degradable plastics packaging materials: assessment...

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Degradable Plastics Packaging Materials:

Assessment and Implication for the Australian

Environment

Materials Science and Engineering

FINAL REPORT

Prepared by: Dr Parveen Sangwan and Dr Katherine Dean

Approved by: Dr Stuart Bateman Theme leader – Sustainable Polymeric Materials

Issue date: 8th June 2011

CSIRO - EP114268

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Whilst the document has been prepared with due diligence and care the contents are subject

to change and as such CSIRO and its employees are not responsible for the results of any

actions taken in reliance on it or for any errors or omissions herein.

CSIRO Copyright 8th June 2011

Please address all enquires to:

The Chief

CSIRO Materials Science and Engineering

Private Bag 33

CLAYTON SOUTH VIC 3169

Australia

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NEPC Project Committee:

Gregory Manning (DSEWPaC)

Peter Marshall (DSEWPaC)

Ian Newbery (NEPC Service Corporation)

Peter Bury (PACIA)

Prof. Graeme George (Queensland University of Technology)

Monika Stasiak (ZWSA)

Ian Harvey (ZWSA)

Anne Maree Casey (DSEWPaC)

CSIRO Materials Science and Engineering (CMSE):

Dr Stuart Bateman (CMSE)

Dr Katherine Dean (CMSE)

Dr Parveen Sangwan (CMSE)

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Table of Contents

Table of Contents...................................................................................................... 4

List of Tables ............................................................................................................ 6

List of Figures ........................................................................................................... 7

1. EXECUTIVE SUMMARY ............................................................................................ 9

2. ABBREVIATIONS....................................................................................................... 17

3. MATERIALS AND METHODS ................................................................................. 18

3.1. MATERIALS ............................................................................................................... 18

3.1.1 Test specimens .................................................................................................... 18

3.1.2 Soil and marine sites for real-time exposure experiments.................................. 18

3.1.3 Soil and marine characteristics for simulated testing ........................................ 20

3.2. METHODS ................................................................................................................. 21

3.2.1 Real-time weathering experiment ....................................................................... 21

3.2.2 Gravimetric analysis........................................................................................... 24

3.2.3 Mechanical properties ........................................................................................ 24

3.2.4 FTIR analysis ...................................................................................................... 25

3.2.5 Accelerated UV exposure.................................................................................... 25

3.2.6 Accelerated Biodegradation ............................................................................... 26

4. RESULTS AND OBSERVATIONS............................................................................ 29

4.1. DIGITAL IMAGES........................................................................................................ 29

4.1.1 On soil and marine real-time exposure .............................................................. 29

4.2. GRAVIMETRIC WEIGHT ANALYSIS ................................................................................ 57

4.2.1 On soil real-time exposure.................................................................................. 57

4.2.2 Marine real-time exposure.................................................................................. 59

4.3. CHANGES IN MECHANICAL PROPERTIES ...................................................................... 60

4.3.1 On soil real-time exposure.................................................................................. 60

4.3.2 Marine real-time exposure.................................................................................. 64

4.4. CHANGES IN CHEMICAL STRUCTURE........................................................................... 66

4.4.1 Accelerated UV exposure using xenon-arc unit.................................................. 68

4.5. RESPIROMETRIC BIODEGRADATION ............................................................................ 69

4.5.1 In soil biodegradation......................................................................................... 69

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4.5.2 In marine biodegradation ................................................................................... 73

5. CONCLUSIONS ........................................................................................................... 76

6. RECOMMENDATIONS: ............................................................................................ 85

6.1. TEST METHODOLOGIES ............................................................................................. 85

6.2. PERFORMANCE CRITERIA FOR A PLASTIC CLAIMING TO BE DEGRADABLE ...................... 86

6.3. BENEFITS AND RISKS ................................................................................................. 88

7. TERMINOLOGY ......................................................................................................... 90

8. APPENDIX A – METHODOLOGY ATTACHED AS SEPARATE

DOCUMENT…..................................................................................................................... 95

9. APPENDIX B – SUPPORTING DATA ATTACHED AS SEPARATE

DOCUMENT....................................................................................................................... 132

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List of Tables

Table 1. Plastic specimens selected for assessment in this study ............................................. 9

Table 2. An overview of degradation of test plastic specimens in real-time exposure tests .. 11

Table 3. An overview of biodegradation of test plastic specimens in simulated environment

exposure tests .......................................................................................................................... 13

Table 4 List of environmental variables for real-time exposure............................................. 14

Table 5 Selection of degradable plastics for assessment ........................................................ 18

Table 6 Soil and marine analysis for real-time testing ........................................................... 19

Table 7 Heavy metal analysis of real time exposure sites ...................................................... 19

Table 8. Soil and marine sample analysis for simulated testing ............................................. 20

Table 9 Digital images of sample A during on soil and marine real-time exposure .............. 30

Table 10 Digital images of sample B during on soil and marine real-time exposure............. 34

Table 11 Digital images of sample C during on soil and marine real-time exposure............. 38

Table 12 Digital images of sample D during on soil and marine real-time exposure ............ 42

Table 13 Digital images of sample E during on soil and marine real-time exposure ............. 46

Table 14 Digital images of sample F during on soil and marine real-time exposure ............. 49

Table 15 Digital images of sample G during on soil and marine real-time exposure ............ 53

Table 16 Summary of sample class and class description ...................................................... 76

Table 17 Summary of test results: On-soil real time exposure study Melbourne (VIC) ........ 79

Table 18 Summary of test results: On-soil real time exposure study Darwin (NT) ............... 80

Table 19 Summary of test results: In marine real time exposure study Williamstown (VIC) 81

Table 20 Summary of disintegration end point for all exposure sites .................................... 82

Table 21 Summary of test results from in-lab biodegradation study...................................... 84

Table 22 List of environmental variables for real-time exposure........................................... 85

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List of Figures

Figure 1 Microbial counts (cfu/ml) in soil and marine samples respectively......................... 20

Figure 2 Digital images of plastic specimens A-G (before exposure).................................... 21

Figure 3 On soil exposure site before and after clearing grass/weeds .................................... 22

Figure 4 On soil exposure set up at Melbourne (left) and Darwin (right) sites ...................... 22

Figure 5 Test specimens and marine real-time exposure set up ............................................. 23

Figure 6 Instron Testing System used for analyzing tensile properties .................................. 25

Figure 7 Film specimens set up in Xenon Weather-Ometer®................................................ 26

Figure 8 Test specimens for accelerated biodegradation study .............................................. 26

Figure 9 Bioreactors set up with test specimens in soil and marine respectively................... 27

Figure 10 NATA certified Respirometric unit at CSIRO Biodegradation testing laboratory,

Clayton VIC ............................................................................................................................ 28

Figure 11 On soil real-time exposure at Melbourne (VIC)..................................................... 58

Figure 12 On soil real-time exposure at Darwin (NT)............................................................ 58

Figure 13 Biofouling of plastic specimens during marine exposure ...................................... 59

Figure 14 Mesh bags containing test specimens after 6 months marine exposure; digital

images showing biofouling of samples in sea over time ........................................................ 59

Figure 15 Marine exposure at Williamstown (VIC) ............................................................... 60

Figure 16 Effect on elongation during on soil exposure at Melbourne (VIC)........................ 61

Figure 17 Effect on elongation during on soil exposure at Darwin (NT)............................... 61

Figure 18 Effect on Modulus during on soil exposure at Melbourne (VIC) .......................... 62

Figure 19 Effect on Modulus during on soil exposure at Darwin (NT).................................. 62

Figure 20 Effect on tensile strength during on soil exposure at Melbourne (VIC) ................ 63

Figure 21 Effect on tensile strength during on soil exposure at Darwin (NT) ....................... 63

Figure 22 Effect on Elongation during marine exposure at Williamstown (VIC).................. 64

Figure 23 Effect on Modulus during marine exposure at Williamstown (VIC) ..................... 65

Figure 24 Tensile strength during marine exposure at Williamstown (VIC) ......................... 65

Figure 25 Carbonyl index during on soil exposure at Melbourne (VIC)................................ 67

Figure 26 Carbonyl index during on soil exposure at Darwin (NT)....................................... 67

Figure 27 Carbonyl index after accelerated UV exposure in xenon-arc................................. 68

Figure 28 Digital images of test samples after biodegradation in soil; samples A and E

disintegrated into smaller size................................................................................................. 71

Figure 29 Cumulative CO2 evolution during biodegradation of test samples in soil ............. 72

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Figure 30 Rate of biodegradation of test samples in soil........................................................ 72

Figure 31 Digital images of test samples after biodegradation in marine; sample B

disintegrated completely, samples A and E were significantly reduced. Arrows point towards

remaining film samples........................................................................................................... 74

Figure 32 Cumulative CO2 evolution during biodegradation of test samples in marine ........ 75

Figure 33 Rate of biodegradation of test samples in marine .................................................. 75

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1. Executive Summary

A rigorous scientific investigation into on-soil and marine degradation of generic

types of degradable plastics currently available in the Australian market was undertaken. The

scope of the study included developing guidance on testing degradable plastics in on-soil and

marine environments under defined conditions and a general approach to assessing

degradation of degradable plastics under defined test conditions.

In stage 1 of this project a report was completed that included a literature review and

methodologies for monitoring the rate of degradation of plastics under real time and

simulated environment conditions typical of litter – on soil and in the marine environment.

These methodologies were designed through consultation with the project Technical Review

committee, the detail of which can be found in Appendix A.

