Multiwall carbon nanotubes (MWNT) are an innovative raw material, coming into the market in larger quantities of several hundred metric tons per year. Carbon nanotubes (CNT) display extraordinary physical properties, such as very high electrical and thermal conductivity combined with the immense strength of the individual nanotube. The challenge involved in using this innovative raw material for rubber products is to transfer the properties of one single nanotube from the microscopic range to a macroscopic composite material, the most critical factors being the careful dispersion of the "entangled" nanotube agglomerates and their uniform distribution in a rubber matrix. Like for conductivity carbon blacks the homogeneity of the CNT filled rubber compounds increases with rising mixing time in an internal mixer while the electrical conductivity decreases. With an innovative mixing technique CNT-masterbatches with a high degree of agglomerate dispersion have been obtained. Using these masterbaches NBR-vulcanisates are very homogeneous and electrically conductive at the same time. Stress values at 300% of 8 MPa at 10 phr filler loading indicate the strong reinforcement potential of this new filler type.
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