The Thermoplastic Guide

[DarthValkyria]

I've been collecting a list of commonly (and not so commonly used) thermoplastics used for armor building. Most can be found on the internet (though some will be more due to international costs) and all have a specialization for their use. Bare with me, I also try to break these down from a Chemistry POV as that is what I am and how I go about thermoplastics. 

 

What Are Thermoplastics?

First and foremost, a thermoplastic is a plastic resin or polymer that, instead of becoming harder and "setting" when heat is applied, actually becomes softer, often to the point where it liquifies. This means that the underlying factor of every single one of these plastics is that you NEED heat in order to manipulate the plastics. You don't want the plastics to reach full liquidation unless you are injecting them or sculpting them like clay. There is a "sweet spot" during the solid phase and liquid phase where the majority of these plastics are best used, where it is still solid with some liquidation. It is very difficult to use the sheet plastics if they have become more liquid than solid, and you'll know when you have reached that point when the plastic looks melty or oozy. This is known as the "glass transition phase" (think solid glass turning to melty glass). Droopy is fine, oozy is not. You will also need forms to mold the heated plastics as they lose their structural integrity in this droopy form, and essentially just slump around unless you are using them to sculpt solid forms. As a general rule, thermoplastics like their own kind, so combining gets tricky. I would advise keeping the first 7 together in terms of "possible combinations" as their adhesive properties are similar. Otherwise, you'll be delving into a lot of toxic solvents for true adhesion of the remaining plastics, if they adhere at all. I have made notes for Polystyrene and ABS. Generally, you can't get anything to "stick" to polystyrene except polystyrene, and that is with solvents. Same for ABS. You will need exterior surface adhesives such as super glue or E-6000, which still do not have a 100% guarantee of holding as they are not molecularly bound to the plastics and can still pop off.

 

Many of these plastics are available in a myriad of thicknesses and sheet sizes, so play around with what you need (Worbla is only one thickness IIRC).

 

One thing I definitely want to stress.......the lower activation temperature a plastic needs, the more chance you have that it will start to soften in regular "hot days" temperatures. Plastics like Friendly Plastic and such will start to soften in a hot summer day, and should not really be used in places that get near those temperatures!!!! Also remember storage since it gets hotter in your car than it is outside.

 

Safety

When you heat these plastics, fumes may be released from them, and it is very important to remember to wear a respirator and do these in a VERY well ventilated area! Garages and exterior spaces are preferred. While not common in all of the products, they are plastics, and plastics off-gas, meaning they create fumes when heat is applied, and the last thing you want to do is inhale those fumes! I used to work with thermoplastics and believe me, there were more than a handful of cases of people passing out on the production floor from not taking proper precautions, though the amount of plastic exposure was much higher than what you would be doing for costumes.

 

The number one issue with thermoplastics is burns. Plastic has a pretty high heat capacity, meaning it can hold a lot of heat energy within itself. When you touch heated thermoplastics, you are feeling every bit of that heat energy, and it can and will burn your skin if not handled properly. Always read information sent with your plastics or look up safety materials on the websites of the manufacturers of whatever you use. Remember, thermoplastics become semi-melty, meaning they conform to the shapes they come in contact with, be it a mold or your body. That means you have the entire heated piece touching and burning your skin. Please be careful when working with thermoplastics!

 

With that said, on to the actual plastics!  

 

The Plastics

1. Worbla- activation temperature for use: 90°C (194°F) for Original, Black, Mesh, and FlameRed, 120°C (248°F) for TranspArt (this is above boiling, so please be careful!

The go-to for nearly every genre of costuming and cosplay. Worbla is comprised of a thermoplastic resin and wood filler. Think elmers glue and paper pulp to make papier mache, but with resins instead of the collagen in glue. You can actually make a less refined version of it yourself using another plastic I'll talk about later (

). It is nontoxic, easy to work with, can be reused for scraps, and has a lot of flexibility in uses. It is sold in very thin sheets, and there is no "skeleton" in the plastic, meaning there is no structure within outside of shredded wood dust, and this means that large areas and areas that have a lot of stuff attached (read, heavy) need a lot of reinforcement in the form of many layers or using a foam core if you only need the aesthetic look vs functionality (aka looking pretty vs trooping). A HUGE bonus is that it stretches, meaning it can be formed over a multitude of shapes including round forms. It is not cheap, and has only recently been available in the US from distributors. This stuff is fantastic for detail work in plastic and for smoother finishes without any added surfacing. There is a textured side and a smooth side that is the adhesive side. Worbla actually comes in several varieties; the original brown, black, red, and transparent. The above description is for original brown Worbla.

