Each piece of
plastic was double-packed in the sterilization bag
(HM304, Hogi Medical, Tokyo, Japan) and placed in
the chamber. Immediately after sterilization, the
plastic materials and the filter paper were placed in
25.6 mL of 0.2 M NaOH (1 mL per 3 cm2 of plastic
material according to the Japanese guideline) and
left for 72 h at room temperature