Design and synthesis of a castor oil based plasticizer containing THEIC and diethyl phosphate groups for the preparation of flame-retardant PVC materials

Article abstract of DOI:10.1039/c6ra25014a

A fine chemical product based on a castor oil containing THEIC and diethyl phosphate groups (THEIC-MR-phosphate) was designed and synthesized, and it was used as a substitute flame retardant plasticizer to prepare PVC materials instead of the commercial plasticizer dioctyl phthalate (DOP). The performance of the PVC materials plasticized with THEIC-MR-phosphate was investigated with TGA, DSC, cone calorimeter analysis, and tensile tests. The results indicated that the addition of THEIC-MR-phosphate improved the flame retardant properties of the PVC materials. The time to ignition (TI) increased from 10 s to 25 s, the pHRR value decreased from 167.5 kW m^-2 to 52.1 kW m^-2, the av-HRR value decreased from 44.7 kW m^-2 to 21.1 kW m^-2, and the t-pHRR value increased from 45.0 s (D-1) to 73.0 s (N-3). These data indicated that the THEIC-MR-phosphate was effective in increasing the PVC material resistance to fire, and it not only decreased the HRR, but also delayed the fire process.

Full text of DOI:10.1039/c6ra25014a

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Design and synthesis of a castor oil based
plasticizer containing THEIC and diethyl phosphate
groups for the preparation of flame-retardant PVC
materials
Cite this: RSC Adv., 2017, 7, 897
a
a
a
ab
Puyou Jia,a Lihong Hu,ab Guodong Feng, Caiying Bo, Jing Zhou, Meng Zhang
*
a
*
and Yonghong Zhou
A fine chemical product based on a castor oil containing THEIC and diethyl phosphate groups (THEIC–MR-
phosphate) was designed and synthesized, and it was used as a substitute flame retardant plasticizer to
prepare PVC materials instead of the commercial plasticizer dioctyl phthalate (DOP). The performance of
the PVC materials plasticized with THEIC–MR-phosphate was investigated with TGA, DSC, cone
calorimeter analysis, and tensile tests. The results indicated that the addition of THEIC–MR-phosphate
improved the flame retardant properties of the PVC materials. The time to ignition (TI) increased from
10 s to 25 s, the pHRR value decreased from 167.5 kW mꢀ2 to 52.1 kW mꢀ2, the av-HRR value decreased
from 44.7 kW mꢀ2 to 21.1 kW mꢀ2, and the t-pHRR value increased from 45.0 s (D-1) to 73.0 s (N-3).
These data indicated that the THEIC–MR-phosphate was effective in increasing the PVC material
resistance to fire, and it not only decreased the HRR, but also delayed the fire process.
Received 10th October 2016
Accepted 15th November 2016
DOI: 10.1039/c6ra25014a
www.rsc.org/advances
alternate material sources for industrial uses. Nowadays,
renewable resources have attracted increasing attention as
1. Introduction
non-petroleum raw materials to prepare chemical products.
Hundreds of plasticizers derived from renewable resources have
been commercially prepared or used, such as a cardanol-based
plasticizer,3 epoxidized cardanol glycidyl ether,4 palm oil poly-
ester,5 epoxidized cardanol diethyl phosphate,6 oleic acid poly-
ester,7 isosorbide dicaprylate ester plasticizer8 and epoxidized
soybean oil.9 The main chemical structure of the vegetable oil
is triacylglycerol, and the main components of triglycerides
are saturated and unsaturated fatty acids, which can be used
as platform chemicals for many polymer and monomer
synthesis.10–13 However, these plasticizers cannot improve the
ame retardant performance of PVC materials, which restricts
their applications in harsh condition with high ame retardant
requirements.
An effect way to improve the ame retardancy of PVC mate-
rials is to add ame retardants such as antimony trioxide
(Sb2O3),14 alumina trihydrate, Al(OH)3,15 or tripentyl phosphate,
trimethyl phosphate, tris(chloropropyl) phosphate, and di-n-
octylphenyl phosphate,16 but the addition of ame retardants
usually decreases the mechanical properties of PVC blends. It is
necessary to prepare PVC materials using ame retardant
plasticizers that can effectively improve both the mechanical
and ame retardant properties of the PVC blends.