 

Black Worbla is similar to the original but has a longer work time before cooling sets the plastic, and has a smoother finish. You have less time for the pieces to adhere before you need to reheat to the activation temperature, but you can get finer details.

 

FlameRED Worbla is designed for theatrical use and is similar to regular Worbla, only it has a built in flame resistant component meant to aid in storage safety. Not necessary for normal trooping costumes unless you store yours in a place prone to fires.

 

TranspArt Worbla is, as it states, transparent, and needs a much higher temperature to get it to soften. Pretty typical for clear plastics. It is friendly to being machined, vacuum formed, and can be tinted or dyed. It has a much higher durability than the other Worblas and is more friendly to forming vs casting or sculpting.

 

Mesh Worbla is very nice for adding to the back of the previously mentioned to add stability and structure without a lot of layers. VERY convenient, but costly.

 

Worbla recommends the use of Rosco's Flexbond primer to seal and smooth out the surface of the finished pieces to prep for painting. I also recommend it. 

They also state that Worbla can pretty much be attached to any surface other than itself with the built in adhesive but may require additional adhesives from epoxies or cements (This does not always work with the styrene-based plastics listed later on).

 

A side note for Worbla, I built a new set of hand plates at Celebration out of it using only a hair dryer. It took a while, but it worked. 

 

2.Terraflex activation temperature for use: unknown, just assume the same for Original Worbla at  90°C (194°F) leatherworking sites have stated 200°F

Terraflex is similar to Original Worbla, and is the proprietary property of Tandy Leather. I haven't been able to find any chemical information on it, but it acts similar enough to Worbla that you can treat it in the same fashion. Being from Tandy Leather means it is also more easily available. It is biodegradable, has the textured side and smooth adhesive side, and is apparently slightly easier to work with than Worbla because it has a longer working time (no word about working time vs black Worbla). Once you heat it up, it does not take as much heat to reheat it up, which does scare me a bit as this denotes partial resin degradation and could mean that the more times you have it in a hot location (e.g. summer trooping or car storage) it could lose integrity and form.

 

According to TandyLeather, if you are attaching it to leather, use EcoWeld Contact Cement as it does not adhere permanently.

 

3. Wonderflex activation temperature for use: ~66°C (150°F) 

Wonderflex has a mesh grid built into it that adds rigidity and durability that the previous plastics lack. It is great for "base" shapes that will have other bits added on. I actually used this as the base for my rebuilt Revan armor and then used other plastics on top of it. You do not get as nice of a surface as with the previous plastics (they do now have a smoother version, but still not as nice), and you can't get stretched forms like domes. You also can't really combine material scraps into usable material again, you can only stick them together at the seams, but this causes weak spots at those seams. Not currently available at physical retailers that I am aware of.

 

4. Kobracast activation temperature for use: 70°C (158°F) 

Think plaster sheets, but made out of plastic. It is AMAZING for creating VERY rigid and sturdy skeletons and bases. It is a mesh that is coated in plastic and acts very similar to plaster rolls. I have used it as bases for head pieces as the grid pattern makes it much lighter than solid sheets, allowing for greater features without the weight. Sort of pricey, but worth it. You can use hot water, heat gun, or hair dryer to soften it. A huge benefit to this plastic is the breathability due to the mesh. I've also used it for body casts where I didn't want to bother with plaster that could still collapse on itself without a lot of layers (think positive mold vs negative mold of plaster).

 

5. Fosshape activation temperature for use: ~93°C (200°F) 

Fosshape is, essentially, plastic felt that, when heat is applied, becomes rigid felt. It looks like felt when it is set up, and this means no smooth surface without a LOT of work and surface sealers. I have not used this in anything except playing around with it because I found it interesting. The #1 application I have seen for it is hat making because it mimics Buckram fabric but has a permanent rigidity due to the plastic. A huge bonus is that you can actually sew it into other fabrics and use it as a stiffener. Downside to Fosshape is that in order to get it to a more rigid state, you have to shrink it with heat to get a dense enough structure for support. This means that rigidity causes about 30-35% shrinkage in size from cut sizes.

