As previously noted, the cross-linking reactions consumed all of the coagent molecules upon UV irradiation and UV irradiation proved to be essential for prevulcanization. The thin films prepared from the pure NR latex irradiated for 2 h without the photoinitiator and the coagent had tensile strengths comparable to the thin films prepared without irradiation from the latex mixture containing the photoinitiator and the coagent. The NMR data and the above comparative assessment of the films formed under different conditions implied that the UV irradiation, the photoinitiator, and the coagent used in this study worked well together. A lack of either UV irradiation or the coagent/photoinitiator, or both, prevented the formation of the chemical cross-links. UV irradiation creates electrondeficient free radicals25 which chemically react with molecules possessing double bonds (i.e., polyisoprene chains, 1,9-ND, Irgacure 1173) and with molecules that have extra lone pairs of electrons (as in 1,9-ND and Irgacure 1173)