Multiwall Carbon Nanotube Reinforcement of HNBR and FKM

Hyperion Catalysis Fibril™ multiwall carbon nanotubes (CNT) were added to three different elastomers: an HNBR, a peroxide cure FKM, and a bisphenol-cure FKM.  The inclusion of the CNT improved tensile strength, tear strength, and energy to break (elongational stress-strain energy to failure) in all three polymer systems.  We determined the CNT levels corresponding to 75 and 90 Shore A durometer. There were large differences between the phr levels of CNT as the sole reinforcing filler to achieve 75 Shore A durometer: 12 phr in HNBR, about 3.5 phr in peroxide-cured FKM, and 2.3 phr in bisphenol-cured FKM. The percolation threshold for conductivity also varied significantly between FKM and NBR. For HNBR, the best improvements were seen for adding either 3 or 7.5 phr of CNT to a carbon-black reinforced base compound. The strength improvement for the bisphenol-cured FKM was remarkable; tensile strength increased significantly. The CNT reinforced compounds based on peroxide cured FKM included numerous compounds with strength between 24-37 MPa, which is remarkable even for this exceptional class of elastomers.  The relationship between CNT concentration and physical and electrical properties for all three polymer systems is discussed.