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Differences in Plastics ABS, PVC, Vinyl, Resin, Polystone


This article will cover various plastics from PVC, to Resin, and their methods, properties and advantages.
Polyvinyl Chloride (PVC)
PVC is a softer plastic, that is typically tinted before being put into the mold. It’s easily paintable (no primer needed) and acrylic paint just typically sticks to it without much of a hitch. It’s relatively cheap plastic. Also, because of its soft properties, sculptors are able to get away with putting in more detail and awkward angles. The downside obviously, is it’s soft, there’s a high chance of leaning figures. PVC is also easily repairable and very durable. You can drop a PVC figure without much problem, and it takes a lot of deliberate strength to tear PVC apart. But at that same note, it is a lot weaker than ABS.
PVC can also be made into a very hard plastic (PVC pipes). This is based on the density of how much plastic is put into an area. They do this with some of the single-leg standing pose figures. By increasing the density and consistency, there is less chance of leaning.
PVC poses some health concerns to most people, and as a figure collector, it should concern you too. To get the soft consistency of PVC, plasticizers must be added to it. Fortunately, it would only be hazardous to you if you ingest the PVC somehow, either through eating, or sticking it in places you’re not supposed to. Hence, baby toys and adult sex toys are considered part of this category. On another note, the PVC manufacturing process produces a lot of dioxins which are environmentally unfriendly. The next time you purchase a PVC figure, be more selective to save the environment, money, space, and general other headaches later on. Some PVC can be recycled (if it has the number 3 on it). So if you’ve had it with that figure you own, and nobody wants to buy it, see if it can be recycled first! Chances are though, you’ll have to throw it out instead…
Vinyl
Vinyl actually isn’t a plastic… or anything at all really. People seem to mistake that Vinyl is a plastic of some sort seen in some Kotobukiya figures. (really old Final Fantasy 8 figures, Star Wars figures, Matrix figures). Most of these Kotobukiya figures are hollow inside, meaning that the figure is constructed out of various hollow tubes put together. In actuality, Vinyl is any compound that includes a “vinyl group” (this gets into chemistry. If you’re interested, look up “Ethylene”). So in essence, PVC is a vinyl. Just that those Kotobukiya figures use a different type of PVC compound that’s a lot softer and thinner, making them highly flexible. “Vinyl Figures” are by far the worst for the environment because of the “softening” additives.
Acrylonitrile butadiene styrene (ABS)
ABS plastic is what your Playstation 1 shell (or other console system plastic shell) is made out of. It’s also what most Gundams are made out of. ABS is much harder, and is typically smooth. You can add texture to it, but it’s typically not a very fine texture. It’s impossible for paint to stick, so it almost always has to be primed first. Also, because of it’s hard nature, it’s impossible to get details that are more than 90 degrees angle, because otherwise the piece will be caught in the mold. That’s why all injection kits edges are always perpendicular. It can be round on the top all the way down to the edge, but it cannot go beyond that 90 degree mark.
ABS is made from a combination of monomers made from propylene, ammonia, butane, and coal. The advantage is that it combines the strength and rigid properties, as well as the rubbery toughness (ABS can bend without snapping). ABS is by far the strongest plastic used for making figurines. So while PVC is soft and rubbery in resilience, ABS is tough and rigid.
Resin (Rosin)
Interestingly enough, resin isn’t really a plastic a all from the technical sense. It’s compound consists of mostly organic ingredients found in plants and trees. What we commonly see in figurines is actually a synthetic resin. This synthetic resin has similar properties to ABS, but it is more brittle. It’s more akin to liquid solidified, almost like soap. The process is similar to epoxy – combining two liquids together to cause a chemical reaction of solidifying. When casting resin, this is essentially what happens. A finished resin cast has the same smoothness as PVC, but has trouble sticking paint. It too has to be primed. Resin is that it’s typically used for hobby kits, and therefore the sculptor doesn’t have to concern too much with technical restrictions of mass production products like PVC and ABS. The pieces are cut up into logical manners to fit within the restriction, and it’s up to the hobbyist to hide the seams, and fit the pieces together. The advantage of resin kits is that it’s soft and easy to sand and cut, while sturdy enough to hold up weight. High quality resin is typically very dense and can withstand quite a bit of pounding, but will shatter under significant pressure, while ABS would simply bounce back. But because of ABS’s toughness, it’s easier to sand resin.
Polystone (Resin compound)
Polystone is a similar property to resin, but is even more brittle! It’s higher quality than resin because of the base materials it uses – mainly it uses minerals such as aluminum hydrate, as opposed to synthetic materials. It’s typically made for mass-produced statues, such as the Final Fantasy 7 polystone cold-casts. From what I can tell, it seems that polystone is the least restrictive. The edges and cuts seem the cleanest, and a fair amount of detail can be put into it. This may be why polystone is the material of choice for mass produced resin cast figures.
Cold Casting (Epoxy)
Cold-Casting is the process of mixing a urethane resin with a metal powder to give the appearance of a shiny metal surface. It can also be used with paint to produce a resin of a certain color. As far as I know, cold casting is quite the opposite of regular casts, which are typically done with moderate temperature plastic molding. I think with cold casting, the liquid resin is already cold, and is freshly mixed. There is a certain amount of time before the mix solidifies into a solid. It’s during this time that the liquid must be poured into the mold. I believe it’s because of this, that you can get such clean lines and smooth surfaces.
Another method I know of for plastic making include heating plastics into solid molds. A solid object is made as a base, and a sheet of plastic is placed on top, and heated. It then melts and conforms to the shape of which it is placed on. The excess is then cut away. This is typically how plastic take-out trays are made. Another is the blow method, where a sheet of plastic is placed into an enclosed mold, heated with hot air. The air blows and expands the plastic to the walls of the mold and is then cooled. This is typically used to make plastic bottles like milk jugs. Vinyl figures can be made using the above manners, though I don’t know how efficient that actually would be.