1. A R T I C L E
Synthesis and application of an environmental epoxy
plasticizer with phthalate-like structure based on tung
oil and cardanol for poly(vinyl chloride)
Fei Song1,2
| Caoxing Huang1
| Xinbao Zhu1
| Chengguo Liu2
|
Yonghong Zhou2
| Puyou Jia2
1
Jiangsu Co-Innovation Center of
Efficient Processing and Utilization of
Forest, Resources, College of Chemical
Engineering, Nanjing Forestry University,
Nanjing, China
2
Institute of Chemical Industry of Forest
Products, Chinese Academy of Forestry
(CAF); Key Lab. of Biomass Energy and
Material, Nanjing, China
Correspondence
Puyou Jia, Chinese Academy of Forestry,
16 Suojin North Road, Nanjing, Jiangsu
210042, China.
Email: jiapuyou@icifp.cn and jiapuyou@
163.com
Funding information
Fundamental Research Funds from the
National Natural Science Foundation of
China, Grant/Award Number: 31822009;
Natural Science Foundation of Jiangsu
Province, Grant/Award Number:
BK20201128; Jiangsu Province Biomass
and Materials Laboratory, Grant/Award
Number: JSBEM-S-202001
Abstract
An epoxidized cardanol tungoleate (ECT) based on tung oil and cardanol was
synthesized through esterification and epoxidation. The chemical structure of
the compound was verified by Fourier transform infrared spectroscopy (FTIR)
and proton nuclear magnetic resonance (1
H-NMR). The plasticizing effects of
ECT as the main plasticizer in poly(vinyl chloride) (PVC) was studied and
compared with the commercial plasticizer dioctyl phthalate (DOP). The ther-
mal migration stabilities, the thermal degradation process and the mechanical
properties of PVC samples and the plasticization mechanism of ECT for PVC
were investigated through the use of volatility, extraction, discoloration, and
tensile tests as well as thermal gravity analysis (TGA), TGA–FTIR analysis,
electronic universal testing machine and dynamic mechanical analysis (DMA).
Compared with DOP, the ECT plasticized PVC can exhibits better thermal sta-
bility, more excellent tensile strength (17.28 MPa) and higher stretchability
(629.41%), which is 1161% higher than DOP (1.37 MPa) plasticized PVC film.
In addition, the migration resistance and volatility stability of ECT are much
better than DOP. Therefore, this fully bio-based plasticizer based on tung oil
and cardanol is a promising alternative plasticizer for PVC and may be an
excellent phthalate substitute from the perspective of human health and sus-
tainable development.
K E Y W O R D S
biopolymers and renewable polymers, blends, plasticizer, poly(vinyl chloride),
thermogravimetric analysis
1 | INTRODUCTION
As one of the world's five major general-purpose plastics,
poly(vinyl chloride) (PVC) has penetrated into all aspects of
human life including building decoration supplies, toys, aux-
iliary medical supplies, electronics, pipeline, handbags,
plastic wrap, clothing, advertising banner, and so on. due to
its remarkable chemical resistance, wear resistance, flame
retardant, electrical insulation, and excellent mechanical
properties.1–3
The pure PVC molecular chain has strong
polarity, which makes its processing and application difficult.
In order to improve this deficiency, corresponding
Fei Song and Caoxing Huang contributed equally to this work.
Received: 11 January 2021 Revised: 26 March 2021 Accepted: 26 March 2021
DOI: 10.1002/app.50809
J Appl Polym Sci. 2021;e50809. wileyonlinelibrary.com/journal/app © 2021 Wiley Periodicals LLC. 1 of 11
https://doi.org/10.1002/app.50809

2. plasticizers are usually added to the PVC base material to
improve its flexibility and plasticity. Phthalate esters (PAEs)
are the most widely utilized plasticizer and account about
80% of the total output because of their remarkable proper-
ties, such as cheap price, low-temperature resistance, high-
plasticizing efficiency, colorless and tasteless.4
However, as
we all known, PAEs are easy to migrate from PVC materials,
and the existence of it may cause endocrine disorders, repro-
ductive system diseases and have potential carcinogenic
risks,5,6
which has brought the safety of some products con-
taining PAEs plasticized PVC into question. What's worse,
relevant studies have also shown that phthalate plasticizers
may be related to the onset of type 2 diabetes, which can
increase the risk of endometriosis in women, increase the
risk of asthma and allergies in children and adults, and cause
autism and other diseases.7,8
In order to solve the problem of the toxicity and easy
migration of plasticizers, governments and organizations
around the world are vigorously developing and promoting
environmentally friendly nontoxic plasticizers, and the use
of bio-based plasticizers to replace PAEs is also increasing.
