posted May 19, 2002 09:22 PM               

In extrusion, and extrusion compounding, everthing plays a role in the process not only the screw geometry. This is why I am a proponent of simulation as a tool in helping to design a process.

For POM a couple of basic suggestions:

1) Low barrels temperatures. Degradation is difficult to control becasue the degradation temperatures are only slightly above the melt temperature.

2) Low screw speed. Lower it even more if formaldehyde is a problem.

3) Deep screw channels lower shear rates and temperature buildup. Shallow channels provide more temperature control. What is best depends on the material, extruder specifications, and type of optimization required. Feeding, melting and mixing only add more dimensions to the screw geometry issue.

Extrusion (especially resins like POM) isn't for the faint hearted (or those with sensitive noses.)

Warning!!! The level of formaldehyde vapors coming off a POM extrusion which is improperly run can be dangerous! Be sure proper personal protective gear is used while developing a process.