Comment by Composite Analytica on 23 Jul 2016 at 09:55:23
We can compare CO2 diffusion of HDPE and PET using CheFEM prologue permeation - mechanical response simulation software. Assuming a temperature of 23 degr C and both materials having a crystallinity of say 60 percent, the results are (D= diffusion coefficient, S = solubility in stp units):
CO2->HDPE: D = 8E-12 m2/s, S = 0.4 cc stp / cc bar
CO2->PET: D = 2E-13 m2/s, S = 0.6 cc stp / cc bar
Permeation of CO2 in PET (P=D x S) is much slower due to the much slower diffusion coefficient.
Sijmon van der Wal