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Elsevier Editorial System(tm) for Polymer Testing
Manuscript Draft
Manuscript Number:
Title: THE USE OF IMAGE ANALYSIS IN EVALUATING THE EFFECT OF
ORGANIC SOLVENTS ONPOLY(ETHYLENE TEREPHTHALATE) BOTTLES
Article Type: Original Paper
Keywords: image analysis, storage stability test, PET, solvent
penetration
Corresponding Author: Dr Sava J Velickovic, Ph D
Corresponding Author's Institution: Faculty of Technology
First Author: Nenad Jevremovic
Order of Authors: Nenad Jevremovic; Marija Dimitrijevic; Tatjana
Volkov-Husovic; Radmila Jancic
Heinemann; Sava J Velickovic, Ph D
Suggested Reviewers: Sergey Nazarenko
School of Polymers and High Performance Materials , University
of Southern Mississippi
[email protected]
Dr Nazarenko is one of the leading experts in the field of
transport phenomena, and has a great
experience in PET diffusion, hise fields are :
Transport phenomena in polymers and polymer based materials:
diffusion of small molecules, polymer
chain interdiffusion, and chain mobility;
Benny FreemanProfessor of Chemical Engineering, University of
Texas at Austin
[email protected]
Dr Freeman is one of the leading experts in the field of
membrane science and has a wide experimental
experience with PET
Hao Ouyang
National Tsing Hua University, Taiwan
[email protected]
Dr Ouyang is a very prominet scientist in the field of solvent
induced crystallizatrion of PET
Opposed Reviewers:
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Dear Sirs,
We present a paper about the use of image analysis for fast and
efficient evaluation of
quality of PET bottles aftere storage stability test.We believe
this paper will be of use
for all those linked with industrial and scientific
investigations of PET, for there is alot of data that can be
deduced from this fast and non-expensive analysis. Hope you
will find it interesting enough to be published in Polymer
Testing
Regards
Sava Velickovic
ver Letter
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THE USE OF IMAGE ANALYSIS IN EVALUATING THE EFFECT OF ORGANIC
SOLVENTS
ON POLY(ETHYLENE TEREPHTHALATE) BOTTLES
N. Jevremovi, M.Dimitrijevi, T. Volkov-Husovi, R.Jani Heinemann,
SJ Velikovi
Faculty of Technology and Metallurgy, University of Belgrade,
Karnegijeva 4, RS-11000 Belgrade,
Serbia
ABSTRACT
In this paper the use of image analysis software in evaluating
the effect of organic solvents on
transparent poly(ethylene terephthalate) (PET) bottles is
presented. The bottles, filled with water,
chlorobenzene or 3,5,5-trimethylcyclohex-2-en-1-one were subject
to Storage stability test, for 14
days at 54 C, photographed and analyzed by Image Pro Plus
software in order to evaluate the
possibility of following the changes in the material only by
image analysis. The results have shown
that dimensional changes and the development of non-transparent
zones in the bottles can be
precisely followed using image analysis, both when the changes
are small, as in case of water, or
significant, as in case of chlorobenzene. It is also shown that
the development of non-transparentzones can be linked to changes of
sample crystallinity, giving further clues to the mechanism of
solvent diffusion in and out of the PET bottles.
KEYWORDS : image analysis, storage stability test, PET, solvent
penetration
1. INTRODUCTION
The effect of organic solvents on the properties of
poly(ethylene terephthalate) (PET) is very
important due to material's wide range of application for
packaging purposes. As PET can be
crystallinic up to 60%, its crystalline structure can
significantly influence its diffusivity and
permeability toward gasses and liquids.
Apart from being used as material for water based products, PET
is sometimes used as a packaging
for products that are dissolved in organic liquids, e.g.
solutions of pesticides. The mixtures of
organic solvents are known to influence the barrier properties
of PET packaging [1-5]. In cases
where the significant amount of organic solvent penetrates into
PET, swelling takes part, increasing
the mobility of the polymer chains and the values of penetrants'
diffusion coefficients [6-9],
decreasing the glass transition temperatures of the polymer.
When crystallizable polymers are
present, so called solvent-induced crystallization can take part
[10]. As a result of solvent transport
through polymer, crystallization takes part in different phases
of the process. In the beginning
amorphous regions undergo reorganization, that later turn to
small crystallites, further transformed
to lamelar zones leading to well defined crystalline regions
[11]. The amount of crystalline domainsin a polymer can be
relatively easily calculated using methods as wide-angle x-ray
diffraction
(WAXD) or differential scanning calorimetry (DSC), optical
microscopy, Fourier transformed infra-
red spectroscopy (FTIR), and other methods [12,13].
