Green secondary plasticizer/thermal stabilizer in PVC processing
JST: Engineering and Technology for Sustainable Development
Vol. 1, Issue 2, April 2021, 131-135
Green Secondary Plasticizer/Thermal Stabilizer in PVC Processing
Chất hóa dẻo/ổn định nhiệt thứ cấp thân thiện môi trường trong gia công PVC
Nguyen Thi Thuy*, Vu Minh Duc, Nguyen Thanh Liem
School of Chemical Engineering, Hanoi University of Science and Technology, Hanoi, Vietnam
Email: thuy.nguyenthi1@hust.edu.vn
Abstract
Replacing 10 php DOP plasticizer by ESO has slightly increased tensile properties of PVC. A variety of
media were used to study the leaching property of PVC and the results showed that the presence of ESO as
a secondary plasticizer improved the leaching characteristic. There was slight difference in the hardness of
the PVC samples with and without the ESO. In general, the PVC material became softer when DOP was
partly replaced by ESO. The hardness of both samples became smaller after soaking in water, 30 wt.%
acetic and 10 wt.% KOH solution and much bigger in other media. After immersion in n-hexane, the 60/0
sample blistered and became very hard, while the hardness of 50/10 sample increased only 12%. The
morphology of fractured surface of the samples after soaking in n-hexane has clearly demonstrated this
result. The replacing 10 php DOP by ESO has also improved remarkably migration characteristic, thermal
properties, and movement and volatilization in hot air. That means, ESO could be used as a secondary
plasticizer/thermal stabilizer in PVC formulation.
Keywords: Green plasticizer, epoxidized soybean oil, PVC
Tóm tắt
Thay thế 10 php hóa dẻo DOP bằng ESO đã làm tăng nhẹ các tính chất kéo của PVC. Một loạt các môi
trường đã được sử dụng để nghiên cứu đặc trưng chiết tách của PVC và kết quả cho thấy đặc trưng chiết
tách đã được cải thiện bởi sự có mặt của ESO. Độ cứng của vật liệu PVC có và không có mặt ESO khác
nhau không nhiều. Nhìn chung, vật liệu PVC trở nên mềm hơn khi DOP được thay thế một phần bởi ESO.
Độ cứng của các mẫu đều giảm nhẹ sau khi ngâm trong nước, dung dịch acetic 30% và KOH 10% nhưng lại
tăng rất mạnh trong các môi trường còn lại. Sau khi ngâm trong n-hexane, mẫu 60/0 bị phồng rộp và trở nên
rất cứng trong khi độ cứng của mẫu 50/10 chỉ tăng 12%. Kết quả này còn được khẳng định bởi cấu trúc hình
thái bề mặt phá hủy mẫu. Hơn nữa, việc thay thế 10 phần khối lượng DOP bằng ESO cũng cải thiện đáng
kể đặc trưng di trú, tính chất nhiệt và đặc trưng di trú và bay hơi trong không khí nóng. Về tổng thể ESO có
thể được sử dụng làm chất hóa dẻo/ổn định nhiệt thứ cấp trong đơn PVC.
Từ khóa: PVC, hóa dẻo thân thiện môi trường, dầu đậu nành epoxy hóa
1. Introduction*
[10,11] that have been used as primary or secondary
plasticizers for PVC. Among them, the epoxidized
soybean oil is heavily used in PVC processing.
Karmalm used an epoxidized soybean oil to form the
network in plastisol PVC [12]. In another work of this
author, the epoxidized soybean oil was used as
primary plasticizer and the thermal stability of PVC
was estimated by yellowness index, transmittance and
chlorine analyses [13]. The epoxidized soybean oil
was also used to improve characteristic and thermal
stability of PVC for food packaging [14]. In Vietnam,
the epoxidized soybean oil was used as secondary
plasticizer in the fabrication of PVC/black coal and
fly ash composites [15].
PVC is one of the most widely used
thermoplastic in the world [1] and is also known for
its hardness, brittleness, and low thermal stability [2].
In order to improve characteristics, additives such as
plasticizers and/or thermal stabilizers should be added
[3]. There are many types of plasticizers and they can
be classified as internal and external [4] or can be
either defined as primary and secondary plasticizers
[5]. In which, phthalate esters-petroleum based
products are the most commonly used plasticizer
family [2,6]. However, they are well-known to be
toxic and will leach from produces into surrounding
media [2]. So, they should be replaced with bio-based
or renewable environmentally friendly resource [2,6].