In stage 2 of the project, six (6) plastic specimens (provided as 20 micron films)

belonging to four (4) major classes of degradable plastics were selected for assessment; these

are summarized in Table 1 below:

Table 1. Plastic specimens selected for assessment in this study

Sample designation Class Class description1

A iii Non-polyolefin with bio-derived component

B iv Bio-derived

C ii Polyolefin with bio-derived component

D i Polyolefin with prodegradant

E iii Non-polyolefin with bio-derived component

F i Polyolefin with prodegradant G - HDPE baseline

1 The full definition of all terms can be found in the glossary of terms found at the end of this document Bio-derived: being derived

from a biological source (not petrochemical), examples of bio-derived polymers include starches, proteins and polylactic acid.

Polyolefin: polymer produced from polymerization of simple olefin (CnH2n); examples are polyethylene and polypropylene produced

from olefin ethylene and propylene respectively. Most commonly derived from a petrochemical resource. Non-polyolefin: polymer

typically derived from a petrochemical resource but not a simple olefin (CnH2n) examples include polyesters such as polycaprolactone; Prodegradant: any substance or a factor that promotes degradation examples include transition metals.

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Real Time Exposure Tests

To capture the diversity of different climates in which these samples may ultimately

end up, samples were set up for real-time exposure on soil (9 months maximum) at two

different sites – Melbourne (temperate climate) and Darwin (tropical climate), and in the

marine environment at the salt water immersion exposure site managed by the Defence Science

and Technology Organisation (DSTO) at Williamstown (VIC). At each sampling time, exposed

specimens were analysed to monitor changes in physical appearance, total weight, tensile

properties (tensile strength, modulus and elongation at break) and chemical structure.

For real-time exposure, comparative disintegration has been predominantly assessed

based on mechanical performance (when elongation was less than 5% of its original value

measured at time zero) and visual imaging (when sample was too damaged to obtain

mechanical properties). This definition is based on current guidelines for aging of polymers

and cannot be used by itself as a measure of degradability.

Differences were observed in the rates of disintegration of test samples at the three

exposure sites selected for the study. In summary, samples A and E (non-polyolefin with bio-

derived component) disintegrated quite rapidly in all three environments (on-soil (temperate

and tropical) and marine), with sample A appearing to be more susceptible to moisture.

Sample B (bio-derived) was highly susceptible to moisture but quite stable on soil (in the

environments in which we tested). Sample C (polyolefin with bio-derived) was sensitive to

UV and marine fouling may have blocked UV leading to a reduced disintegration rate in the

marine environment.

Samples D and F (polyolefin with prodegradant) showed similar trends to sample C

in which marine fouling may have reduced the UV exposure and thus ability to disintegrate

and/or degrade. Sample G (baseline HDPE) showed similar trends to the other polyolefin

containing samples (albeit generally a longer degradation time) with the exception of sample

D. The differences in disintegration of sample D and the baseline HDPE may have been due

to variation in base polyolefin formulation (for example the addition of processing

stabilisers). For comparison all samples and environments have been summarised in the

Table 2 below with simple trend lines overlaid.

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Table 2. An overview of degradation of test plastic specimens in real-time exposure tests

C

F

G

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DEA

B

Marine

(Melbourne)

BDGAC

E

FOn-soilTropical

(Darwin)

BDA

G

C

F

EOn-soil

Temperate (Melbourne)

97654321months

C

F

G

8

DEA

B

Marine

(Melbourne)

BDGAC

E

FOn-soilTropical

(Darwin)

BDA

G

C

F

EOn-soil


97654321months

Simulated Environment Exposure Tests

To determine the rate of biodegradation on exposure to simulated soil and marine

environments, plastic specimens were first subjected to accelerated UV exposure using xenon-

arc lamps for 1 month followed by biodegradation under simulated soil and marine conditions

for 5 months at 28°C – the results from this study are summarised in Table 3 with trend lines

overlaid. A standard error of ±5% should be considered when comparing percentage

biodegradation values.

Simulated in-soil, samples A and E (non-polyolefin with bio-derived component)

showed the highest biodegradation, reaching 59.5% and 69.5% biodegradation respectively.

Sample C (polyolefin with bio-derived component) obtained the next highest level of

biodegradation (23.4%). Sample B (bio-derived) obtained a biodegradation level of 10.7%

indicating that bio-derived materials can have longevity provided temperature and moisture are

minimised. Samples D and F (polyolefin with prodegradant) obtained biodegradation levels of

4.2% and 10.9% respectively, which are within error or the baseline HDPE 6.8%.

Simulated marine water, sample B (bio-derived) showed the highest biodegradation reaching

99.9%, showing its susceptibility to moisture. Samples A and E (non-polyolefin with bio-

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derived component) followed reaching 87.0% and 69.7% biodegradation respectively. Sample

C (polyolefin with bio-derived component) obtained the next highest level of biodegradation

(55.4%) It is noteworthy that sample C had the highest carbonyl index value among all the

polyolefin based samples and its rate of degradation was higher in soil and marine relative to

samples D, F, and G; this means it was more oxidised. Samples D and F (polyolefin with

prodegradant) obtained biodegradation levels of 35.9% and 27.5% respectively and the

baseline HDPE 21.1%, indicating that moisture could play a significant role in increasing the

biodegradation of polyolefins containing prodegradants.

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Table 3. An overview of biodegradation of test plastic specimens in simulated environment exposure tests

% Biodegradation (after 150 days)

0-10 11-20 21-30 31-40 41-50 51-60 61-70 71-80 81-90 91-100

On-soil simulated

environment at

28°C

D (4.2)

G

(6.8)

B (10.7)

F (10.9)

C (23.4) A (59.5) E (69.5)

Marine simulated

environment at

28°C

F (27.5)

G

(21.1)

D (35.9) C (55.4) E (69.7) A (87.0) B (99.9)

* please note that a standard error of ± 5% should be considered when comparing % biodegradation values

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Key findings and recommendations

Broadly, the test results obtained from exposure of plastic samples to real-time

conditions and in-lab simulated conditions indicate that the rate of disintegration and

degradation of non-polyolefin based samples (in all test environments) and bio-derived

sample (particularly in the marine environment) is faster relative to polyolefin based samples.

However, the study found that it was difficult to quantify the degree of disintegration and

degradation under natural conditions, as there were a large number of variable factors that

could influence the biodegradability of test materials. The list of potential environmental

variables is outlined in Table 4.

Table 4 List of environmental variables for real-time exposure

pH

Precipitation

Temperature

Sunlight

Salinity

Element contents such as carbon, nitrogen and heavy metals Microbial activity

Fouling

Tides/water currents

Wind velocity

Under natural conditions it was also difficult to differentiate between disintegration

(where sample has fragmented and been lost from the test frames) and degradation in which

sample is ultimately mineralised, for this reason it is recommended that real-time weathering

experiments could not be used as a stand-alone system to assess degradation. It is further

recommended that other chemical methods such as carbonyl index (specifically for

polyolefins containing prodegradants) and molecular weight also be used as a measure of

degradation of the materials. Although it must be noted that both these chemical methods

cannot be used when sample has been lost from the test frames.

It is recommended the real-time weathering experiment at different exposure sites be

repeated, in different seasons or years to gain better insight into the rate and extent of

biodegradation of these materials under natural environmental conditions. It is also

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recommended the samples of various film thickness are also included in the testing to study the

effects of film thickness on degradation rates.

The in-lab study was relevant in terms of quantitatively measuring the rate of

biodegradation of these test materials under accelerated test conditions. Caution is advised in

using these test results in predicting the performance of test materials in real-time for a

number of reasons. Firstly, the in-lab study exposed samples to sequential steps of UV

exposure followed by biodegradation, whereas in real-time these steps would occur

simultaneously; this variation could affect the final result. Also in the marine study we have

not considered the effect of biofouling that could affect the biodegradation rate. These and

other variable factors must be considered.

Recommended performance criteria for a plastic claiming to be degradable

It is difficult to ascertain performance criteria for a plastic claiming to be degradable

in real-time exposure conditions. We recommend the only performance criteria which can be

specified is for embrittlement and this would be defined as the time required for the film to

reach 5% or less of its original elongation at break in real-time exposure conditions, it is

recommended that embrittlement cannot be used by itself as a measure of degradability

For the results to be valid in the laboratory test in marine water or soil we recommend the

following criteria must be met:

A negative reference of exactly the same base polyolefin as that containing pro-

oxidant additive must be included in the study for comparison

The degree of biodegradation of the positive reference material must be more than

60% at the plateau phase or at the end of the test

The CO2 evolved from the replicate blanks (marine water or soil) are within 20% of

the mean at the plateau phase, or at the end of the test

For a plastic claiming to be degradable in a simulated laboratory environment it must achieve

both of the following performance criteria:

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After an accelerated photo-oxidation process the sample must be embrittled (film to

reach 5% or less of its original elongation at break) or reach an appropriately low

molecular weight.

and

The degree of biodegradation of the material must be more than 60% at the plateau

phase or at the end of the biodegradation test.

This 6 month (1 month UV exposure plus 5 months biodegradation) study did not provide

conclusive evidence of the length of time that would form an appropriate criterion for a plastic

claiming to be degradable. It could be considerably longer than 5 months biodegradation

undertaken in this study (for polyolefins with prodegradants up to 2 years may be required to

achieve these levels of biodegradation, it is however recommended that an upper time limit

must be defined in any standard and/or test protocol which is developed).

Assessing toxicity risks from the degradation process was outside the terms of this study.

Conclusion

The results from the study will assist policy makers, technical experts and legislators to

develop relevant test protocols and hence Australian standards to assess and certify

performance of degradable plastics on soil and in marine environments and policies over the

use of different types of plastic packaging materials. However, the study highlights the

difficulty of developing standards for degradability on soil and in marine environments due the

variability of performance in different end environments.

