Thermal stability of the blends obtained by DSC
thermograms is employed in QT4 software for performing
the statistical analysis, and the results are
presented in Figure 4 and Table III. Overall degradation
temperature of the blends, shown in Figure 4,
stands within 370–3858C for different compounds.
This temperature range is similar to the degradation
temperature of the neat rubber vulcanizate. These
results suggest that the degradation temperature of
the rubber/resin blend is dominated by the rubber
component. Camino et al.16 reported that the weight
loss of NBR, degradation of NBR obtained by thermogravimetric
analysis, begins at about 3508C,
which is in agreement with the results obtained in
this study. They16 also came into the same conclusion
about the mixture of NBR and novolac PH, that
the degradation temperature is dominated by NBR.
The results illustrated in Figure 4-c indicate that
the resin content has a negligible effect on the degradation
temperature of the rubber/resin blends. It is
shown that the rubber curing ingredients has a
minor effect on the degradation temperature of the
NBR blends. However, for SBR blends, the sulfur
content is found to be the most effective parameters
influencing the degradation temperature. As shown
in Figure 4(a), degradation temperature decreases
almost from 385 to 3728C by increasing the sulfur
content from 2 to 10 phr. This is probably attributable
to the structure of the sulfur linkage produced
in the SBR network which could be mainly polysulfi-
dic. This explanation is in agreement with the swelling
characteristics of the SBR compounds in which
the polysulfidic linkages are thought to be dominant
due to hindrance effect of benzene side group. The
higher the sulfur content, the more polysulfidic linkages
are produced. It is well known that polysulfidic
bonds have low thermal stability, leading to the thermal
decomposition of the vulcanized rubber at lower
temperatures