Interestingly, this increase in cross-link density of SBR is rather marginal compared to the (approximately) 15-fold increase in the slope of the core region of SBR W504h with respect to the unexposed sample, as observed from AFM. This can be explained by the temperaturedependent gain in modulus of aged SBR with respect to that of unaged SBR. The gain in G' for the 504 h aged SBR is higher at 25 °C (23-fold) than at 80 °C (5-fold), the two temperatures being the measurement temperatures for AFM and NMR, respectively. This is, of course, without denying that the modulus in DMTA is a combined effect of, both, the skin and core regions.