Nitrile elastomer, elongation

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.

While thermal and oxidative effects on elastomer properties are quite detrimental, the effect of high temperature, high-pressure exposure to H2S is usually catastrophic. Trace amounts of H2S are found in most wells, and even 5% can cause serious problems for most elastomers within a few weeks when temperatures exceed 120°C. In this environment. Nitrile elastomers become brittle and lose essentially all elongation and resilience. This effect is shown in Table 16A.4 in which several... 

Fig. 1. Retention of elongation of vulcanized elastomers at 150°C. A, nitrile mbber, NBR B, ethylene—propylene—diene mbber, EPDM C, acryflc...

Fig. 1. Elongation retention of vulcanized elastomers at 150°C A, nitrile B, ethylene-propylene-diene monomer (EPDM) C, acrylate D, fluorocarbon (31).

The comparison between the effects brought about during EB-irradiation of natural rubber, ethylene-propylene terpolymer (EPDM) and nitrile rubber emphasizes the satisfactory behavior of the last polymer [99C1, GOBI]. The gel fraction, chain scission and modification of the networks in these elastomers explain the changes in mechanical properties, i.e. the modulus increased and the elongation at break decreased with an increase in the irradiation dose (Fig. 66). 

Fig. 66 Comparation on the effect induced by EB-irradiation in some elastomers (electron raiergy 10 MeV). The data were taken from [GOBI], tensile strength (b) elongation at break (c) modulus at 50 % elongation (white) natural rubber (grey) ethylene-propylene diene terpolymer (black) nitrile rubber.

The ionene-type viologen elastomers having poly(butadiene-co-acrylonitrile) (NBV) were obtained by the reaction of a, a -dichloro-p-xylenc (DCX), A, A -bipyridine (BP) and dimethylamine-terminated liquid nitrile rubber (AT-NBR). The tensile properties of these elastomers were found to depend upon the number of cation-site in a structural unit of the ionene, and to attain A6 MPa in tensile strength and 3A0% in elongation at break without any reinforcement and vulcanization. 

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