Green Secondary Plasticizer/Thermal Stabilizer in PVC Processing

JST: Engineering and Technology for Sustainable Development 
Vol. 1, Issue 2, April 2021, 131-135 
131 
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* 
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 
ISSN: 2734-9381 
https://doi.org/10.51316/jst.149.etsd.2021.1.2.22 
Received: September 08, 2020; accepted: April 02, 2021 
[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]. 
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. 
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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. 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. 
Table 1. The compositions in PVC formulation 
No Compositions Remarks 
1 PVC 100 
2 DOP Changeable 
3 ESO Changeable 
4 Heat stabilizer 2 
5 Acid stearic 0.2 
6 ... ned 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. 
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. 
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. 
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. 
3. Results and Discussion 
3.1. The effect of ESO content on tensile properties 
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 
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. 
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. 
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. 
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. 
This result is consistent with the results in our 
published work [17]. 
Fig. 2. The effect of ESO on the leaching property of 
PVC in media: (a) water, acid and base (b) oil and 
n-hexane 
Table 2. The shore A of PVC in media 
Medium 
Shore A 
60/0 50/10 
Air 68.5 68.3 
Water 67.0 66.9 
KOH 10% 65.9 65.4 
Sunflower oil 72.8 72.3 
n-hexane * 76.4 
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 
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leaching property of PVC when 10 php DOP in 
formulation was replaced by ESO. 
Fig. 3. The SEM of 60/0 (a) and 50/10 (b) samples 
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. 4. The effect of ESO on migration property 
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. 
Fig. 5. The effect of ESO on migration and 
volatilization of PVC 
3.5. The effect of ESO on thermal property 
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 
(a) 
(b) 
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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. 
4. Conclusions 
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 
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. 
Acknowledgements. 
Authors thank Mr. Nguyen Tien Thanh for his 
assistant. 
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