I have magnesium surrounded PLA polymer. I put the samples in Body fluid having water mostly so it means the water diffuses into PLA and reach magnesium surface. Then corrosion of magnesium starts which releases hydrogen gas at interface of Mg-PLA.
My question is that how fast hydrogen can easily diffuse out of the surrounding PLA matrix considering that PLA is also fully saturated with water. To sum up hydrogen would have escaped through free volumes PLA if it had been dry but now those free volumes are occupied by water.
Syed Wahaaj Ali Rizvi
For example, in response to your question. It's like comparing your question to the question. Where will the rate of diffusion of hydrogen in air or water be higher? In gases, the diffusion rate of molecules is higher than in liquids. Therefore, in a dry membrane, the rate of hydrogen diffusion will be higher than in a hydrated one.
Dear Syed
The hydrogen would escape ,ie.,diffuses, faster in a single phase,i.e.,air,than in two phase system,i.e.,air and water,especially the two phase system has a condensed phase like water.
Thanks to both of you Yuri Mirgorod & Khaled J. Habib ... I am looking for some quantitative comparison of hydrogen diffusion across 1) dry PLA and 2) fully water saturated PLA. I have searched a lot on internet about values of diffusion of coefficients of hydrogen from PLA but no luck yet. People worked on other gases but are not reporting diffusion coefficient of hydrogen.
Dear Syed,
PLA is attractive biopolymers useful for inhalable particle formulations owing to their biocompatibility and biodegradability. H2 diffusivity values are in PLA, 10–10 cm2 s–1 range, and their migration occurs by thermally activated process with 39 ± 1 kJ mol–1 activation energy. In gases, diffusion rate is likely to be more. A diffusion coefficient of hydrogen is higher in the gas.
Ashish
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