CONTAMINANTS IN RECYCLCED PET PLASTIC

					                                NOTE

This online version of the thesis may have different page formatting and
     pagination from the paper copy held in the Swinburne Library.
          CONTAMINANT LEVELS
                             IN
         RECYCLED PET PLASTIC




                             By
                    LIDIA KONKOL




A thesis submitted in fulfilment of the requirements for the
             degree of Doctor of Philosophy
                     November, 2004
         Environment and Biotechnology Centre
           Swinburne University of Technology
                 Victoria 3122, Australia
                                                                       Acknowledgments




                       ACKNOWLEDGMENTS


I would like to dedicate this thesis to my loving family members and partner for all their
support, understanding, optimism and encouragement throughout my academic years.


I am particularly grateful to my supervisors Dr R. F. Cross, Dr I. Harding and Dr E.
Kosior for their guidance and valuable suggestions. A special thank-you goes out to Dr
Reg Cross for motivating and assisting me in writing papers.


I would like to express my gratitude to my friend Larry Bautista from Philip Morris for
assisting me with the static headspace work and for being a great friend.


Finally I would like to thank my fellow postgraduate students and Swinburne staff,
especially Savithri Galappathie, Sheila Curtis and Andrew Smairl, for their friendship
throughout my academic years.




                                            i
                                                                            Preface


                                   PREFACE


I hereby declare that, to the best of my knowledge, this thesis contains no material
previously written or published by another person except where reference is made in
the text. I also declare that none of this work has been previously submitted for a
degree or similar award at another institution.




                                           ii
                                                                       Table of contents



                        TABLE OF CONTENTS


ACKNOWLEDGEMENTS                                                                  i
PREFACE                                                                          ii
TABLE OF CONTENTS                                                                 iii
LIST OF FIGURES                                                                  x
LIST OF TABLES                                                                   xv
ABBREVIATIONS                                                                     xviii
ABSTRACT                                                                         xx



CHAPTER 1: INTRODUCTION                                                          1



CHAPTER 2: LITERATURE REVIEW                                                     3



2.1     BACKGROUND                                                               3
2.1.1   Definition of PET and its applications in the food industry              3
2.1.2   Manufacture of PET bottles                                               4
2.1.3   Improving gas barrier properties of PET                                  5


2.2     FOOD CONTACT CONSIDERATIONS FOR VIRGIN PET                               7
2.2.1   Introduction                                                             7
2.2.2   Sorption considerations in food contact applications                     8
2.2.3   Factors contributing to the degree of sorption                           9
        2.2.3.1        Properties of sorbate                                     10
        2.2.3.2        Polymer chemical and morphological properties             11
        2.2.3.3        Solubility parameter                                      12
        2.2.3.4        Polymer physical properties                               13
        2.2.3.5        Temperature                                               14
        2.2.3.6        Time                                                      15
2.2.4   Migration considerations in food contact applications                    16
2.2.5   Factors affecting the extent of migration                                18

                                            iii
                                                                             Table of contents



        -         External factors                                                     18
        -         Polymer and migrant factors                                          19
2.2.6   Potential migrants resulting from the manufacture of PET                       21
        -   Residual compounds resulting from manufacture identified in PET            21
2.2.7   Reaction by-products formed during PET manufacture                             25
        -         Acetaldehyde                                                         25
        -         Oligomers in PET                                                     26
        -         Oligomer migration from PET                                          28
2.2.8   Additives                                                                      29
2.2.9   Global migration                                                               30
2.2.10 Other compounds identified in PET                                               30


2.3     FOOD CONTACT CONSIDERATIONS FOR RECYCLED PET                                   31
2.3.1   Introduction to recycling                                                      31
2.3.2   Modes of recycling                                                             31
        2.3.2.1          Re-use: Zeroth order recycling                                32
        2.3.2.2          Primary recycling                                             32
        2.3.2.3          Physical reprocessing: Secondary recycling                    32
                         -       The Visy process                                      33
        2.3.2.4          Tertiary recycling                                            33


