Materials That Withstand Temperatures
Question:
My company manufactures thermoformed items such as plates, cups, and containers. Most of these are made from polystyrene, but our testing indicates that the polystyrene will melt or distort in the microwave or under food service heat lamps. What materials are available that would withstand these temperatures, yet still be economical for single-use containers?
- Meltdown
Answer:
Dear Meltdown - You have found the primary shortcoming of polystyrene, which is a low softening temperature. Polystyrene will sag and distort at about 200 degrees F, lower than the boiling point of water. Most foods are water-based, so heating to boiling or steaming will destroy the polystyrene container. Worse yet, the polystyrene will partially dissolve in fatty foods, contaminating the food with plastic.
There are two material types that can handle most microwave and heated food service applications. Polyethylene terephthalate (PET) has useful properties up to 400 degrees F, but is much more expensive than polystyrene. Polypropylene (PP) softens at around 300 degrees F, high enough to easily withstand boiling water and steam. Polypropylene is both lighter in weight and lower in cost than polystyrene. To increase the stiffness of polypropylene, talc is often used as a reinforcing agent. Supplied as a fully formulated product, talc filled PP is competitive in cost with polystyrene. Such materials can be tailored for microwave, frozen food, and food service applications.
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