relationship of diffusion/permeation coefficient versus relative humidity  

Posted by Martin Tenpierik on August 02, 2005 at 17:11:14:


At Delft University of Technology, we are doing research on vacuum insulation panels. The panels we use consist of an open- celled core material (fumed silica) which is after evacuation tightly sealed into a high barrier film. This film is a bi- or trilaminate metallized composite polymer film of 97 mu (3 metallized PET layers and 1 HDPE or LLDPE layer). For estimating service lives of these panels, permeation models have been developed. Since however the permeance (or permeation coefficient for single-layered polymers) of these films depends on temperature and relative humidity, these relationships must be known also. The temperature effect can be modelled according to an Arrhenius equation. Does anyone know a relationship between permeance or permeation coefficient (or diffusion coefficient) and relative humidity for thin metallized composite films.

Kind regards,
Martin Tenpierik

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