Evaluating the potential for recycling all PET bottles into new food packaging

To evaluate the feasibility of recycling all PET bottles into food packaging, realistic estimates of the maximum concentration of contaminants that might be expected in the polymer are needed. To estimate the maximum concentration of a contaminant that might be in PET from the storage of non-food substances, sorption experiments into two types of PET were performed. These test materials were 0.8mm thick amorphous PET (a relative sink for contaminants) and commercial PET bottle wall. Using a commercial shampoo containing 1% lindane (C6H6Cl6), the test materials were stored in contact with the shampoo at 20 and 40 degrees C for 231 days. This commercial shampoo also represents an extreme case because it contains 7% acetone, a solvent which swells PET, further enhancing sorption of chemicals. Additional sorption experiments into PET were performed by preparing solutions of 10% toluene in Miglyol (a fractionated coconut oil), 10% benzophenone in Miglyol, 5% 2-butoxyethoxy ethanol (2-BE) in 50/50 water/ethanol, and 10% methyl stearate in heptane. Sorption data from the shampoo into PET illustrate Fickian behaviour. Specifically, the amount of sorption at room temperature is approximately40 times less than that at 40 degrees C. The amount of lindane sorbed into PET from the shampoo after 231 days was 0.1 and 3.7 mgdm(-2) at 20 and 40 degrees C respectively. These values correspond to 28 and 765 mg kg(-1) on a mass/mass basis. All sorptions are within the ranges measured and published by other authors using surrogate contamination testing schemes. Additionally, actual bottles from recycle bins were analysed for the amout of contamination. Results are discussed in terms of potential consumer exposure to non-food contaminants in food containers made of recycled PET and in relation to the surrogate testing methods recommended by the Food and Drug Administration (FDA) for determining the compatibility of a PET recycling process to produce containers suitable for food-contact use.