Trip Allen has a suggestion for manufacturers that want to make sure the plastic parts they paint can be recycled easily: Don't paint them.
Allen and his Richmond, Calif.-based company, MBA Polymers Inc., have researched the idea of using a high-pressure, high-temperature water environment to separate coatings from plastics.
That approach, which has not been commercialized, does work, Allen said at the Society of Plastics Engineers' Global Plastics Environmental Conference, held Feb. 18-19 in Detroit. But there are issues.
Because many types of coatings are applied to the many different types of plastic parts, there is no one good temperature to remove paint, said Allen, chief technical officer and vice president of MBA. Various coatings and plastics will react differently at different temperatures, Allen said. The process works best when there is a uniform waste stream that can be processed consistently.
Paint chips, if not removed, can degrade the strength of recycled plastic and create surface imperfections.
Allen's company looked at a variety of methods - including the use of solvents and mechanical techniques such as abrasion - to separate paint from plastics before settling on a close examination of the heat-and-water treatment. Temperatures ranged from about 302Ã¸-392Ã¸ F in a pressurized tank.
``We found that the pressurized water systems did have a broad attack,'' Allen said.
The trick to the process is to use a high enough temperature to affect the paint but not the properties of the polymers, Allen said. The bottom line, he said, is that plastic parts being designed for recycling should avoid paint.