2.3.3   Recycled PET for food contact purposes                                         34
        2.3.3.1          Consumer misuse/reuse                                         35
        2.3.3.2          Sorption from the original contents of the bottle             35
2.3.4   Threshold of regulation                                                        39
2.3.5   Validation of recycling process – the challenge test                           40
        2.3.5.1           Introduction                                                 40
        2.3.5.2           Challenge test process                                       42
        2.3.5.3           Challenge test studies                                       42
                         -       Refillable plastic bottles                            42
                         -       Secondary recycled plastic bottles                    44
2.3.6 Estimated level of real contaminants in recycled PET                             47
2.3.7   Methods of reducing contamination                                              48
        2.3.7.1          Functional barrier                                            48

                                               iv
                                                                    Table of contents




2.4     EXTRACTION AND ANALYSIS OF POLYMERS                                    50
2.4.1   Modes of extraction                                                   50
2.4.2   Parameter optimisation                                                51
        2.4.2.1       Time                                                    51
        2.4.2.2       Temperature                                             52
        2.4.2.3        Pressure                                               54
        2.4.2.4        Nature of extraction solvent                           54
        2.4.2.5        Particle size                                          57
        2.4.2.6       Migrant shape/size                                      58
2.4.3   Modes of separation and analysis                                      59


2.5     PURPOSE OF THIS THESIS                                                60


2.6     OUTLINE OF THIS THESIS                                                 62




CHAPTER 3: MATERIALS AND METHODS                                              64



3.1 METHOD FOR CHAPTER 4                                                       64
3.1.1   Chemicals                                                             64
3.1.2   Preparation of stock standards                                        67
3.1.3   Soxhlet calibration standards                                         67
3.1.4   Dissolution calibration standards                                     67
3.1.5   Gas chromatography-mass spectroscopy (GC-MS) analysis                 68
3.1.6   Commercial Visy treatment of curbside PET                             68
3.1.7   Laboratory preparation of polymer before analysis                     69
3.1.8   Soxhlet extraction conditions                                         69
3.1.9   Sonication                                                            70
3.1.10 Total dissolution extraction conditions                                70
        3.1.10.1 Total dissolution by TFA – Qualitative analysis              70
        3.1.10.2 Total dissolution by TFA – Quantitative analysis             70
        3.1.10.3 Total dissolution by HFIP – Qualitative analysis             70

                                            v
                                                                         Table of contents



3.1.11 Crystallinity analysis                                                      71


3.2      METHOD FOR CHAPTER 5                                                      71
3.2.1.   Chemicals                                                                 71
3.2.2.   Crystallinity analysis                                                    71


3.3      METHOD FOR CHAPTER 6                                                      71
3.3.1    Preparation of stock standards                                            71
3.3.2    Soxhlet calibration standards for external standardisation                72
3.3.3    SPME                                                                      72
3.3.4    Static Headspace (SHS)                                                    73
3.3.5    Quantitative analysis by SHS                                              73
3.3.6    GC/MS Conditions – SPME                                                   73
3.3.7    GC/MS Conditions – SHS                                                    74



CHAPTER 4: SEMI-VOLATILE CONTAMINANTS                                               75

AND        LEVELS OF OCCURRENCE IN WASHED AND
DRIED SHREDDED PET


4.1      GENERAL INTRODUCTION                                                       75
4.1.1    Purpose of the chapter                                                     75
4.1.2    Brief outline of chapter                                                   76
4.1.3    Selecting the right extraction solvent for Soxhlet extraction              76


4.2      QUALITATIVE STUDY OF CONTAMINANTS IN WASHED                               79
         AND DRIED PET FLAKE
4.2.1    Introduction to Soxhlet extraction of washed and dried flake              79
4.2.2    Choosing a suitable low boiling solvent                                   79
4.2.3    GC/MS analysis of DCM extracts of washed and dried flake                  84
4.2.4    Qualitative analysis of washed and dried flake extracted by               93
         total dissolution
4.2.5    Running the extracts on polar column                                      98


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                                                                         Table of contents



