The changes occurring in the samples due to weathering are represented as a ratio of coupling constants and their distribution after 504 h and 988 h of weathering to their corresponding values at 0 h in Figure . The chemical groups have been arranged from left to right in the sequence of resonances as NR-only → mixed → SBR-only. In the case of NR (Figure ), one can observe that the polymer cross-link density reduces after weathering to 504 h, and is analogous to the observations made using the low-field experiment. The increase in its coupling width is an indication of the formation of newer chain lengths. This aspect is pronounced in the CH and CH2 moieties as these sites are directly affected by the various reactions (S-modification, chain scission, cross-linking, etc) occurring in the vicinity. The methyl molecule benefits from its absence in direct chemical changes and gives a consistently low σln due to its ability to rotate about its bond with the main chain. Here, it is important to note that despite the observed widening, the average absolute value of σln after 504 h of weathering is about 0.410. Relative Weathering SBR to 504 h leads to an average increase of about 35% across all chemical environments of the rubber (Figure ) and complements the results of the low-field. Unlike in NR, the change in coupling distribution width is almost identical for all the proton environments.