XNBR - Carboxylated nitrile rubber Carboxylated nitrile rubbers are made by copolymerizing nitrile and an organic acid monomer. This process gives an excellent resistance against the abrasion and an improved oil resistance; rolls rubber lined with XNBR have the same resistance to the abrasion of conventional polyurethanes but with a wide thermal range: constant temperature at 130°C is supported, with excursion at 145/150°C.