4.2.6   Possible origin of the components                                          99


4.3     QUANTITATIVE STUDY OF CONTAMINANTS IN WASHED                               102
        AND DRIED PET FLAKE
4.3.1   Introduction                                                               102
4.3.2   Study of extraction kinetics for flake ground to 0-300 µm                  103
4.3.3   Particle size variation                                                    116
4.3.4   Kinetic studies for the larger particle sizes                              121
4.3.5   Comparison of contaminant levels in different 70 g grabs from the          140
        original 15 kg sample
4.3.6   Validation of the Soxhlet extraction methodology                           142
               4.3.6.1 Total dissolution compared with Soxhlet extraction          142
4.3.7   Particle size range and degree of crystallinity                            148
4.3.8   Investigation of the relative levels of contaminants in the two types      153
        of flake
4.3.9   Representative sampling                                                    159
4.3.10 Levels of contaminants in flake and the threshold of regulation             160



CHAPTER 5: SEMI-VOLATILE CONTAMINANTS                                              162

AND LEVELS OF OCCURRENCE IN EXTRUDED PET
PELLETS FROM CURBSIDE COLLECTION


5.1     GENERAL INTRODUCTION                                                        162
5.1.1   Purpose of the chapter                                                     162
5.1.2   Brief outline of this chapter                                              164


5.2     KINETICS OF SOXHLET EXTRACTION FROM EXTRUDED                               165
        AND ANNEALED PET
5.2.1   Pellets ground to 0-300 µm                                                 165
        5.2.1.1 Pellets ground to 0-300 µm: The relationship between               171
                extraction kinetics and contaminant molecular weight.
5.2.2   Annealed pellets ground to >300-425µm                                      174


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                                                                       Table of contents



5.2.3   Annealed pellets ground to >425-700 µm                                   176
5.2.4   Unground annealed pellets                                                178
5.2.5   The effect of particle size reduction upon measured contaminant levels   182
        in extruded and annealed pellets


5.3     ANNEALED VERSUS AMORPHOUS EXTRUDED PELLETS                               189
5.3.1   Kinetics of extraction from amorphous pellets                            189
5.3.2   Variation of DCM uptake with PET crystalline structure                   195
5.3.3   Contaminant diffusion coefficients out of amorphous and annealed PET     199
5.3.4   Contaminant loss during the annealing of pellets                         204


5.3     FLATTENING AMORPHOUS PET PELLETS                                         205


5.4     LEVELS OF CONTAMINANTS IN PELLETS AND                                    208
        THRESHOLD OF REGULATION


5.5     CONCLUSIONS                                                              211




CHAPTER 6: VOLATILE CONTAMINANTS AND                                             213

LEVELS OF OCCURRENCE IN EXTRUDED PET FLAKE
AND PELLETS FROM CURBSIDE COLLECTION


6.1     GENERAL INTRODUCTION                                                      213
6.1.1   Purpose of the chapter                                                   213
6.1.2   Background to thermal extraction                                         213
6.1.3   Brief outline of chapter                                                 216


6.2     QUALITATIVE SPME STUDY OF CONTAMINANTS                                   217
        IN PET EXTRUDED PELLETS
6.2.1   Comparison of the compounds extracted by different fibres                217
6.2.2   Effect of temperature on extraction                                      223

                                           viii
                                                  Table of contents



6.2.3   Effect of mass of sample on extraction              235
6.2.4   Effect of adsorption time                           242
6.2.5   Effect of extraction time on extraction             243


6.3     QUANTITATIVE SPME AND STATIC HEADSPACE STUDY        249
        OF RECYCLED PET


6.3.1   Quantitation using the CX/PDMS fibre                249
6.3.2   SPME using PDMS, an absorption fibre                249
6.3.3   Static headspace analysis (SHS)                     253
6.3.4   Quantitative analysis of PET                        258
6.3.5   Multiple headspace extraction (MHE)                 258
6.3.6   External standardisation (ES)                       260


