What is thermocol? And what is its manufacturing process?

What is it:

Thermocol is a synthetic substance created from another synthetic substance called polystyrene. Polystyrene is a hydrocarbon derived from petroleum and is very, very versatile. Polystyrene is also used to make Styrofoam. It is comprised of molecules of Styrene and Benzene. It is harmful to both the human body if ingested and to the environment if not properly disposed of. 

To make Thermocol, polystyrene beads are made. These beads are then heated or steamed to rather extreme temperatures, causing them to both expand and fuse together. These beads, once fully expanded, are comprised of 95% percent air, the polystyrene making up the other 5%. As such, there is a vast amount of space taken up by comparatively little material. This also makes the material incredibly light, and fairly durable for how little density it possesses.

Because it is made of petroleum, Thermocol will dissolve if exposed to any sort of petroleum solvent. It is also incredibly water absorbent, especially when compared to Styrofoam. Styrofoam is created by mixing polystyrene with other chemicals to form a liquid. Instead of being heated like Thermocol, it is cooled and expands during this process, much like water expands when it is frozen. What is interesting is that Styrofoam and Thermocol, at their bases, are chemically identical (C8H8). It is the treatment and manufacturing properties that produce these differences. 

When Thermocol, in its final stage, is compared to Styrofoam, several differences in physical properties become evident. Firstly, while both absorb water, Thermocol can and does absorb much more than Styrofoam. It can absorb 2-4% by its volume, while Styrofoam can only absorb up to 0.5%. 

Secondly, Styrofoam insulates against heat much more efficiently than Thermocol. Styrofoam has what is called a closed structure, meaning there is many fewer air pockets and gaps within the material when compared to Thermocol. Air is a very good conductor of heat, as is water. Thus, Thermocol many air pockets, as well as its ability to absorb a lot of water, relatively speaking, reduce its ability to be an insulator against heat. This issue can be mitigated by placing the material between nonporous materials to keep them dry and the air within them unaffected by the atmosphere around them. 

Thirdly, the density of Thermocol is, on average, much less than Styrofoam. This is due, again, to the air pockets present within the material created during the manufacturing process. Both materials do have variable density. This variation is intentional, with denser versions made for more heavy-duty jobs like refrigeration or insulation.

Lastly, both Thermocol and Styrofoam are highly flammable. Due to their chemical composition, when burned, they release toxic fumes than are harmful, and can be fatal, to humans. Specifically, the fumes can be deadly to the nervous system, which is quite important to any sort of bodily function. Because of this danger, both materials are disposed of in safe, controlled conditions. If proper safety guidelines are followed, little to no damage to the environment will occur.


Thermocol and Styrofoam are present in most people’s everyday lives. Construction, packaging, medical, and food companies all use these two materials. Things like takeout food, medicine, and tech are all packaged with these two materials. Due to Styrofoam’s higher average density, it is more often used in refrigeration and medicine. Thermocol on the other hand, due to its lower density and cheaper manufacturing cost, is more often used for roofing insulation and packaging things like shipped products and food.


One very interesting thing about Thermocol is that it is often used in art to design sculptures. As such, many craft variants of Thermocol exist, allowing artists to create intricate designs with the synthetic substance. Its price and ease of manipulation make it a popular choice. Here are some Thermocol craft options for you:

Where to Buy
Craft Foam 17 x 11 x 1 In. 6-Pack Rectangle Block for DIY Arts and Crafts
Craft Foam Block - 6-Pack Rectangle Polystyrene Foam Brick
DIYASY 80 Pcs White Foam Balls 0.8-2 Inches Craft Styrofoam Balls Assorted Sizes Art Decoration Balls for Christmas Ornament and DIY