Is it possible to dissolve PLA without harm to a Polyurethane or Silicone Mold?

I am currently undergoing a research project involving the development of a prototype using PLA in combination with a surrounding soft transparent silicone, resin or polyurethane mold. The goal is to make the core of the prototype out of PLA (preferably) or ABS, cast a polyurethane mold around it, and then dissolve the PLA core without any harm to the silicone/polyurethane using a solvent. The end product would be similar to a boiled egg without the egg yolk (yellow part) with a hole at the top.

Are there any popular solvents used today that break down PLA to a liquid-based solution so that it can easily pour out of the prototype while not affecting the structure of the polyurethane/silicone?

I've heard that PLA breaks down in a solution of lye, but I haven't tried it myself, so I don't know if it pours out or has to be removed with tools. If you try this, be careful; that stuff can burn you badly - wear gloves and safety goggles.

Andrew Werby
www.computersculpture.com