6.4     CONCLUSION                                          262



CHAPTER 7: CONCLUSIONS                                      264


APPENDIX                                                    268


BIBLIOGRAPHY                                                269




                                            ix
                                                                         List of figures


                             LIST OF FIGURES


Figure
2.1      Formation of PET (polyethylene terephthalate)                            2


2.2      Structure of PEN                                                         5


2.3      Drawing of the bottom part of a PET soft drink bottle                    6
         illustrating sorption, migration and permeation


2.4      A summary of the disadvantages of “flavour scalping”                     8


2.5      Sorbate, polymer and external factors effecting sorption in PET          9




2.6      Formation of dimethyl terephthalate and terephthalic acid from          22
         xylene


2.7      Formation of bis-(2-hydroxyethyl)terephthalate (BHET)                   24
         from dimethyl terephthalate and ethylene glycol


2.8      Formation of PET from BHET                                              25


2.9      Formation of acetaldehyde from PET                                      26


2.10     Cyclic oligomers identified in PET                                      27


2.11     Chemolysis reactions used in tertiary recycling                         34


4.1      Plot of the number of mmole of solvent absorbed at 3 h versus           83
         (δPET - δsolvent)
                                                                          List of figures


4.2    Chromatogram of DCM extract for washed and dried flake                     87


4.3    Mass spectrum and structure of (a) cyclic dimer and (b) dimer ether         92


4.4    Chromatogram of TFA/heptane extract for washed and dried flake              97


4.5    Chromatogram of HFIP extract for washed and dried flake                    99


4.6    Schematic presentation of the three subsequent steps in solvent            105
       extraction


4.7    Soxhlet extraction kinetic study of washed and dried flake ground to 106
       0-300 µm. Compounds identified at levels below 200 ppb


4.8    Soxhlet extraction kinetic curves of trimethylnaphthalene isomers          107
       extracted from washed and dried flake ground to 0-300 µm


4.9    Soxhlet extraction kinetic study of washed and dried flake ground           108
       to 0-300 µm. Compounds identified at levels above 200 ppb


4.10   The standard deviations associated with data points defining               109
       kinetic curves that do not follow the general trends of Figure 1


4.11   Soxhlet extraction kinetic study of washed and dried flake ground
       to 0-300 µm. Ethylene glycol analysed on an EC-Wax Econo-cap
       column


4.12   Ratio of amount extracted at 8 h (A8) to amount extracted after 24 h (Ae)
       (as a percentage) versus contaminant molecular weight


4.13   “Venn diagram” grouping the contaminants according to their functional
       group types
                                                                        List of figures


4.14   Ratio of amount extracted at 8 h (A8) to amount extracted after 24 h (Ae)
       (as a percentage) versus estimated solvent strength parameter


4.15   Amount of contaminant extracted from flake ground to different particle
       sizes (compounds below 200 ppb)


4.16   Amount of trimethylnaphthalene contaminants extracted from flake ground
       to different particle sizes


4.17   Amount of contaminant extracted from flake ground to different particle
       sizes (compounds above 200 ppb)


4.18   The standard deviations associated with data points defining curves that do
       not follow the general trends of Figure 4.15 – 4.17


4.19   Soxhlet extraction kinetics of flake ground to >300-425 µm. Contaminants
       below 120 ppb


4.20   Soxhlet extraction kinetics of flake ground to >300-425 µm. Contaminants
       between 120 ppb and 300 ppb


4.21   Soxhlet extraction kinetics of flake ground to >300-425 µm. Contaminants
       above 400 ppb


4.22   Soxhlet    extraction    kinetics   of   flake   ground   to   >300-425    µm.
       Trimethylnaphthalene isomers


4.23   Soxhlet extraction kinetics of flake ground to >425-700 µm. Contaminants
       below 100 ppb


4.24   Soxhlet    extraction    kinetics   of   flake   ground   to   >425-700    µm.
       Trimethylnaphthalene isomers
                                                                      List of figures


