PFG-NMR measurement of self-diffusion coefficients of long-chain -olefins and their mixtures in semi-crystalline polyethylene

The self-diffusion coefficients of C6-C16 long-chain -olefins and their mixtures in semi-crystalline polyethylene were measured through the pulsed field gradient nuclear magnetic resonance (PFG-NMR). The effects of chain length, polyethylene (PE) type, and co-monomer type in PE on the diffusion coefficients were investigated. Moreover, the influence of halohydrocarbon, cycloalkanes, and arene solvents on the diffusion coefficients of C12 -olefin in PE was characterized. The results have demonstrated that the diffusion coefficient of the single-component -olefin in PE decreases exponentially with the increase of the carbon number of -olefin, and the crystallinity and crystal morphology of PE play a more important role than the co-monomer type in determining the diffusion coefficients of -olefins. In addition, the apparent diffusion coefficients were used to represent the diffusion behaviors of the -olefin mixtures in PE. Owing to the presence of other hydrocarbon solvents, namely trichloromethane, cyclohexane, and benzene, the diffusion coefficients of C12 long-chain -olefin in PE are significantly enhanced, and such promoting effect of the hydrocarbon solvents in polyolefin elastomer (POE) is much stronger than those in high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE). (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44143.