Styrene casting test, not a complete failure

[Oldmopars]

So, the other day I bought a can of MEK to use as a solvent to join styrene (AKA model glue). It "melts" styrene. This gave me an idea. I took some sprue and chopped it up into real small bits and put it in a jar with the MEK. I stirred it till it all melted. I now had "melted" styrene.

I did not have modeling clay handy, so I used some silly putty. This is where the part failure came in, I did not know that Silly Putty reacts with MEK. However it did give me enough positive results to want to explore this further.

I could only cast things like hub caps or other things that are one sided. The melted styrene needs to be exposed to the air to off gas, so I can't pour it into an enclosed mold. But, it shows promise for replicating small items. I could mold in 2 halves and glue together.

This is no replacement for Resin casting or 3D printing, but could come in handy to make a replacement for a missing hub cap, valve cover, etc.

I think I need to try this with Modeling clay, or some other non-chemical based clay. Something organic would not react with the MEK.

Anyway, here is the first try with a silly putty mold.

 

[Ace-Garageguy]

Don't really expect to get anything usable with "melted" styrene.

The MEK is a solvent, and as it dissolves the plastic, which goes into suspension in the solvent, the mixture's volume increases over what the original volume of the plastic is. Obviously.

So, when it "dries", the MEK solvent evaporates back out, the part shrinks by a rather large percentage, and will most likely also warp because of uneven evaporation for any number of reasons.

[Snake45]

I experimented with this a couple decades ago and found it just didn't work very well. There are better and easier ways to achieve the desired results. 

[Oldmopars]

I am aware that this would never work for anything of any size. But, for a small part it may work. Making a mold out of silicon and casting it is a fair bit of work for one small part. I am hopeful that this could work for real small parts and be faster and easier.

If nothing else, it will be fun to play with. Only loss is an oz. of MEK and some old sprue. I have plenty of spare time.

[jeffdeoranut]

ive had fair results with bits of styrene and the old testors liquid cement in the glass bottle...

[Snake45]

34 minutes ago, jeffdeoranut said:

ive had fair results with bits of styrene and the old testors liquid cement in the glass bottle...

The principal ingredient of Testor liquid cement is MEK. 

[kitbash1]

My 2 cents on this.

Scott. MEK is a known cancer causing chemical, and is very dangerous stuff to handle. I worked in the printing field for over 35 years and we used MEK as a cleaning solvent. When we used it we had to have on, Rubber gloves, a resporator and safety glasses. MEK was banned for use in our industry in 1998, because of a number of people were getting sick from exposure to MEK and other chemicals with high levels of VOC's ( Volitile Organic Compounds ). If you want to play around with this stuff, it's your choice to do so. It's your health.  If it was me, I'd stear clear of this stuff. 

Edited December 10, 2018 by kitbash1

[Chariots of Fire]

Looks like it would not be worth it to try.  Rubber mold material and casting resin will give the best results, even for small parts.  If MEK is nasty stuff to begin with I'd stay clear of it.

[peteski]

Like Bill said, the solvent which makes styrene liquid has to evaporate in order for the styrene to solidify again. Regardless of how small the part being cast is, there will be shrinkage, pinholes, etc.  Not really work the effort (unless mediocre-quality parts are what you are after).

[Oldmopars]

15 hours ago, kitbash1 said:

My 2 cents on this.

Scott. MEK is a known cancer causing chemical, and is very dangerous stuff to handle. I worked in the printing field for over 35 years and we used MEK as a cleaning solvent. When we used it we had to have on, Rubber gloves, a resporator and safety glasses. MEK was banned for use in our industry in 1998, because of a number of people were getting sick from exposure to MEK and other chemicals with high levels of VOC's ( Volitile Organic Compounds ). If you want to play around with this stuff, it's your choice to do so. It's your health.  If it was me, I'd stear clear of this stuff. 

You do know that MEK is what Model Cement is made of right? Plastruct Plastic Weld says MEK right on the bottle, Testors and Tamiya solvents are MEK. So, if I wanted to stay away from MEK, I would get out of doing models.

I am only doing this for fun, I do not have any grand plans to start making hundreds of parts this way even if it does work. If it does work and I can get decent parts out of it, it will be more like 5 parts per year, hardly the exposure level that will kill me. I will get more exposure to MEK with every model I build.

[Ace-Garageguy]

A little applied science and striving for repeatability would be good if you really want to try to make this work...which I believe at this time to be not likely.

To control part-quality-destroying shrinkage, you'll need to determine the absolute minimum amount of solvent required to liquefy a given mass of styrene scrap.

Accuracy matters. For instance, if you get something like a 20% volume increase with the liquefied material, you can, of course, look for a 20% shrinkage rate when the stuff dries.

So, in that case, a mold that's made from an existing part would produce a copied part that's 20% smaller than the original in overall volume. Not really acceptable (and this is why tooling for many metal-casting processes is made larger that the desired finished part...to compensate for shrinkage).

On the other hand, if it's only around 5%, you might get away with making small parts.

 

 

[Snake45]

I've been playing with trying to make small parts like this for years, without resorting to liquid silicone and resiin. 