4.25   Soxhlet extraction kinetics of flake ground to >425-700 µm. Contaminants
       above 200 ppb


4.26   Soxhlet extraction kinetics of whole flake. Contaminants below 70 ppb


4.27   Soxhlet extraction kinetics of whole flake. Trimethylnaphthalene
       isomers


4.28   Soxhlet extraction kinetics of whole flake. Contaminants between 70 ppb
       and 200 ppb


4.29   Soxhlet extraction kinetics of whole flake. Contaminants above 200 ppb.


4.30   Soxhlet extraction kinetics of whole flake. Ethylene glycol


4.31   Log-log plot of levels of contaminants determined by total dissolution
       versus levels extracted by sonication and comparison with the ideal
       relationship (y=x): for flake ground to small particle sizes


4.32   Variation in contaminant levels between two 70 g grabs of flake from the
       original 15 kg bag. Analyses were performed on PET ground to the 0-300
       µm particle size in each case


4.33   Log-log plot of levels of contaminants determined by total dissolution
       versus levels extracted by Soxhlet and comparison with the ideal
       relationship (y=x): for flake ground to medium and large particle sizes and
       for unground flake


4.34   Log-log plot comparing the contaminant concentrations extracted from
       unground flake by TFA versus the amount extracted from unground flake by
       Soxhlet extraction
                                                                      List of figures


4.35    Percentage of amount extracted from the >425-700 µm particle size range to
        the amount extracted from the 0-300 µm particle size range plotted versus
        contaminant molar mass


4.36    Log amount extracted from crystalline particles versus log amount extracted
        from amorphous particles, for each particle size range.


4.37    Log amount extracted from whole amorphous pellets versus log amount
        extracted from flattened amorphous particles.


5.1     Soxhlet extraction kinetic study of annealed pellets ground to 0-300 µm.
       Compounds identified at levels below 10 ppb.


5.2    Soxhlet extraction kinetic study of annealed pellets ground to 0-300   µm.
       Trimethylnaphthalene isomers.


5.3    Soxhlet extraction kinetic study of annealed pellets ground to 0-300 µm.
       Compounds identified at levels between 11 ppb and 130 ppb.


5.4    Percentage of contaminant extracted at 1 h versus molecular weight.


5.5    A log-log plot of the amounts of contaminants extracted at 24 h versus the
       amounts extracted at 3 h for >300-425µm.


5.6    A log-log plot of the amounts of contaminants extracted at 24 h versus the
       amounts extracted at 3 h for particles >425-700 µm.


5.7    Soxhlet extraction kinetic study of unground annealed pellets. Compounds
       identified at levels below 2 ppb.


5.8    Soxhlet extraction kinetic study of unground annealed pellets. Compounds
       identified at levels below 13 ppb.
                                                                         List of figures


5.9    Soxhlet extraction kinetic study of unground annealed pellets. Compounds
       identified at levels below 70 ppb.


5.10   Typical variations in contaminant levels measured from the same batch of
       annealed pellets ground to the three particle sizes.


5.11   Extreme examples of the variation in contaminant levels.


5.12   An example of the experimental spread (means ± standard deviation) for
       divergent measurements of a contaminant in the three particle sizes derived
       from the same batch of annealed pellets.


5.13   Log-log plot of the amounts of contaminants extracted from >425-700 µm
       particles versus the amounts extracted from 0-300 µm particles.


5.14   A log-log plot of the amounts extracted at 3 h versus the amounts extracted at
       24 h for unground amorphous pellets.


5.15   Soxhlet extraction kinetic study of unground amorphous pellets. Compounds
       identified at levels below 4 ppb.


5.16   Soxhlet extraction kinetic study of unground amorphous pellets. Compounds
       identified at levels below 11 ppb.


5.17   Soxhlet extraction kinetic study of unground amorphous pellets. Compounds
       identified at levels below 13 ppb.


5.18   Soxhlet   extraction   kinetic      study   of   unground   amorphous    pellets.
       Trimethylnaphthalene compounds.


