Question on styrene properties

flyonthewall · 11-22-2005, 11:39 AM

One for the real techies here...

I'm considering a complete change in the way I produce my castings and going down the route of hot melt vinyl rubber in place of messy RTV silicone.

To cut a long story short, the hot melt stuff requires heating upto 150 C - 160 C and should be poured at 140 C - 150 C.

Therefore my question is; as most of my masters I'll be making casts of are mainly made of styrene plastic, I want to know if styrene will withstand having a liquid of that temperature poured onto it without it warping etc?

drunken monkey · 11-22-2005, 12:00 PM

by hot melt vinyl, are you talking about the stuff that you can get at tiranti's in london (in blue/green and white); the stuff you can simply melt down and re-use?
that stuff takes quite a while to cool and seeing as styrene can warp by just being next to a radiator (or even just boiling water) i wouldn't hold out much hope about it holding it's form when in prolonged contact with the vinyl.

have you though about making a master using something like alginate or even the silicon, then cast a positive then use the hot melt stuff over the new cast?
a bit long winded but saves the original.

Ferrari TR · 11-22-2005, 12:01 PM

150C...?!?
well plastic goes soft above 185f, if you meant 50C
you should be ok depending on how long it takes for the material to cool.

flyonthewall · 11-22-2005, 12:06 PM

Quote:

Originally Posted by drunken monkey

by hot melt vinyl, are you talking about the stuff that you can get at tiranti's in london (in blue/green and white); the stuff you can simply melt down and re-use?
that stuff takes quite a while to cool and seeing as styrene can warp by just being next to a radiator (or even just boiling water) i wouldn't hold out much hope about it holding it's form when in prolonged contact with the vinyl.

have you though about making a master using something like alginate or even the silicon, then cast a positive then use the hot melt stuff over the new cast?
a bit long winded but saves the original.

That's the stuff. Have you used it?

I'm thinking that as the parts are going to be set in plasticine to make a two part mold, there should be plenty of support for the part not to warp in any way.

mike@af · 11-22-2005, 12:12 PM

Curious, Chris, why do you want to change your mold material?

drunken monkey · 11-23-2005, 09:21 AM

i've used it but not the extent that i would say that i'd be the best source of advice.

back in my study days, i used it on several occasions when i needed to make quick molds.
as i implied above, i used to first make a 'perfect' first positive cast (usually using alginate for the neg - plaster or the clear resin positive) and then use the hot vinyl to make negative molds from the cast positive which i KNOW won't melt or warp.

admittedly, this was mostly down to my always being a bit nervous about pouring hot liquid over the original, especially when the original was my face or my hands...

from what you say about packing out the void spaces with plasticine (i'd recommend using proper red clay), i can't imagine that the plastic would warp. I can't how-ever, claim to know at what temperature that the plastic melts.

flyonthewall · 11-23-2005, 04:48 PM

Quote:

Originally Posted by GTmike400

Curious, Chris, why do you want to change your mold material?

Because of the fact its significantly cheaper and reuseable, it would be a much better material to use for the new method I have conjured up to increase kit production. After 3 years or so of casting kits, the process has become more than tedious and its something I don't enjoy doing anymore. My production turnaround is very low and most of my time is taken up with casting which means I have very little time to make new stuff nevermind make any actual display models. If i'm able to increase production by at least three fold then it will ease the burden and mean I'll actually be able to build some models for once.

D_LaMz · 11-23-2005, 04:56 PM

is casting your major source of income?

flyonthewall · 11-24-2005, 07:01 AM

Quote:

Originally Posted by D_LaMz

is casting your major source of income?

Yes. I'm not a rich man though.

mickbench · 11-24-2005, 10:12 AM

Quote:

Originally Posted by flyonthewall

Yes. I'm not a rich man though.

Well, share something in common there then. I'm not a rich man either. Whatever anyone says, IT work DOESN'T pay good money, even system Architects / Consultants are not paid as well as some think.

Good luck on streamlining.. Hope it gets you more time so you can start building your models again.

Or do what the IT sector does - "Outsource"..!! Those in IT will understand..

SchuberT · 11-30-2005, 04:09 PM

Hate to ressurrect a dead post... but I figured I would try to contribute....

http://www.plastruct.com/Pages/Properties.html
http://www.plastictroubleshooter.com...melt_temps.htm

I don't know if you use plastruct, but the info they have on their Styrene may be helpful. They say they use "Hi-Impact Polystyrene" and at the second link it says Polystyrene has a melting temperature of 350-390 degrees F. 150 degrees C is about 302 degrees F. That's quite a difference, but I don't know the temperature at which the styrene softens... and I think that's the information you need most.

The best idea I can think of is make some sort of dummy part to be molded and see what happens from there.

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