Annealing
Stress Relief and Dimensional Stability in Plastics
Stress relief is a heat treatment process for plastics used to specifically relieve internal stresses and improve the strength, dimensional stability, and heat resistance of components. Internal stresses often arise during manufacturing or further processing, such as during injection molding, extrusion, or machining.
If these stresses remain in the component, warping, cracking, or dimensional changes may occur during subsequent use—especially when exposed to temperature fluctuations or mechanical stress. Annealing can prevent such damage from occurring later or at least significantly reduce it.
During the tempering process, the plastic is heated slowly and evenly. The maximum temperature is maintained at a constant level over an extended period of time, allowing internal stresses to dissipate. This is followed by a very slow and controlled cooling process down to room temperature. This uniform temperature profile is crucial for preventing new stresses from forming in the component.
Tempering improves the long-term stability of plastic components and ensures greater process and operational reliability, particularly for components with tight tolerances or high requirements for dimensional stability.
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Silvio Stranek
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Email. s.stranek@htr.at
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Sales, Technical Consulting / Quotes (Styria, Vienna, Lower Austria, Carinthia, Slovenia)
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Phone: +43 (0) 664 / 88 64 15 06
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Your Questions, Answered
We have compiled a list of frequently asked questions to help you better understand our services.
What is the purpose of tempering?
The purpose of annealing is to relieve internal stresses in the plastic, making components more dimensionally stable, stronger, and more resistant to thermal effects.
When is tempering recommended?
Tempering is recommended following manufacturing or machining processes that induce stresses in the material, as well as for components that will later be subjected to thermal or mechanical stress.
How does the tempering process work?
The plastic is slowly heated, held at its maximum temperature for a specified period of time, and then cooled very slowly to room temperature.
Does annealing alter the mechanical properties?
Tempering can improve strength and heat resistance. However, the goal is not to change the microstructure, as is the case with metals, but rather to stabilize the existing state of the material.
Which plastics can be tempered?
Many engineering plastics can be heat-treated. The exact temperatures and holding times depend on the material and are determined based on the properties of the specific plastic.
Why is slow cooling important?
Cooling too quickly would cause stress to build up in the material again. Slow cooling ensures that the reduction in stress is permanently maintained.