As this study incorporates a cross section of degradable plastics from the marketplace the

results could also be integrated into a sustainable design program (such as the Design for

Sustainability Program – PACIA) for the design and manufacturing of plastic materials or

products. These design criteria would need to take into account the whole of life of the

plastic material or product including its end use.

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2. Abbreviations

FTIR Fourier Transform Infrared Spectroscopy

NATA National Association of Testing Authorities

ASTM American Society for Testing and Materials

ISO International Organization for Standardization

CFU Colony Forming Units

PVC Poly Vinyl Chloride

UV Ultra Violet

VIC Victoria

CO2 Carbon dioxide

ThCO2 theoretical carbon dioxide

LOI Loss on Ignition

Mw Molecular weight

CI Carbonyl Index

IR Infra Red

nm nanometre

cm centimetre

mm millimetre

mg milligram

% percentage

Kg Kilogram

L Litre

ml millilitre

hrs hours

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3. Materials and methods

3.1. Materials

3.1.1 Test specimens

Approximately 20 micron films of six (6) different degradable plastics were selected

for assessment by Technical Review committee and delivered to CSIRO. These samples

belonged to the following four (4) major classes of degradable plastics:

i) Polyolefin with prodegradant

ii) Polyolefin with bio-derived component

iii) Non-polyolefin with bio-derived component

iv) Bio-derived

HDPE film of similar thickness was included as baseline sample. The specimens were

marked A – G; sample identification and description of classes is provided in Table 5.

Table 5 Selection of degradable plastics for assessment

Sample designation Class Class description


B iv Bio-derived




F i Polyolefin with prodegradant

G - HDPE baseline

3.1.2 Soil and marine sites for real-time exposure experiments

Soil exposure site: CSIRO locations at Melbourne and Darwin were selected for on

soil real-time exposure studies. Exposure sites were selected away from shade/trees to allow

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maximum exposure to sunlight. Soil samples were collected from the surface (0-2 cm) and

transported to laboratory in clean containers. Soil samples were analytically tested at NATA

certified Environmental division of ALS laboratory Group (Victoria). Test results are presented

in Table 6 and Table 7.

Marine exposure site: Marine samples were collected from Williamstown site managed by

Defence Science and Technology Organisation (DSTO). Samples were analysed at NATA

certified Environmental division of ALS laboratory Group (Victoria) and results are provided

below in Table 6 and Table 7. A description of real-time experimental sites is included in

Appendix B

Table 6 Soil and marine analysis for real-time testing

Test Soil Melbourne Soil Darwin Marine Williamstown

pH 5.4 5.7 7.97

Salinity - - 41 g/kg

Organic matter 5.4 % 2.6 % 2 mg/L

Total Nitrogen as N 6630 mg/kg 1910 mg/kg 0.4 mg/L

Table 7 Heavy metal analysis of real time exposure sites

Metals Soil Melbourne mg/kg

Soil Darwin mg/kg Marine Williamstown mg/L

Arsenic <5 <5 0.005

Cadmium <0.1 <0.1 0.0010

Chromium 4 47 <0.001

Copper 10 <5 0.013

Lead 19 9 <0.001

Molybdenum <2 <2 0.013

Nickel 2 2 0.004

Selenium <5 <5 <0.01

Zinc 32 15 0.007

Mercury <0.1 2.6 <0.0001

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3.1.3 Soil and marine characteristics for simulated testing

Samples were collected from Melbourne and Williamstown locations, where real-time

exposure studies were being conducted. Samples were transported to the laboratory in clean

containers. Any visibly large pieces of plants/foreign material were removed and 8 mm or 1

mm sterile sieves (for soil and marine samples respectively) were used for sieving. Samples

were processed for microbial count within 2-3 hrs of collection to estimate colony forming

units (CFU) counts (Figure 1) and the remaining samples were stored in dark at 4°C ± 2°C

until further analysis.

SOIL MARINE

Figure 1 Microbial counts (cfu/ml) in soil and marine samples respectively

Analytical testing was performed at NATA certified Environmental division of ALS

laboratory Group (Victoria) and results are presented below in Table 8.

Table 8. Soil and marine sample analysis for simulated testing

Test Soil Melbourne Marine Williamstown

pH 7.1 7.99

Salinity - 41 g/kg

Moisture content 21.8% -

Loss on ignition 6.7% -

Total Nitrogen as N 4260 mg/kg 0.4 mg/L

CFU/ml 3 × 10-7 1 × 10-6

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3.2. Methods

3.2.1 Real-time weathering experiment

Samples were intended for the measurement of tensile properties during degradation

therefore specimens A-G were cut into tensile bars before exposure (Figure 2). Exposure of

samples to real-time on soil and marine conditions was scheduled for maximum period of 9

months; sampling each week during 1st month and then monthly over next 8 months.

Figure 2 Digital images of plastic specimens A-G (before exposure)

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On soil exposure: A patch of land was cleared of grass/vegetation and allowed to condition for

a week (Figure 3). To allow specimens maximum contact with soil surface, the frames were

firmly nailed into the ground. Samples were clamped to the metal frames and set-up at

Melbourne and Darwin exposure sites as shown in Figure 4.

At each sampling time, at least 5 replicate tensile bars for specimens A-G were collected,

lightly brushed to remove adhering soil particles followed by air-drying overnight in a fume

hood and stored away from light in desiccators. Samples were analysed to monitor changes in

physical appearance, tensile properties and chemical structure.

Figure 3 On soil exposure site before and after clearing grass/weeds

Figure 4 On soil exposure set up at Melbourne (left) and Darwin (right) sites

Marine exposure: An exposure raft was made from polyvinyl chloride (PVC) tubing and

nylon mesh bags (>98% Transmission in UV region 300-400 nm; see Appendix) containing

the specimens A-G were tied firmly to the raft using cable ties. Each bag contained a set of 5

replicate tensile bars and marked with appropriate sample designation. The raft was positioned

horizontally such that bags containing specimens float freely on water surface (Figure 5). At

each sampling time, samples were collected and air-dried in fume-hood overnight and stored in

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desiccators at room temperature in dark. Samples were analyzed for changes in appearance,

tensile properties and chemical structure.

Test specimens in nylon mesh bags Sample labelling

Exposure raft set up at the marine exposure site (Williamstown, VIC)

Figure 5 Test specimens and marine real-time exposure set up

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3.2.2 Gravimetric analysis

Specimens of each plastic test sample were weighed before exposure (time=0) and at

each sampling time with an analytical balance (0.1 mg accuracy; Sartorius Australia Pty Ltd).

Test results were averaged on 5 replicates unless reported otherwise. The percentage weight

loss was determined as follows:

% weight loss = to

tsto

W

WW )( × 100

where, Wto and Wts refer to the weight of samples at time 0 (before exposure) and at specific

sampling time, respectively.

3.2.3 Mechanical properties

The test method ASTM D882 – Standard Test Method for Tensile Properties of Thin

Plastic Sheeting was followed for the measurement of tensile strength, modulus and percentage

elongation using an Instron Universal Testing System (Model 3366; Figure 6) with BlueHill® 2

software (Instron Pty Ltd, Australia). Specimens were cut to the size Type IV dumbbell

specification (ASTM D638-Standard Test Method for Tensile Properties of Plastics). Thin film

grips were used to hold the samples and avoid any damage to the specimens. All tests were

performed using a crosshead speed of 50mm/minute. The test results were averaged on 5

replicates, unless reported otherwise.

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Figure 6 Instron Testing System used for analyzing tensile properties

3.2.4 FTIR analysis

A Fourier transform infrared spectroscopy (FTIR) spectrum was acquired for all test

specimens before exposure and at each sampling time using Perkin Elmer FTIR Spectrum 100

spectrometer. The spectra were taken as an average of 16 scans from 4000-450 cm-1. Oxidation

of degradable polymers results into increased levels of carbonyl peaks which are considered as

an indirect measurement of extent of oxidation therefore, special attention was paid to the

carbonyl region (1760-1665 cm-1). Carbonyl Index (CI) was calculated from an average of 3

replicate samples by means of absorbance ratio of the IR bands at 1715-1735 cm-1 (carbonyl

peak), and the 1465 cm-1 (CH2 scissoring peak).

3.2.5 Accelerated UV exposure

The samples were subjected to accelerated UV exposure for a maximum period of 28

days using Ci-4000 Xenon Weather-Ometer® (ATLAS) at NATA certified testing facility

(Australian Wool Testing Authority, Melbourne VIC). Samples were irradiated at 340 nm in

accordance with international standard ISO 4892-2:2006 (Method A; cycle 1). Lamps were

calibrated at the start of 28 days exposure cycle for each specimen. Since large quantities of

test material were required, samples were wrapped around the specimen racks enclosed in

nylon mesh to prevent loss of materials in the event of disintegration (Figure 7). Oxidized

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samples were stored in desiccators in dark and FTIR analysis of oxidized samples was done to

monitor changes in chemical structure of test specimens before and after accelerated UV

exposure.

Figure 7 Film specimens set up in Xenon Weather-Ometer®

3.2.6 Accelerated Biodegradation

UV exposed test specimens (A-G) were cut into same size, less than 5 mm x 5 mm

(Figure 8), to minimize variability in speed of biodegradation due to differences in their

shapes. Microcrystalline cellulose powder was used as positive reference material.

