Supplemental

Evaluating Weathering of Food Packaging Polyethylene-Nano-clay

Composites: Release of Nanoparticles and their Impacts

Changseok Han1, Amy Zhao1, and Eunice Varughese2, E. Sahle-Demessie*1

1U.S. EPA, Office of Research and Development, National Risk Management Research Laboratory, 26 W. Martin Luther King Drive

2U.S. EPA, Office of Research and Development, National Exposure Research Laboratory, 26 W. Martin Luther King Drive

* Corresponding author. Tel.: +1 (513) 569 7739; fax: +1 (513) 569 7677.

Email address: sahle-demessie.endalkachew@epa.gov (E. Sahle-Demessie).

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Table S1. Property of Cloisite® 20A

Moisture (%) < 3%

Color Off white

Packed bulk density (g/L) 175

Density (g/cm3) 1.77

X-ray results (d001, nm) 3.16

[BYK Addtives & Instruments., Technical Data Sheets, Available at https://www.byk.com/en/additives/additives-by-name/cloisite-20.php, accessed on March 11, 2017]

Estimation of Nano-clay Contents

To estimate the content of nano-clay in each sample, two LDPE composite samples (i.e., PM1

and PM2) were dried at 80 oC for 4 hr to remove water and then incinerated at 650 oC for 12 hr to

obtain nano-clays in the samples. The content of nano-clay in the samples were determined

based on their weight changes at each process step. The detail information was provided in Table

S2.

Table S2. Weight of samples at each step and estimated nanoclay contents in the samples

Stage PM1 PM2

Before drying 565.6 mg 566.4 mg

After drying(80 oC, 4 hr) 561.9 mg 564.4 mg

After calcination(650 oC, 12 hr) 18.8 mg 30.6 mg

Estimated nano-clay content 3.3 wt% 5.4 wt%

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Analytical Method

Ozone Concentration Analysis

The ozone generator is sensitive to moisture, therefore, the dew point of raw gas should be low

(less than -30oC). The ozone generator has a facility to cool using a water jacket, and the

temperature in the ozone generator maintained at 10°C. The power controller for the unit runs

on 120V AC with a power controller to vary the output power and consumes a maximum 500

watts of power.

The method involves determination of ozone which is generated from an ozone generator. The

ozone is trapped in a solution of excess KI (3%). The solution is converted to iodine (I2) by

ozone which is then titrated with a standard solution of sodium thiosulfate (Na2S2O3). In order to

determine the output of the ozone generator by passing the ozone gas through a KI trap (Traps A

containing a known volume 50 mL 3% KI + 150 mL ozone free water). Quantitatively

transferred these contents into an Erlenmeyer flask and added 10 mL of 2N H2SO4, and titrated

with standardized 0.01N (Ref: EPA method: Adapted from Standard Methods for the

Determination of Water and Waste Water, 18th ed : 2350 E. Semi-Batch Method Ozone

Demand/Requirement)

Ozone dose, mg/min =

A×N×24t

A = mL titrant for Trap A, N = normality of Na2S2O3, and t = ozonation time, min.

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Figure S1 Digital microscope images of raw (a) PM1, (B) PM2, (c) ozone aged PM1, and (D) ozone aged PM2 (All images were taken with a magnification).

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Raw Films PM1 PM2

419 h Ozone exposed PM1 PM2

(A) (B)

(C) (D)

Figure S2. Isothermal chemiluminescence test results for PM1 and PM2 before and after accelerated weathering (A: Pristine PM1, B: Pristine PM2, C: UV aged-PM1, D: Ozone aged-PM1, and E: Ozone aged-PM2).

Figure S3. TGA results of film samples that are ozone aged (A) PM1 and (B) PM2 samples

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Figure S4. Carbonyl index of ozone-aged PM1 and PM2 samples with different ozone treatment durations.

Figure S5. High angle X-ray diffraction patterns of (A) PM1 and (B) PM2.

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Figure S6. Scanning electron microscopic images of UV-aged PM1 sample.

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Figure S7. Scanning electron microscopic images of UV-aged PM2 sample.

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Figure S8. Mass of each element in unit mass of raw PM1 (black) and raw PM2 (gray) films.

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Figure S9. EDS analysis for (A) raw PM1 and (B) PM2 films.

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Figure S10. ICP analysis for (A) UV aged and (B) Ozone aged PM1 and PM2, and calculated

mass of element based on total mass in polymer ash from (C) UV and (D) Ozone aged PM1 and

PM2 samples.

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