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For the use in packer elements for oil exploration, rubber materials are required that can withstand high mechanical loads, high temperatures, and aggressive chemical media. To fulfill these demands, we designed composites of hydrogenated acrylonitrile butadiene rubber filled with both carbon black and short cut aramid fibers. Scanning electron micrographs indicate a strong connection between the resorcinol formaldehyde latex fiber coating and the peroxide‐cured rubber matrix. During the preparation of the test specimens, especially care was taken to obtain samples with very well‐defined fiber orientations. We studied the effect of fiber anisotropy on the hardness and on the mechanical properties under uniaxial elongation and cyclic compression at room temperature and 150°C. The strongest reinforcing effect is observed when the fibers are oriented along the main direction of deformation. For tensile test, this is the case, as expected, for fibers oriented parallel to elongation. For compression tests on cylindrical specimens, we find that the fiber orientation perpendicular to compression direction is most effective. At 20–40% strain, tensile tests exhibit a pronounced yield stress which is likely the result of the loss of adhesion between the rubber matrix and the fibers. Repeated loading and unloading compression tests reveal a considerable stress softening effect between the first and second cycle for fiber‐filled composites. At 150°C, the rubber composites soften considerably, but small amounts of fiber still induce a significant reinforcement. POLYM. COMPOS., 39:3212–3226, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Equilibrium swelling data with a range of solvents for non-filled cured rubber samples were used to determine Hansen three-dimensional solubility parameters (HSPs) of seven HNBR grades with nominal acrylonitrile contents from 21 to 49 % using the HSPiP computer program. The results showed that the increase of acrylonitrile contents for HNBR grades led to increase of polar component ( δ) and hydrogen bonding component ( δ), but with little changes of dispersion component ( δ). By using the so far obtained HSPs it is possible to explain and predict the swelling behaviors of the fully formulated HNBR-based vulcanizates in industrial oils (IRM 903 was selected for testing), in a reference bio-fuel (Fuel C was selected for testing) and in bio-diesel (FAME was selected for testing). In these liquids, the volume swellings decreased with increasing of Ra values (calculated by HSPs), and to a certain extent, can be calculated with a modified Flory-Rehner equation by assuming that fillers would not swell in question. [ABSTRACT FROM AUTHOR]

Hydrogenated acrylonitrile butadiene rubber (HNBR) was chosen to develop peroxide cured and carbon black N220 (CB) reinforced high modulus vulcanizates with possible applications in packers for oil exploration. HNBR vulcanizates are investigated by Rubber Processing Analyzer RPA 2000 and stress-strain tests conducted both in elongation and compression mode. All the mechanicals properties were tested both at room temperature (RT) and 150 °C in order to reflect application of packers. The results show that the modulus of CB filled HNBR vulcanizates increases with the increase of CB loadings in shear, tensile and compression mode. The physical interactions resulting from CB reinforcements show a stronger temperature-dependence than chemical crosslinks formed by curing agent. So the addition of reinforcing carbon black will have limited benefit for producing packer compounds with high enough modulus at high temperature, but more amount of curing agent will contribute to a stable high enough modulus. It is testified the filler-filler interaction is more temperature dependent than filler-rubber interaction and more chemical crosslinks increase the filler-rubber bonding and slightly decrease the filler-filler interaction, which is confirmed by the reinforcement factors. Compression tests show a strong dependence on the geometry of the samples and the compressive Payne Effect is examined by the multiple compression cycles. It gets stronger as the CB loading is increased. [ABSTRACT FROM AUTHOR]