Modified vegetable oil is a superior environmentally
friendly plasticizer, which is degradable and harmless to
the human body.9
In addition, it has good lubricity and
dispersibility to PVC, and the plasticized products have
excellent flexibility and good light and heat stability.10
In
recent years, many vegetable oils and their derivatives
have been developed as environmentally friendly plasti-
cizers, such as tung oil,11
soybean oil, cottonseed oil,12
and castor oil.13
In addition, cardanol, an important
renewable resource obtained as a by-product of the
cashew nut processing industry, is also widely used in the
synthesis of green plasticizers.14
The principle of phthalate plasticizers is based on the
fact that each repeating unit of PVC has a polarized
carbon-chlorine bond. This structural feature makes the
polarized part (aromatic ring and ester bond) of the
phthalate plasticizer molecule pass van der Waals force
and dipole–dipole, polymer interacts to achieve the pur-
pose of plasticizing PVC.15
For bio-based plasticizers,
especially vegetable oil-based plasticizers, in addition to
ester bonds, epoxy bonds are usually included, which can
act as a HCl scavenger during the thermal aging process
of PVC, bringing excellent thermal and light stability to
PVC.16
In this work, a new type of plasticizer derived from
tungoleic acid and cardanol, epoxidized cardanol
tungoleate (ECT), was synthesized (Scheme 1), which
can completely replace the traditional phthalate plasti-
cizers used for PVC. The results indicate that this renew-
able bio-based plasticizer has a phenyl ester structure and
functional epoxy bonds, which can provide PVC with
excellent compatibility, thermal stability, plasticity and
migration resistance, and provide new ideas for the devel-
opment of special bio-based plasticizers.
2 | EXPERIMENTAL
2.1 | Materials
Dichloromethane, oxalyl chloride, triethylamine, ethyl
acetate, tetrahydrofuran (THF), 3-chloroperoxybenzoic
acid (85%), sodium chloride, anhydrous sodium sulfate,
and sodium bicarbonate were kindly provided by Aladdin
Co., Ltd. Tungoleic acid (acid value:189.8 KOH/g) was
SCHEME 1 The compounds used in this study and the conversion of tungoleic acid and cardanol into ECT. ECT, epoxidized cardanol
tungoleate [Color figure can be viewed at wileyonlinelibrary.com]
2 of 11 SONG ET AL.

3. purchased from Refined Oil And Fatty Co., Ltd. (Anhui,
China). Cardanol was commercially available from Jinan
Ren Yuan Chemical Co., Ltd. (China). PVC was procured
from Hanwha (KM-31, South Korea) with K value 65.0
and degree of polymerization 1300 ± 100.
2.2 | Preparation of cardanol tungoleate
A detailed description of the synthesis of cardanol
tungoleate (CT) is as follows: Tungoleic acid (50 g,
0.18 mol) and dichloromethane (150 ml) were mixed in
500 ml three-necked flask equipped with a magnetic stir-
rer and a reflux condenser, and then oxalyl chloride
(23 g, 0.18 mol) was added to react at 25
C for 3 h. After
slowly adding the mixture of cardanol (50 g, 0.16 mol),
trimethylamine (18 g, 0.18 mol) and 50 ml dic-
hloromethane the system was heated to 50
C for 12 h.
Finally, precipitate was removed by suction filtration,
and 7 wt% sodium bicarbonate solution and saturated
NaCl solution was used to wash the filtrate several times
until it cleaned to neutral pH by a separating funnel. The
organic layer was collected and then dried with anhy-
drous sodium sulfate and filtered. The methylene chlo-
ride was removed by a rotary evaporator to obtain CT as
the brown-red transparent viscous liquid. The acid value
of CT was 1.33 mg KOH/g and its determination was in
accordance with the Chinese standards GB/T 1668–2008.
CT was stored in a refrigerator at 4
C for later use.
2.3 | Preparation of ECT
CT (50 g) and ethyl acetate (100 ml) were added into a
500 ml flask, and perform magnetic stirring in an ice-
water bath (5
C). 3-Chloroperoxybenzoic acid (92 g)
dissolving in 200 ml of ethyl acetate was dropped into
the reaction system through a constant pressure
separatory funnel and the temperature was controlled
to be lower than 5
C. Then the reaction was heated to
25
C for 2 h with the precipitation of benzoic acid.
