Manufacturers like Xiaomi often put a transparent cover on the box of their mobile phones, but this accessory is also a common option that users use to protect their devices. Problem? It turns yellow at last.

These cases are often made from TPU (Thermoplastic Polyurethane), which is a great polymer for many reasons: it’s durable, flexible and inexpensive. What is not so great is its material deterioration.this causes the polymer to have that ugly yellowish appearance over time. And it is almost impossible to combat this problem.

And TPU conquered the world (rightfully so)

There is an entire industry around cases and covers for our mobile phones. At the same time, a huge It generated $21.4 billion in revenue in 2018 all over the world.

In fact, one wonders how many manufacturers have influenced the design of their mobile phones so much, when in reality there are many users. they almost “ignore” this effort by attaching a case to these devices.

Covers allow customize skin but also protects against drops, bumps or scratches. The options are many in formats and materials, but among the most popular cases are the clear TPU ones, taken from silicone cases and of course a great option for many.

The applications of this elastomer are actually beyond mobile safes. It is applied in elastic textile fibers, 3D printing filaments, automobile components, sporting goods, shoe soles or agricultural, livestock or fishing products.

Material also recyclableIt is an excellent option for these cases due to its high resistance to abrasion, high cushioning capacity and resistance to fats or oils.

All these advantages join another foundation: its low cost, making these covers often very affordable, and that is why some manufacturers include them as part of the accessory kit in the box of the mobile phones they sell. But the material, of course, is not perfect.

Plastics and UV light do not mix

The problem with these caps is that deterioration of the material causes them to turn yellow. In fact, and as explained by scientist and engineer John Wegner, the original material is actually yellow in origin. Shell manufacturers simply apply a blue tint to make the final finish transparent.

Source: MundoXiaomi

The plastic used in these cases consists of long chains of polymer molecules. held together by chemical bonds of varying strength. “They’re not linked together, but a series of helical chains that will start to separate (melt) when exposed to enough heat,” Wegner said.

In addition, the chains that make up the TPU material have a special refraction/reflection property of light. Changing the chains changes the light response and ultraviolet light breaks these bonds over timeleads to shorter, more complex sequences.

Heat accelerates this effect. and this causes the final effect on the aging of plastics due to ultraviolet light that you can get more details in this study.

Better buy another safe

As a result, as with silicone cases and many other materials, ultimately exposure to the sun and outside can cause these materials to degrade. This is what happens with TPU cases as well, causing yellowing that worsens over time. The question is: can it be prevented?

Some say yes: on the Internet and on platforms like YouTube or TikTok methods that promise to work and revert those cases back to their original appearance (or nearly).

Our colleagues from MundoXiaomi have already mentioned these popular methods. These include cleaning with soap and water, isopropyl alcohol and even give these covers a bleach bath.

There’s quite a bit more, as our colleagues from Xataka Android have made clear. In his unique analysis tried to “resurrect” three transparent shells Six different ways, including 40 volumes of hydrogen peroxide and even Mercadona’s magic cleaner.

The result in both cases? Unable to recover original orientation some of these covers, and indeed none of the methods analyzed, failed to particularly improve their appearance. What they did was, yes, leave them clean and disinfected, but the yellowish surface remained there.

The solution is actually not very dramatic: ideally, just buy another cover. Considering that this material is recyclable, it is not a serious situation to replace the yellowing cover with a new one after a certain period of time.

Also, significant yellowing of these covers usually takes several months and the speed at which we change our mobile generally (2-3 years) it will probably cause us to use at most a few caps during its lifetime if we use this type.

As they explain in Xataka Android, always also choose a case in a different material or color: It could also be humiliating, but the effect probably won’t be as visible as affecting TPU cases and covers.