Atlanta — Drying of PET—important before injection molding performs — is a huge expense, and 40-year veteran Pete Stoughton said inline measurement is a good way to check.
“Constant inline moisture analyzer, that's the key,” Peter Stoughton said at the Annual Blow Molding Conference.
PET absorbs moisture, and if is improperly dried before processing, the excess moisture can cause black spots. Stoughton said moisture also can cause defects that are not visible. For example, a very small amount of water in the PET will sever the polymer chains, reducing properties such as lowering the molecular weight, he said.
But preparing the material is costly. Drying PET can consume up to 25 percent of the total energy used in a preform molding operation, he said.
“PET dryers are energy hogs,” Stoughton said. “They consume huge amounts of energy for the job that they do. And a majority of that is wasted energy.”
Stoughton has 40 years in the industry, working with PET and dry technology. He started his consulting firm, Polymer Drying Services, in 2009 after a 35-year career Conair Group, the auxiliary equipment manufacturer.
He gave a 101 lesson in drying, saying that key variables include dew point, airflow, temperature and drying time.
“There are no shortcuts,” Stoughton said.