PFOA and PFOS diffusion through LLDPE and LLDPE coextruded with EVOH at 22 °C, 35 °C, and 50 °C

摘要

Diffusion of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) through 0.1 mm and 0.75 mm LLDPE and 0.1 mm and 0.75 mm LLDPE coextruded with ethyl vinyl alcohol (denoted as CoEx) at room temperature (23 °C), 35 °C, and 50 °C is examined. These tests had negligible source depletion throughout the monitoring period, indicating limited contaminant partitioning and diffusion through the LLDPE. At 483 days, 23 °C receptor PFOA and PFOS concentrations, c_r, were ＜8 μg/L (c_r/ c_o ＜ 3.2 × 10~(-4)) for all tests, and at 399 days elevated temperature receptor concentrations were ＜ 0.4 μg/L (c_r/c_0 ＜ 1.6 × 10~(-5)) at 35 °C and ＜0.5 μg/L (c_r/c_o ＜ 2.0 × 10~(-5)) at 50 °C for both PFOA and PFOS. LLDPE partitioning coefficient, S_(gf) was 0.9-1.4 (PFOA) and 2.8-5.3 (PFOS) based on sorption tests at 23 °C. Based on the best estimates of permeation coefficient, P_(gCoEx). for CoEx was consistently lower than P_(gLLDPE), For PFOA, CoEx had P_(gCoEx) ＜ 0.26 × 10~(-16) m~2/s at 23 °C, ＜11 × 10~(-16)16 m~2/s (35 °C), and ＜ 10 × 10~(-16) m~2/s (50 °C) while LLDPE had P_(gLLDPE)＜ 3.1 × 10~(-16) m~2/s(23 °C),＜13 × 10~(-16) m~2/s(35 °C),and＜19 × 10~(-16) m~2/s (50 °C). For PFOS, CoEx and LLDPE had P_(gCoEx) ＜ 0.55 × 10~(-16) m~2/s and P_(gLLDPE) ＜ 3.2 × 10~(-16) m~2/s (23 °C), P_(gCoEx) ＜ 8.3 × 10~(-16) m~2/s and P_(gLLDPE) ＜ 40 × 10~(-16) m~2/s (35 °C), and P_(gCoEx) ＜ 8.2 × 10~(-16) m~2/s and P_(gLLDPE) ＜ 52 × 10~(-16) m~2/s (50 °C). These values are preliminary and may change (e.g., decrease) as more data comes available over time. The P_g values deduced for PFOA and PFOS are remarkably lower than those reported for other contaminants of concern, excepting BPA, which exhibits similar behaviour.