A theory of case II diffusion
Noreen Thomas
A.H. Windle
2134/11412
https://repository.lboro.ac.uk/articles/journal_contribution/A_theory_of_case_II_diffusion/9236678
A theory is proposed to explain the transport behaviour of organic penetrants in glassy polymers in terms
of two basic parameters: the diffusivity of the penetrant, D, and the viscous flow rate of the glassy
polymer, 1/170. The rate controlling process for transport in these systems is considered to be diffusion
of solvent down an activity gradient coupled with time-dependent mechanical deformation of the
polymer glass in response to the swelling stress. The theory combines these two factors and is able to
predict a wide range of observed transport phenomena from Fickian diffusion kinetics at one extreme to
so-called Case II and Super-Case II behaviour at the other. The existence of a sharp front separating
swollen and unpenetrated polymer is shown to result from the concentration dependence of the viscous
flow rate.
2013-01-10 15:07:50
Diffusion
Sorption
Poly(methylmethacrylate)
Stress
Relaxation
Case II
Materials Engineering not elsewhere classified