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Name: Diane D.
Status: educator
Grade: 9-12
Location: NY

Hello. I am an art teacher and we do experiment with combining mediums. Since we often use plastic containers as well as tins, my students and I are interested in learning more about plastics and recycling them. Could you tell me which plastics are used to be recycled into the foam food containers that restaurants use? What does the "new" foam consist of? What toxic chemicals are released from the convergence or melting of the original plastics and how are they contained during the process?

Hello Diane,

As a general statement, one type of plastic cannot be recycled into a chemically different type. Foam food containers are typically expanded polystyrene ("Type 6" recycling designation). There are 7 different common plastics designated for recycling. These are: Type 1 Polyethylene Terepthalate (e.g. soft drink bottles), Type 2 High Density Polyethylene (e.g. milk jugs), Type 3 PVC (e.g. some cling films, and blister packaging), Type 4 (Low Density Polyethylene (e.g. plastic bags and Tupperware), Type 5 Polypropylene (e.g. margarine tubs), Type 6 Polystyrene (insulation foam sheets, plastic models, cheap toys), and Type 7 (everything else!, but commonly polycarbonate and ABS).

The entire purpose of having these distinct types of recyclables, is to prevent one type of plastic from getting mixed up with other types. One type can also not be converted into another type. The idea is that (for example) recycled plastic identified as Type 1 (Polyethylene Terepthalate) can be ground into small pellets and either mixed up to 20% with "virgin" plastic of the same type to make new plastic articles of the same material. Similarly, old milk jugs (Type 2 H.D. Polyethylene) can be ground up and used to make new milk jugs.

But it is not possible (or at least not practical) to take one type of plastic and make a different one from it. The purpose of recycling is to be able to reuse plastic, not to chemically change it. In the case of foam food containers, health regulations generally require them to be made of virgin polystyrene, because safety requires knowing exactly where the raw polystyrene came from, and that it meets Food and Drug standards.

No common plastics liberate any toxic materials when processed properly. You may be thinking of the recent health scare of polycarbonate water containers containing very small amounts of Bisphenol-A (one of the chemicals used to make polycarbonate). This has nothing to do with heating during the molding process, but rather, it can result if the original process to make the polycarbonate in the first place, is not carefully controlled.

Bob Wilson

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