene and styrene and a copolymer of methyl methacrylate, butadiene and styrene (MBS), which is used as a modifier for poly(vinyl chloride). It is also used as an intermediate in the production of chloroprene, adiponitrile and other basic petrochemicals. The worldwide use pattern for butadiene in 1981 was as follows (%) SBR + SBL, 56 BR, 22 CR, 6 NR, 4 ABS, 4 hexamethylenediamine, 4 other, 4. The use pattern for butadiene in the United States in 1995 was (%) SBR, 31 BR, 24 SBL, 13 CR, 4 ABS, 5 NR, 2 adiponitrile, 12 and other, 9 (Anon., 1996b). 

ANs are those that contain a majority of nitrile polymers. They provide good gas barrier, chemical resistance, and low taste and odor transfer with good impact properties when modified with rubber. Extruded sheet is used extensively in food packaging and rigid packaging applications. This crystalline TP is most useful in copolymers. Its copolymer with butadiene is nitrile rubber. Acrylonitrile-butadiene copolymers with styrene (SAN) exist that are tougher than PS. It is also used as a synthetic fiber and as a chemical intermediate. 

Use Primary accelerator in natural and nitrile rubber and SBR, plasticizer and vulcanization retarder in neoprene type G, cure modifier in neoprene type W, oxidation cure activator in butyl. For extruded and molded goods, tires and tubes, wire and cable, sponge. 

Recently, nanocomposites were prepared with different grades of nitrile rubber with acrylonitrile contents of 19%, 34%i, and 50%i, with SBR (23%i styrene content), and with polybutadiene rubber with Na-montmorillonite clay. The clay was modified with... 

VERs are available as both rigid and flexible epoxy resins. The flexible epoxy resins generally have a depressed glass-transition temperature, Tg, and inferior chemical resistance. Nitrile-rubber-modified VER (I) appeared on the market in the mid- to late 1970s. These elastomer-modified VERs show improved fatigue resistance over unmodified VER (2). 

Beilstein Handbook Reference) AI3-14636 BRN 0773905 CCRIS 243 N,N -Diethyl-thiocarbamide 1,3-Diethylthiourea 1,3-Diethyl-2-thiourea N,N -Diethylthiourea N,N-Diethyl-2-thiourea EINECS 203-308-5 HSDB 4106 NCI-C03816 NSC 3507 Pennzone E Thiate H Thiourea, N,N -diethyl- U 15030 Urea, 1,3-diethyl-2-thio- USAF EK-1803. Accelerator for mercaptan-modified chloroprene rubber. Antidegradant for natural, nitrile-butadiene, styrene-butadiene, and chloroprene rubbers. Crystals mp = 78° bp dec. Xm = 234, 265 nm (c = 6310, 7244, MeOH) slightly soluble in CCI4, soluble in H2O (0.1 - 0.5 g/100 ml), EtOH, very soluble in Et20 LDso (rat orl) = 316 mg/kg. ElfAtochem N. Am. 

Lewis and co-workers (42) developed improved powder coatings with nitrile rubber-modification of an appropriate epoxy base (solid resin admixture) cured with an imidazoline-accelerated modified phenolic type hardener. Model coatings ground to 55 pm particle size, electrostatically applied to metals, cured 10 170°C, gave excellent therraocycling results as well as retained resistance to solvent attack. Elastomer-modified epoxy powder coatings have been covered extensively by Gelbel, Romanchick and Sohn in Chapter 5 of this volume. 

Earlier, McKown (43) had shown that nitrile-rubber modified type solid epoxies (EEW 900) could be prepared and applied succes-... 

One can rationalize a need for small rubber inclusions in some of the newer approaches to waterborne and high solids epoxy coating systems. Water-thinned epoxy coating compositions are described (48) where the two-component system consists of a nitrile rubber modified epoxy resin in the epoxide component and a styrene/ butadiene/methylmethacrylate latex modifier for an emulsion-based polyamide hardener component. Showing improved adhesion, impact and water resistance, the paint has good wetting characteristics and can be formulated to a high solids content at low viscosity. 

Unplasticized PVC present some processing difficulties due to its high melt viscosity in addition, the finished product is too brittle for some applications. To overcome these problems and to produce toughening, certain polymeric additives are usually added to the PVC. These materials, known as impact modifiers, are generally semicompatible and often some what rubbery in nature [14]. Among the most important impact modifiers in use today are butadiene-acrylonitrile copolymers (nitrile rubber), acrylonitrile-butadiene-styrene (ABS) graft terpolymers, methacrylate-butadiene-styrene (MBS) terpo-lymers, chlorinated polyethylene, and some polyacrylates. 

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