Abstract
The potential advantages of introducing anisotropic properties into a rubber compound by replacing some particulate filler with short fibre have been investigated. The control compound (containing no fibre) was based on NR and contained 60 pphr (N330) carbon black. In the fibre filled compound, 15 pphr of the carbon black was replaced with an equivalent volume of Santoweb fibre (10 pphr). Specimens with strong fibre orientation were produced and tensile, tear, compression, and shear properties measured at different angles to the orientation. Stretching parallel to fibre orientation resulted in a stiffness at low elongations × 3·5 higher than in the control compound. However, the tensile and tear strengths were lower than the control compound, probably owing to the high stresses at the fibre surfaces leading to fibre pullout. Maximum tensile and tear strengths were obtained when fibre orientation was at angles of 20° and 45°, respectively, to the stretching direction. Stiffness at a small (5%) compression was greater when fibres were oriented parallel to the compression direction. At greater compressions, fibre buckling reduced the stiffening effect. When fibres were oriented at 45° to the plane of shearing, shear stiffness in one direction was twice the shear stiffness in the opposite direction and twice the value for the control compound. Together with greater stiffness, this orientation led to low heat loss during dynamic shearing at a particular stress amplitude (40% of the value for the control compound).
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