Forum adverts like this one are shown to any user who is not logged in. Join us by filling out a tiny 3 field form and you will get your own, free, dakka user account which gives a good range of benefits to you: No adverts like this in the forums anymore. Times and dates in your local timezone. Full tracking of what you have read so you can skip to your first unread post, easily see what has changed since you last logged in, and easily see what is new at a glance. Email notifications for threads you want to watch closely. Being a part of the oldest wargaming community on the net. If you are already a member then feel free to login now.

Does anyone know at what point does GW plastic starts to become somewhat less solid.
Can I bake it at 120*C without it losing shape or degassing ?

The mind boggles. Why would you want to know? And what's stopping you trying it with a junk or cheap piece in your own oven?

Could be for using an oven baked clay for conversions. In which case, I had asked Raffa from Massive Voodoo about using something like FIMO for conversions and he had suggested putting the model in boiling water to bake (boil?) the clay. I haven't actually tried it, so I'd still say... experiment with something crappy before doing it for real.

Put some empty sprues in the oven and find out

Always a good idea to put plastic with unknown properties in the oven, don't worry about the gases coming off, I mean there harmless right.

 General Annoyance wrote:
Put some empty sprues in the oven and find out

Along with an oven thermometer

And stream it to youtube.

Gases/fumes WILL come off when the plastic is heated.

It WILL start to loose its shape when heated

If you are using it a form for polymer clay you WILL have structural problems.

Feel free to try and let us know the outcome.

Polystyrene starts to flow at its glass transition temperature, which is about 100C. I've caused heat damage to models with boiling water before, so by 120C you're probably going to have issues.

Technically it doesn't "melt" in to a puddle until 240C, but it starts to flow well before then.

Can't comment on what temperature you'll start to see fumes though.

 Rolsheen wrote:
Always a good idea to put plastic with unknown properties in the oven, don't worry about the gases coming off, I mean there harmless right.

They're toxic if I remember right so be careful if you do this. Won't kill you unless you try to sniff it all up or something, but it's not good for you either.

I just know that GW figures will warp if left in a car during summer heat and it was before noon.

 n0t_u wrote:

 Rolsheen wrote:
Always a good idea to put plastic with unknown properties in the oven, don't worry about the gases coming off, I mean there harmless right.

They're toxic if I remember right so be careful if you do this. Won't kill you unless you try to sniff it all up or something, but it's not good for you either.

Sarcasm

 Rolsheen wrote:

 n0t_u wrote:

 Rolsheen wrote:
Always a good idea to put plastic with unknown properties in the oven, don't worry about the gases coming off, I mean there harmless right.

They're toxic if I remember right so be careful if you do this. Won't kill you unless you try to sniff it all up or something, but it's not good for you either.

Sarcasm

Maybe chemical safety on an internet forum isn't the best place for sarcasm where text doesn't convey emotion brilliantly and some readers might not be native english speakers

To be honest I wouldn't have thought 120C was enough to get the plastic to start releasing fumes, it's above the glass-transition temperature but still well shy of the melting point and hopefully not going to be burning it.... but I've never tried is so I dunno.

A long time ago i studied material properties and my first employment as an engineer made me revisit the many material properties of plastic and polystyrene among other things. English is not my native language so some of the following terms might not be correct both due to language and poor memory. The glastemperature of PS is around 100C, but It might be different for different plastics (Polystyrene) depending on what type of additives are in the plastic. The glastemperature is when the plastic gets soft and you can bend it and reshape it without disturbing/breaking the moleculechains to much, they will resettle in a solid shape when cooled. The meltingpont of PS is somewhere around 240C and its when it turns from a mallable soft plastic into a liquid one. This temperature is also flexible depending on the actual composition of the PS as you can use additives to both lower and raise both the glass and melting points slightly. Since polymers behave different than metals when heated you could have localized melts before reachin this temperature though.
Emissions from PS can be toxic depending on the additives in the plasic. Pure PS gives of carbondioxide and water when burned, but additives changes the emmisions a lot. Sometimes carbonmonoxide is formed and long chains of polymer can break away as well. Neither of these are healty to inhale as they can disrupt the bloods ability to transport oxygen and even disturb the lungs capacity to filter air. They dont have much impact on the eniviromet if released as they are usually absored into other compunds after they react with oxygen. Pieces of solid plastics are different though as they normaly dont break down in a natural way by bacterias and the enviroment and thus remain for a long time. Generally you need more heat to release fumes from a material, but plastic can release fumes at lower temperatures as well. The lower temperature fumes are usually more dangerous than if you use a high temperature as less material reacts and forms carbondioxide. The most dangerous additives to any plasics are usually the compounds that are added to prevent the plastic from igniting or catch fire, these are released at high teperatures though so as long as you are not trying to burn the plasic those will still be bound.
Anyway... The amount of plastic we are talking about here should not be a problem for your health. Unless you plan on doing this often. It might smell bad, and the smell might attach to surfaces in the kitchen, but other than that it shouldnt be an issue. If you plan on doing this a lot i suggest a simple breathing mask and good ventilation.