Figure 8 Test specimens for accelerated biodegradation study

Soil and marine samples collected from CSIRO locations in Melbourne and

Williamstown were used as sources of inoculum during this study. In order to increase the

organic matter content of soil, 4% mature compost was added. Test material to inoculum ratio

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was 4 g/400 g soil and 1 g/L marine, and 2 replicate samples for each test specimen were

tested.

Each test specimen (A-G) was mixed with soil and marine samples in proportion

mentioned above and filled into bioreactors (glass jars holding the test mixture) as shown in

Figure 9. All bioreactors were then placed in NATA certified biodegradation testing unit

(Figure 10) and set up to allow continuous supply of CO2 -free humidified air to bioreactors

and discharge of respired gases to CO2 gas analyser. Testing is performed at temperature 28°C

± 1°C for a max period of testing 5 months). Test requirements, procedure and data analysis

details were included in the Step 1 Methodology Project report see Appendix A.

Figure 9 Bioreactors set up with test specimens in soil and marine respectively

28

Blank soil Soil w/test film Marine w/test film

Figure 10 NATA certified Respirometric unit at CSIRO Biodegradation testing laboratory, Clayton VIC

29

4. Results and observations

This section includes test results of degradation of plastic specimens under real-time and

accelerated on soil and marine environmental conditions. After 9 months exposure, only

samples C and D were collected as rest were lost in the sea.

4.1. Digital images

Digital photographs of test specimens were taken at each sampling time to monitor

changes in their physical appearance during real-time exposure to soil and marine

environment (see Table 9 to Table 15).

4.1.1 On soil and marine real-time exposure

During on-soil weathering, test samples are primarily exposed to solar radiations (UV

and visible) air humidity, temperature and rainfall, and simultaneously subjected to the action

of microorganisms present in the soil. Generally it is understood that abiotic factors initiate

oxidation of high molecular weight polymers into lower molecular weight products which are

then easily biodegraded and assimilated by microorganisms. In marine environment, samples

are simultaneously exposed to sunlight, oxygen, moisture, temperature, biofouling (typical

colonization by marine algae and invertebrates) and microbial activity. All or some of these

factors contribute towards deterioration and/or degradation of the plastic materials depending

their chemical composition and conditions at the marine exposure site. We observed

differences in the rates of degradation and disintegration of test samples at the three exposure

sites selected for the present study and observations are presented in the following sections.

Sample A samples became brittle and started disintegrating after approx 2 months of real-

time exposure on soil and the environmental effect was more rapid at Darwin site as compared

to Melbourne/Highett site. The test sample disintegrated and no intact samples could be

retrieved after 4 months of on-soil exposure. Biofouling of samples was observed within 4

weeks of exposure in sea. As the time progressed, the samples crumpled and algae covered

film surface, restricting UV exposure and providing a nutrient rich environment for microbial

activity. The plastic materials were observed to slowly disintegrate under these conditions.

30

Table 9 Digital images of sample A during on soil and marine real-time exposure

EXPOSURE

PERIOD/SITEMELBOURNE (ON SOIL) DARWIN (ON SOIL) WILLIAMSTOWN (MARINE)

BEFORE

EXPOSURE

MONTH 1

31

MONTH 2

MONTH 3

MONTH 4

32

MONTH 5

NO SAMPLE REMAINED

MONTH 6

NO SAMPLE REMAINED

NO SAMPLE REMAINED

MONTH 7

NO SAMPLE REMAINED

NO SAMPLE REMAINED

33

MONTH 8

NO SAMPLE REMAINED

NO SAMPLE REMAINED

MONTH 9

NO SAMPLE REMAINED

NO SAMPLE REMAINED

LOST IN THE SEA

Sample B became brittle on exposure to moisture & sunlight and lost its structural integrity after almost 2 months of on soil exposure. No intact

samples were recovered after 6 months of on-soil exposure. Effect was more pronounced in marine environment; samples started disintegrating after

just 4 week of exposure. Samples crumpled and break easily upon handling. Marine algae covered the film surface and contributed towards

deterioration of the samples over time.

34

Table 10 Digital images of sample B during on soil and marine real-time exposure

EXPOSURE


BEFORE

EXPOSURE

MONTH 1

35

MONTH 2

MONTH 3

MONTH 4

36

MONTH 5

MONTH 6

MONTH 7

NO SAMPLE REMAINED

37

MONTH 8

NO SAMPLE REMAINED

MONTH 9

NO SAMPLE REMAINED

NO SAMPLE REMAINED

LOST IN THE SEA

Sample C disintegrated relatively faster (within 2 months) at Darwin site as compared to Melbourne/Highett (3 months). No more intact samples

could be seen after 3 months of on-soil exposure. Marine environment had visible effects on the structural integrity of test samples. Biofouling effect

was observed after exposure for just 2 months and it progressed rapidly over time contributing towards disintegration and degradation of the test

samples.

38

Table 11 Digital images of sample C during on soil and marine real-time exposure

EXPOSURE

PERIOD/SITEMELBOURNE (ON SOIL) DARWIN (ON SOIL) MELBOURNE (MARINE)

BEFORE

EXPOSURE

MONTH 1

39

MONTH 2

MONTH 3

MONTH 4

40

MONTH 5

NO SAMPLE REMAINED

NO SAMPLE REMAINED

MONTH 6

NO SAMPLE REMAINED

NO SAMPLE REMAINED

MONTH 7

NO SAMPLE REMAINED

NO SAMPLE REMAINED

41

MONTH 8

NO SAMPLE REMAINED

NO SAMPLE REMAINED

MONTH 9

NO SAMPLE REMAINED

NO SAMPLE REMAINED

Sample D was observed to retain its form over relatively longer period of exposure (approx 6 months), although sample brittleness increased over

time and they tend to break easily. Similarly, weathering in marine resulted in biofouling of samples but their structure remained intact during 9

months of exposure period.

42

Table 12 Digital images of sample D during on soil and marine real-time exposure

EXPOSURE


BEFORE

EXPOSURE

MONTH 1

43

MONTH 2

MONTH 3

MONTH 4

44

MONTH 5

MONTH 6

MONTH 7

45

MONTH 8

MONTH 9

Sample E disintegrated rapidly under real-time soil environmental conditions; within 1 month exposure at Darwin site and after 2 months exposure

at Melbourne site. Films became very brittle and no intact sample was recovered after 2 months of on-soil exposure. Film samples deformed upon

exposure to marine conditions. Biofouling of samples was observed within 1st month of marine exposure and further affected their rate of

disintegration and deterioration over time.

46

Table 13 Digital images of sample E during on soil and marine real-time exposure

EXPOSURE


BEFORE

EXPOSURE

MONTH 1

47

MONTH 2

MONTH 3

NO SAMPLE REMAINED

MONTH 4

NO SAMPLE REMAINED

NO SAMPLE REMAINED

MONTH 5 NO SAMPLE REMAINED NO SAMPLE REMAINED

NO SAMPLE REMAINED

48


NO SAMPLE REMAINED


NO SAMPLE REMAINED


NO SAMPLE REMAINED


NO SAMPLE REMAINED

Sample F test specimens disintegrated after 4 weeks on soil exposure at Darwin site and within 3 months exposure at Melbourne site. Once

disintegrated, samples were lost to strong winds and/or rainfall. During marine exposure, biofouling of samples was observed although samples

retained their form during 9 months exposure period.

49

Table 14 Digital images of sample F during on soil and marine real-time exposure

EXPOSURE


BEFORE

EXPOSURE

MONTH 1

50

MONTH 2

NO SAMPLE REMAINED

MONTH 3

NO SAMPLE REMAINED

MONTH 4

NO SAMPLE REMAINED

NO SAMPLE REMAINED

51

MONTH 5

NO SAMPLE REMAINED

NO SAMPLE REMAINED

MONTH 6

NO SAMPLE REMAINED

NO SAMPLE REMAINED

MONTH 7

NO SAMPLE REMAINED

NO SAMPLE REMAINED

52

MONTH 8

NO SAMPLE REMAINED

NO SAMPLE REMAINED

MONTH 9

NO SAMPLE REMAINED

NO SAMPLE REMAINED

LOST IN THE SEA

Sample G specimens became brittle as on-soil weathering progressed, and disintegration of samples was observed after 2- 3 months exposure

period. Film samples break easily and no intact samples could be recovered after 3 months. Marine exposure resulted in discoloration of films owing

to marine conditions and growth of algae on its surface.

53

Table 15 Digital images of sample G during on soil and marine real-time exposure

EXPOSURE


BEFORE

EXPOSURE

MONTH 1

54

MONTH 2

MONTH 3

MONTH 4

NO SAMPLE REMAINED

55

MONTH 5

NO SAMPLE REMAINED

NO SAMPLE REMAINED

MONTH 6

NO SAMPLE REMAINED

NO SAMPLE REMAINED

MONTH 7

NO SAMPLE REMAINED

NO SAMPLE REMAINED

56

MONTH 8

NO SAMPLE REMAINED

NO SAMPLE REMAINED

MONTH 9

NO SAMPLE REMAINED

NO SAMPLE REMAINED

LOST IN THE SEA

57

4.2. Gravimetric weight analysis

Difference in weights of samples before and after exposure to real-time on soil and

marine conditions was used to monitor degradation of test materials over time. Precautions

were taken to gently handle the samples so as to minimize damage, if any.

4.2.1 On soil real-time exposure

As the time exposure time progressed, the samples started becoming brittle. It was

estimated that initially samples appeared to have gained weight instead of losing and this could

be attributed to dirt/soil adhering to the films or moisture absorbed during exposure period.

