Solvent ingress into polymeres

An interesting application of the profile NMR-MOUSE is the study of dynamic transport processes happening at the material surface, like the ingress of solvents into solid materials. An example of such a material is fuel tank wall, which consist of a multi-layer structure composed of two PE layers separated by a barrier of ethylene vinyl alcohol copolymer (EVOH) used to block the diffusion of volatile compounds through the tank wall. This layer is glued to the two polyethylene plates by means of two thin resin layers. The figure shows a profile measured through the tank wall with a resolution of 50 µm. The measurement time for one complete profile was about two hours. It can be seen that the different layers can clearly be identified. To prove the efficiency of the barrier layer, the diffusion of the gasoline inside the tank wall was followed after exposing the regrind side of the tank to gasoline (RON 91) by measuring profiles of the tank wall. The profiles show the diffusion front moving into the PE layer and stopping at the barrier. After 163 h a gasoline saturation of the regrind is reached, while the barrier layer keeps the other side almost unaffected. To verify the long-term efficiency of the barrier layer, experiments for longer exposure times are required.

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