Investigation of aging in polymer networks by T1ρ material property NMR imaging

Material property (MAP) imaging was found to be a promising method for the investigation of aging processes in elastomer materials. Based on conventional parameter-selective imaging, MAP imaging directly reveals the properties of the material by use of a theoretical description to relate the measured nuclear magnetic resonance data—in this investigation, T1ρ values—with the properties of the material. Following this concept, T1ρ images with different strengths of lock amplitude have been acquired for a rubber sample consisting of four pieces of natural rubber that were oxidatively aged under different conditions. The data were analyzed using a defect-diffusion model and transformed into images of those material parameters, which were found to be suitable for the characterization of the aging process. Images correlating with the crosslink density and the power law of T1ϱ dispersion were obtained indicating the degree of aging.