Today’s topic is the “melting point.” It may sound basic, but as the name implies, this refers to the temperature at which a solid turns into a liquid.
The most familiar example is probably ice. Ice is solid. When you apply heat, it melts into water—a liquid. This happens at 0°C, which is the melting point of ice. As we all know, water becomes solid or liquid around 0°C. It’s such a common phenomenon that we don’t even think about it, but this is the definition of a melting point.
If we ended the article here, it would be far too short—and you might scold us for it! (laughs) So let’s go a little further and tie it into another important concept: heat resistance.
Many of you enjoy browsing hardware stores or 100-yen shops—myself included! It’s just fun to see what’s on display. If you look closely at plastic products, you’ll often see labels like “Heat Resistant up to XX°C.”
But what does that temperature really mean?
In fact, there are several temperature-related indicators used for plastics, such as:
- Heat deflection temperature
- Glass transition temperature
- Continuous use temperature
- And of course, the melting point
So what does “heat resistance” actually refer to?
You might be thinking, “Isn’t it just the melting point?”
Good guess, but no—it’s not about using plastic products right up until they melt! (laughs)
The correct answer is: “Continuous Use Temperature.”
Please don’t try to use plastics up to their melting point anymore! (laughs)
For reference, here are a few typical melting points of common resins:
- PE (Polyethylene): approx. 130 °C
- PP (Polypropylene): approx. 170 °C
- PTFE (Polytetrafluoroethylene): approx. 320 °C
- PEEK: approx. 330 °C
These vary significantly by material.
What about continuous use temperatures (i.e. heat resistance)?
Again, it depends heavily on the material. But even among similar-looking products at 100-yen shops, you’ll often see different heat resistance values depending on the manufacturer.
So how do manufacturers decide what temperature to list?
To be honest… it’s often a bit arbitrary.
Let’s take a closer look at PP (polypropylene) products. For example, you might see one washbasin labelled as heat-resistant up to 80 °C, while another says 100 °C—or even 120 or 130 °C!
However, in our industry, we would never claim heat resistance as high as 120–130 °C for PP. So when I see those numbers in shops, I can’t help but mutter to myself:
“No way that’s accurate!”
“There’s no chance it’ll survive that heat!”
“What are they thinking!?”
Call it a professional habit. (laughs)
I understand why manufacturers might want to advertise the highest possible temperature, but it’s a bit of a stretch…
So, how about our own products—specifically, plastic bearings?
These are even more sensitive than everyday consumer items, because external factors such as load and rotation come into play.
That’s why plastic bearings often can’t withstand the full heat resistance values listed in material manufacturers’ datasheets.
For example, if someone asks, “What’s the heat resistance of a PP bearing?”—we generally recommend a maximum of around 70 °C.
And even that is the upper limit. Depending on the applied load and speed, the bearing might not last even at 70 °C.
Plastic bearings are designed for specialised environments. Material selection requires experience and consideration of multiple conditions—not just temperature, but also mechanical and environmental factors.
So, dear readers… (here comes the sales pitch—thank you for bearing with me! 😊)
If you’re unsure which material to choose, please don’t hesitate to get in touch. We’ll be happy to listen and offer advice based on your application needs.
