Figure 4 shows scanning electron micrographs of the fractured surfaces of the NR
vulcanisates blended with different types of fillers at 50-phr loading. Figure 4(a) shows an
agglomeration of filler particles in the DRB-filled NR vulcanisate. This is expected because the
Maejo Int.
interfacial interaction was weak due to the hydrophobic character of NR and the hydrophilic
character of DRB. In the case of CaCO3 filler, the filled NR vulcanisate showed several holes on the
fractured surface on which the CaCO3 particles were left (Figure 4(c)), which suggests that the
interfacial interaction between the filler particles and the rubber was weak, resulting in the
deterioration of the vulcanisate. Arayapranee and Rempel [14] also reported that the use of CaCO3
as filler in NR/EPDM blends gave rise to many holes on the fractured surface due to a weak
interfacial interaction. They found deterioration of the blend properties such as tensile and tear
strength when compared with unfilled NR/EPDM blends. Figure 4(b) reveals that the clay particles
were well dispersed without agglomeration within the rubber matrix. The dispersion of clay was
better than that of the other fillers, thus contributing to a greater tensile and tear strength of the clayfilled
vulcanisate.
(