When you hear the term “weather resistance,” you might guess from the kanji that it has something to do with the weather—and you’d be right. In this article, we’ll take a closer look at what weather resistance means, especially in relation to plastics.
Plastic materials are used in many outdoor applications. Think of rain gutters, plumbing, car bumpers, or dashboards. You’ve probably seen some older plastic components that have become faded, warped, or even cracked and brittle over time. Why does this happen?
The answer lies in weather resistance—a material’s ability to withstand environmental changes when used outdoors.
But what exactly causes plastic to deteriorate? Let’s look at the typical symptoms and causes:
● Symptoms of Deterioration
- Discolouration
- Warping
- Cracking
- Hardening
● Causes of Deterioration
- Ultraviolet (UV) radiation from sunlight
- Oxidation
- Heat
- Moisture (e.g. rain)
Other contributing factors include atmospheric ozone and pollution, but UV radiation is by far the most significant.
In general, plastics do not naturally offer high weather resistance. However, some materials stand out. One of the best-known examples is Teflon, which is highly resistant to UV degradation—so much so that it’s used on the roof of the Tokyo Dome. Other plastics with good resistance include acrylic (PMMA) and polycarbonate (PC).
For industrial parts like piping, gutters, or wastewater tanks—where outdoor durability is essential—polyvinyl chloride (PVC) is commonly used. PVC is considered to have relatively good weather resistance. Still, it’s not immune: after years of exposure to sunlight, wind, and rain, even PVC will gradually degrade.
Another example is something very familiar: laundry pegs. They’re exposed to intense sunlight and occasional rain. Many are made from polypropylene (PP)—a material that, surprisingly, has poor natural weather resistance. Over time, bright colours fade, and the pegs eventually snap. So why is PP so widely used?
The simple answer: it’s cheap. While weather-resistant plastics like PC are available, they cost significantly more. So manufacturers (and many consumers) tend to choose PP for everyday products, even if they don’t last as long.
It’s a trade-off: buy a low-cost product that may not last, or spend more for long-term durability.
Which type are you?
Personally, I tend to go for the PP version—can’t help it! (laughs)
That said, plastic technology is advancing. Studies show that colouring plastics with carbon black can reduce UV degradation. Additives like antioxidants and UV absorbers are also being used to increase durability.
Turns out plastics can be as delicate as some of us! (laughs)
But back to the topic—hopefully you now have a clearer picture of what weather resistance means.
At Kashima Bearings, our plastic bearings are often used in environments that require high weather resistance. Some are installed in UV-based water purification systems, others in solar tracking systems for photovoltaic panels. And in more unusual cases, they’ve even been used on archaeological excavation sites.
