Comment by Composite Analytica on 22 Sep 2009 at 11:04:36
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Dear Kurt,
The diffusivity of Xylenes and Ethyl Benzene into LDPE and HDPE can be extracted from available reference data. Temperature dependency can be estimated using Arrhenius Law. Below we list some of the diffusvities. However, note that with regard to pollution of potable water pipelines, the thermodynamics (resulting in a certain solubility of the chemicals in the polymer, giving rise to an actual drive force for diffusion, swellling or stress cracks) is just as - or even more - important than the actual diffusion coefficient.
Diffusion coefficients (theoretical minimum figures while obtained at 1% of actual vapour pressure):
temperature: 23 degrees Celsius,
system pressure: 1 bar
partial pressure: 1% of actual vapour pressure (chemical activity approaches 0):
Toluene - LDPE: 1 E-12 m2/s (@ 1% of vapour pressure)
Xylene - LDPE: 1 E-12 m2/s (@ 1% of vapour pressure)
Toluene - HDPE: 3E-13 m2/s (@ 1% of vapour pressure)
Xylene - HDPE: 5E-13 m2/s (@ 1% of vapour pressure)
Kind Regards,
Sijmon
Composite Analytica