The aim of image analysis is to give a quantitative description
of an image, or to recognise shapes,
if morphological characteristics can be attributed to the
properties of the object studied. It can be
applied in various areas of sciencematerials science, biomedical
sciences, robotics etc. Signals
that are collected by the visual unit (e.g. a camera) can be
processed to compare and analyze various
object characteristics, as maximum and minimum radius,
characteristic angles, areas, roundness
levels of hue and saturation, and many others.
Corresponding author. Phone +381113303805, fax +381112620227,
e-mail: [email protected]
anuscript
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2. EXPERIMENTAL
Materials. Polyethylene terephtalate (PET poly JADE Brand CZ 302
Bottle grade polyester
chips) was used to produce 50 ml bottles by injection moulding
on ASB 50 injection moulding unit
( at Hemotehna PET plant, Subotica, Serbia). The bottles were
filled with chosen organic liquids, or
water, or left empty and then closed and sealed with HDPE caps.
Out of the bottles thus produced,
the bottles with masses as similar as possible were chosen for
experiment.The chosen organic solvents were Chlorobenzene (Aldrich,
p.a.), Xylene (JT Baker, p.a) and 3,5,5-
trimethylcyclohex-2-en-1-one (Isoforone, Brentag, p.a)
TABLE 1
Storage stability test.The bottles were then subject to Storage
stability test (CIPAC 1-MT 46.1.3).
This method consists of keeping the bottles at a constant
temperature of +54 1 0C for 14 days, and
this way it simulates the 2 years of shelf life. The bottles
were left to cool at ambient temperature
after the selected time has passed. Bottles were then opened and
the contents removed. The bottles
were left at ambient temperature to dry until constant mass was
obtained and no traces of anysolvents left were visible.
Image analysis. The images of the samples were taken using NIKON
D80 digital camera with
resolution of 10.3 Mpixels, and maximum resolution was used. All
samples were photographed
from 30 cm distance, using 50 cm focus, using the flash, against
the non-reflecting black
background. Each bottle was photographed three times in three
different positions. These are shown
in Figure 1. The pictures were taken before and after the
experiment in order to establish the
dimension change, and the bottom of the bottle was photographed
after the experiment to establish
the amount of nontransparent areas that are not present in the
sample before the storage stability
test.
FIGURE 1
Images were then processed using Adobe Photoshop CS3, and kept
as a tiff format image. These
images were used in establishing the dimensional changes of the
bottles and measuring the
transparency level of the bottles before and after the storage
stability test. These values were
obtained using Image Pro Plus 4.0 software (Media Cybernetics).
The operations used to analyze
the images were calibrating, measuring, filtering, defining area
of interest, measuring, thresholding
and adaptive thresholding.
In order to measure the dimensional change of the bottles during
the storage stability test, the bottle
contour of a virgin sample (that was not subject to storage
stability test) was taken using Image Pro
Plus, and 30 points for correlation were established. It was
done with all the samples, and their
contours were compared to the virgin sample contour by
establishing a reference point in the middle
of the bottle contour height and measuring the difference of all
the other points from the virgin
contour.
This is shown in Figure 2.
FIGURE 2
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The second part of the image analysis was the calculation of the
type and area percentage of the
base of the bottle that has shown visual change, becoming
non-transparent after the storage stability
test, which may be connected with the change in crystallinity of
the sample. It is done by using the
adaptive thresholding option in Image Pro program. In order to
sort out pixels whose histogram
intensity is higher than the threshold as shown in Figure 3.
FIGURE 3
Differential scanning calorimetry. DSC thermograms were recorded
using Perkin-Elmer PE II in
the temperature range 50-180 C under nitrogen (26 ml/min),
heating rate 10 C/min.
3. RESULTS AND DISCUSSION
Mass change. The initial masses of all the bottles were between
12.05 and 12.10 g. After theexperiment was over they were measured
again to evaluate any possible change of mass.
The results are given in Table 2, as the average value of three
samples for each set of solvents.
TABLE 2
It can be seen that, during the test, the empty bottles have
undergone a slight mass loss, which can
probably be attributed to residual amount of moisture present
that remained during processing,
despite the fact that PET was dried before the processing. Even
the samples that were filled with
water turned out 0.1% lighter than their initial mass, showing
that the amount of water penetrating
into material was negligible.
