Three questions about drying plastics that everyone should know how to answer. The quiz first appeared in the January 2011 article, "You Must Dry Hygroscopic Resins,"
by John Bozzelli.
Q 1. Molecular sieves are often used in desiccant canisters to extract the moisture from the air circulating through the dryer. At what temperature should these desiccant canisters operate to keep the air dry?
A. Molecular sieves operate best at 120 to 130 F.
Q 2. What is the proper temperature needed to drive the moisture off the desiccant for regeneration?
A. For molecular sieves, regeneration temperature is 410 to 450 F. For cone ceramic type, 350 F.
Q 3. What is the only correct method for measuring moisture in plastics—weight loss or moisture-specific analysis?
A. Moisture-specific is the only correct method!
To properly understand the differences in performance between PET and PBT we need to compare apples to apples—the semi-crystalline forms of each polymer.
One of the more prominent trends in processing is the need for higher plastic pressures to mold parts.
The reason you dry certain plastics is to get the moisture out. But why does the moisture have to be taken out before processing?