The heat treatment of plastics and polymers is essential to ensure tight tolerances are maintained during precision machining, bonding and polishing and to avoid cracking and crazing.
Heat treating also eliminates internal stresses and ensures better mechanical and thermal properties.
The process of heating the polymers is more complex. When polymers are cooled, they will often become very brittle. When heated, the polymers will first become flexible before melting
Heat treatment types:
Normalizing gives plastic material a higher resistance to internal stresses and makes a uniform structure. The material must heat to a specific temperature to change its properties. After heating, the polymer is cooled down at a controlled rate.
Annealing is the second type of heat treatment procedure. Once the annealing process is done the polymer and or other synthetic materials are more malleable and have an improved ductility and wear resistance.
Plastic annealing is recommended if:
- The end-use circumstances require stress relief that has to have properties impossible to achieve through materials or the product design
- You have to remove stress after machining
- The material would crack in the post-polishing process due to surface stresses.