Carboxylated nitrile rubber XNBR

Blends of carboxylated nitrile rubber (XNBR) with EPDM are likely to provide an attractive combination of properties including oil resistance, heat and ozone resistance, high tensile strength, modulus, and hardness. However, the polar curing ingredients often diffuse from the nonpolar to polar component, thereby producing cure rate mismatch and inferior properties. Three different measures have been used to overcome the cure rate mismatch [29] ... 

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... 

Most of the earlier efforts have been paid in changing the surface character of clay minerals. Albeit the modified clay minerals are fairly compatible with the polar rubber like acrylonitrile butadiene rubber (NBR), carboxylated nitrile rubber (XNBR), chloroprene rubber (CR), etc., its dispersion in nonpolar rubbers like NR, styrene butadiene rubber (SBR), ethylene propylene diene rubber (EPDM), butadiene rubber (BR), etc. is rather unsatisfactory. Figure 8.3(a) and (b) display the state of dispersion of organomodified... 

Roychoudhury et al. showed that the double peak of a blend of ENR-50 with chlorosulphonated polyethylene (CSM) at 1 1 weight ratio was changed to a single one (at 2.7 °C) when carboxylated nitrile rubber (XNBR) was added in the stock at 50 wt% (i.e. ENR-50/CSM/XNBR 25/25/50). Additionally, an exothermic peak was detected at 205 °C during a differential thermal analysis of a 33.3/33.3/33.3 mixture of this ternary blend. Taking into consideration that CSM, XNBR and ENR are soluble in chloroform whereas their blend is insoluble, the exothermic peak was attributed to self-crosslinking behaviour of this ternary compound (in the absence of curatives). 

This material is also now being considered for oil field service, possibly because of its exceptional abrasion resistance and higher mechanical strength at elevated temperatures. The resistance of carboxylated nitrile rubber (XNBR) to hydrogen sulphide will increase the evaluation of XNBR for oil well usage. Overall heat and oil resistances, however, are similar to those of standard nitriles. ... 

Carboxylated nitrile rubber (XNBR) has better abrasion resistance than regular NBR. Their applications are automotive seals, industrial footwear, mechanical goods, textile spinning cots, adhesives, packings, flat drive belting, hoses, industrial wheels, oil well specialties, and roll covers. 

Carboxylated Nitrile Rubber (XNBR), which contains carboxyl groups ranging from approximately 1% to 8%, offers much higher abrasion, hardness, modulus, tensile, and tear resistance. In order to achieve the best properties the compound must contain zinc oxide or preferably zinc peroxide as well as sulfur or peroxide cure systems. The various grades available in North America are given in Tables 2.9 and 2.10. 

Polymers that contain carboxylic acid functionality, such as carboxylated nitrile rubber (XNBR), can also be cross-linked with a divalent metal oxide, either zinc oxide, zinc peroxide, or magnesium oxide. The organo-metallic cross-link supplements the traditional sulfur or peroxide generated cross-links to provide superior toughness and abrasion resistance. In XNBR, the amount of ZnO depends on its surface area, with 5 phr at 9 m /g surface area being used compared with 9 phr at 3.5 m /g surface area. Standard XNBR grades are best cured with zinc peroxide or low... 

VULCANISATION SYSTEMS FOR CARBOXYLATED NITRILE RUBBERS (XNBR)... 

Polymer International 49, No.l, Jan.2000,p.ll5-21 VULCANIZATION OF CARBOXYLATED NITRILE RUBBER(XNBR) BY A MIXED ZEVC PEROXIDE-SULPHUR SYSTEM Ibarra L Alzorriz M... 

A new type of sulphidic crosslink arising from reaction between carboxylated nitrile rubber(XNBR) and bis(diisopropyl)thiophosphoryl disulphide was shown to be capable of improving the mechanical properties of the XNBR vulcanisates. It was also found that these sulphidic crosslinks in combination with metallocarboxylate crosslinks produced a significant effect in XNBR vulcanisation. Some investigations were carried out using a methyl iodide probe to elucidate the formation of chemical linkages during cure. Attempts were also made to establish the relationship between the structure and physical properties of the XNBR vulcanisates. 18 refs. 

Journal of Applied Polymer Science 60, No.9, 31st May 1996, p.1349-59 CURE SYNERGISM EV CARBOXYLATED NITRILE RUBBER(XNBR) VULCANISATION EV PRESENCE OFTHIOPHOSPHORYL DISULPHIDES AND AMEVE DISULPHIDE/ THIAZOLE ACCELERATORS Biswas T Basu D K... 

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