In a natural setting, chemical and physical changes of polymeric materials occur due to various environmental stresses like heat, humidity, solar radiation (UV), atmosphere, etc., in a process referred to as weathering. These detrimental factors eventually cause an early failure due to cracking, surface erosion, loss of flexibility, change in color, and breakdown of the chains. In elastomers, the unsaturated bonds are especially prone to these attacks. The susceptibility of aromatic rings to UV has been known, too. The temperature dependence, characterized by an Arrhenius or slightly non-Arrhenius behavior, yields activation energy (Ea) of photodegradation values around 12-20 kJ/mol for aromatic thermoplastics and 27-50 kJ/mol for aliphatic thermoplastics. As much as the extent of weathering a polymer can undergo depends on its chemical structure, the constituent additives present in a polymer composition and the associated thermal history of the polymer system regulate its longevity. The micro-and macrostructural integrity of cross-linked elastomers are directly linked to the density of cross-linking. Generally, a continuous rise in elastic recovery and stiffness is obtained with increasing cross-link density. Properties like tensile and tear strength, toughness, and resistance to fatigue increase up to a particular loading of the cross-linker and reduce gradually thereafter. Study of the network density becomes all-the-more necessary but tricky when dealing with technologically and commercially viable polymer systems like elastomer blends. In elastomer blends, differences in the phase-specific cross-link densities can occur by a preferential distribution of the cross-linker in either polymer phase, where migration of the cros-slinker across the interfaces can occur. Apart from the extent of reactivity between a curative and an elastomer phase, blend properties such as polymer component ratio, viscosities of the constituent polymers, etc. as well as the mixing procedure, dictate the migration of the additives. In blends with phases having largely different curing rates, depletion of cross-linker due to its uptake in the phase with the higher curing rate can induce migration of cross-linker from the other phase, thus depriving the other phase. This results in a cure imbalance and expectedly large differences in the performance of the blend phases and the blend itself. Processes like weathering intensify these differences. All these factors warrant a phase-specific elucidation of cross-link densities for establishing structure-property relationships, and for product development.