Epoxidized vegetable oils are suitable candidates
because they have many epoxy groups and
renewable sources [7]. There are many types of
epoxidized oils as linseed oil [8-9], rubber seed oil
In the presence work, the epoxidized soybean oil
was used as green secondary plasticizer/thermal
stabilizer in PVC processing. Beside tensile
properties, some tests as a leaching, migration,
migration and volatilization in hot air were performed
to estimate characteristics of PVC. The thermal
property of PVC was studied by using TGA analysis.
ISSN: 2734-9381
Received: September 08, 2020; accepted: April 02, 2021
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Vol. 1, Issue 2, April 2021, 131-135
2. Materials and methods
2.1. Materials
The epoxidized soybean oil (ESO) with oxirane
content of 6.2% was purchased from Henan Go
Biotech Co., Ltd, China. The PVC TH-1000R was
provided by Taiyo Vinyl Corporation, Japan. The
heat stabilizer was purchased from Huike, China. The
processing aid Metablen 551J was furnished by
Mitsubishi Chemical, Japan. The DOP plasticizer,
stearic acid 401 and PE wax SCG were of China,
Indonesian and Thai origin, respectively.
2.2.2. Analytical techniques
Morphology: Morphologies of samples were
studied by using a scanning electron microscope
(SEM, JSM-6360/6360LV Japan).
Tensile properties: Tensile strength of samples
was determined according to ASTM D638 standard
by using Lloyd, England.
Thermal property: The thermal properties were
analysed by thermogravimetric analysis (TGA) on a
(DTA/DSC/TGA) Labsys Evo S60/58988 (France).
Shore test: The shore A hardness of samples was
determined according to ASTM D2240 standard by
using Teclock GS 709, Japan.
2.2. Methods
The purpose of this study was to replace a part
of DOP in the PVC recipe with ESO. Therefore,
some PVC materials with different ESO contents
were prepared to evaluate the properties and thus to
provide the most suitable ESO content for replacing a
part of DOP in PVC recipe. The compositions in
formulation of PVC materials were presented in
Table 1.
Leaching test: The leaching of plasticizers from
plasticized PVC sample was carried out based on
ASTM D 1239-98 standard. The PVC specimens
were dipped in media such as distilled water, 30wt.%
acetic acid solution, 10wt.% potassium hydroxide
solution, n-hexane and sunflower oil in 24 hours at
23±1oC and 50±5% relative humidity. The extracted
PVC specimens were rinsed with flowing water,
wiped up and dried in a Memmert convection oven at
40oC for 24 hours. The weight of PVC specimens
before and after immersed was measured. Three
specimens were tested to obtain an average value.
Table 1. The compositions in PVC formulation
No
1
Compositions
PVC
Remarks
100
2
DOP
Changeable
Migration test: The migration of plasticizers
from plasticized PVC films to other film as filer
paper was investigated at room temperature over a
two-week period or 60oC for 48 hours in a
convection oven. The exudation of the plasticizers
was evaluated by placing a rectangular plasticized
PVC sheets of 20×50 mm2 surface area and about 500
µm thickness between two pieces of filter paper of
the same shape. These systems were kept in contact
by sandwiching between two glass microscopy slides
and binder clips. The weight gain of filter papers and
weight loss of plasticized PVC specimens were
calculated and the amount of plasticizer that migrated
from plasticized PVC specimens to filter papers was
averaged from three test specimens.
3
ESO
Changeable
4
Heat stabilizer
Acid stearic
PE wax
2
5
0.2
0.5
3
6
7
Procession aid
2.2.1. List of operations
The mixer: Firstly, PVC and additives were pre-
mixed at 100oC in a mixing device at a mixing speed
of 2400 rpm for 10 minutes then cooled quickly to
50°C and continued to mix for 5 minutes and then
incubated at room temperature in 24 hours. Secondly,
the Hakke Polylab System Rheomix was used to mix.
The mixture was introduced gradually during the first
minute. The mixing time and speed were kept
constant with a duration of 5 minutes and 50 rpm at
temperature of 180oC. Finally, the PVC-based sample
was collected and flattened with a steel roller before
being stored in plastic bags at room temperature.
Migration and volatilization test: The
rectangular plasticized PVC sheets of 20×50 mm2
surface area and about 500 µm thickness were heated
in an air circulating oven at 100oC for 8 days. The
change of weight was measured after heat treatment.
At each specified time, the samples were taken off
and weighted. The variation of the mass was
evaluated as a function of time.
The hot press machine: The PVC-based samples
o
were heated at 200 C and pressed at 130 kg/cm² by
using Gotech model GT-70140-P30C to get thin films
of 500 µm thickness on average or cylindrical blocks
of 8 cm diameter and 3mm thickness.
