The critical design factor for the engineer is the performance value of a
property at the maximum operating temperature specified for the minimum life
of the part. For automotive engine components, part life requirements can be
up to 5000 hrs. The temperature encountered by a component varies
significantly depending on the application, its proximity to the engine,
driving behavior and ambient conditions. As these can vary enormously,
performance at 170ºC and for 5000 hours is taken as the reference point. For
actual parts, each engineer should determine their own requirements and
suitable safety standards.
The chart below shows that PA6 exhibits better long term performance at high
temperatures than PA66 and should be the preferred material for any
application running for extended periods above 150ºC. The better end-of-life
properties of PA6 by up to 60% can be exploited in the design stage, either to
reduce the amount of material needed to ensure a specific performance, or by
extending durability or part life guarantees.
When operating temperatures are above 100°C, parts dry out rapidly and the
effect of moisture absorption on properties
can be ignored.