When the reaction was complete, use the same method
as above to post-process the product to obtain ECT as
the brownish yellow transparent viscous liquid. The
epoxy value was 6.34% and its determination was in
accordance with the Chinese standards GB/T
1667–2008.
2.3.1 | Preparation of PVC films
PVC (5 g) was dissolved in 40 ml of THF at 40
C and
mixed with 0.5 g, 1 g, 2 g, 3 g of ECT, 3 g dioctyl phthalate
(DOP) respectively. The mixture was fully dissolved by
magnetic stirring, and then sonicated for 30 min to remove
air bubbles. The samples were poured into petri dishes
(d = 19 cm) followed by slowly air drying at ambient tem-
perature for 1 days then under reduced pressure for 1 days
to remove traces of THF and to obtain thin films. The for-
mulations are shown in Table 1.
2.3.2 | The FTIR measurements
Fourier transform infrared spectroscopy (FTIR) spectros-
copy of the tungoleic acid, cardanol, CT, and ECT was per-
formed on a Nicolet IS 10 IR spectrometer (Nicolet Co.) in
a range of 4000 500 cm−1
and the resolution of 4 cm−1
.
2.3.3 | 1
H NMR measurements
1
H NMR spectra were confirmed by a Bruker ARX
300 nuclear magnetic resonance spectrometer with
CDCl3 as the solvent and tetramethylsilane as the inter-
nal standard.
2.3.4 | Thermogravimetric analyzer
Thermal gravity analysis (TGA) measurements were per-
formed NETZSCH TG 209F1 (Netzsch Instrument Crop.,
Germany) in a nitrogen atmosphere was used with a heating
rate of 10
C/min and a temperature range of 35–600
C.
2.3.5 | TGA-FTIR analysis
The TGA-FTIR spectrum of the film was measured by an
experimental system consisting of a 409PC thermal ana-
lyzer (Netzsch, Germany) and NicoletiS10 FTIR (Nicolet
Instrument Crop.). Approximately 10 mg of PVC film
was heated from 40 to 600
C at a rate of 10
C/min under
TABLE 1 Formulation of the PVC films
PVC films PVC (g) ECT (g) DOP (g)
PVC 5 – –
ECT-10 5 0.5 –
ECT-20 5 1 –
ECT-40 5 2 –
ECT-60 5 3 –
DOP-60 5 – 3
Abbreviations: DOP, dioctyl phthalate; ECT, epoxidized cardanol tungoleate;
PVC, poly(vinyl chloride).
SONG ET AL. 3 of 11

4. N2 atmosphere. Collect spectra with a resolution of
4 cm−1
in the range of 4000–500 cm−1
.
2.3.6 | Dynamic mechanical analysis
The dynamic mechanical analysis (DMA) was per-
formed via a DMTA Q800 (TA Instruments) with gas
cooling accessory to observe the α-transitions of the
PVC films under investigation. Rectangular samples of
geometry 80 (L) × 10 (W) × 4 (T) mm3
. The oscillatory
frequency of the dynamic test was 1 Hz. The tempera-
ture was raised at a rate of 3
C/min in the range of
−80 to 100
C.
2.3.7 | Measurements of acid value,
epoxy value, and thermal stability
Determination of acid, epoxy values was in accordance
with the Chinese standards GB/T 1668–2008 and GB/T
1667–2008, respectively. According to the GB/T 9349–
2002 standard, the discoloration test was carried out to
analyze the thermal stability of the film.
2.3.8 | Migration test
Volatility test was according to ISO176:2005 (determina-
tion of plasticizer loss of activated carbon determination).
Extraction tests were according to ASTMD 1239–98.
The PVC film was immersed in distilled water, 30%
(wt/vol) acetic acid, 10% (wt/wt) sodium hydroxide, 50%
(wt/wt) ethanol and petroleum ether at 23 ± 1
C and
50 ± 5% relative humidity.
2.3.9 | Tensile properties test
Tensile properties test was measured by a CMT4000 uni-
versal testing machine (according to ISO 527-2: 1993)
with stretching rate of 20 mm/min. Each named sample
need test at least four times.
