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karisud · Newbie Joined: 02 Jun 2010 Posts: 17 Location: Maine

I'm looking at using IPP (poly propylene) instead of the High Impact Polystyrene.

Has anyone else done this? Any advice?
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karisud · Newbie Joined: 02 Jun 2010 Posts: 17 Location: Maine

Answered my own question with some research. Posting it here in case anyone is interested. Conclusion: NOT the best item to use!

Properties
IPP is a semi-crystalline thermoplastic which has difficult form characteristics with
sheet sag inevitable. Chemically inert and very flexible with minimum moisture
absorption make it suitable for a wide range of applications. High forming temperature
but no drying required. Many grades of IPP are available containing fillers and
additives. Co polymer as opposed to homo-polymer PP is recommended for vacuum
forming, as the copolymerisation process helps reduce stiffness and broaden the melt
and glass transition temperatures increasing thermoforming ability.

Formability
Difficult – Translucent material goes clear when in its plastic state – occurs within
temperature band of approx 10°C and provides excellent indicator to forming
temperature. Good temperature control required in conjunction with a sheet level
facility.
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jdougn · Posted: Wed Jun 09, 2010 7:15 am Post subject:

Where'd you find the info on the characteristics? That could be a really useful source of information.

I've experimented around with a few plastics and still find ABS to work best for what I'm doing. Some plastics, like HDPE, telegraph every change in mold density directly through the sheet to the finished surface. For example, if there is a spot of bondo to fill a flaw, that same shape will telegraph right through the sheet to the finished surface.

Thanks for posting the information.
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karisud · Newbie Joined: 02 Jun 2010 Posts: 17 Location: Maine

There's a UK site that lists the specs and chemical characteristics of different kinds of plastics and also talks about temps, states, etc.

Had to pull up a Celsius to Fahrenheit converter, but LOTS of good info!

http://isites.harvard.edu/fs/docs/icb.topic604638.files/FormechVacuumGuide.pdf
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stormtrooperguy · Expert Joined: 24 Sep 2009 Posts: 126

wow, that pdf is great. thanks for posting!