The hardness of rubber products containing fiber treated with a coupling agent (as shown in Figure 2) was higher than for those with untreated fiber. The modulus of rubber products (Figure 3) also increased in the case of treated fiber. Introducing the coupling agent also improved the tensile strength (Figure 4) and abrasion resistance (Figure 5), compared with the products in which the fiber was not treated. Conclusively, the overall mechanical properties of the cured rubber were improved when the fiber was treated with a coupling agent before compounding. This is partly due to a better fiber distribution in the rubber matrix which can be seen in the SEM photograph shown in Figure 8. It was also assumed that chemical bonding occurred between the fiber and rubber as explained above. However, this should be confirmed experimentally in future work.