Some of the grass or soil particles were found embedded into the films and difficult to remove

easily. Visual assessment suggested that samples disintegrated relatively faster at Darwin site

as compared to those exposed at Melbourne. An overall %weight loss for samples A, B, C, D,

E and G was observed at Melbourne site. In comparison, film samples B, D and G at Darwin

exposure site showed loss in their total weights just before they disintegrated; samples A and C

were estimated to gain weight and samples E and F could not be analysed as they disintegrated

within first month of exposure (Figures 11 and 12). A summary of test results for each test

sample before their disintegration is provided in Table 17 and 18

58

-250

-200

-150

-100

-50

0

50

0 1 mth 2 mths 3 mths 4 mths 5 mths 6 mths 7 mths 8 mths 9 mths

On-soil exposure at Melbourne site (months)

% w

eig

ht

chan

ge

D A B C E F G

Figure 11 On soil real-time exposure at Melbourne (VIC)

-250

-200

-150

-100

-50

0

50

0 1 mth 2 mths 3 mths 4 mths 5 mths 6 mths 7 mths 8 mths

On soil exposure at Darwin site (months)

% w

eig

ht

chan

ge

A B C D F G

Figure 12 On soil real-time exposure at Darwin (NT)

59

4.2.2 Marine real-time exposure

Samples exposed to marine environment showed biofouling effect early during exposure

period and it progressed rapidly with time (Figures 13 and 14). Test specimens were found

covered with green algae and other invertebrates (suggesting onset of biofouling), and as the

exposure period progressed, films crumpled and started disintegrating. After 8 months, the

frame to which samples were attached broke and samples A, B, E, F and G were lost in the sea.

Figure 13 Biofouling of plastic specimens during marine exposure

Figure 14 Mesh bags containing test specimens after 6 months marine exposure; digital images showing

biofouling of samples in sea over time

60

As the samples wrinkled and folded over, the exposure to sunlight and other marine

conditions was non-uniform across the samples. In addition to biofouling, moisture absorbed

by test specimens could have affected weight measurements of specimens, thus resulting into

inconsistent weight analysis data presented in this study (Figure 15). An overall increase in

weight for all samples was observed.

-400

-350

-300

-250

-200

-150

-100

-50

0

50

0 1 mth 2 mths 3 mths 4 mths 5 mths 6 mths 7 mths 8 mths 9 mths

Marine exposure at Williamstown (months)

% w

eig

ht

chan

ge

A B C D E F G

Figure 15 Marine exposure at Williamstown (VIC)

4.3. Changes in mechanical properties

Tensile properties such as elongation, modulus and tensile strength of test specimens

were analysed to monitor effect of on-soil and marine weathering on mechanical properties of

film specimens analysed in this study.

4.3.1 On soil real-time exposure

Elongation vs exposure time. Results obtained in this study suggested that all test specimens

(A-G) showed significant reduction in elongation properties under on-soil weathering

conditions at both exposure sites (Figures 16 and 17). Data analysis suggested that this effect

was more rapid in Darwin samples in comparison to those exposed at Melbourne location.

61

0

100

200

300

400

500

600

0 1 2 3 4 5 6 7 8 9

Exposure period (months)

Elo

ng

atio

n a

t b

reak

(%

)A

B

C

D

E

F

G

Figure 16 Effect on elongation during on soil exposure at Melbourne (VIC)

0

100

200

300

400

500

600

0 1 2 3 4 5 6 7 8 9


Elo

ng

atio

n a

t b

reak

(%

)

A

B

C

D

E

F

G

Figure 17 Effect on elongation during on soil exposure at Darwin (NT)

Modulus vs exposure time. Data analysis suggested that an overall increase in modulus was

observed for samples A, C and D due to samples becoming brittle with time (Figures 18 and

62

19). Film samples E, F and G did not show any change in modulus before they disintegrated

within first 2 months of exposure period.

0

400

800

1200

1600

2000

0 1 2 3 4 5 6 7 8 9


Mo

du

lus

(MP

a)

A

B

C

D

E

F

G

Figure 18 Effect on Modulus during on soil exposure at Melbourne (VIC)

0

400

800

1200

1600

2000

0 1 2 3 4 5 6 7 8 9


Mo

du

lus

(MP

a)

A

B

C

D

E

F

G

Figure 19 Effect on Modulus during on soil exposure at Darwin (NT)

63

Tensile strength vs exposure time. Results suggested that tensile strength of most test

samples reduced during exposure period. However, sample D maintained tensile strength for a

longer period of time (measurable up to 9 months) and sample B maintained tensile strength

for 5 months followed by a rapid drop off (Figures 20 and 21).

0

20

40

60

80

100

0 1 2 3 4 5 6 7 8 9


Ten

sile

str

ess

at m

ax lo

ad (

MP

a)

A

B

C

D

E

F

G

Figure 20 Effect on tensile strength during on soil exposure at Melbourne (VIC)

0

20

40

60

80

100

0 1 2 3 4 5 6 7 8 9


Ten

sile

str

ess

at m

ax lo

ad (

MP

a)

A

B

C

D

E

F

G

Figure 21 Effect on tensile strength during on soil exposure at Darwin (NT)

64

4.3.2 Marine real-time exposure

Elongation vs exposure time. The data analysis suggested overall decrease in tensile strength

during marine exposure (Figure 22), with samples C and D and the reference PE (sample G)

maintaining a measureable elongation at break up to 8 months of exposure .

0

100

200

300

400

500

600

0 1 2 3 4 5 6 7 8 9


Elo

ng

atio

n a

t b

reak

(%

)

A

B

C

D

E

F

G

Figure 22 Effect on Elongation during marine exposure at Williamstown (VIC)

Modulus vs exposure period. The data analysis suggested overall decrease in tensile strength

during marine exposure (Figure 23), with polyolefin based samples (C, D, F and G)

maintaining a measureable modulus up to 8 months of exposure.

65

0

400

800

1200

1600

2000

0 1 2 3 4 5 6 7 8 9


Mo

du

lus

(MP

a)A

B

C

D

E

F

G

Figure 23 Effect on Modulus during marine exposure at Williamstown (VIC)

Tensile strength vs exposure period. It was observed that tensile strength of all the test

samples reduced during exposure to marine conditions (Figure 24).

0

20

40

60

80

100

0 1 2 3 4 5 6 7 8 9


Ten

sile

str

ess

at m

ax lo

ad (

MP

a)

A

B

C

D

E

F

G

Figure 24 Tensile strength during marine exposure at Williamstown (VIC)

66

4.4. Changes in chemical structure

Degradation of polymers is subject to its physio-chemical structure, environmental

conditions (such as sunlight, temperature, moisture, pH and salinity) and microbial activity.

Polyolefins are known to degrade by an oxo-biodegradation mechanism. During exposure to

abiotic conditions such as UV or thermal conditions, low molecular weight oxidation products

are formed which are subsequently biodegraded and assimilated by environmental

microorganisms. The biodegradation of oxidized polyolefin fraction opens up the whole

structure and facilitate diffusion of water and other soluble compounds inside thus accelerating

the biodegradation process.

As mentioned earlier in the report, carbonyl index (CI) provides a means of quantifying

the oxidative degradation of polymers and predict changes in molecular weight (as Mw

decreases upon oxidation, the CI increases). Samples collected at each sampling time were

analysed by FTIR and carbonyl index was calculated for polyolefin based samples C, D, F and

G. Each one of these original samples (i.e. before exposure) had a CI value of 0.00. Later it

was observed that CI of degradable polyolefin samples increased on exposure to soil

environment suggesting initiation of degradation process. Sample F showed rapid increase in

CI at both the exposure sites; Melbourne and Darwin (0.08 and 0.17 respectively) followed by

sample C (0.13 and 0.11 respectively) and sample G (0.03 and 0.04 respectively). Sample D

did not show any change in CI during initial 4 months of on-soil exposure but as the time

progressed slight increase in CI was observed (approx 0.04 after 9 months exposure) (Figures

25 and 26).

67

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

0.22

0 1 2 3 4 5 6 7 8 9 10

Melbourne on soil exposure (months)

Car

bo

nyl

ind

ex (

CI)

Sample C

Sample D

Sample F

Sample G

Figure 25 Carbonyl index during on soil exposure at Melbourne (VIC)

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

0.22

0 1 2 3 4 5 6 7 8 9 10

Darwin on soil exposure (months)

Car

bo

nyl

ind

ex (

CI)

Sample C

Sample D

Sample F

Sample G

Figure 26 Carbonyl index during on soil exposure at Darwin (NT)

Degradable polyolefin-based test films exposed to marine environment were also

analysed and no changes in CI were observed. Comparative FTIR spectra of all test specimens

are presented in Appendix B.

68

4.4.1 Accelerated UV exposure using xenon-arc unit

During present study, all the test films (A-G) were exposed to accelerated UV irradiations

for a period of 28 days and CI was calculated for polyolefin based samples. As mentioned

earlier, the CI of un-exposed polyolefin based samples C, D, F and G was 0.00. A marked

increase in CI value (approx 0.2) was observed for sample C after UV treatment indicating

oxidation of test material and formation of low molecular weight products (Figure 27). The CI

for polyolefin samples D, F and G was estimated to be approx 0.04, 0.02 and 0.003

respectively. Based on these results it is hypothesised that an extended period UV exposure

might be required for abiotic oxidation of these materials into lower molecular weight

products. However, molecular weight analysis of these oxidized samples is necessary to make

any further comments on their oxidation levels.

Comparative FTIR spectra of mesh bag and all 7 xenon-arc exposed test specimens are

presented in Appendix B.

