If you’re shopping for a smartphone case, your choices in the material are often silicone, polycarbonate, hard plastics, and Thermoplastic Polyurethane (TPU). If you’re wondering what TPU is, we’re going to (figuratively) break it down.
What’s a Thermoplastic?
Plastic, as you probably know, is a (usually) synthetic material made from synthetic polymers. Polymers are substances made up of monomers. Monomer molecules form long chains with their neighbors, creating huge macromolecules.
Plasticity is the property that gives plastics their name. To be plastic simply means that a solid material can be permanently deformed. Plastics can be reshaped by molding, extruding, or applying pressure.
Thermoplastics get their name from how they react to heat. Thermoplastics become plastic at certain temperatures, which is when they are shaped as needed. When they cool down, their new shape becomes permanent until they are heated up again.
The temperatures needed to make thermoplastics pliable are much higher than, for example, your phone will ever be subjected to. So there’s little chance that a thermoplastic product will lose its shape during normal use.
Fused Deposition Modelling 3D printers, which is currently the most common 3D printer on the market, use thermoplastics. A filament of the plastic is fed through an extruder and the printer creates its product in layers that rapidly cool and solidify.
What About Polyurethane?
Polyurethane (PU) refers to a class of organic polymers that are joined by urethane links. “Organic” in this case refers to organic chemistry, which centers around carbon compounds. Carbon is the basis for life as we know it, hence the name.
One of the things that make polyurethane special is that it’s not a specific chemical compound. Polyurethane can be made from a number of different monomers. This is why it’s a “class” of polymers.
Because you can make PU from different materials, it means that different PUs have different properties. Most polyurethane is made into foam, such as kitchen sponges.
Why TPU Is Great for Protecting Devices
Although TPU is made from a variety of materials, products made from TPU generally have elasticity, transparency, and low weight. TPU can be quite thin and retain its strength. The combination of elasticity and strength makes TPU a good choice for protective cases since the material won’t crack, tear, or break under the types of forces a dropped device is normally subjected to.
Another bonus property of TPU is its strong resistance to oils and liquids. So the natural oil and sweat from your fingers shouldn’t stain it!
TPU Is Everywhere
TPU has such a wide range of applications that you almost certainly have a lot of the stuff lying around. Car dashboard panels, power tools casings, hoses, tubes, cable sleeves, shoes, and more are made from or use TPU.
It’s also a fine choice for a smartphone case material, but your phone is already made from some incredible materials such as polycarbonate and Gorilla Glass. So perhaps you don’t have to make the choice at all, and can be one of the brave folks that go caseless. On the other hand, if you really love customizing your phone’s look, there’s an argument to be made for having multiple phone cases.
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