Differences in the molecular weight and the temperature dependences of self-diffusion and zero shear viscosity in linear polyethylene and hydrogenated polybutadiene

G. B. McKenna, K. L. Ngai, D. J. Plazek

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73 Scopus citations

Abstract

Within the context of a generalized coupling model we can support the hypothesis that, while the mode of relaxation for self diffusion (D) and shear flow (η) are the same, the entanglement interactions are different. We assume that there are two distinct coupling parameters nD and nη for self diffusion and shear flow respectively. The model predicts the molecular weight and temperature dependences to be scaled by the relevant coupling parameters as: η∝[M2exp(Ea/kT)] 1 (1-nη) and D∝M[M2exp(Ea/kT)] -1 (1-nD). for melts with Arrhenius temperature dependences. We have found that nn=0.43 and 0.42 for polyethylene (PE) and hydrogenated polybutadiene (HPB) which scale η as M3.5 and M3.4. Also the apparent flow activation energies E*a of 6.35 kcal mole-1 for PE and 7.2 kcal mol-1 for HPB scale to primitive activation energies Ea of 3.6 and 4.2 kcal mole-1 for PE and HPB respectively. On the other hand the M-2 dependence of D results in nD=1/3. Then the reported activation energies for self-diffusion in PE and HPB of 5.49 and 6.2 kcal mole-1 scale to primitive activation energies of 3.7 and 4.1 kcal mole-1, respectively.

Original languageEnglish
Pages (from-to)1651-1653
Number of pages3
JournalPolymer
Volume26
Issue number11
DOIs
StatePublished - Oct 1985

Keywords

  • hydrogenated polybutadiene
  • molecular weight differences
  • polyethylene
  • self-diffusion
  • zero shear viscosity

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