INFLUENCE OF IODINATION ON TRIBOLOGICAL PROPERTIES OF ACRYLONITRILE-BUTADIENE RUBBER

Surface modification of acrylonitrile-butadiene copolymer (NBR) vulcan izates by treatment with an iodine solution results in a significant d ecrease in the coefficient of friction. The effect of modification is attributed to formation of a thin surface layer, incorporating iodine species, which has a higher modulus than the bulk material. The surfac e layer also has an increased roughness which, combined with the incre ased local stiffness, causes the reduction in friction. These factors overcome an observed increase in the surface energy after modification , which would act to increase the friction. NBR subjected to iodinatio n kept its bulk elasticity, which plays an important part in the mecha nism of deformation of the elastomer under conditions of friction, and ensures that the modified NBR retains its properties in engineering a pplications. The durability of the surface modification is attributed to interactions between iodine and nitrile groups from the acrylonitri le monomer units. (C) 1997 John Wiley & Sons, Inc.