OK, I wasn't sure where to post this.  We're having a discussion here at work about the shrinkage rate of certain plastics and what happens to the plastic as it shrinks.  Our problem is we want to mold a piece of glass in an opening that is going to be made from polycarbonate structural foam as was wondering about the shrinkage rate.

Question:  If I co-mold a piece of glass in an opening of a PC foam part will the glass be free to move around in its opening?

Our conversation moved into theory, we think - take a flat round donut shaped part.  When this part shrinks, does the donut hole get bigger?  What about the outside surface, does it get smaller?

Something to think about...

Steve