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.

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

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Dissertation (Ph.D.)--University of Toledo, 2007. / Typescript. "Submitted as partial fulfillment of the requirements for The Doctor of Philosophy Degree in Engineering." Bibliography: leaves 200-205.

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published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

The effect of various inorganic and organic additives as possible nucleating agents on the crystallisation behaviour of P. E. T. and the suosequent influence on the morphological and mechanical properties has been examined. Various methods of mixing(: the polymer and additive were investigated and a method involving the screw-Extrusion of the polymer and the additive was ultimately adopted. Crystallisation studies were carried out using differential scanning calorimetry under dynamic and isothermal modes. The results produced under conditions of isothermal crystallisation were analysed by means of a computer. Despite differences between batches of polymer all the additives with the exception of indigo produced a nucleating effect in the polymer as indicated by an increase in the rate of crystallisation compared with that of the base polymer. Two organo-metallic substances (sodium benzoate and sodium stearate) proved to be the most effective in this respect by decreasing the degree of supercooling of the polymer by 20 [degrees]. Morphological studies were carried out on isothermally crystallised samples, after etching and replication using a transmission electron microscope. A nodular structure whose dimensions were sensitive to both the nucleating agent and the temperature of crystallisation was observed. Mechanical testing of samples direct from the D. S. C. was carried out using a compression method. The breaking loads were found to vary with both the type of nucleating agent used and the crystallisation temperature chosen. A separate study involving the exanination of the resulting fracture surfaces by scanning electron microscopy revealed that a, high breaking load was associated with a fine discontinuous structure whereas lower breaking loads were characterised by a more continuous linear appearance. This implies a higher energy of fracture due to the increased surface area of the fracture surface of the former.