Nitrile rubber characteristics

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. 

The original route to acrylonitrile was the catalytic reaction of HCN with acetylene. That was a combination of two compounds that together had all the characteristics youd like to avoid—poisonous, explosive, corrosive, and on and on. But during World War II, acrylonitrile became very important as a comonomer for synthetic rubber (nitrile rubber). Later, the growth for acrylonitrile came from synthetic fibers like Orion, Acrylon, and Dynel. 

Block copolymers based on nitrile rubber and on epoxy and phenolic resins and on polystyrene (50-54) have been intensively studied in Russia The generated block copolymers were investigated by turbidimetric and IR methods. Thermomechanical experiments were also run on fractions. As may be seen from Fig 13, fractions which combine the properties of the polymers (Curves 2,3, and 4) were obtained together with fractions characteristic of the raw rubber (Curve 1) and of the resin (Curve 5). The copolymer is soluble in solvents which are typical for both components. Solubility studies on the products showed that for any given ratio of the original components, 15 to 20% of the resin combines with the rubber. The properties of the block copolymer, however, depend on the initial ratio of components nitrile rubber confers elasticity and the phenolic resin processability. 

Akutin (52) performed an exhaustive study on the influence of processing conditions and the nitrile rubber/poly(vinyl chloride) ratio on the mechanical characteristic of the product. The experiments were carried out in a Brabender Plastograph at 160-180° C and rotor speed of 10-50 rpm. The polyfvinyl chloride) molecular weight was 83500. A resin with an epoxy group content of 20.75% was added to the blend as plasticizer and stabilizer. Figure 29 shows that the... 

Schonherr [43] has described the combination of decomposition in a thermogravimetry oven and FTIR spectroscopy for the identification of base polymers in elastomers, as exemplified for nitrile rubber, and has presented infrared spectra for decomposition products of various rubbers. The same author [36] studied use of the integrated TG-FTIR system for the identification of sixteen vulcanised rubbers in mechanical goods reporting the characteristic infrared spectra of the degradation products at temperatures ranging from 334 °C to 635 °C. 

PVC can be chlorinated (CPVC) and be alloyed with other polymers like ABS, acrylics, polyurethanes, and nitrile rubbers to improve its impact resistance, heat deflection, and processability. Although these vinyls differ in having literally thousands of varying compositions and properties, there are certain general characteristics that are common to nearly all these plastics. Most materials based on vinyls are inherently TP and heat sealable. The exceptions are the products that have been purposely compounded with TSs or crosslinking agents are used. 

Butyl rubber like Hypalon, Neoprene or nitrile rubber is a speciality polymer which can be compounded for a soft, deformable elastic vulcanisate similar to the other elastomers, but having certain distinctive characteristics, like low permeability to all gases and resistance to ageing and ozone cracking. Butyl has poor oil resistance and medium low temperature flexibility. 

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. 

Phenolic based adhesives are outstanding in their wetting characteristics and strength. In the unmodified form, however, they tend to be brittle. To overcome this problem, phenolic based adhesives usually contain a rubber modifier to increase the crack resistance of the adhesive. The first modified phenolic contained polyvinyl butyral and was known as the "Redux" adhesive. Many modern phenolic adhesives contain nitrile rubbers (copolymers of acrylonitrile and butadiene) as the modifiers. An example of a phenolic based film adhesive is AF-30 which is listed in Table 1 along with its physical properties. This film... 

Nitrile rubber, also known as nitrile-butadiene rubber (NBR), is a copolymer of acrylonitrile and butadiene (Fig. 1). As a base polymer for Rubber-based adhesives, it provides a number of specialized properties, which supplement those summarized in the article Rubber-based adhesives typical characteristics. NBR adhesives comprise a range of materials that may differ in proportion of comonomer or may be compounded with other resins. NBR adhesives are characterized by high oil and plasticizer resistance, excellent heat resistance and high adhesion to metallic substrates. 

Sahoo, S., Bhowmick, A.K. Influence of ZnO nanoparticles on the cure characteristics and mechanical properties of carboxylate nitrile rubber. J. AppL Polym. ScL 106, 3077-3083 (2007)... 

Nitrile rubber is a copolymer of butadiene and acrylonitrile. The main advantages of the nitrile rubbers are their low cost, good oil and abrasion resistance, and good low temperature and swell characteristics. 

Many polymers have their own process characteristics. NR and SBR process very easily on a two-roll mill. Other polymers process differently. Nitrile rubbers are well known for bagging (non-adherence to the rolls), while other polymers, especially those that are chlorinated, tend to stick firmly to the mill roll. Consequently, specific solutions have been found for each polymer s processing idiosyncrasies. 

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. 

A nitrile masterbatch, see Table 8.3, was used in all experiments pertaining to nitrile rubbers. Hycar 1042 (Zeon Chemicals) is a general purpose NBR (acrylonitrile content is 33%) with good processing characteristics and high physical properties. 

The plastics that have been discussed above have the common characteristic that they may be considered somewhat structural if fabricated in a relatively thick cross section, or relatively nonstructural and even flexible if fabricated in thinner sections. Other types of plastics are given the general term elastomer and have the quality of being stretchy and easily deformed at the surface. They also often contained plasticizing additives and may range from nonpolar materials like natural rubber to significantly polar materials like nitrile rubber. Thermal or... 

In addition to these developments, work has been carried out to improve the standard range of nitrile rubbers by designing polymers with better colour and reduced mould-fouling characteristics, and an attempt to rationalize the range and thereby simplify polymer choice has also occurred. 

Kim JT, OhTS LDH (2003) Preparation and characteristics of nitrile rubber (NBR) nanocomposites based on organophilic layered clay. Polym Int 52 1058... 

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