3. Results and Discussion
3.1. The effect of ESO content on tensile properties
The manual punch press: Once the films are
made, they had to be shaped before testing. A manual
punch press was used for this purpose.
The tensile properties of PVC are the
characteristics that most clearly show the plasticizing
effect of both primary and secondary plasticizers. In
this experiment, the change in the plasticizer content,
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including both primary and secondary, significantly
This result is consistent with the results in our
published work [17].
affected the tensile properties of PVC. The loading of
ESO raised and DOP decreased, tensile strength and
elongation at break increased and reached to the
maximum value at the DOP/ESO ratio of 50/10 and
tended to reduce if the ESO content exceeded the
point. As can be seen in Fig.1, there was the
improvement of 5 and 6% in tensile strength and
elongation at break, respectively.
Fig. 1. The effect of ESO content on the mechanical
properties of PVC
Like the tensile strength and elongation at break,
the presence of ESO also affected the tensile modulus
of PVC. However, this effect was more evident when
the ESO content was high. An increase of 11.6 or
12% of the modulus of PVC sample was observed
when the DOP/ESO ratio was 40/20 or 35/25.
Fig. 2. The effect of ESO on the leaching property of
PVC in media: (a) water, acid and base (b) oil and
n-hexane
In general, the plasticizing effect of the
secondary plasticizer was most evident when 10 php
(parts per hundred polyvinylchloride) of DOP was
replaced by ESO in the PVC formulation.
Table 2. The shore A of PVC in media
Shore A
Medium
60/0
68.5
67.0
65.9
72.8
*
50/10
68.3
66.9
65.4
72.3
76.4
Air
Water
3.2. The effect of ESO on leaching property
In addition to plasticizing role, the extraction
properties of plasticizer as DOP are also of great
interest. In many cases, the extraction of plasticizers
like DOP to the environment limits the application of
PVC. Epoxidized vegetable oils are considered to be
a secondary plasticizer and also have the effect of
improving the extraction properties [16]. In this
experiment, the leaching test of 60/0 (the PVC using
only 60 php DOP) and 50/10 (the PVC using 50 php
DOP and 10 php ESO) sample in media was
performed and the result was showed in Fig.2.
KOH 10%
Sunflower oil
n-hexane
Any increase or decrease in the weight of the
sample after immersing leads to a change in
compositions, which in turn will change the
properties of the PVC. The tiny molecules of water or
30 wt.% acetic solution penetrated into material,
interposed the macromolecule chains, making the
macromolecule chains more flexible, resulting in less
hard materials. Therefore, the shore A hardness of
both samples after soaking in these media was
slightly lower than that of non-immersing samples
(table 2). The additives extracted from the sample
will make material harder. Thus, the shore A hardness
of both samples after soaking in sunflower and n-
hexane was bigger than that of non-soaking samples.
Especially, after soaking in n-hexane, the hardness of
50/10 sample increased by 12% while 60/0 sample
was blistered and became very hard, exceeding the
scale of Teclock GS 709 machine (table 2). This
result demonstrated the ability to improve the
The increase in weight in media as water and
30 wt.% acetic solution proved that the process by
which the tiny molecules of media penetrated into the
samples dominated the process by which additives
were extracted from material into the medium. In
media like 10 wt.% potassium hydroxide solution,
sunflower oil and n-hexane, the opposite was true due
to the reduction of weight after immersing (Fig.2).
The more increase of sample weight in water and
30 wt.% acetic solution and the less decrease in
remaining media indicated the improvement in
leaching property by the presence of 10 php ESO.
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leaching property of PVC when 10 php DOP in
formulation was replaced by ESO.
3.4. The effect of ESO on migration and
volatilization
The Fig.5 showed that, the loss weight of
samples raised over time. The loss weight of two
samples was rather equal in the first day. After that,
the loss weight of 50/10 sample was little smaller
than that of 60/0 sample. If the test was prolonged,
the difference was greater. The loss weight of 50/10
and 60/0 samples after 8 test days was 1.89 and
2.09%, respectively. That means, the presence of
ESO in PVC formulation had a positive effect on the
decrease in migration and volatilization of additives.
(a)
(b)
Fig. 5. The effect of ESO on migration and
volatilization of PVC
Fig. 3. The SEM of 60/0 (a) and 50/10 (b) samples
3.5. The effect of ESO on thermal property
At a magnification of 200, a lot of holes and
cracks were observed on the fracture surface of the
60/0 sample (Fig.3a), but they were very difficult to
observe on the fracture surface of the 50/10 sample
Fig.3b). The morphology of fracture surface of both
samples once again confirmed the positive role of
secondary plasticizer as ESO.
