Polyolefin processors molding and extruding products for automotive, medical, and certain other markets sometimes predry
materials to remove surface moisture and, in effect, "preheat" or soften the material to facilitate melting.
A laboratory twin-screw extruder, Brabender Model D6/2 was used for blending the predry
Immersion or spray rinsing can be followed by an optional hot air predry
. After a final vacuum dry to remove any moisture remaining in blind holes, dry air is returned to the treatment chamber.
for three days in a shallow, mesh-bottomed tray through a combination of sun and passive air movement.
"We were putting materials in to dry way ahead of time, and on bigger jobs we needed two drying systems to do that: One dryer to predry
material and then, of course, a production dryer to keep it dry and running."
The new masterbatches are based on Ampacet's Formula X PET technology platform, which eliminates the need to predry
PET colors and allows for feeding at the extruder throat--thus reducing feed-throat clogging and screw slippage, and improving color dispersion.
Molders must predry
grades containing conductive fillers that draw moisture into the polymer.
New extrusion technology from Welex Inc., Blue Bell, Pa., gives processors another option to extrude PET and PLA sheet without needing to predry
or crystallize the material.