3 | RESULTS AND DISCUSSION
3.1 | Synthesis and characterization
The FTIR spectra of tungoleic acid, cardanol, CT, and
ECT are shown in Figure 1(a). In the CT spectrum,
the characteristic peaks at 1706 cm−1
representing
carboxyl C O tensile vibration of tungoleic acid and
bands at 3328 cm−1
representing the phenolic
hydroxyl stretching vibration of cardanol disappeared,
new characteristic bands appeared at 1762 cm−1
for
ester-group C O stretching vibrations, indicating that
the esterification reaction of tungoleic acid and car-
danol was successful. For the FTIR spectra of ECT,
the bands at 3013 cm−1
ascribing to C H stretching
disappeared, new bands at 911 and 825 cm−1
arising
from the epoxy group appeared, indicating that the
double bond in the alkyl chain from tungoleic acid
and cardanol on ECT was successfully epoxidized. To
further confirm the structure, we acquired the 1
H
NMR spectra of the CT, and ECT (Figure 1(b)). The
FIGURE 1 (a) FTIR spectra of tungoleic acid, cardanol, CT, and ECT. (b) 1
H NMR spectra of CT and ECT. CT, cardanol tungoleate;
ECT, epoxidized cardanol tungoleate [Color figure can be viewed at wileyonlinelibrary.com]
4 of 11 SONG ET AL.

5. chemical shifts of these peaks matched the protons of
the molecular structures for CT, and ECT. Further-
more, the characteristic peaks of the protons marked
9 and 13 moved down from 5.40–6.12 ppm to 2.89–
3.12 ppm, which was caused by the epoxidation of the
double bond.
3.2 | Thermal stability evaluated
by discoloration test
The discoloration process of ECT-10, ECT-20, ECT-40,
ECT-60, and DOP-60 at 180
C over time is shown in
Table 2. The pure PVC lasted the shortest (30 min) before
starting to turn black. The PVC plasticized with 60 wt%
ECT (ECT-60) lasted the longest (120 min) before starting
to turn black. And PVC plasticized with 60 wt% DOP
(DOP-60) started to turn black at 90 min, which is the
same as the performance of the sample ECT-10. In addi-
tion, as the content of the plasticizer ECT increases, the
time point when the sample starts to turn black gradually
increases. These results indicate that better thermal sta-
bility was in the PVC plasticized with ECT than in the
DOP plasticized PVC.
3.3 | Thermal stability evaluated
by TGA analysis
Figure 2 presents the TGA and DTG curves, and correlative
data for PVC, ECT-10, ECT-20, ECT-40, ECT-60, and DOP-60
with 5%, 30%, 50%, and 70% mass loss temperatures (T-5%,
T-30%, T-50%, and T-70%), and char yield at 600
C are listed in
Table 3. Initial degradation (T-5%) of PVC and DOP-60
occurred at 169.0 and 242.3
C, while ECT-60 displayed initial
degradation at 251.8
C. In addition, as the content of plasti-
cizer ECT increases, the T-5% gradually increases. Compared
with DOP-60, the T-5%, T-30%, T-50%, T-70%, and char yield of
ECT-60 were significantly higher. Therefore, the ECT plasti-
cized PVC film has higher thermal stability than DOP plasti-
cized PVC film, which is in good agreement with the results
of the discoloration test. This is mainly because the epoxy
group of ECT can react with HCl,11,17
thereby delaying ther-
mal decomposition. In addition, ECT has a molecular weight
much larger than DOP. These factors allow ECT to provide
PVC with greater thermal stability than DOP.
To further illustrate the thermal degradation behavior of
PVC films, we took DOP-60 and ECT-60 as examples and
performed TGA-FTIR analysis. As shown in Figure 3, the
main gasses released during thermal degradation of DOP-60
TABLE 2 Discoloration test results for the PVC films at 180
C [Color table can be viewed at wileyonlinelibrary.com]
Samples
Discoloration test (min)
0 30 60 90 120 150 180
PVC
ECT-10
ECT-20
ECT-40
ECT-60
DOP-60
Abbreviations: DOP, dioctyl phthalate; ECT, epoxidized cardanol tungoleate; PVC, poly(vinyl chloride).
