EVALUATING ORGANIC-COMPOUND MIGRATION IN POLY(ETHYLENE-TEREPHTHALATE)- A SIMPLE TEST WITH IMPLICATIONS FOR POLYMER RECYCLING

The safety of recycled plastics for food contact use is largely dictat ed by the ability of postconsumer organic contaminants to absorb into recycled materials and later diffuse from containers made from recycle d plastics into the food supply. Diffusion and solubility data for org anic contaminants in poly(ethylene terephthalate) (PET) are scarce. An approach for determining permeability constants, diffusion coefficien ts and solubility constants of slowly migrating contaminants in PET is described. Compounds (neat or in admixture) were heat-sealed in packe ts made from thin (0 . 00127 cm) PET films. Packets were placed in con tainers with GC sampling closures. Headspace (volatile compounds) or a n external liquid medium (non-volatile compounds) was analysed for eme rgence of the compound. Diffusion coefficients were determined from no n-steady state diffusion equations, permeability constants were determ ined from steady state permeation, and solubility constants were calcu lated from diffusion and permeability values. Diffusion coefficients ( 25 degrees C) ranged from 10(-9) to <10(-16) cm(-2)/s. The diffusion c oefficient of benzene increased dramatically with concentration. Compo unds with high permeation increased the transport rate of slower perme ating volatiles.