When organic solvents were present, the results were somewhat
different. All three solvents in theexperiments have penetrated
into PET bottles, and their mass was higher than initial, showing
a
significant mass increase in case of chlorobenzene.
From these results it is very interesting to see how did this
solvent penetration, and its subsequent
diffusion through PET, influence the dimension of the bottles,
change in crystallinity, and whether
the image analysis could give some clue on the paths and
specific points of solvent penetration. In
order to elucidate that problem, two parameters were followedthe
dimension change of sample
bottles, and the decrease in transparency that was observed at
bottoms of the sample bottles.
Change of dimensions of sample bottles. By comparing the contour
of all the sample bottles with
the reference bottle that was not subject to storage stability
test, the amount of dimensional change
and the locations of greatest diversion from the reference
bottle contour were established.
FIGURE 4
From the diagram it can be seen that the most important
diversion from the referent contour is to beseen at the bottle
neck, where the screw thread is located, and at the parts where the
bottle contour
changes its angle. It also happens at the lower part of the
bottle, at the point where base of the bottle
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begins, but in a lesser amount. It is also interesting to note
that while water and isoforone show only
positive diversionsfrom the original contour, i.e. the bottles
are wider than they were before the
original experiment, in case of chlorobenzene, the large part of
contour has gone inwards, what is
shown as a lessening of the contour dimension.
These changes have proven that the dimensional change of the
bottle as a result of storage stability
test can compromise the quality of the sealing properties of the
bottles, for the largest dimensionchanges that are seen in the
screw thread zone imply that the contact between screw cap and
the
bottle can be reduced, letting some of the solvent
evaporate.
Development of non-transparent zones at the base of the bottle.
It was also noted that the
completely transparent bottles develop the non-transparent zones
at the base of the bottle after the
storage stability test. It was assumed that the reason for that
might be the development of the zones
with higher crystallinity that decrease the transparency. It is
known that the recycling of PET gives a
material with higher crystallinity, so it can be assumed that
penetration of a solvent should ease the
relaxation of the polymer chains and enable the formation of
increased crystallinity zones. If that
can be assumed that the highest degree of crystallinity would be
achieved in the zones where the
largest amount of solvent penetratedit can give some clues of
the solvent penetration mechanismin the given material.
The amount and distribution of non-transparent zones was also
investigated using Image Pro Plus
program. These are given in Table 3.
TABLE 3
From the results it is visible that the non-transparency in case
of water is very small, only two
zones, covering less than 3% area, three times more is seen when
isoforone was applied, and more
than third of the entire base area became non transparent after
the storage stability test whenchlorobenzene was used. The
roundness of the zones was similar when larger areas were
covered,
while in case of water the roundness was different.
It is also interesting to note that the non-transparent zones
concentrate against the middle of the base
of the bottle, indicating that the changes are linked to
irregularities of the structure, for at the middle
of the base of the bottle there is a trace of mould riser that
has a different structure. These
investigations show that this is the location where solvent
enters.
Differential scanning calorimetryIt was also interesting to see
if the non-transparency stems from
higher level of crystallinity, that would be a result of solvent
entry, giving the polymer chains room
to reorganize and increase the level of crystallinity in these
zones. In order to investigate that DSC
analysis of both transparent and non-transparent zone from the
same base of bottle was performed.
The DSC traces are shown in Figure 5.
FIGURE 5
The peaks that correspond to melting of PET were compared to
theoretical value of 140.1 J/g for
100% crystalline PET[14], and the results show that the
transparent part is 28.5% while the non-
transparent sample's crystallinity is 32.5 %, confirming that
the non-transparency can stem from
higher crystalline value. The DSC traces have also shown that no
relevant amount of solvent ispresent in the samples. The
possibility of calculating the crystallinity of the sample using
only
image analysis software will be discussed in future papers, as
this investigation is in progress.
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4. CONCLUSION
In this paper the possibility of using image analysis for
investigating the effect of various solvents
on the PET bottles during storage stability test was
investigated. It was shown that the dimensional
changes of the bottles can be recorded in great detail by using
the image analysis software. It is also
possible by choosing the right filters to identify zones where
the level of crystallinity has increasedduring the test, and these
zones can be quantified. This investigation has shown that image
analysis
can be a facile way to follow the changes in transparent PET
products, which can be of great use in
the applications where fast analysis of large number of samples
has to be performed.
ACKNOWLEDGEMETS
This investigation was supported by the Ministry of Science and
Technological Development of the
Republic of Serbia, through projects 142023,19038 and 142016. We
are indebted to Joachim
Heinemann for all the photographs in this paper.
