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PAI is a material capable of achieving levels of performance that even semi-crystalline engineering polymers like PEEK, PPS, and PPA cannot. But you have to be willing to work for that performance, and the annealing process is an essential part of this.
TPUs form physical, rather than chemical, crosslinks that can be broken by reheating. Formation of these crosslinks can be sped up by annealing, which improves a variety of properties.
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You can forgo the elevated mold temperatures normally recommended for high-performance semi-crystalline materials. But it’s risky and likely to yield parts that under-perform expectations … assuming that they emerge from the annealing process looking anything like the drawing.
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For these polymers, annealing is done to establish a level of crystallinity that cannot be practically obtained within the parameters of a normal molding cycle. Here’s some guidance on setting annealing time and temperature.
In amorphous polymers, annealing is performed to draw down the internal stresses to a level not achievable within the conditions of a normal molding process. But a few parameters are important to achieving the desired results.
Relatively rapid cooling rates in processing introduce internal stress. If functional problems in use result, annealing may draw down the stress to levels that may not be achievable during processing.