I once made a frame out of plastic sprue and added clay around it to try and make some model trees. These were to be baked in 120 degrees. The plastic expanded more than the clay and cracked the clay that was hardening, It was not what I wanted to happen, but the results were cool anyway. I didnt get enough strength out of the branches though, both because of the cracks but also the thin plastic., So i scrapped that idea after that. Dont worry about the fumes, but the shape might be a problem. Keep experimenting!

I'm just wondering what the OP is trying to accomplish.

If you're trying to recycle and make something with the plastic it's easier if you grind and granulate the plastic first.

Actually it's a question I'd love to know the answer to, for the purposes of conversions. Specifically re-posing limbs by heating the plastic to softening point. I've done so with a jet flame lighter, but its a crude approach to it, as there's such a small temperature band between the plastic softening and just outright melting and warping the part. If I knew the melting point, I could use a heat source of an appropriate temperature. It would be great to be able to use this tenchnique reliably -far faster and less hasslesome than reposing with wire and putty.

 oldzoggy wrote:
Does anyone know at what point does GW plastic starts to become somewhat less solid.
Can I bake it at 120*C without it losing shape or degassing ?

No. You cannot bake it. The plastic visconcity runs around 90-100 or so, it softens, and the plastic is pliable, but you don't want to start touching it bare handed.

Remember, friend, THESE models have a tendency of being turned into blobs on a good sunny day in your car. They are not, as well, Kiln models. GW preheats the plastic into liquid form, casts in in metal dyes, and cranks them out assembly line style.

As to the "Plastic Fumes", That's not really an issue unless you are huffing your boiled down puddled plastic, like a jackass.

As to the reason for the OP, I could see using the sprues to put to recycle use. Boil them back down and cast the reused plastic sprues.


Automatically Appended Next Post:

 thegreatchimp wrote:
Actually it's a question I'd love to know the answer to, for the purposes of conversions. Specifically re-posing limbs by heating the plastic to softening point. I've done so with a jet flame lighter, but its a crude approach to it, as there's such a small temperature band between the plastic softening and just outright melting and warping the part. If I knew the melting point, I could use a heat source of an appropriate temperature. It would be great to be able to use this tenchnique reliably -far faster and less hasslesome than reposing with wire and putty.

DO you have a soldiering iron, or a styro cutter? Another thing to maybe use would be a hair dryer.

 Grot 6 wrote:


DO you have a soldiering iron, or a styro cutter? Another thing to maybe use would be a hair dryer.

Have a hot wire styro cutter. A pretty basic one. Yeah, I'll try that and the dryer. Thanks.

I've used a hot wire styrofoam cutter to go through GW plastic models before.

I'll admit, part of me is curious as well, since I was thinking of sculpting some details on an already-assembled Knight with Sculpey.. and now I stand curious on what effect that might have. Of course, that bake point is 130C, which is in the threshold we're discussing.

Of course, part of this is resin as well, which is another ball of wax.. I know it gets soft around that temperature as well, so this could be either useful or destructive..

Hair dryer will do the trick. Be careful.

I am not sure of the temperatures, but here are my experiences:

When using the restic, firmcast, resin, whatever you call the mock plastic, I always loved when with minor heat you could bend and reform the positions of arms, legs and such with ease.

However, when I tried this same trick to styrene plastic, it took considerably more heat and it would only bend in the area where you applied direct heat. It finally took me holding it over a candle flame. I could hold the restic next to my work lamp bulb for a minute and bend anything beautifully. The styrene actually started to misshape before it would bend easily.