Release of silver from silver doped PET bottles

Development of active packaging based on polymers doped with silver has gained increasing interest. PET bottles were produced by injection and stretch blow molding under addition of silver phosphate (Ag₃PO₄) glass at 3 % and 10 % (w/w) and of AgPURE masterbatch at 10 % (w/w) which contained 6500 ppm silver nanoparticles (AgNPs). These bottles underwent release tests. Silver released into distilled water, 0.5 % and 3 % (w/w) acetic acid was quantified using inductively coupled plasma mass spectrometry (ICP-MS). The amount of silver released ranged from 2 μgL⁻¹ to 72 μgL⁻¹ after 10 days at either 21 °C or 43 °C. For PET bottles containing AgNPs no release of silver was detected. Release was dependent on percentage of antimicrobial filler in the polymer, temperature, and acidic strength. Diffusion coefficients of silver ion (Ag⁺) in PET were observed to be between 3.2 × 10⁻¹⁷ and 1.7 × 10⁻¹⁵ cm²/s. Bottles containing 3% (w/w) did not exceed the proposed specific migration level of 0.05 mg Ag per kg food, whereas bottles containing 10 % (w/w) did.