The purpose of this thesis was to determine which contaminants were present in washed and dried shredded poly(ethylene terephthalate) (PET, flake) obtained from curbside collection and to determine whether their concentrations were above the US FDA threshold of 215 ppb. Over thirty semi-volatile contaminants were extracted from the treated flake by Soxhlet extraction using dichloromethane as a PET swelling solvent and gas chromatography-mass spectroscopy for identification and quantification. Soxhlet extraction of flake ground to 0-300 �m was effectively completed by 24 h, whereas sonication reduced the extraction time to 3 h. In contrast Soxhlet extractions on flake ground to a larger particle size range (>300-425 �m and >425-700 �m) were completed within four hours, possibly due to less aggregation in the extraction thimble. In the finely ground flake (0-300 �m) the levels of most contaminants were below 215 ppb, but six were not. Dodecanoic acid was present at about 1200 ppb, 2-butoxyethanol was approximately 1000 ppb, limonene, benzophenone and methylsalicylate were above 800 ppb and 2-methylnaphthalene near 215 ppb. After analogous method development the levels of all diffusible compounds in extruded PET pellets were below the threshold of 215 ppb.
The Soxhlet extraction technique was validated by comparison with total dissolution by TFA for two of the three particle size ranges obtained by grinding the PET flake (>300-425 �m and >425-700 �m) and for the unground flake. Further validation was achieved by the comparison of contaminant levels determined by total dissolution with TFA and sonication with DCM using flake ground to the 0-300 �m size range. The levels of contaminants were found to increase with decreasing particle size range, but XRD measurements of degrees of crystallinity were similar for each PET particle size range, thus showing that the differences in contaminant levels were not due to variable percentages of the amorphous material from the tops and bottoms of shredded bottles, relative to the amounts of crystalline PET from the mid-sections of the bottles. Hence it was postulated that the variations in contaminant levels were due to selective grinding of the more highly contaminated surfaces, whilst the larger particles incorporated the less contaminated interior material.
The analysis of the more homogenous annealed (extruded) pellets indicated that contaminant levels between the analogous particle size ranges were equivalent. This observation validated our interpretation of the high levels of contaminants found in finely ground flake being due to selective surface grinding where high levels are expected. When analysing volatiles, static headspace analysis was performed on flake and extruded pellets due to the limitations surrounding SPME. External standardisation was used as the method of quantification and the levels of toluene, undecane and p-xylene in extruded pellets were found to be below 38 ppb and therefore within the 215 ppb FDA-set threshold for flake and pellets.
| Identifer | oai:union.ndltd.org:ADTP/216519 |
| Date | January 2005 |
| Creators | Konkol, Lidia, lkonkol77@hotmail.com |
| Publisher | Swinburne University of Technology. Environment and Biotechnology Centre |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://www.swin.edu.au/), Copyright Lidia Konkol |
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