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

0.22

After 1 month xenon-arc exposure

Car

bo

nyl

ind

ex (

CI)

Sample C

Sample D

Sample F

Sample G

Figure 27 Carbonyl index after accelerated UV exposure in xenon-arc

69

4.5. Respirometric biodegradation

The oxidized test specimens (A-G) were exposed to simulated soil and marine conditions

in a biodegradation test unit and their rate of biodegradation was assessed over a period of 5

months.

4.5.1 In soil biodegradation

Digital images of the samples were taken at the end of the test (Figure 28). It was found

that degradable film samples A and E disintegrated into smaller pieces over time and in the end

it was difficult to separate them from soil particles. Other test samples namely, B, C, D, F and

G did not show any marked changes to their sample structure.

A slow but steady increase in the cumulative CO2 was observed for all seven test samples

(Figure 29). Results suggested that biodegradation of reference sample cellulose, and oxidized

test samples A and E was initiated within a week of incubation in soil. The rate of

biodegradation of the cellulose was more than 70% after 45 days and it reached approx 100%

at the end of the test. Meanwhile test samples A and E achieved 60% and 70% biodegradation

respectively (Figure 30) suggesting that non-polyolefin based samples were biodegradable in

soil under the specified set of conditions. The remaining test samples B, C, D, F and G had an

extended lag phase and a relatively slower rate of biodegradation. Sample C appeared to

degrade more steadily after almost 3 months of incubation in soil and it reached approx 23% at

the end of the test. Initially it was observed that the rate of biodegradation of blank soil sample

was higher relative to soil containing samples F and G. This may have been due to microbial

activity in the soil being influenced by addition of these two test samples but it quickly

recovered to normal after approx 2 weeks. Further work would have to be done to confirm the

exact reason for this observation. Film sample B, D, F and G did not show any relevant

changes in their rate of biodegradation over 5 months period (11%, 4%, 11% and 7%

respectively). Sample B which is made from bioderived products did not biodegrade

significantly under soil conditions. It is possible that abiotic and/or biotic trigger to initiate

biodegradation of sample B was lacking in the present test system. Samples C, D, F and G

were polyolefin-based samples and carbonyl index results suggested that sample C showed

highest concentration of carbonyl groups among these samples. Since, polyolefins degrade by a

combination of oxidation and biodegradation process, it is likely that these test samples did not

70

oxidize completely to generate low- molecular weight products that could be easily degraded

and assimilated by soil microorganisms.

Soil is a complex heterogeneous environment. Its physio-chemical properties could

influence the activity and structure of its microbial communities. The results obtained in this

study reflect the rate of degradation of test materials under specific set of environmental

conditions and soil characteristics. Any natural variation in the test conditions could result into

variable test data. It is recommended to repeat the tests using soil from different sites, and

using set of different test conditions (UV exposure, temperature, pH and moisture) to obtain a

more reliable test results.

71

A B C D

E F G cellulose

Figure 28 Digital images of test samples after biodegradation in soil; samples A and E disintegrated into smaller size.

Arrows point towards remaining film samples

72

0

5

10

15

20

25

30

0 20 40 60 80 100 120 140

Number of days

Cu

mu

lati

ve C

O2

(g/v

esse

l, M

ean

)Blank soil

A

B

C

D

E

F

G

Cellulose

Figure 29 Cumulative CO2 evolution during biodegradation of test samples in soil

-10

0

10

20

30

40

50

60

70

80

90

100

110

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

Number of days

Deg

ree

of

bio

deg

rad

atio

n (

%)

Soil A

Soil B

Soil C

Soil D

Soil E

Soil F

Soil Cellulose

Soil G

Figure 30 Rate of biodegradation of test samples in soil

73

4.5.2 In marine biodegradation

Test specimens were exposed to accelerated marine conditions in laboratory and changes

in their physical appearance was monitored at regular intervals. Sample A sample size

appeared to disintegrate and degrade during marine exposure, followed by sample E. On the

other hand, sample B did not show any change for first 2 months and then started disintegrating

slowly and by the end of 5 months no intact pieces were visible. Digital images of test

specimens after approx 5 months of exposure in marine are presented below (Figure 31).

On analysis of the rate of biodegradation during the initial 3 weeks of the study it was

observed that the blank marine sample had higher rate of CO2 evolution relative to marine

containing test specimens. This may have been due to microbial activity in the marine water

being influenced by addition of these two test samples but it quickly recovered to normal

thereafter (Figure 32 and 33). Further work would have to be done to confirm the exact reason

for this observation. The rate of biodegradation of cellulose in marine water was more than

60% after approx 83 days and it reached almost 90% at the end of the test (Figure 33). Samples

A and E biodegraded to approx 87% and 70% suggesting that these materials were easily

biodegradable in marine under specified set of conditions. Biodegradation of sample B started

relatively slow and after almost 3 months it rapidly increased and completely disintegrated

and/or biodegraded by the end of the test. These results suggested that specified marine

conditions (especially moisture and/or marine microorganisms) played an important role

during biodegradation of sample B. A steady rate of biodegradation was observed for sample C

and it achieved approx 55% biodegradation by the end of the test. Polyolefin-based samples D,

F and G were found to biodegraded at extremely slow rates, achieving approx 36%, 28% and

21% respectively after 5 months exposure.

Degradation of degradable plastics in marine is subject to UV exposure, biofouling and

microbial activity under aerobic marine conditions (floating plastics) or anaerobic marine

sediments (non-floating plastics). In the present study, samples were oxidized using accelerated

UV exposure and then subjected to aerobic marine conditions under laboratory conditions. The

test results obtained in this study exclude the impact of biofouling on these test materials. It is

not clearly understood what impact, if any, biofouling would have on the rate of

biodegradation of these test specimens. It is therefore suggested to repeat the test under

different set of test conditions (pH, temperature, duration of UV exposure) and using sea water

from other locations (same or different seasons/years) to obtain reliable data.

74

A B C D

E F G cellulose Figure 31 Digital images of test samples after biodegradation in marine; sample B disintegrated completely, samples A and E were significantly reduced. Arrows point

towards remaining film samples

75

0

5

10

15

20

25

0 20 40 60 80 100 120 140

Number of days

Cu

mu

lati

ve C

O2

(g/v

esse

l, M

ean

)Blank marine

A

B

C

D

E

F

G

Cellulose

Figure 32 Cumulative CO2 evolution during biodegradation of test samples in marine

-10

0

10

20

30

40

50

60

70

80

90

100

110

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

Number of days

Deg

ree

of

bio

deg

rad

atio

n (

%)

Marine A

Marine B

Marine C

Marine D

Marine E

Marine F

Marine Cellulose

Marine G

Figure 33 Rate of biodegradation of test samples in marine

76

5. Conclusions

A rigorous scientific investigation into degradation of generic types of degradable

plastics currently available in the Australian market, to study their performance and impact on

two relevant litter environments in Australia - on soil and marine was completed.

In stage 1 of this project a report was completed that included literature review and

methodologies for monitoring the rate of degradation of plastics under real time and simulated

environment conditions typical of litter – on soil and in marine. These methodologies were

designed through consultation with the project Technical Review committee are described in

detail in Appendix A.

In stage 2 of the project, six (6) plastic specimens belonging to four (4) major classes of

degradable plastics were selected for assessment (Table 16).

Table 16 Summary of sample class and class description

Sample designation Class Class description2


B iv Bio-derived




F i Polyolefin with prodegradant

G - HDPE baseline

To capture the diversity of different climates in which these samples may ultimately end up

samples were set up for real-time exposure on soil (9 months maximum) at two different sites –

2 The full definition of all terms can be found in the glossary of terms found at the end of this document Bio-derived: being derived

from a biological source (not petrochemical), examples of bio-derived polymers include starches, proteins and polylactic acid.

Polyolefin: polymer produced from polymerization of simple olefin (CnH2n); examples are polyethylene and polypropylene produced

from olefin ethylene and propylene respectively. Most commonly derived from a petrochemical resource. Non-polyolefin: polymer

typically derived from a petrochemical resource but not a simple olefin (CnH2n) examples include polyesters such as polycaprolactone; Prodegradant: any substance or a factor that promotes degradation examples include transition metals.

77

Melbourne (temperate climate) and Darwin (tropical climate), and in marine conditions at the

salt water immersion exposure site managed by The Defence Science and Technology

Organisation (DSTO) at Williamstown (VIC). At each sampling time, exposed specimens were

analysed to monitor changes in physical appearance, colour, total weight, tensile properties

(tensile strength, modulus and elongation at break) and chemical structure. A detailed summary

of sample analysis over time at all three sites is shown in tables 17 to 19 for on-soil temperate

climate, on-soil tropical climate and in marine respectively. The weight variation and

mechanical properties reported in these tables are the last measureable test result before

disintegration of each sample.

For real-time exposure, comparative disintegration has been predominantly assessed

based on mechanical performance (when elongation is less than 5% of its original value

measured at time zero) and visual imaging (when sample is too damaged to obtain mechanical

properties). This definition is based on current guidelines on aging of polymers and cannot be

used by itself as a measure of degradability.

At the tropical (Darwin) real-time soil exposure site sample A and E (non-polyolefin

with bio-derived component) and samples C (polyolefin with bio-derived component)

disintegrated in 2 months. Samples D and F (polyolefin with prodegradant) showed some

variability. Sample D disintegrated in 5 months and sample F started to disintegrate after 1

month with no sample retrievable after that point. Sample B (bio-derived) disintegrated after 6

months. HDPE disintegrated at month 3 and no sample retrievable after 4 months.

At the temperate (Melbourne) real-time soil exposure site sample A and E (non-

polyolefin with bio-derived component) disintegrated relatively quickly in 4 and 2 months

respectively, sample C (polyolefin with bio-derived component) disintegrated in 3 months.