Poly(vinyl chloride) materials with their excellent mechanical
strength, thermal stability, ame retardancy and insulation
characteristics have been widely used as a high performance
resin in many products, such as food packaging, blood bags,
pipes, children toys, medical devices, wire, and cable.1 However,
pure PVC resin cannot be processed and applied because of its
high mechanical strength. To get exible and durable PVC
materials, pure PVC resins are usually mixed with a large
amount of plasticizer. The main commercial plasticizers are
dioctyl phthalate (DOP) and dibutyl phthalate (DBP). These
phthalates easily diffuse to their surroundings and reduce the
performance of PVC products. The loss of plasticizer causes
changes in the long-term properties of PVC products and their
potential toxicity to the human body.2 In addition, plasticized
PVC with DOP burns easily, which restricts its application in the
products that require ame retardant properties, such as wire
and cable. The raw materials for these plasticizers include
petroleum. The scarcity of petroleum resources and the rising
cost of petroleum products has led to the development of
aInstitute of Chemical Industry of Forest Products, Chinese Academy of Forestry (CAF),
National Engineering Lab for Biomass Chemical Utilization, Key Lab on Forest
Chemical Engineering, State Forestry Administration, Key Lab of Biomass Energy
and Materials, 16 Suojin North Road, Nanjing 210042, Jiangsu Province, P. R.
China. E-mail: yhzhou777@sina.com
Our research group prepared a series of ame retardant
plasticizers derived from vegetable oil and explored the retar-
dant mechanism of PVC plasticized with the ame retardant
bInstitute of New Technology of Forestry, Chinese Academy of Forest (CAF), Beijing
100091, P. R. China
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plasticizers. The ame retardant plasticizer based on castor oil sulfuric acid, chloroform, and dioctyl phthalate (DOP) were
(PPC) was synthesized from castor oil, formic acid, phosphate, kindly provided by the Nanjing Chemical Reagent Co., Ltd.
hydrogen peroxide (H2O2) and diethyl phosphate.17 The diethyl Polyvinyl chloride (PVC) was supplied by Hanwha (KM-31, South
phosphate connected to the chemical structure of glycerin tri- Korea).
laurate played the ame retardant role in the re process. The
ame-retardant performance of COPE was carried out by
promoting PVC blend carbonization and forming a consoli-
2.2 Synthesis
2.2.1 Synthesis of methyl ricinoleate (MR). Castor oil (50 g),
anhydrous methanol (10 g) and KOH (0.45 g) were mixed in
a 250 mL ask with a mechanical agitator, thermometer and
condenser tube with stirring at 45 ꢁC for 6 h. Then, the mixture
dated coating covered on the PVC matrix, which prevented the
materials from ring. In order to improve the ame retardant
performance of the plasticizer, the phosphorus content of the
plasticizer was enhanced, and the new ame retardant plasti-
was neutralized with a sulfuric acid solution and allowed to
cizer based on castor oil (FRC) was prepared and achieved the
settle in a liquid separating funnel. The upper oil liquid was
washed with an acid solution and distilled water until the pH ¼
7. Methyl ricinoleate was obtained aer removing the water with
expected results.18 In addition, a soybean oil based phosphate
ester (SOPE) was prepared using the same ame retardant
group.19 All three kinds of vegetable oil based ame retardant
plasticizers improved the thermal stability and ame retardancy
of the PVC materials. However, the mechanical properties of the
PVC materials gradually weakened with the addition of these
plasticizers because many of the hydroxyl groups connected to
the chemical structure of the plasticizers and reduced the
plasticizing effect on the PVC. They are only used as a secondary
plasticizer mixed with DOP to plastify the PVC resin. To
enhance the plasticizing effect of the plasticizer, a new ame
retardant chlorinated phosphate ester based on castor oil
(CPECO) was prepared and applied in the PVC materials.20
Hydroxyl groups were not found in the chemical structure. The
results illustrated that the thermal stability and ame retard-
ancy of the PVC materials improved drastically, and the
migration stability was better than that of DOP. However, the
mechanical properties of the PVC materials were not obviously
enhanced. The reason is that the macromolecular and
branching structure of the plasticizer reduced the mobility of
the PVC chain. Based on these reasons, it is necessary to prepare
novel ame retardant plasticizers derived from vegetable oils as
the main plasticizer for PVC resin.
ꢁ
a rotary evaporator at 60 C.
2.2.2 Alcoholysis of castor oil methyl with THEIC (THEIC–
MR). Methyl ricinoleate and THEIC in a 1 : 1 molar ratio were
placed in a 250 mL ask. Tetrabutyl titanate (1 wt% of methyl
ricinoleate) was added to the solution as a catalyst. The mixture
was stirred at 230 ꢁC for 3 h in a N2 environment. The THEIC–
MR was obtained aer washing with distilled water and
removing the water with a rotary evaporator.
