In the case of NR, contrary to SBR, the Dres appears to remain unchanged upon weathering up to 168 h. However, the broadening of coupling distribution suggests the modification of covalent bonds. The conventional sulfur-vulcanization system is known to majorly produce polysulfidic bonds. The broadening of coupling distribution is thus suggestive of the reformation of polysulfidic bonds into shorter variants like the mono-and disulfidic bonds. The same observation has been made earlier with NR exposed to thermo-oxidative aging at 80 °C. Upon continued weathering the bulk of NR undergoes a reduction in cross-link density due to the decomposition of main chains. These changes are also evident in the distribution width.