HNBRs

Two suppliers to the U.S. market are Bayer and Nippon Zeon. The estimated volume used in the United States is 500 700 t/yr. Hydrogenated nitrile mbber (HSN or HNBR) compounds compete with EKM, EVMQ, ECO, ACM, and high ACN content nitrile mbbers. Big applications include automotive timing belts, blowout preventors, drill pipe protectors, and numerous oil and fuel pump components. 

S. Hayashi, M. Oyama, K. Hashimoto, and T. Nakagawa, "New Improved Low Temperature Hydrogenated Nitrile Rubber (HNBR)," paper presented at theH.CA. Racbber Division Meeting, Detroit, Mich., Oct. 8—11,1991. 

Polynorbomene (PNR), polyoctenamer and hydrogenated nitrile rubber (HNBR)—this chapter... 

The available data in Table 6 reveal that palladium complexes are excellent catalysts for selective hydrogenation of C=C in NBR. Recent attempts to recover the catalyst (see Section VII) after hydrogenation and lower the cost of the metal make it an attractive supplement in the industrial production of HNBR. 

The available studies indicate that diimide has been used as a reducing agent for the preparation of HNBR. It has been used mainly as an alternative for hydrogenation of nitrile rubber latex. The use of diimide to hydrogenate low-molecular weight olefines is well known in the organic literature [93]. Diimide can be conveniently generated in situ by thermal treatment of solutions of p-tolu-enesulfonyl hydrazide or oxidation of hydrazine. 

Figure 1 IR spectra of 1-NBR and 2-5-HNBR with 58, 71, and 99.9 mol% hydrogenation, respectively. Source Ref. 11.

Figure 1 illustrates the IR spectra of NBR and HNBR samples with different concentrations of residual double bonds [11]. The CN stretching vibration is observed at 2222 cm in NBR and HNBR. The peak at 1440 cm is for C—H deformation of —CH2— groups. The =C—H out of plane deformations of trans, vinyl, and cis double bonds are observed at 970 cm", 920 cm", and 730 cm", respectively. These peak absorbances decrease gradually, and a new peak at 723 cm" appears on the spectrum of HNBR for—CH2— rocking vibration [when (CH2)n n > 4] [11,78]. The CN stretching vibration is taken as an internal standard and the... 

The classic chemical technique for measuring the degree of unsaturation in diene polymers is iodometry (iodine value) [102]. Kubo et al. [103] extensively measured the iodine value to determine the amount of residual double bonds present in the HNBR. However, this method exhibited significantly poorer precision as compared with IR and NMR spectroscopies [99-101]. Acid... 

The gum strength of HNBR is much higher in comparison to NBR [11] (Fig. 4). With the increase in degree... 

Figure 5 Comparison of HNBR with fluoroelastomer (FPM), NBR and XNBR in Sour Crude Oil (sour gas = 20% H2S + 65% CH4 + 15% CO2). Source Bayer AG, Germany.

Low temperature flexibility of HNBR is better than NBR. With the increase of the degree of hydrogenation. 

The high strength and high-elasticity retention over a wide range of temperatures imparts HNBR with a good retention of dynamic behavior. Stein et al. [120] have... 

Figure 6 Performance profile of HNBR compared to NBR and FPM. Source Bayer AG, Germany.

Hydrogenated nitrile rubber is much more stable than NBR at elevated temperature. Bhattacharjee et al. [134] performed a high-temperature degradation (30-800°C) of HNBR and NBR in nitrogen atmosphere... 

Figure 7 Thermogravimetric and differential thermogravimetric curves of NBR and HNBR. Source Ref. 134.

---