2.2.3 Synthesis of castor oil based ame retardant plasti-
cizer containing THEIC and diethyl phosphate groups (THEIC–
MR phosphate). THEIC–MR and diethyl chlorophosphate in
a molar ratio of 1 : 3 were dissolved in 100 mL of chloroform.
The mixture was placed in a 250 mL ask and stirred at 60 ꢁC for
3 h to nish the reaction. The THEIC–MR phosphate was ob-
tained aer removing the chloroform with a rotary evaporator.
The synthetic route for the THEIC–MR phosphate is presented
in Fig. 1.
2.3 Preparation of PVC materials
The PVC resin and plasticizer (DOP and THEIC–MR phosphate)
were dissolved in 100 mL of THF in accordance with the
formulation shown in Table 1. The mixture was thoroughly
agitated using a mechanical agitator at 160 rpm for 1 h at 60 ꢁC
In this work, we designed and synthesized a ne chemical
product using castor oil containing THEIC and diethyl phos-
phate groups (THEIC–MR phosphate), and the product was
used as a ame retardant plasticizer for PVC materials. Its
1
chemical structure was characterized with FT-IR and H NMR.
The performance of the PVC materials plasticized with the
THEIC–MR phosphate was investigated using TGA, DSC, cone
tests and tensile tests. To the best of our knowledge, the
synthesis and application of a castor oil based ame retardant
plasticizer containing THEIC and diethyl phosphate groups for
PVC has never been reported. We believe that a novel ame
retardant plasticizer can be obtained from castor oil. Further-
more, ame retardant PVC materials can be prepared and used
in harsh conditions. This study will provide a new route for the
efficient use of castor oil.
2. Experimental
2.1 Materials
Castor oil, caustic potash (KOH), anhydrous methanol, tetra-
butyl titanate, tetrahydrofuran, 1,3,5-tris(2-hydroxyethyl)
cyanuric acid (THEIC), diethyl chlorophosphate, concentrated Fig. 1 Synthetic route of THEIC–MR phosphate.
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Table 1 Formulation of PVC materials
PVC materials
PVC
D-1
N-1
N-2
N-3
PVC (g)
DOP (g)
THEIC–MR phosphate (g)
20
0
0
20
12
0
20
9
3
20
6
6
20
0
12
until the mixture was clear and transparent. The samples were
then placed in Petri dishes (diameter 12 cm) and dried at
ambient temperature for a week to remove traces of the residual
solvent and to obtain thin lms.
Fig. 2 FT-IR spectra of products.
2.4 Characterizations
MR compared to that of castor oil, which was attributed to the
hydroxyl absorption peak of MR.17,18 In the THEIC–MR spec-
trum, a stronger absorption peak appeared at around 3297
cmꢀ1, corresponding to the hydroxyl absorption peak of the
THEIC groups. The carbonyl groups (C]O) of THEIC–MR
appeared at 1659 cmꢀ1, and the tertiary amine of THEIC–MR
appeared at 1124 cmꢀ1, indicating MR alcoholysis with THEIC.
Comparing the spectrum to that of THEIC–MR showed that the
hydroxyl absorption peak disappeared at around 3297 cmꢀ1 in
the THEIC–MR phosphate spectrum and a new absorption peak
appeared at 1027 cmꢀ1, which was attributed to the vibration
absorption peak of P–O–C. The vibration absorption peak of
P–C appeared at 977 cmꢀ1, and another new absorption peak
appeared at 800 cmꢀ1, which corresponded to the vibration
absorption peak of P–O–CH2CH3.17,18
The Fourier transform infrared (FT-IR) spectra of the products
were obtained on a Nicolet iS10 FTIR (Nicolet Instrument Crop.,
USA) Fourier transform infrared spectrophotometer. The
spectra were acquired in the range of 4000 cmꢀ1 to 500 cmꢀ1 at
a resolution of 4 cmꢀ1
.
1H NMR measurements were conducted on an AV-300 NMR
spectrometer (Bruker Instrument Crop., Germany) at
a frequency of 400 MHz with CDCl3 as the solvent and tetra-
methylsilane (TMS) as an internal standard.
