PEEK Compression Molded Rod

Compression moulded PEEK exists for two reasons, and only one of them is about properties. The commercial reason is that compression moulding has no minimum run quantity, so a single large billet can be made without committing to a long extrusion run - which is why large diameters and odd sizes exist in this form at all. The technical reason is stress: an extruded bar cools from above 630F under pressure, and the resulting thermal and crystallisation stresses grow with cross-section until a thick bar cracks or moves on the machine. Annealing afterwards does not undo it.

The trade is orientation. Extrusion aligns the polymer chains along the axis, which flatters an axially tested bar - extruded stock reads substantially stronger and stiffer in tension and bending. Compression moulding gives a more isotropic billet that is tougher in impact and, in bearing grades, carries a markedly higher limiting PV, while compressive strength and heat deflection come out the same. So specify compression moulded for diameters and thicknesses extrusion cannot justify, for one-off large sections, and for parts machined well off-axis or hogged from the middle of a billet, where extruded orientation is a liability rather than an asset.