Vacuum molding polypropylene over polyurethane foam
Vacuum molding polypropylene over polyurethane foam
(OP)
I am working on a project that a mold is machined out of polyurethane foam. Polypropylene sheet is then vacuum molded over the polyurethane foam mold. Unfortunately, the polypropylene and polyurethane seem to bond slightly, as the surface of the PP becomes ruffed up like the PU Foam surface. We have to use the PP sheet, but it has to have a smooth surface. Many molds are made, due to each product being unique.
Is there a cost effective material that can replace the PU foam that is easily machinable, or maybe a coating that can be put on the PU Foam that will reduce surface bonding?
Thank you for any assistance.
Rosej3570
Is there a cost effective material that can replace the PU foam that is easily machinable, or maybe a coating that can be put on the PU Foam that will reduce surface bonding?
Thank you for any assistance.
Rosej3570





RE: Vacuum molding polypropylene over polyurethane foam
What else did you expect forming over a rough mould with material above it's Tg?
Try hardwood - sand and polish it. Your forming will reproduce whatever your mould is.
If it's only one side is important, make a female version so the "correct" side is not against the PU mould.
Cheers
Harry
www.tynevalleyplastics.co.uk
RE: Vacuum molding polypropylene over polyurethane foam
One idea I had was to coat the PU foam mold with latex. Much like a latex sheath, or possibly dipping the mold in latex.
Any thoughts on this?
Thanks.
RE: Vacuum molding polypropylene over polyurethane foam
For really durable results, coat with polyester or epoxy.
Regards
Pat
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RE: Vacuum molding polypropylene over polyurethane foam
RE: Vacuum molding polypropylene over polyurethane foam
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You still need a master model but your urethane would work for that. I think the National Composites Center in Dayton has one of their machine available for trials.
RE: Vacuum molding polypropylene over polyurethane foam
a simple two component epoxy or polyurethane.
After the coating cures on your plug, apply a coating of mold release that can be buffed. There is no way that the parts will stick after pulling down the sheet.