Thermogravimetric analysis (TGA) was carried out using
a TG209F1 TGA thermal analysis instrument (Netzsch Instru-
ment Crop., Germany) in a N2 atmosphere (50 mL minꢀ1) at
a heating rate of 10 ꢁC minꢀ1. The samples (5 mg) were placed
ꢁ
ꢁ
into platinum pans and scanned from 40 C to 600 C.
The glass transition temperature (Tg) was characterized
using a NETZSCH DSC 200 PCꢁanalyzer aꢁt a heating rate of 20 ꢁC
minꢀ1 and scanning from 40 C to 600 C.
The successful preparation of the THEIC–MR phosphate was
also detected with 1H NMR. The 1H NMR spectrum of castor oil
was detected in our previous study. Fig. 3 presents the 1H NMR
spectrum of MR, and as seen in Fig. 3, the peak for the protons
of the –OH at d ¼ 1.3 were weaker than that seen in castor oil.
The peaks for the protons of –(CH2)– connected to the glycerol
ester could not be observed at 4.1–4.3 ppm, which indicated
that the alcoholysis reaction occurred between the castor oil
and anhydrous methanol.17,18 Fig. 4 presents the 1H NMR
spectrum of THEIC–MR. New peaks appeared at 4.0 ppm and
The combustion properties were evaluated using a cone
calorimeter. All samples (100 ꢂ 100 ꢂ 2 mm3) were exposed to
a FTT200 cone calorimeter (FTT Instrument Crop., UK) under
a heat ux of 35 kW mꢀ2 according to ISO-5660 standard
procedures.
Tensile modulus, tensile strength, and elongation at break
for all the PVC blends were determined according to GB/T
1040.1-2006 (China) under ambient conditions using an
E43.104 Universal Testing Machine (MTS Instrument Crop.,
China).
1
4.2 ppm compared to the H NMR spectrum of MR, and these
peaks were attributed to the protons of the –(CH2)– of the
THEIC groups in THEIC–MR. Multiple absorption peaks
appeared at 3.5 ppm and 3.6 ppm and corresponded to the
protons of the different –OH groups in THEIC–MR. These data
illustrated that THEIC–MR was obtained. The 1H NMR
The migration degree of the plasticizer was tested according
to ASTMD1239-98 and our previous work.20
Anti-aging tests were carried out with a thermal aging oven at
ꢁ
185 C. Anti-aging properties were evaluated by observing the
change in color with increasing time.
3. Results and discussion
3.1 Synthesis and characterization of the plasticizer
The successful preparation of THEIC–MR phosphate was
conrmed by FT-IR. Fig. 2 shows the FT-IR spectra of castor oil,
MR, THEIC–MR and THEIC–MR phosphate. The FT-IR spec-
trum of castor oil was detected in our previous study.17 Aer
alcoholysis with anhydrous methanol, a stronger absorption
peak appeared at around 3410 cmꢀ1 in the FT-IR spectrum of Fig. 3 1H NMR spectrum of MR.
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DOP and THEIC–MR-phosphate in the temperature range of
300–500 ꢁC. This illustrated that the THEIC–MR-phosphate
enhanced the thermal stability of the PVC materials in the
temperature range 300–500 ꢁC. The carbon residue rate of D-1,
N-1, N-2 and N-3 was 8.60, 13.11, 15.08 and 17.78%, respec-
tively, at 600 ꢁC. The char residue of the PVC materials
increased gradually with the addition of the THEIC–MR-
phosphate, which proved that the THEIC–MR-phosphate
enhanced the char yield.
Fig. 4 1H NMR spectrum of THEIC–MR.
3.2.2 DSC of PVC materials. DSC was used to probe the
glass transition temperature (Tg) of the PVC materials. Tg is
a good criterion for determining the chain mobility of the
polymers and compatibility of the PVC and plasticizer.26–29 It is
essential to study the Tg of plasticizers for practical application
as a plasticizer, which leads to a soening or plasticization of
the polymeric materials. Fig. 7 shows the DSC curves of the PVC
materials. PVC exhibited an exothermic peak at approximately
87.6 ꢁC. The Tg of N-1, N-2 and N-3 increased gradually as DOP
was replaced with THEIC–MR-phosphate in the PVC materials.
ꢁ
ꢁ
ꢁ
The Tg of N-1, N-2 and N-3 were 34.9 C, 46.4 C and 67.4 C,
respectively. The drop in Tg for the PVC materials corresponds
to a general increase in disorder, free volume, and mobility of
the macromolecules. The results indicated that the compound
plasticizer (DOP and THEIC–MR-phosphate) reduced the Tg of
the PVC materials; the plasticizing effect of DOP was lower than
that of the THEIC–MR-phosphate.
