I am aware that the curing of platinum RTV silicones is inhibited in the presence of urethanes, however, I synthesized a silicone sheet and a polyurethane block and allowed each their respective cure and demould times before placing them atop one another.
The silicone has since caused the surface of the polyurethane to exude a large amount of oil, the surface of the silicone has done similar. Both the silicone and polyurethane do contain softener to achieve the desired mechanical properties, is the surface simply leeching? What can be done to prevent this?
I suspect silicone oil has exhuded from the silicone sheet. You can run FTIR scan on the oil to see if it is silicone oil. you would need to put a barrier between the materials to prevent this or use a different silicone product.
Good suggestion about tracking residue via FTIR. Have you seen similar behavior in the two elastomers if not kept in contact? What is the softening agent in the polyurethane? Plasticizers are common but they do not often leave an exudate film.
I have seen silicone exhude silicone oil when under heat/pressure or when exposed to solvent. Polyurethanes are usually more stable and less likely to exhude.
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