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REFERENCES
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and uptake kinetic in
poly(ethyleneterephthalate), Polymer 1999;40: 3487
[2] G.E. Serad, B.D. Freeman, M.E. Stewart, A.J. Hill, Gas and
vapor sorption and diffusion
in poly(ethylene terephthalate), Polymer 2001;42:6929[3] S.N.
Dhoot, B.D. Freeman, M.E. Stewart, Sorption and transport of linear
and branched
ketones in biaxially oriented polyethylene terephthalate,
Polymer 2004;45:5615
[4] J. Lin, S. Sheongin, S. Nazarenko, Oxygen solubility and
specific volume of rigid
amorphous fraction in semicrystalline poly(ethylene
terephthalate), Polymer 2002;43:4733
[5] K. Hirogaki, I. Tabata, K. Hisada, T. Hori, An investigation
of the interaction of
supercritical carbon dioxide with poly(ethylene terephthalate)
and the effects of some additive
modifiers on the interaction, J. of Supercritical Fluids
2005;36:166
[6] G.F. Billovits, C.J. Durning, Penetrant transport in
semicrystalline poly(ethylene
terephthalate) Polymer 1988;29(8):1468
[8]C.J. Durning, L. Rebenfeld, W.B. Russel, Integral sorption
with induced crystallization.
Polym Eng Sci, 1986;26(15):1066[9] A.R. Berens, Transport of
plasticizing penetrants in glassy polymers . Polym Prepr
1989;30(1):5
[10] K. Mizoguchi, K. Terada, T. Hirose, Y. Kamiya,
Crystallization of poly(ethylene
terephthalate) under high- pressure gases.Polym. Commun., 1990;
31(4):146
[11]J. Radhakrishnan, A. Kaito. Structure formation during the
isothermal crystallization oforiented amorphous poly(ethylene
terephthalate) films. Polymer, 2001;42:3859
[12] H. Ouyang, W.H. Lee, W. Ouyang, S.T. Shuie, T.M. Wu,
Solvent-Induced
crystallization in poly(ethylene terephthalate) during Mass
transport: Mechanism and boundary
condition. Macromolecules, 2004;37:7719
[13] H.Ouyang, W.H. Lee, M.C. Shih, Three stages of
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[14] Advanced Thermal Analysis Laboratory, Table of properties
of lineal macromolecules
and small molecules, University of Tennessee, Knoxville, USA, p.
15, 1996
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TABLES
Table 1. Sample bottle numbers according to the solvent
usedSample number Solvent
1-3 -
4-6 Water
7-9 Chlorobenzene
13-15 Isoforone
bles
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Table 2. Change of mass of the sample PET bottles after the
storage stability test
Solvent Sample mass after experiment, % of initial mass
No solvent 99.76
Water 99.90Chlorobenzene 106.65
Isoforone 101.24
Xylene 100.89
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Table 3. The amount of non-transparent zones at the base of the
bottles after the Storage stability
test
Solvent Area, % RoundnessNumber
of zones
water 2.70 9.08 2chlorobenzene 34.3 4.40 3
Isoforone 9.17 4.09 8
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FIGURE CAPTIONS
Figure 1. The photographs of the bottles used in image analysis
(sample 5 shown in picture)
a) before the experiment, b) after the experiment c) the bottom
of the bottle after theexperimentFigure 2.Calculation of
dimensional changes after the storage stability test by comparing
the tested
sample dimension to a reference sample
Figure 3. Calculation of the amount and type of non-transparent
zones of the base of the bottle after
the storage stability test
Figure 4. The diversion of experimental points from the referent
contour of the bottle. The end
zones refer to screw thread zone, while the zone around point 15
is the bottle base
Figure 5. DSC curves of transparent (dotted line) and
non-transparent part (solid line) of the base
of the bottle after Storage stability test with
chlorobenzene.
gure
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FIGURES
FIGURE 1
a) b) c)
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FIGURE 2
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FIGURE 3
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FIGURE 4
-5 0 5 10 15 20 25 30 35
-0,16
-0,14
-0,12
-0,10
-0,08
-0,06
-0,04
-0,02
0,00
0,02
0,04
0,06
0,08
0,100,12 black - water
red - chlorobenzene
blue - isoforon
measurement point
diversionfro
mt
hereferencecontour,cm(
?)
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FIGURE 5
60 80 100 120 140 160 180 200 220 240 260 280 300 320 340
0,05
0,10
0,15
0,20
T,oC
mCal/s
