Why Phone Cases Turn Yellow
Clear cases are a great way to protect your phone while still showing off its color and design. But they have one flaw; slowly turning yellow. Which makes your phone look old and dirty. So why does this happen?
Well, the yellowing is caused by a few factors. The first is oxidation. When plastics are exposed to oxygen, it begins a slow degradation process, that breaks down the polymer chains and results in a yellow tint. But not all plastics oxidize at the same rate.
For example, hard plastics like polycarbonate take much longer to oxidize. While soft plastics like TPU, or thermoplastic polyurethane, oxidize faster. That’s why soft, bendable clear cases can turn yellow in less than a year.
While those made from polycarbonate tend to remain clear longer. But there is one problem with hard plastics; they break instead of bending. So taking the case on and off or dropping it with your phone inside makes it more vulnerable to cracks compared to soft TPU plastics.
That’s why Apple’s clear case says it’s, “Crafted with a blend of polycarbonate AND flexible materials.” That means they added TPUs to make the case bendable, but it will cause yellowing eventually. Which they go on to admit, saying, “all materials and coatings are optimized to prevent yellowing over time.” And while it does take longer for their cases to turn yellow compared to the competition, it will happen eventually.
And direct sunlight makes things even worse. Since its ultraviolet rays break down the plastic’s molecular bonds and further accelerates oxidation. That’s why your clear case may look fine before a vacation, but have a yellowish tint or hotspot after returning.
Finally, even if a hard plastic case is kept out of the sun, contact with your skin will also contribute to yellowing. As the porous plastic reacts with the dirt and oils transferred from your hands.
So technically there is no way to completely stop this yellowing from happening. Although you can slow the process by choosing a clear case made primarily from polycarbonate, keeping it in a bag or pocket instead of direct sunlight, and regularly cleaning the case with soap and warm water.
Or, you can just buy a new one once it starts turning yellow.