Samples D and F (polyolefin with prodegradant) showed some variability. Sample D

disintegrated in 5 months and sample F started to disintegrate at 3 months with no sample

retrievable after that point. Sample B (bio-derived) disintegrated after 6 months. HDPE had

disintegrated at month 4 and no sample retrievable after 5 months.

At the real-time marine exposure site, sample B (bio-derived) disintegrated rapidly

within a month, samples A and E (non-polyolefin with bio-derived component) disintegrated

within 2 months. Sample C (polyolefin with bio-derived component) disintegrated after 9

months (but was heavily fouled after 6 months). Sample D (polyolefin with prodegradant) was

still intact at 9 months and sample F (polyolefin with prodegradant) and the baseline HDPE

78

were still intact at 8 months (it must be noted that both samples F and HDPE may have still

been intact at 9 months but they were lost at sea due to extreme weather conditions).

79

Table 17 Summary of test results: On-soil real time exposure study Melbourne (VIC)

Sample Class description Appearance Weight variation

Elongation Stress Modulus CI

A Non-polyolefin w/bio-derived component

Brittle and disintegrated after 4 months

-18% -91% -79% +40% NA

B Bio-derived Brittle and disintegrated after 6 months

- 27% -52% -5% -11% NA

C Polyolefin w/ bio-derived component


- 25% -86% -81% +81% 0.13

D Polyolefin with prodegradant Brittle, disintegrated after 5 months

- 15% -99% -83% +22% 0.04

E Non-polyolefin w/bio-derived component

Disintegrated after 2 months - 12% -95% -59% -12% NA

F Polyolefin with prodegradant Brittle and disintegrated after 3 months

+35% -83% -91% -13% 0.08

G HDPE baseline Brittle and disintegrated after 4 months

-41% -99% -53% -3% 0.03

80

Table 18 Summary of test results: On-soil real time exposure study Darwin (NT)

Sample Class description Appearance Weight variation

Elongation Stress Modulus CI



+9% -98% -55% +61% NA

B Bio-derived Brittle and disintegrated after 6 months

-25% -84% -82% +19% NA



+25% -99% -77% +33% 0.10

D Polyolefin with prodegradant Brittle, disintegrated after 5 months

-6% -99% -70% +57% 0.03


Disintegrated within 2 month No intact sample left

-92% -43% +4% NA

F Polyolefin with prodegradant Disintegrated after 1 month No intact sample left

-99% -64% - 0.04

G HDPE baseline Brittle and disintegrated after 3 months

-30% -99% -61% -12% 0.03

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Table 19 Summary of test results: In marine real time exposure study Williamstown (VIC)

Sample Class description Appearance Weight

variation

Elongation Tensile Modulus CI


Crumpled and lost structure after 1 month

+96% -81% -53% -52% NA

B Bio-derived Brittle and lost form within 1 month

+14% -63% -45% - NA


Wrinkled and lost form after 8 months

+61% -82% -67% -32% 0.00

D Polyolefin with prodegradant Wrinkled but maintained form even after 9 months

+121% -66% -57% -43% 0.00


Crumpled and lost structure after 2 months

+54% -87% -60% +>100% NA

F Polyolefin with prodegradant Wrinkled but maintained form even after 8 months

+106% -93% -65% -61% 0.00

G HDPE baseline Wrinkled but maintained form even after 8 months

+44% -73% -55% -33% 0.00

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The results from Tables 17 to 19 have been simplified and summarised in Table

20 below, with simple trend lines overlaid. The disintegration end point is described

as the time at which samples could not be tested or tensile elongation was less than

5% of the original elongation of unexposed systems.

In summary samples A and E (non-polyolefin with bioderived component)

disintegrated quite rapidly in all environments, with sample A appearing to be more

susceptible to moisture. Sample B (bioderived) was highly susceptible to moisture but

quite stable on soil (in the environments in which we tested). Sample C (polyolefin

with bioderived) was sensitive to UV and marine fouling blocking UV, which may

have reduced the disintegration rate in the marine environment. Samples D and F

(polyolefin with prodegradant) showed similar trends to samples C in which marine

fouling may have reduced the UV exposure and thus ability to disintegrate and/or

degrade. Sample G (baseline HDPE) showed similar trends to the other polyolefin

containing samples (albeit a longer disintegration time) with the exception of sample

D. Variation in base polyolefin formulation (for example the addition of processing

stabilisers) could also account for some variable disintegration in polyolefin

containing samples.

Table 20 Summary of disintegration end point for all exposure sites

C

F

G

8

DEA

B

Marine

(Melbourne)

BDGAC

E

FOn-soilTropical

(Darwin)

BDA

G

C

F

EOn-soil


97654321months

C

F

G

8

DEA

B

Marine

(Melbourne)

BDGAC

E

FOn-soilTropical

(Darwin)

BDA

G

C

F

EOn-soil


97654321months

83

To determine the rate of biodegradation on exposure to simulated soil and marine

environment, plastic specimens were first subjected to accelerated UV exposure using

xenon-arc lamps for 1 month (approximately 1 month exposure in xenon-arc is

equivalent to 8-12 months real time exposure, although it must be noted that this is

highly variable due to climate differences) followed by biodegradation under simulated

soil and marine conditions for 5 months at 28°C, the results are described in detail

below and summarised in Table 21.

Simulated in-soil, samples A and E (non-polyolefin with bio-derived component)

showed the highest biodegradation, reaching 59.5% and 69.5% biodegradation

respectively. Sample C (polyolefin with bio-derived component) obtained the next

highest level of biodegradation (23.4%). Sample B (bio-derived) obtained a

biodegradation level of 10.7% showing that bio-derived materials can have longevity

provided temperature and moisture are minimised. Samples D and F (polyolefin with

prodegradant) obtained biodegradation levels of 4.2% and 10.9% respectively, within

error or the baseline HDPE 6.8%.

Simulated marine water, sample B (bio-derived) showed the highest

biodegradation reaching 99.9%, showing its susceptibility to moisture. Samples A and

E (non-polyolefin with bio-derived component) followed reaching 87.0% and 69.7%

biodegradation respectively. Sample C (polyolefin with bio-derived component)

obtained the next highest level of biodegradation (55.4%) It is noteworthy that sample

C had the highest carbonyl index value among all the polyolefin based samples and its

rate of degradation was higher in soil and marine relative to samples D, F, and G, this

means it was more oxidised. Samples D and F (polyolefin with prodegradant) obtained

biodegradation levels of 35.9% and 27.5% respectively and the baseline HDPE 21.1%,

indicating that moisture can play a significant role in increasing the biodegradation of

polyolefins containing prodegradants.

It is noteworthy that sample C had the highest CI value among all the polyolefin

based samples and its rate of degradation was higher in soil and marine relative to

samples D, F, and G.

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Table 21 Summary of test results from in-lab biodegradation study

Sample Class description Carbonyl index after xenon-arc exposure

% Biodegradation in

Soil (after 150 days)

% Biodegradation in

Marine (after 150 days)

A Non-polyolefin w/bio-derived component NA 59.5 87.0

B Bio-derived NA 10.7 99.9

C Polyolefin w/ bio-derived component 0.2 23.4 55.4

D Polyolefin with prodegradant 0.04 4.2 35.9

E Non-polyolefin w/bio-derived component NA 69.5 69.7

F Polyolefin with prodegradant 0.02 10.9 27.5

G HDPE baseline 0.00 6.8 21.1

Cellulose NA 103.2 91.4

* please note that a standard error of ± 5% should be considered when comparing % biodegradation values

85

6. Recommendations:

6.1. Test Methodologies

Scope

The study presents a guide to testing of degradable plastics on soil and marine

environments under defined conditions and a general approach to compare and rank

degradation of degradable plastics under defined test conditions. This study describes

methods of real-time exposure and a simulated environment in the laboratory.

Real-time conditions

This study specifies a method to establish disintegration and degradability of

degradable plastics under real-time exposure conditions, where test samples are exposed to

different environmental conditions, for example tropical and temperate climates for on soil

and marine exposure. Any natural variation in the test conditions could result in variable test

data, see Table 22 for the list of potential environmental variables. Although intended for

marine (salt water) environments, the marine exposure process might be used with outdoor

brackish water and fresh water environments as well.

Table 22 List of environmental variables for real-time exposure

pH

Precipitation

Temperature

Sunlight

Salinity

Element contents such as carbon, nitrogen and heavy metals Microbial activity

Fouling

Tides/water currents

Wind velocity

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Simulated environment in the laboratory

In the laboratory a two tier system was used, this involved an accelerated photo-

oxidation process (Tier I) and biodegradation measured via CO2 evolution (Tier II). It is also

suggested that a third tier (Tier III) be added to assess the toxicity of residues from the

biodegradation step. In Tier I specimens were first subjected to accelerated UV exposure

using xenon-arc lamps for 1 month, followed by biodegradation (Tier II) under simulated soil

and marine conditions for 5 months at 28°C. At the end of the test, biodegradability in soil

and marine was determined by measuring the carbon-dioxide evolved in a closed

respirometer. The results reflect the rate of degradation of test materials under specific set of

environmental conditions.

It is suggested that laboratory results are not extrapolated to actual real-time exposure

environments due to the variability in the natural environment.

6.2. Performance criteria for a plastic claiming to be degradable

Real-time conditions

It is difficult to ascertain performance criteria for a plastic claiming to be degradable

in real-time exposure conditions. We recommend the only performance criteria which can be

specified is for embrittlement and this would be defined as the time required for the film to

reach 5% or less of its original elongation at break in real-time exposure conditions, it is

recommended that embrittlement cannot by itself be sued as a measure of degradability. It is

further recommended that other chemical methods such as carbonyl index (specifically for

polyolefins containing prodegradants) and molecular weight also be used as a measure of

degradation of the materials. Although it must be noted that both these chemical methods

cannot be used when sample has been lost from the test frames.