SONG ET AL. 5 of 11

6. and ECT-60 are H2O, CO2, CO, HCl, and benzene.13,18
Spe-
cifically, In the second degradation stage (460
C), there are
peaks at 3500–3800 cm−1
representing H2O, peaks at
2940 cm−1
belonging to HCl, peaks at 2968 and 1465 cm−1
ascribing to benzene, peaks at 1743, 1268, and 1122 cm−1
representing carbonyl containing compounds. In addition,
the characteristic peaks of C O C (at 1072 and 910 cm−1
)
can be observed in the spectrum of ECT-60 (Figure 3(d)).19
This is because the epoxy group absorbs the HCl and olefins
produced by the degradation of PVC, or due to ring-opening
reaction of PVC polymer chain and epoxy group, as shown
in Figure 4. Therefore, the characteristic peak intensity of
HCl in the infrared spectrum, ECT-60 is significantly lower
than DOP-60. These results indicate that the presence of
epoxy groups allows ECT plasticized PVC films to have bet-
ter thermal stability than DOP plasticized PVC films.
3.4 | Mechanical properties
DMA technology is often employed to measure the visco-
elasticity of films, which can show the change of tan δ
with temperature. Among them, the temperature at the
maximum of the tan δ versus temperature curve is
defined as the glass transition temperature (Tg), which is
an important indicator to measure plasticization effi-
ciency. Figure 5 shows the tan δ versus temperature
curve of the PVC samples, the relevant Tg values are
listed in Table 4. As depicted in Figure 5, only one peak
was observed in the curve of each sample, indicating that
ECT had good compatibility with PVC.20
In Table 4, the
Tg values of ECT-10, ECT-20, ECT-40, and ECT-60 were
46.2, 43.1, 27.4, and 25.4
C, respectively—considerably
lower than that of pure PVC (81.6
C). It can be seen that
the Tg of ECT-40 and ECT-60 are significantly lower than
that of ECT-10 and ECT-20. An interpretation of this can
be seen in Figure 6. The chlorine atom on the PVC
molecular chain has an electron withdrawing effect, so
the hydrogen atom connected to it shows electro-
positivity. The electronegative oxygen atoms in the ester
group and epoxy group on ECT form a hydrogen bond
interaction with the positive hydrogen atoms on the PVC
molecular chain, and the benzene ring with
electropositiveness due to the ester group forms a hydro-
gen bond interaction with the chlorine atom. In addition,
the long nonpolar alkyl chain of ECT can lubricate the
PVC molecular chain, thereby increasing the volume of
the amorphous region of the film,21
resulting in a
FIGURE 2 (a) TGA and (b) DTG curves of PVC, ECT-10, ECT-20, ECT-40, ECT-60, and DOP-60 in N2 atmosphere. DOP, dioctyl phthalate;
ECT, epoxidized cardanol tungoleate; PVC, poly(vinyl chloride); TGA, thermal gravity analysis [Color figure can be viewed at wileyonlinelibrary.com]
TABLE 3 TGA dates of PVC, ECT-
10, ECT-20, ECT-40, ECT-60, and
DOP-60
Samples T-5%/
C T-30%/
C T-50%/
C T-70%/
C Char yield (600
C)/%
PVC 169.0 286.0 303.9 433.1 7.52
ECT-10 162.1 274.6 314.6 447.1 11.57
ECT-20 172.0 287.0 317.0 449.5 11.07
ECT-40 214.2 276.7 336.7 454.2 10.55
ECT-60 251.8 299.3 349.3 449.3 9.44
DOP-60 242.3 286.0 302.3 335.9 3.97
Abbreviations: DOP, dioctyl phthalate; ECT, epoxidized cardanol tungoleate; PVC, poly(vinyl chloride).
6 of 11 SONG ET AL.

7. decrease in Tg. The Tg of DOP-60 was lower than that of
ECT-60 due to ECT have a greater molecular weight
(622.5), so it is more stable in PVC than DOP (391) mole-
cules. This result could be explained by the relationship
of the molecular weight to the Tg through Florry-Fox
equation,
Tg = Tg∞ −
K
Mn
, ð1Þ
where Tg∞ is the glass transition temperature at a theo-
retical limit of infinite molecular weight and K is an
empirical parameter linked to the free volume. This was
explained in terms of the greater free volume of chain
ends: decreasing the molecular weight leads to an
increase in concentration of chain ends, and thus total
free volume, lowering the Tg
22
.