5.19   Sorption kinetics of DCM into amorphous and annealed pellets.
                                                                       List of figures


5.20    A plot of the (amount of DCM sorbed /amount sorbed at equilibrium) versus
        the square root of time.
5.21    A plot of At/Ae (amount extracted/amount extracted at equilibrium from
        annealed pellets) versus the square root of time (a representative plot;
        naphthalene).


5.22    A plot of calculated diffusion coefficients versus molecular weights (for
        annealed pellets).


5.23    A plot of fraction extracted at 2 h versus molecular weights (for amorphous
        pellets).


5.24    A log-log plot of the amounts of contaminants extracted from amorphous
        pellets versus the amounts extracted from ground annealed pellets.


6.1    Ground annealed pellets: contaminant area (abundance) versus extraction
       temperature for three different particle sizes using the CX/PDMS fibre.


6.2    Effect of incubation temperature on extraction of 6g of unground
       extruded pellets using the CX/PDMS fibre.


6.3    Effect of incubation temperature on extraction of 1g of unground
       extruded pellets using the CX/PDMS fibre.


6.4    Effect of incubation temperature on extraction of 0.3g of unground
       extruded pellets using the CX/PDMS fibre.


6.5    Effect of extraction time on abundance.


6.6    Superimposed chromatograms obtained from the analysis of pellets using the
       PDMS (bold) and CX/PDMS (fine) fibres.


6.7    Effect of incubation temperature on extraction of 6g of unground extruded
       pellets using the 100 µm PDMS fibre.
                                                                      List of figures


6.8    Chromatograms for extruded pellets obtained by (a) SHS and (b) SPME using
       the CX/PDMS fibre.


6.9    Effect of incubation temperature for the SHS of extruded PET pellets.


6.10   Multiple headspace analysis of flake ground to 425–700 µm.
                    LIST OF TABLES


Table
2.1     Comparative properties of PET versus PEN.


2.2     A list of FDA food simulants.


2.3     A list of EEC food simulants.


2.4     Threshold values for the maximum permitted contaminant
        concentration in polymers and food simulant.


2.5     Surrogates used in a challenge test performed by Franz and Welle
        (1999a).


2.6     The estimated level of contaminants in PET after each recycling stage.


2.7     Hildebrand solubility parameters for different solvents and polymers.


3.1     Contaminants identified in washed and dried PET flake and the
        standards used.


4.1     Hildebrand solubility parameters of some solvents and PET.


4.2     Hildebrand solubility parameters of hexane, 2-propanol, ethanol and
        PET.


4.3     Compounds identified in ground washed and dried PET flake [“x”
        denotes presence of compound in virgin (V) and recycled (R) PET].


4.4     Compounds extracted from washed and dried flake by total dissolution
        using TFA/heptane [“x” denotes presence of contaminant in virgin (V)
        and recycled (R) PET].
4.5    Constituents of PET were also extracted by total dissolution using
       HFIP [“x” denotes presence of contaminant in virgin (V) and recycled
       (R) PET].


4.6    Soxhlet extract run on an EC-Wax Econo-cap column.


4.7    The percentages of naphthalene derivatives extracted at 8 h alongside
       their molecular structure.


4.8    Contaminant levels (and standard deviations) [in ppb, in flake ground
       to 0-300 µm] determined by total dissolution with TFA, compared to
       extraction by sonication in DCM.


4.9    Contaminant levels (and standard deviations) [in ppb, in flake ground
       to 0-300 µm] determined by total dissolution with TFA, compared to
       extraction by sonication in DCM: anomalies for (a) m-cymene
       [TFA>DCM] and (b) limonene, cineole and γ-terpinene [DCM>TFA].
       (All levels are in ppb by mass.)


4.10   Flake ground to >300-425 µm particle size and extracted for 3 h and
       then re-extracted for another 24 h.


4.11   Levels of contaminants (and their standard deviations) determined by
       Soxhlet extraction with dichloromethane (DCM) compared with total
       dissolution by trifluoracetic acid (TFA) followed by extraction with
       heptane: for flake ground to medium and large particle sizes, and for
       unground flake. (All levels are in ppb by mass.)