Simulated environment in the laboratory

For the results to be valid in the laboratory test in marine water or soil (as described in

ISO 17566:2003) the following criteria must be met:

87

A negative reference of exactly the same base polyolefin as that containing pro-

oxidant additive must be included in the study for comparison

The degree of biodegradation of the positive reference material must be more than

60% at the plateau phase or at the end of the test

The CO2 evolved from the replicate blanks (marine water or soil) are within 20% of

the mean at the plateau phase or at the end of the test

The standard guide D6954-04 recommends that materials reach a Mw of 5000dal or

less in Tier I, prior to the biodegradation step (Tier II). We believe a comprehensive study

should be undertaken on the changes in molecular weight of the polymers before, during and

after degradation steps to clarify a) if this is a valid and b) if 1 month of xenon-arc exposure

is sufficient.

This has particular relevance when studying the differences in degradation of sample D

and the baseline HDPE. Sample D containing an oxo-degradable additive may have had a

significantly different base polyolefin formulation (for example the addition of processing

stabilisers). To solve this issue all oxo-degradable polyolefin samples submitted for testing

must be tested in parallel with the same grade of base polyolefin as a reference.

For a plastic claiming to be degradable in a simulated laboratory environment it must

achieve both of the following performance criteria:

After an accelerated photo-oxidation process the sample must be embrittled (film to

reach 5% or less of its original elongation at break) or reach an appropriately low

molecular weight, see also discussion above in relation to D6954-04.

and

The degree of biodegradation of the material must be more than 60% at the plateau

phase or at the end of the biodegradation test

This 6 month (1 month UV exposure plus 5 months biodegradation) study did not provide

conclusive evidence of the length of time that would form an appropriate criterion for a plastic

claiming to be degradable. It could be considerably longer than 5 months biodegradation

undertaken in this study (for polyolefins with prodegradants up to 2 years may be required to

88

achieve these levels of biodegradation, it is however recommended that an upper time limit

must be defined in any standard and/or test protocol which is developed).

Assessing toxicity risks from the degradation process was outside the terms of this study.

6.3. Benefits and Risks

Benefits

The results from the study will assist policy makers, technical experts and legislators to

develop relevant test protocols and hence Australian standards to assess and certify

performance of degradable plastics on soil and in marine environments and policies over the

use of different types of plastic packaging materials.

As this study incorporates a cross section of degradable plastics from the marketplace

the results could also be integrated into a sustainable design program (such as the Design for

Sustainability Program – PACIA) for the design and manufacturing of plastic materials or

products. These design criteria would need to take into account the whole of life of the

plastic material or product including its end use.

Risks

Broadly, the test results obtained from exposure of plastic samples to real-time

conditions and in-lab simulated conditions indicate that the rate of disintegration and

degradation of non-polyolefin based samples (in all test environments) and bio-derived

sample (particularly in the marine environment) is faster relative to polyolefin based samples.

However, the study found that it was difficult to quantify the degree of disintegration and

degradation under natural conditions as there were a large number of variable factors in

natural environment that could influence the biodegradability of test materials. It is

recommended the real-time weathering experiment at different exposure sites be repeated, in

different seasons or years to gain better insight into the rate and extent of biodegradation of

these materials under natural environmental conditions. It is also recommended the samples

of various film thicknesses are also included in testing to study the effects of film thickness

on degradation rates. A comprehensive study of the changes in molecular weight of the

polymers before, during and after degradation steps would also add value and understanding

to studies of this kind. Under natural conditions it was also difficult to differentiate between

disintegration (where sample was fragmented and lost from the test frames) and degradation

89

in which the sample is ultimately mineralised, for this reason it is recommended that real-

time weathering experiments could not be used as a stand-alone system to assess degradation.

The in-lab study was relevant in terms of quantitatively measuring the rate of

biodegradation of these test materials under accelerated test conditions. Caution is advised in

using these test results in predicting the performance of test materials in real-time for a number

of reasons. Firstly, the in-lab study exposed samples to sequential steps of UV exposure

followed by biodegradation, whereas in real-time these steps would occur simultaneously, this

variation could affect the final result. Also in the marine study we have not considered the

effect of biofouling which could affect the biodegradation rate. These and other variable

factors must be considered.

Any natural variation in the test conditions (UV exposure, temperature, pH and

moisture) and site location (soil/marine characteristics, marine population, salt-

content, tides) could result in variable test data and reversal of results when ranking

samples.

Microbes in a particular environment may favourably biodegrade one particular

polymer in preference to another, this could also cause reversal of results when

changing environments.

90

7. Terminology

Abiotic

Non-living physical and chemical factors in the environment such as light, temperature,

atmospheric gases etc

Assimilation

to consume and incorporate nutrients into substance of the body

Algae

Represent a large and diverse group of simple, typically autotrophic organisms, ranging

from unicellular to multicellular forms

Biodegradation

the process of breaking down of organic substances by microorganisms in the presence of

oxygen to carbon dioxide, water, biomass and mineral salts or any other elements that are

present

Bio-derived: being derived from a biological source (not petrochemical), examples of

bio-derived polymers include starches, proteins and polylactic acid.

Biofouling

process in which marine organisms like bacteria, diatoms (single-celled algae), seaweed

or barnacles (a type of marine crustacean) attach to substrates in contact with water for a

period of time

Bioreactors

glass vessels that contain compost/soil (source of inoculum) with or without test materials

Blank

refers to compost samples without any added test materials

Brittle

state of material when it fails without significant deformation (strain) when subjected to

stress

Carbonyl Index

is the ratio of the intensity (or total area) of the carbonyl absorption band (i.e C=O) in the

FTIR spectrum to that of another band (such as C-H stretching or bending) in the

91

spectrum. Increase in carbonyl index after exposure maybe an indication that oxidation

occurred during the exposure

Colony Forming Units

measure of living or viable bacterial and fungal numbers

Crumple

collapse; to contract into irregular fold

Degradation

the process of breakdown of an organic compound under the influence of one or more

environmental factors such as heat, light or chemicals and resulting into undesirable

change in the in-use properties of the material

Desiccators

sealable laboratory equipment containing suitable desiccant used for storage of moisture

sensitive materials

Disintegration

physical falling apart of a material into small fragments

Deterioration

decline in the quality of structures over a period of time due to the chemical or physical

action of the environment

Elongation

The percentage elongation reported in the tensile test is the maximum elongation of the

gage length divided by the original gage length

Fouling

unwanted accumulation of either living organisms (biofouling) or non-living substances

(inorganic or organic)

Fume hood

ventilation device used to limit the exposure to hazardous dust or vapours

Gravimetric analysis

consists of set of methods for the quantitative determination of an analyte based on the

mass of a solid

Herbicide

92

A type of pesticide used to kill unwanted plant growth

Inoculum

in microbiology terms, inoculum is the biological material (such as bacterial, fungi or

viral cells) added to the medium to start a culture (microbial growth)

Invertebrates

group of animals with no backbone, found in both terrestrial and aquatic habitats, and

includes animals ranging from sponges, corals and seastars etc to insects, crabs and

worms etc.

Irradiation

process by which an item is exposed to UV or other radiations

Loss on ignition

is an analytical test method and it consists of incinerating a sample of the material at a

specified temperature until its mass ceases to change. It is widely used as an indication of

the amount of organic matter content in the material

Mature compost

is a complex organic materials that has been transformed into a stable humus by

microorganisms

Microorganisms

microscopic size organisms such as bacteria, fungi and viruses

Microcrystalline

a crystallized substance that contains small crystals visible only through microscopic

examination

Modulus or modulus of elasticity

mathematical description of an object’s tendency to be deformed elastically when a force

is applied to it (λ = stress/strain)

Moisture content

refers to quantity of water in a mass of soil or compost; expressed in percentage by

weight of water in the mass

93

Non-polyolefin: polymer typically derived from a petrochemical resource but not a

simple olefin (CnH2n) example include polyesters such as polycaprolactone

Pesticide

any substance that prevents, destroys, repels any pest

Plastic

A material that contains large molecular weight organic polymeric substances as an

essential ingredient

pH

is the measure of acidity or basicity of a solution

Polyolefin

polymer produced from polymerization of simple olefin (CnH2n); examples are

polyethylene and polypropylene produced from olefin ethylene and propylene

respectively. Most commonly derived from a petrochemical resource.

Prodegradant

any substance or a factor that promotes degradation

Respirometry

science used in determining the rates of degradation of any organic or biological material

that releases quantifiable gasses

Tensile strength

the maximum strength that a material can withstand before failure

Temperate

climate without extremes of temperature and precipitation

Tropical

climate with a constant temperature mainly above 18°C

Theoretical amount of evolved carbon dioxide

the maximum theoretical amount of carbon dioxide evolved after completely oxidizing a

chemical compound, calculated from the molecular formula and expressed as milligrams

of carbon dioxide evolved per milligram or gram of test compound

94

Total organic carbon

all the carbon present in organic matter

Vegetation

refers to the ground cover provided by plants

Weed

refers to unwanted plant species that grows and reproduces aggressively

Weathering

is a complex interaction of physical, chemical and biological processes that alters the

physical and chemical state of materials

8. Appendix A – methodology attached as separate document

9. Appendix B – supporting data attached as separate

document

degradable plastics packaging materials: assessment...

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