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steam molding polystyrene

Hi,

I am looking for some info on hobbyist steam molding of styrafoam starting from the raw compressed styrene pellets, and using steam to expand them. I have the basic info but am wondering if anyone here has experience doing this already or knows some detailed info on steam pressure/temperature/time etc related to expansion size of the styrene pellets, also if there are any biodegradable alternatives.

I am thinking of using a wood mold filled with partly expanded pellets, and then putting that in a steamer for 1atm steam to expand the pellets further to the shape of the mold, and then if necessary either a vacuum or drying stage afterwards. I think the styrafoam could develop significant force so obviously the wood mold would have to be structurally strong enough to not break from the expanding pellets.

cheers, Jamie

Reply to
Jamie M
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Ask on rec.crafts.metalworking, and ignore the fact that 80% of the traffic is right-wing political. If there's not an expert on that group, there will almost certainly be someone with some expertise.

Is steam necessary to the process, or can you blow hot air through the mold?

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Tim Wescott 
Control systems, embedded software and circuit design 
I'm looking for work!  See my website if you're interested 
http://www.wescottdesign.com
Reply to
Tim Wescott

As I understand it you need 200C, so superheated steam, and ridiculous pressure. Canned polyester foam is easily available and expands at room temperature.

Biodegradable alternatives? I've seen some sort of foamed corn starch used in packaging.

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  \_(?)_
Reply to
Jasen Betts

Hi,

Thanks. I think steam is required as there is "liquid pentane" or something in the raw pellets, which vaporizes from the steam, causing the pellets to expand proportionately to how much of the pentane turns into a gas, or something like that anyway.

cheers, Jamie

Reply to
Jamie M

I've seen at least one web page that had some tips on how to do it with a DIY setup, but it still looked pretty messy.

I looked at doing it industrially many years ago (seemed to make more sense to make packaging on-site rather than shipping air around) but it was too, too much with boiler regulations, handling of flammable blowing agents and several pieces of large equipment required including storage silos for aging the pellets.

--sp

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Best regards,  
Spehro Pefhany 
Amazon link for AoE 3rd Edition:            http://tinyurl.com/ntrpwu8
Reply to
Spehro Pefhany

Hi,

I think 200C is under 250psi pressure.

cheers, Jamie

Reply to
Jamie M

Hi,

I wonder how much pressure would be on the mold due to the expanding foam if the mold itself is in a pressure vessel, ie with 200C 250psi steam.

cheers, Jamie

Reply to
Jamie M

Don't know, but I think the molding pressure is pretty low anyway, way less than 250psi IIRC. Maybe 5 bars.

--sp

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Best regards,  
Spehro Pefhany 
Amazon link for AoE 3rd Edition:            http://tinyurl.com/ntrpwu8
Reply to
Spehro Pefhany

Yes, but not by much!

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Mike Perkins 
Video Solutions Ltd 
www.videosolutions.ltd.uk
Reply to
Mike Perkins

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