To explore the interaction between plasticizer and
PVC, we investigated the ECT-10, ECT-20, ECT-40, ECT-
FIGURE 3 FTIR spectra of pyrolytic volatiles evolved during the combustion (a and b) DOP-60 and (c and d) ECT-60. DOP, dioctyl phthalate;
ECT, epoxidized cardanol tungoleate; FTIR, Fourier transform infrared spectroscopy [Color figure can be viewed at wileyonlinelibrary.com]
FIGURE 4 Illustrative scheme of epoxy groups enhance the thermal stability of PVC. PVC, poly(vinyl chloride)
SONG ET AL. 7 of 11

8. 60, and DOP-60 by using FTIR analysis. Figure 7 shows
the FTIR spectra of the ECT-10, ECT-20, ECT-40, ECT-
60, and DOP-60. In Figure 7(a), the peaks at around
1434 and 1426 cm−1
represented the amorphous CH2
and crystalline CH2 of PVC,23,24
respectively. It can be
seen from Figure 7(a) that with the increase of the
plasticizer ECT content, the ratio of the peak area of
the amorphous state to that of the crystalline state
shows an increasing trend, indicating that the amor-
phous area in the film increases, which is consistent
with the Tg results. In Figure 7(b), the peaks at around
692 cm−1
represented the C Cl stretching vibration.
With the increase of the ECT, the peak of C Cl
stretching vibration shifted toward low frequency,
from 693.07 cm−1
of ECT-10 to 692.10 cm−1
of ECT-60,
which is due to the interaction of C Cl in PVC with
the polar groups (ester group and epoxy group) of
ECT, reducing the bond force constant of the C Cl
bond. In addition, the peak value of DOP-60 was
greater than that of ECT-60, indicating that ECT had
more polar groups than DOP.
Figure 5(b) shows the stress–strain curves of ECT-
10, ECT-20, ECT-40, ECT-60, and DOP-60, and the
FIGURE 5 (a) DMA curves for PVC, ECT-10, ECT-20, ECT-40, and ECT-60; (b) stress–strain curves for ECT-10, ECT-20, ECT-40, ECT-
60, and DOP-60. DMA, dynamic mechanical analysis; DOP, dioctyl phthalate; ECT, epoxidized cardanol tungoleate; PVC, poly(vinyl
chloride) [Color figure can be viewed at wileyonlinelibrary.com]
TABLE 4 Tensile properties and Tg of PVC films
Samples Tensile strength (MPa) Elongation at break (%) Modulus of elasticity (MPa) Tg (
C)
PVC / / / 81.6
ECT-10 30.67 ± 1.95 413.64 ± 27.76 527.46 ± 73.83 46.2
ECT-20 24.82 ± 1.24 481.85 ± 20.04 5.77 ± 0.95 43.1
ECT-40 21.77 ± 1.51 535.49 ± 11.48 5.02 ± 1.10 27.4
ECT-60 17.28 ± 0.55 629.41 ± 28.10 2.64 ± 0.068 25.4
DOP-60 1.37 ± 0.27 500.04 ± 30.79 0.42 ± 0.10 12.8
Abbreviations: DOP, dioctyl phthalate; ECT, epoxidized cardanol tungoleate; PVC, poly(vinyl chloride).
FIGURE 6 Schematic illustration of the potential interaction
between ECT and PVC molecule. ECT, epoxidized cardanol
tungoleate; PVC, poly(vinyl chloride) [Color figure can be viewed at
wileyonlinelibrary.com]
8 of 11 SONG ET AL.

9. tensile strength, elongation at break and modulus of
elasticity are concluded in Table 4. It can be observed
from Figure 5(b) and Table 4 that with the increase of
the plasticizer ECT content, the elongation at break of
the PVC sample continues to increase, while the tensile
strength and modulus of elasticity gradually decrease.
This indicates that the addition of ECT increases the
flexibility and movement ability of the PVC molecular
chain to a certain extent, and the effect becomes more
obvious as the content increases. ECT-60 has the largest
elongation at break (629.41%), which is better than that
of DOP-60 (500.04%). Although the tensile strength and
elastic strength of ECT-60 are the lowest in ECT's
plasticizing system, it is significantly better than DOP-
60. This is mainly attributed to the fact that ECT has a
structure similar to DOP (phenyl ester structure). And,
the epoxy group in the middle position of the long aliphatic
chain has a strong electrostatic interaction with the PVC
molecular chain, so that the long aliphatic chain can be
fully inserted between the PVC molecular chains, thus total
free volume is increased. Furthermore, the larger molecu-
lar weight of ECT also helps to optimize the mechanical
properties of the film. It can be concluded that the pre-
pared ECT can be used as a primary plasticizer to improve
the toughness of PVC, and only a lower amounts of ECT
can be required to reach the same flexibility as DOP.