Molds can be made with common silicone caulk. The best I've found is Permatex black. The best results come from using several thin layers of the stuff, which of course requires several days of curing time. Lately I've been playing with Alumilite Mold Putty, which is easy and fast to use in small quantities (only mix what you need, no waste). $30 full price at Hobby Lobby but with your 40% off coupon you can be out the door for under $20 including tax. Good stuff! 

https://www.hobbylobby.com/Crafts-Hobbies/Clay-Molding-Sculpting/Casting/Mold-Putty/p/27710

For making the parts I like J-B Weld, which is also inexpensive and very easy to use, as the mixing ratio is 1:1 and it's not particularly critical. Nearly any good 12 or 24 hour cure epoxy works well, too. Don't use the 5-minute stuff. 

[peteski]

9 hours ago, Snake45 said:

I've been playing with trying to make small parts like this for years, without resorting to liquid silicone and resiin. 

Molds can be made with common silicone caulk. The best I've found is Permatex black. The best results come from using several thin layers of the stuff, which of course requires several days of curing time. Lately I've been playing with Alumilite Mold Putty, which is easy and fast to use in small quantities (only mix what you need, no waste). $30 full price at Hobby Lobby but with your 40% off coupon you can be out the door for under $20 including tax. Good stuff! 

https://www.hobbylobby.com/Crafts-Hobbies/Clay-Molding-Sculpting/Casting/Mold-Putty/p/27710

For making the parts I like J-B Weld, which is also inexpensive and very easy to use, as the mixing ratio is 1:1 and it's not particularly critical. Nearly any good 12 or 24 hour cure epoxy works well, too. Don't use the 5-minute stuff. 

Sure, your methods will yield acceptable results.  Your parts are molded  use materials which set (harden)  by a chemical reaction, not by solvent evaporation.

Edited December 11, 2018 by peteski

[wisdonm]

I have had success making small parts, largest was an intake manifold, using straight super glue (CA).

 

Here I made a brake rotor and caliper. The original is the gray one on the right

[peteski]

Super glue (CA glue) also hardens (sets) by a chemical reaction, not by solvent evaporation.

[FredRPG]

UV cure resin is another inexpensive option.  You can get a small bottle and a cheap UV light on Amazon for under 20 bucks. Works great for making headlight lenses.

[Oldmopars]

Well, more playing around. I got some of that molding polymer that you melt in hot water and form around stuff. (See Blue Stuff). I then used my melted (In MEK) styrene and molded a new door handle for my Van, I am changing the sliding door to a pair of singing doors and needed a new style handle.

It worked very well. I poured in a large amount of styrene so that as it set and the MEK left, there would be enough left for my handle. It worked great. I let it dry for a day and now I have a very nice styrene door handle. I know this does have limited uses, but this worked for me.

I also cast the same thing with Epoxy and now with Superglue/CA. Going to see what one I like the best.

[68shortfleet]

I too have experimented with this. I am using Evergreen stock melted into Tamiya ultra this glue. I made my mold from a half used leftover tube of Permatex blue automotive RTV cause I had it laying around.

I started with something simple. This is the fan from the Revell 32 Ford kits.

On the left is the kit piece, on the right is my first part out of the mold, not really useable in my book, in the middle is the second part out of the mold, this is a pretty decent part and showed me that this is possibly a viable method for a one off part. Your not gong into production with this.

[Oldmopars]

7 minutes ago, 68shortfleet said:

I too have experimented with this. I am using Evergreen stock melted into Tamiya ultra this glue. I made my mold from a half used leftover tube of Permatex blue automotive RTV cause I had it laying around.

I started with something simple. This is the fan from the Revell 32 Ford kits.

On the left is the kit piece, on the right is my first part out of the mold, not really useable in my book, in the middle is the second part out of the mold, this is a pretty decent part and showed me that this is possibly a viable method for a one off part. Your not gong into production with this.

I came to the same conclusion, I wanted a way to replicate just one part without a huge hassle. I have found that the Epoxy was a little better in some ways, but requires I use CA glue to put things together. I would never try to replicate a large item, or a large number of items this way. But, it can be done and it does work in a very small scale.

[68shortfleet]

I have also done the stock-ish firewall from the Revell 32 Ford Rat Roaster kit.

I didn't have as good of success with it. I have a useable part, but did get a little(very minimal) shrinkage as some mentioned would happen, but I also got a little bit of warping that would be easily fixed once its glued to the car body. The bigger problem I had was pin holes throughout the part. Haven't found a way to overcome that with liquid styrene.

However, I do believe that any of these small molds that I have made would easily accept resin also. Which should produce a better part.

[Ace-Garageguy]

I have to give you guys credit for getting better results than I believed you really could. Not show quality, but a LOT better than I'd expected. Nice job of perseverance.  

[Belugawrx]

Thanks for these tips guys..good stuff

On 12/10/2018 at 11:35 PM, wisdonm said:

 

 

 

Hey Don is that silly putty..?

[Snake45]

Has anyone tried casting using embossing powder and the heat gun that melts it? I have both, but haven't tried it yet. 

[wisdonm]

Don't think so, just something I had laying around. I think silly putty would be shiner.

[Foxer]

I've used melted plastics (using liquid glue) and it works fine for small parts. The problem at the start here is using silly putty that reacted with the MET. It had nothing to do with using plastic. The only limitation is the curing light has to reach every part of the part to cure it. Silicone casting rubber is the easiest mold maker also. Otherwise, taek all the advice to make your part making last longer than necessary.

For small parts there's nothing faster or simpler than using a Bondic type light-cured plastic. Look here.