Clear, thermoformed food packaging used to be mainly polystyrene and PET, but newer materials barrier-layer plastics, polypropylene and bioresins such as polylactic acid make it more complex, according to panel members at the Society of Plastics Engineers' Thermoforming Conference in Milwaukee.
When you're processing all five different clear materials, it can be a real challenge to keep them separate, said Rick Esser, who is in charge of thermoforming at Plastic Ingenuity Inc. of Cross Plains, Wis. We spend a lot of time separating the materials from the beginning.
Esser said Plastic Ingenuity also carefully cleans grinders and tubing for material handling.
Training employees in the new materials is important, Esser said, but that education is in the trenches since there aren't a lot of classes on some of the resins.
Luke Gross said you have to make sure regrind is kept separate, since the materials can contaminate each other. Gross is executive vice president and general manager at Mullinix Packages Inc. in Fort Wayne, Ind.
Mark Strachan, president of Global Thermoforming Technologies Inc., urged formers to keep tight control of all incoming materials. He suggested clearly marking bins and grinders for each specific clear resin, and creating story boards to show which parts are made with which material.
Global Thermoforming Technologies is a consulting firm in Fort Lauderdale, Fla.