FIGURE 7 FTIR spectra of ECT-10, ECT-20, ECT-40, ECT-60, and DOP-60. DOP, dioctyl phthalate; ECT, epoxidized cardanol
tungoleate; FTIR, Fourier transform infrared spectroscopy [Color figure can be viewed at wileyonlinelibrary.com]
FIGURE 8 Mass losses of PVC films after (a) volatilization and (b) extraction testing. PVC, poly(vinyl chloride) [Color figure can be
viewed at wileyonlinelibrary.com]
SONG ET AL. 9 of 11

10. 3.5 | Volatility and extraction resistance
Figure 8(a) shows the mass loss of the ECT-10, ECT-20,
ECT-40, ECT-60, and DOP-60 after the volatility test.
The volatility losses of the plasticized samples ECT-10,
ECT-20, ECT-40, ECT-60, and DOP-60 were 1.95%,
1.77%, 1.32%, 1.16%, and 17.14%, respectively. Obvi-
ously, ECT has excellent migration resistance in PVC,
and is greatly superior to DOP. Figure 8(b) shows the
extraction loss of the ECT-10, ECT-20, ECT-40, ECT-
60, and DOP-60 during extraction in distilled water,
30% (wt/vol) acetic acid, 10% (wt/wt) sodium hydrox-
ide, 50% (wt/wt) ethanol and petroleum ether. Exuda-
tion losses for ECT plasticized PVC in distilled water,
50% (wt/wt) ethanol and petroleum ether were signifi-
cantly lower than DOP-60. The exudation loss of ECT
plasticized PVC in 30% (wt/vol) acetic acid and 10%
(wt/wt) sodium hydroxide was roughly equivalent to
DOP. The polarity and structure of the plasticizer have
a decisive influence on the migration resistance and
solvent extraction resistance of the plasticizer in
PVC.25
The abundant epoxy groups and higher molecu-
lar weight give ECT stronger intermolecular interac-
tions and higher compatibility with PVC than that of
DOP, thus obtaining more excellent migration stability
and volatility in PVC.
4 | CONCLUSIONS
In this work, tung oil and cardanol were successfully
converted into epoxidized ECT through esterification
and epoxidation, with an epoxy value of 6.34%. Discol-
oration test, TGA analysis, and TGA-FTIR analysis
showed that ECT could significantly improve the ther-
mal stability of PVC film, and the thermal stability of
the plasticized PVC film by ECT was better than that of
commercial DOP. DMA analysis and tensile test
showed that the incorporation of ECT significantly
improved the flexibility of PVC film, and the more the
content, the more significant the effect. The largest
elongation at break (629.41%) was found in ECT-60.
Compared with DOP-60 (1.37 MPa), the tensile strength
of ECT-60 (17.28 MPa) has increased by 1161%. The Tg
of ECT-60 and DOP-60 were 25.4 and 12.8
C, respec-
tively. Migration resistance and extractability tests
showed that the migration resistance stability of ECT
was significantly better than DOP, with lower migra-
tion in distilled water, 50% (wt/wt) ethanol and petro-
leum ether and lower than that of DOP. These results
indicate that the plasticizer ECT has good compatibility
with PVC and is not easy to migrate out. This research
established a framework for the use of all bio-based
plasticizers. According to current work, epoxidized ECT
based on tung oil and cardanol has a good application
prospect in PVC.
ACKNOWLEDGMENTS
This work was supported by the National Natural Science
Foundation of China (31822009), the Natural Science
Foundation of Jiangsu Province(BK20201128) and the
Fundamental Research Funds from Government of
Jiangsu Province Biomass and Materials Laboratory
(JSBEM-S-202001).
CONFLICT OF INTERESTS
The authors declare that there is no conflict of interests
regarding the publication of this article.
ORCID
Puyou Jia https://orcid.org/0000-0002-3372-9135
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How to cite this article: Song F, Huang C,
Zhu X, Liu C, Zhou Y, Jia P. Synthesis and
application of an environmental epoxy plasticizer
with phthalate-like structure based on tung oil and
cardanol for poly(vinyl chloride). J Appl Polym Sci.
2021;e50809. https://doi.org/10.1002/app.50809
SONG ET AL. 11 of 11