Fig. 5 1H NMR spectrum of THEIC–MR-phosphate.
spectrum of the THEIC–MR phosphate is shown in Fig. 5, and
the absorption peak at 0.7 ppm is attributed to the protons of
–CH3 in THEIC–MR phosphate. These protons appeared to be
stronger than that seen in THEIC–MR, and the absorption peak
at 2.6 ppm corresponded to the protons of –(CH2)n– in the
THEIC–MR phosphate.19,20 In addition, the absorption peak at
3.6 ppm was weaker than that of THEIC–MR, and all of the
results indicated that THEIC–MR-phosphate was obtained.
3.2.3 Cone calorimetric tests. There are many chlorine
groups connected to the chemical structure of PVC, and they
make PVC hard to burn. The addition of ammable DOP makes
PVC materials easy to burn. Cone tests were used to investigate
the combustibility of PVC materials when DOP was replaced
with THEIC–MR-phosphate. These tests can provide data to
study the thermal degradation, smoking emission and heat
release in detail.30,31 The detail cone calorimeter data were
collected from cone tests and are shown in Table 2. The peak
HRR (pHRR) value, average HRR (av-HRR), time to ignition,
total smoke release, time to peak of HRR (t-pHRR), peak MLR
(pMLR), THR and average MLR (av-MLR) of the PVC materials
were compared. As can be seen in Table 2, the time to ignition
(TI) increased from 10 s (D-1) to 25 s (N-3), indicating that the
THEIC–MR-phosphate made PVC materials more difficult to
burn than the DOP. In the meantime, the pHRR value decreased
from 167.5 kW mꢀ2 (D-1) to 52.1 kW mꢀ2 (N-3). The av-HRR
3.2 Performance of the plasticizer and property of the PVC
materials
3.2.1 TGA of PVC materials. TGA was used to investigate
the thermal degradation behaviors of the PVC materials. Fig. 6
presents the TGA curves of the PVC materials. As seen from
Fig. 6, all of the TGA curves exhibited two steps in the thermal
degradation. The rst step in the temperature range 200–350 ꢁC
corresponded to dehydrochlorination21,22 and thermal decom-
position of the plasticizer (DOP and THEIC–MR-phosphate).
The second step occurred between 350 and 500 ꢁC and was
attributed to the cyclization of the conjugated polyene
sequences to form aromatic compounds.23–25 The thermal
degradation rate increased gradually with the replacement of
Fig. 6 TGA curves of PVC materials.
900 | RSC Adv., 2017, 7, 897–903
Fig. 7 DSC curves of PVC blends.
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Table 2 The detailed cone calorimeter data
pHRR
av-HRR
t-pHRR
(s)
pMLR
av-MLR
THR
Time to ignition
(TI) (s)
Total smoke release
Sample
(kW mꢀ2
)
(kW mꢀ2
)
(g sꢀ1
)
(g sꢀ1
)
(MJ mꢀ2
)
(m2 mꢀ2
)
D-1
N-1
N-2
N-3
167.5
144.8
118.3
52.1
44.7
43.4
34.4
21.1
45.0
60.0
65.0
73.0
0.227
0.224
0.186
0.172
0.039
0.025
0.009
0.001
9.0
8.5
5.6
4.6
10
17
18
25
663.0
540.0
497.0
246.0
value decreased from 44.7 kW mꢀ2 (D-1) to 21.1 kW mꢀ2 (N-3), (N-1, N-2 and N-3) was that the SPR curves of D-1 were higher
and the t-pHRR value increased from 45.0 s (D-1) to 73.0 s (N-3). and sooner than the others. This indicated that D-1 released
These data indicated that the THEIC–MR-phosphate was more smoke aer the re than the others. The smoke was
effective in suppressing the susceptibility of PVC materials to mainly a compound of combustion. The other PVC materials
re, as they not only decreased the HRR, but also delayed the plasticized with THEIC–MR-phosphate released less smoke
re process. The decrease of THR from 9.0 MJ mꢀ2 (D-1) to 4.6 because the thermal degradation of the THEIC–MR-phosphate
MJ mꢀ2 (N-3) further showed that the THEIC–MR-phosphate promoted the formation of a char residue. The char residue
acted as a ame retardant plasticizer for PVC.
acts as a smoke-suppressant in the combustion of PVC mate-
The peak MLR (pMLR) and average MLR (av-MLR) for D-1 rials. The smoke-suppressant effect caused the lags in the SPR
were 0.227 g sꢀ1 and 0.039 g sꢀ1, respectively. However, when peaks of N-1, N-2 and N-3.
