What does “PBT content” in keycaps actually mean?

Why do so many people obsess over this number?
And as an ordinary consumer, should you even care?

 First, it’s true that PBT has a real “content” concept.PBT isn’t something you run into every day; it’s normally chosen when you need heat resistance and mechanical strength, such as automotive connectors or LED heat sinks. Even many injection-molding technicians have limited exposure to it.

Over the past few years of interviews I’ve found that, when technicians have used PBT at all, it’s usually GF+PBT (GF = glass fiber). PBT is rare.
In the early days of the keycap industry, most factories weren’t familiar with PBT’s quirks .The molds they designed were flawed from the start. Some simply copied the tooling practices meant for ABS keycaps, placing gates and parting lines in the wrong spots. As a result, molds that couldn’t inject good productions.

Common defects include:

• Sink

• Stress marks

• Flash (burrs) 

At this point, opting for a modified resin becomes the more rational choice.

• Blending PC, ABS, etc. into PBT markedly improves its flow and lowers viscosity.
• Adding PET or glass fiber (GF) to PBT enhances warpage resistance and other mechanical properties.
• Various additives are then introduced to counteract any side effects brought on by these modifications.
• Therefore, the metric “PBT content” is real—not a fabrication.

So, does any of this actually matter to the consumer?

Yes—and no.

Where it does matter：

• Adding other resins really does alter PBT’s physical properties.
  Blending in PC lowers the ability to take dye during dye-sub; dark colors come out lighter.
• Adding ABS reduces the heat-resistance rating, making high-temperature dye-sub harder or impossible.
• Introducing glass fiber (GF) makes the caps more brittle, decreasing toughness.
  PBT itself is a very hard, “dry” resin. Injection-mold a large part in it and, compared with ABS, the surface feels noticeably rougher. ABS feels a little “slicker” or “wetter.”

Any additives will shift that tactile friction. But “feel” is subjective—some people love it, some hate it.

Where it doesn’t matter：

• First and foremost: you can’t tell what the “PBT content” is just by using the caps; in day-to-day use they feel the same.
• For normal typing, the difference is effectively zero. Apart from marketing buzzwords, it’s hard to see any real impact on the average consumer.