Annealing Conditions

PGA rods are normally extruded at very low line speed and cooled down gradually through multiple cooling stages. This controlled cooling prevents cracking from thermal shock and allows the polymer to crystallize without accumulating excessive internal stress. However, because PGA exhibits significant volumetric shrinkage, it is still advisable to anneal the rod after extrusion to stabilize dimensions and relieve residual stress.

For most applications, low‑temperature annealing is sufficient to relax internal stress in the amorphous regions without triggering secondary crystallization. But when the rod will undergo more aggressive machining—such as deep grooves, threading, or heavy material removal—a high‑temperature anneal is preferred because it provides deeper stress relief and improves dimensional stability, even though it may cause dimensional changes and reduce material ductility slightly due to additional crystal perfection.

Low‑temperature annealing can be performed at 90–110 °C for about 6 hours, using a gradual temperature ramp‑up and ramp‑down. High‑temperature annealing typically requires 160–180 °C, where the polymer chains have enough mobility to fully reorganize.