 

6. Friendly Plastic activation temperature for use: 38°C (100°F) 

Polycaprolactone, aka Friendly Plastic, aka Plastimake, aka ShapeLock, aka Polymorph, aka InstaLock is a low temp plastic that is usually sold as tiny beads that you place into water at 100 degrees and turns into a sticky blob that you can then use to sculpt and mold. This is also the plastic that Worbla is comprised of, only without the sawdust. It says that it is great for making shapes, sculpting, and creating smooth surfaces, but every time I have ever attempted to use it, it just gets stuck to my fingers and I get angry. Possible user error, but even so, it is a precise replication of user error that I prefer to not deal with outside of making my own Worbla. You've been warned.

 

7. Sintra activation temperature for use: ~66°C (150°F) 

Sintra is the plastic that most signs are made of. It is a sheet version of PVC pipes you see at home improvement stores. It is thicker than Worbla, which means more durability, and is generally available locally at sign stores, plastic supply warehouses, and sometimes even Hobby Lobby/Michael's type retail stores. It is also cheaper. What it makes up for in availability, it lacks in usability. It is not as versatile as Worbla for details, but it is fantastic for larger areas and forms. It doesn't require much support due to its durability, which means you'll use less, and that costs less. You can soften it by placing it in hot water for a more even heat coverage. 

 

8. Polystyrene (aka "Styrene") activation temperature for use: 100°C (212°F) 

Styrene itself is a petroleum-derived colorless liquid. Polystyrene is what we are used to seeing everyday. Different variations of it are used in everyday plastics from buckets to bins, styrofoam, keyboards and computer mice. It is more brittle than ABS and has less impact durability. Common uses are injection molding and vacuum forming. There is a type of Polystyrene calls HIPS (high impact polystyrene) that has much more durability and usability, and is often used as the filament plastic in 3D printing, toys, packaging, and plastic shelving. Polystyrene is best used for larger area pieces or pieces with few angles or sides similar to Sintra, as you will get very little manipulation from it outside of fully melting for injection molds or vac forming. I've seen it available at Wal-Mart, Home Depot, and plastic supply warehouses. The activation temperatures for this and ABS are varied due to the different types of each, and you should consult the manufacturer of the plastic you use for proper instructions. Adhesion to itself can be done with poly cements (plastic cement) or solvents that chemically melt the plastic and bond it to itself, creating a single piece of plastic instead of attached pieces. You can also use surface adhesives such as epoxys or plastic fusion. If you are attaching a a different type of plastic, a surface adhesive such as superglue or E6000 is needed.

 

9. ABS activation temperature for use: ~82°C (185°F) 

Acrylonitrile Butadiene Styrene, aka ABS, is another type of styrene polymer. While both are derivatives of styrene, ABS and polystyrene can not be attached to one another through solvent adhesives. The bonds in ABS are too strong and will not release the styrene molecules in order to allow bondage. The only real way to attach them is through a topical adhesive such as superglue, but this compromises the durability and it will most likely pop off from normal use. ABS is also injection and vac form friendly, and is probably the most common plastic people in the 501st are introduced to due to this. Most armor is ABS due to the increased durability over polystyrene and HIPS. Again, large areas and areas with few angles and sides are best. Available at any plastic supply place. The activation temperatures for this and polystyrene are varied due to the different types of each, and you should consult the manufacturer of the plastic you use for proper instructions. Adhesion to itself can be done with poly cements (plastic cement) or solvents that chemically melt the plastic and bond it to itself, creating a single piece of plastic instead of attached pieces. You can also use surface adhesives such as epoxys or plastic fusion.

 

10. PVC and C-PVC activation temperature for use: don't heat these! Especially C-PVC!

Polyvinyl chloride and chlorinated polyvinyl chloride are sometimes used, though not as often. Pipes and rigid sheets (sintra) are made from it, and while their application in the costuming world is limited, they are worth mentioning. Often used for structural purposes in costumes or as long prop handles, I would advise never heating these directly outside of basic frictional heat from drilling or sawing if you don't have pipe cutters (the thermoplastic title ends at "heated and injected by the manufacturer"). Proper use of the pipes requires solvents, but unless you're going to have liquids flowing through them, regular surface adhesives are just fine. Even hot glue should work with a bit of roughing up first with sand paper.

 

While this may not be the "COMPLETE GUIDE TO THERMOPLASTICS", I hope it does give you some insight into the ever-expanding options that are available to the costuming and cosplay communities and how they are best utilized.

Edited September 30, 2016 by DarthValkyria

[NightShine]

As a big thermoplastic user myself, this is a great guide you've put up! now everyone can enjoy the wonders of these amaze materials!!