3.3. The effect of ESO on migration property
The migration characteristic of plasticizer was
estimated in two media. The weight of additive as
DOP and ESO moving to the surface after 2 weeks at
25oC or 48 hours at 60oC of the 50/10 sample was
smaller than that of the 60/0 sample (Fig.4). It
demonstrated that the ESO was not only effective in
plasticizing PVC (Fig.1) and improving in leaching
property (Fig.2), but also had a positive effect in
reducing the migration of additives to material
surface (Fig.4).
Fig. 6. TG (a) and dTG (b) thermograms of 60/10 and
50/10 samples
The decomposition curve behavior of two
samples was rather similar and both took place in two
stages. This was shown very clearly on the dTG
curves (Fig.6b). In the first stage, the 60/0 sample
began to disintegrate at 232oC while it increased to
270oC if 10 php DOP in PVC formulation was
replaced by ESO. However, the maximum
degradation temperature of 50/10 sample was 298oC
Fig. 4. The effect of ESO on migration property
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and 17oC lower than that of 60/0 sample in first stage
and about 455oC in the second stage. The weight loss
of first stage of 60/10 sample was 60,89% and it
became 51,15% as 10 php ESO substituted for DOP
in 50/10 sample. The weight loss at 600oC of 50/10
sample was 71.1% and 5.39% lower than that of
60/10 sample. That means, the presence of ESO has
improved the thermal property of PVC.
[7]. H. Hosney, B. Nadiem, I. Ashour, I. Mustafa, A.
ElShibiny. Epoxidized vegetable oil and bio-based
materials as PVC plasticizer. J. Appl. Polym. Sci. 135
(20), 46270 (12pages), 2018.
[8]. O. Fenollar, D. Garcia-Sanoguera, L. SanchezNacher,
J. Lopez, R. Balart. Effect of the epoxidized linseed
oil concentration as natural plasticizer in vinyl
plastisols. J. Mater. Sci. 45, pp. 4406-4413, 2010.
4. Conclusions
[9]. M. P. Arrieta, M. D. Samper, M. Jiménez-López, M.
Aldas, J. López. Combined effect of linseed oil and
gum rosin as natural additives for PVC. Ind. Crops
Prod. 99, pp. 196-204, 2017.
By replacing the 10 php DOP plasticizer with
ESO, a slight increase in tensile properties was
observed. A variety of media were used to study the
leaching property of PVC and the results showed that
the presence of 10 php ESO as a secondary plasticizer
improved the leaching characteristic. The hardness of
two samples became smaller after soaking in water,
30 wt.% acetic and 10 wt.% KOH solution and much
bigger in other media. The shore A hardness of 50/10
sample increased by 12% while sample 60/0 was
blistered and became very hard. The morphology of
fractured surface of the samples after soaking in n-
hexane has clearly demonstrated this result. The
replacing 10 php DOP by ESO has also improved
[10]. R. Joseph, K. N. Madhusoodhanan, R. Alex, S.
Varghese, K. E. George, B. Kuriakose. Studies on
epoxidised rubber seed oil as secondary
plasticiser/stabiliser for polyvinyl chloride. Plast.
Rubber Compos. 3(5), pp. 217-222, 2004.
[11]. D. Balkose, T. O. Egbuchunam, F. E. Okieimen.
Formulation
and
properties
evaluation
of
PVC/(Dioctyl Phthalate)/(Epoxidized Rubber Seed
Oil) plastigels. J. Vinyl Addit. Technol. 14(2), pp. 65-
72, 2008.
remarkably
migration
characteristic,
thermal
properties, and movement and volatilization in hot
air. That means, ESO could be used as a secondary
plasticizer in PVC formulation.
https://doi.org/10.1002/vnl.20142
[12]. P. Karmalm, T. Hjertberg, A. Jansson, R. Dahl, K.
Ankner. Network formation by epoxidized soybean
oil in plastisol poly (vinyl choride), Polym. Degrad.
Stabil. 94, pp. 1986-1990, 2009.
Acknowledgements.
Authors thank Mr. Nguyen Tien Thanh for his
assistant.
[13]. P. Karmalm, T. Hjertberg, A. Jansson, R. Dahl.
Thermal stability of poly (vinyl chloride) with
epoxidized soybean oil as primary plasticizer. Polym.
Degrad. Stabil. 94, pp. 2275-2281, 2009.
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