4.12   Levels of contaminants (and their standard deviations) determined by
       Soxhlet extraction with dichloromethane (DCM) compared with total
       dissolution by trifluoracetic acid (TFA) followed by extraction with
       heptane: anomalies for (a) m-cymene [TFA>DCM] and (b) limonene,
       cineole and γ-terpinene [DCM>TFA]. (All levels are in ppb by mass.)
4.13    Percentages of crystallinity for amorphous and crystalline fractions of
        washed and dried flake ground to different particle sizes.


4.14    Percentages of crystallinity for two batches of unsegregated washed
        and dried flake ground to different particle sizes.


4.15    Mass of amorphous and crystalline flake ground to different particle
        sizes.


4.16    Levels of contaminants in amorphous and crystalline flake ground to
        different particle sizes (analysed by sonication in DCM for 3 h). (All
        levels are in ppb by mass.)


5.1     Amounts of contaminants extracted from annealed pellets
        ground to 0-300 µm by Soxhlet extraction and sonication (standard
        deviation, n=3 for 3 h; n=2 for 15 h).


5.2     Flattened and whole amorphous pellets extracted by sonication and
        Soxhlet extraction.


5.3     Levels of contaminants in ground flake (0-300 µm), unground flake
        and extruded pellets.


6.1     Compounds extracted by four different fibres from ground flake (x
        indicates assignment and n/a = “not analysed” due to the inclusion of a
        solvent delay time).


6.2    Area of benzene and limonene after reducing the fibre exposure time
       from 30 minutes to 5 minutes.


6.3    Comparison of concentrations determined in flake and pellets by
       Soxhlet
      and static headspace analysis. Standard deviations are in parentheses. All
      values are in ppb.


6.4   Concentrations (ppb) of three compounds determined by static headspace
      but not Soxhlet. Standard deviations are in parentheses.
                                                                              Abbreviations



                             ABBREVIATIONS

A list of abbreviations for words not defined in the main body of the thesis.


MDPE                                         medium density polyethylene
LDPE                                         low density polyethylene
LLPE                                         linear low density polyethylene
PP                                           polypropylene
PE                                           polyethylene
PS                                           polystyrene
HDPE                                         high density polyethylene
PVC                                          polyvinyl chloride

PMMA                                         poly(methyl methacrylate)
MEG                                          monoethylene glycol
DEG                                          diethylene glycol
GPC                                          gel permeation chromatography
TLC                                          thin layer chromatography
HPLC                                         high performance liquid chromatography
SFC                                          supercritical fluid chromatography
MAE                                          microwave accelerated extraction
SFE                                          supercritical fluid extraction
ASE                                          accelerated solvent extraction
HPLC-UV                                      high performance liquid chromatography-
                                             ultra violet detection
SEC                                          size exclusion chromatography
GC/MS                                        gas chromatography/mass spectrometry
GC/FID                                       gas chromatography/flame ionisation
                                             detection
BHT                                          butylated hydroxy toluene
DEHP                                         di-(2-ethyl hexyl) phthalate
DEP                                          diethyl phthalate
DiOP                                         diisooctyl phthalate
BEHA                                         bis-(2-ethyl hexyl) adipate
                                          xviii
                                           Abbreviations



BHA           4-(1-methyl-1-phenylethyl)-phenol
Tinuvin P     2-(2’-hydroxy-5-
              methylphenyl)benzotriazole
DiBP          diisobutyl phthalate
DBP           dibutyl phthalate
DOA           dioctyl adipate
SEC-HPLC      size exclusion chromatography-high
              performance liquid chromatography
XRD           X-ray Diffraction
SML           Specific migration limit




            xix
                                                                                Abstract



                                  ABSTRACT


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 µm 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 µm and >425-700 µm) were
completed within four hours, possibly due to less aggregation in the extraction thimble.
In the finely ground flake (0-300 µm) 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 µm and >425-700 µm) 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 µm 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.


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                                                                                 Abstract



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.




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Description: CONTAMINANTS IN RECYCLCED PET PLASTIC