Rubber components have long been reinforced with fibers or fabric for numerous applications, such as hoses, belts and tires. Woven/knitted fabric or filament is normally used for this. Short fibers and short fiber pulp (short fibers in a highly fibrillated form) are also suitable for reinforcement, and increasing use has been made of these options for a number of years now.
Using short fiber pulp increases the component’s strength (modulus) and thus changes its physical/mechanical properties. It also dispenses with the need for conventional reinforcing solutions (fabric) and results in improvements to certain properties that could not be achieved, for example, using fillers such as carbon black or silica alone.
Rhenogran® AFP-40/EPDM (GE 1909) and Rhenogran® P91-40/EPDM are two products from a series of predispersed, polymer-bound aramid short fiber pulp master batches. They are suitable for use in many high-quality technical rubber goods, usually on the basis of EPDM and HNBR. Rubber products made from such compounds are usually used in the automobile and mechanical engineering industries. Particularly where high standards have to be met in terms of quality, physical properties as well as the resistance of the parts to temperature and aggressive media, Rhenogran® P91 and Rhenogran® AFP are the materials of choice. Rhenogran® AFP-40/EPDM and Rhenogran® P91-40/EPDM are used as highly reinforcing additives.
Good mixing and dispersing properties, easy metering as well as integration and orientation of the fiber pulp in the rubber mixture are decisive for the end quality of the rubber products. EPDM and HNBR mixtures reinforced with aramid fiber pulp are used in many different applications, for example in belts, hoses, seals and molded parts. Good long-term temperature stability (>150 °C), dynamic load capacity and good resistance to media, in particular to oil (HNBR products) are made possible. Rhenogran® AFP is manufactured by a new process to achieve ultimate dispersability.
Depending on the orientation of the fiber bundles, aramid fiber pulp in elastomer components produces an unusual high level of reinforcement, in particular at low elongation. The steel elasticity of aramid fibers leads to enormous modulus increase even when only few parts (phr) are used. While the reinforcement effect of filling materials is only felt at high elongation levels, and a higher degree of cross-linking only contributes towards a modulus increase at medium elongation levels, the use of aramid pulp in the field of low elongation creates a new field of application for designing materials with extremely high strength. The uniaxial orientation of the fibers and the associated strength anisotropy are ideal for the use of applications in which high loads occur with medium or low elongation in one direction. In particular, these are power transmission belts, pressure hoses or special tires (motorcycle, off-road vehicle).