However, the tensile strength was reduced when more fiber or coarser
fiber was used. This confirmed the results obtained by van Rossem(2) that continuity in the rubber phase was reduced when a higher amount of fillers was used. In the case of coarser fiber, even though the aspect ratio is greater, the poor adhesion between fiber and rubber and less surface area of filler markedly affected the tensile strength. It was also noticed that the positions where the specimen breakage occurred were frequently at the interfaces between rubber and fiber. Evidently, this implies that adhesion between two components was relatively poor, which can be confirmed by its abrasion resistance.