I mold Lexan (polycarbonate film) in my Vacuum forming table which I built. I have made molds out of a product named MOLD MAX 60. It's used in the film industries (movies) for molding thousands of props. It's made by SMOOTH-ON and has heat resistant tendencies up to 560 F.
A question: why are you heating something up for 10 minutes???? What substrate are you trying to form?
I've run numerous thicknesses of plastics and the most I've had to heat it for is about 1 minute. Once I see movement in the plastic (about 30 - 40 seconds) I turn my vacuum on (which sits below the mold) and leave the heat (mounted 3.5" above the mold) on for between 5 and 30 seconds, with the vacuum on and it forms around my mold.
I just noticed the date of your post, not realizing it was 2013. Will post anyway.
