Short Fibers Rubber Composites: the Comparative Properties of Treated and Discontinuous Cellulose Fibers

Composites produced by dispersion of selected short cellu lose fibers in elastomeric matrices are useful engineering materials. These fibers are pre-treated to provide dispersion in conventional mixing equip ment while minimizing fiber damage, and to give bonding to utilize the rubber reinforcing ability of the fiber. In the uncured composite, the fibers contribute higher green tensile strength, and almost no die swell on extru sion. The vulcanized composites show a monotonic increase in Young's Modulus and a decrease in ultimate elongation with increasing fiber load ing. As with many composites, the tensile strength is less than the matrix strength at very low fiber loading, but at higher fiber levels the matrix is reinforced and the composite tensile strength exceeds the matrix strength. The stiffening action of the fibers provides a harder material with greatly reduced solvent swelling characteristics compared to the matrix rubber. Finally, the tensile properties of the composite are precisely related to the orientation of the fibers in the matrix which can vary from uniaxial to random.