Introduction
PEEK stands for Polyether Ether Ketone. It’s a strong plastic used in industries like aerospace, automotive, and medical devices.
PEEK is known for its heat resistance, toughness, and chemical stability. But molding it is not easy. It needs very high temperatures. It shrinks a lot as it cools. And you must control how its structure forms during cooling. If you don’t, the part may warp, crack, or fail.
This article walks you through these challenges and how to solve them.
Challenge 1: Very High Temperatures
PEEK melts at a high temperature—between 370°C and 400°C.
Most standard molding machines can’t handle this without overheating or breaking down. That’s why you need specialized equipment. These machines must keep:
- Barrel temperatures at 380–400°C
- Mold temperatures at 200–300°C
Both must stay steady. If they drop too low, the plastic won’t flow right. If they get too high, the part might lose its shape or burn.
Using accurate temperature controllers helps keep things stable.
Challenge 2: Shrinkage and Warping
PEEK shrinks as it cools. Most plastics do, but PEEK’s shrinkage rate is high—between 1.2% and 2.5%.
If cooling isn’t even, the part can warp or crack. Cooling too fast in one area creates internal stress, which builds up inside the part. Later, that stress may cause problems.
To reduce this, use:
- Balanced cooling channel designs
- Simulation tools to model how the part cools
- Post-mold heat treatment, also called annealing, to gently release stress
(Source: Injection Molding Handbook, Rosato & Rosato)
Challenge 3: Crystallinity Control
PEEK is a semi-crystalline polymer. This means part of its structure is ordered like a crystal, and part is random.
The way it cools affects how much of that structure becomes crystal. If cooling is uneven, some areas will be softer or weaker than others. That can cause:
- Lower mechanical strength
- Dimensional instability
- Poor performance in the field
To fix this, control your mold temperature and cooling rate carefully. After molding, annealing helps the molecular structure settle evenly. This improves long-term strength and keeps the part from changing shape over time.
(Source: SABIC Design Guidelines for High-Performance Polymers)
Summary of What You Should Focus On
To mold PEEK correctly and avoid defects, focus on:
- Using machines that can handle very high heat
- Keeping barrel and mold temperatures stable
- Designing cooling channels that allow even cooling
- Running mold flow and cooling simulations early
- Using post-molding heat treatment (annealing) to reduce stress
- Monitoring and controlling crystallinity with proper thermal management
Conclusion
PEEK can handle some of the toughest jobs. But to mold it well, you need to be just as tough on your process.
High heat, shrinkage, and crystallinity all require attention. With the right tools and careful control, you can produce parts that perform exactly as they should.