DOP was replaced with THEIC–MR-phosphate, these parame-
Fig. 10 shows the MLR curves of the PVC materials. Two
ters for N-3 were lower than that of D-1. The results indicated mass loss stages could be observed, and these are attributed to
that the ame retardant effect of THEIC–MR-phosphate came the two mass loss stages of the PVC materials. This was similar
from promoting the formation of the char residue, which could to the TGA curves. The mass loss of the PVC materials occurred
rmly protect the underlying PVC material from burning.
before 50 s, which corresponded to the HCl elimination reac-
HRR is used to evaluate the combustion performance of PVC tion. The cyclization of the conjugated polyene sequences to
materials. The HRR curves of the PVC materials are presented in form aromatic compounds occurred aer 50 s. The mass loss
Fig. 8. A signicant difference between the HRR curves of D-1 and was caused by the thermal degradation of PVC materials and
the others was a sharp and high peak at around 41 s in the HRR mainly produced smoke. The MLR curves of D-1 were higher
curve of D-1. The peak of HRR gradually became at and low as than that of the other materials throughout the whole
the DOP was replaced with THEIC–MR-phosphate, which can be combustion process, which illustrated that the PVC materials
observed in Fig. 8 (N-1, N-2 and N-3). The times of the HRR peak plasticized with THEIC–MR-phosphate released less smoke
for N-1, N-2 and N-3 were 60 s, 65 s and 73 s, respectively. These than D-1, and THEIC–MR-phosphate provided
a smoke
data illustrated that once the PVC materials were ignited, D-1 suppression effect during the whole combustion process.
burnt and released heat quickly. However, N-1, N-2 and N-3 Furthermore, more char residue was retained in the solid
were hard to burn and released less heat than D-1. The reason phase, and the formed char residue covered the surface of the
for this is that the THEIC–MR-phosphate promoted the forma- PVC matrix. It made the PVC materials (N-1, N-2 and N-3) more
tion of compact and expansive charred layers that covered the thermally stable and ame retardant compared to D-1.
surface of the PVC matrix, and these layers acted as excellent
In addition, the THR curves of the PVC materials are shown
barriers to mass transport and as heat insulation. The conclusion in Fig. 11. The detailed THR data are summarized in Table 2. It
was consistent with the char residue aer the cone tests.
can be found that the THR decreased from 9.0 MJ mꢀ2 (D-1) to
To evaluate the smoke suppression performance of PVC 4.6 MJ mꢀ2 with the addition of the THEIC–MR-phosphate.
materials, the smoke production rate (SPR) with time is shown Fig. 10 shows that the THR value of D-1 was less than that of
in Fig. 9. The obvious difference between D-1 and the others
Fig. 8 HRR curves of PVC blends.
Fig. 9 SPR curves of PVC blends.
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3.2.4 Tensile tests. The tensile strength, elongation at break
and modulus of elasticity were used to evaluate the plasticizing
effect of the plasticizer. Table 3 shows the tensile strength,
elongation at break and modulus of elasticity of all the PVC
materials. Pure PVC showed a higher tensile strength of
26.60 MPa and lower elongation at break of 167.21% compared
to the others. The addition of DOP into the PVC blends caused
a signicant decrease of 13.08 MPa in the tensile strength and an
increase in the elongation at break of 605.35. When DOP was
gradually substituted with THEIC–MR-phosphate in the PVC
materials, the tensile strength of the PVC blends increased from
13.08 MPa (D-1) to 15.20 MPa (N-3), and the elongation at break
decreased from 605.35 (D-1) to 391.98% (N-3). These data indi-
cated that the plasticizing effect of the THEIC–MR-phosphate
was lower than that of DOP. The DSC data further illustrated
that the plasticizing effect of the THEIC–MR-phosphate was
lower than the DOP. We inferred that the compatibility of DOP
with PVC was better than that of the THEIC–MR-phosphate. The
smaller relative molecular mass and ortho phenyl ester structure
make DOP easier to dissolve in the PVC matrix.
Fig. 10 MLR curves of PVC blends.
3.2.5 Migration stability. Fig. 13 presents the migration
degree of all PVC materials. As seen from Fig. 13, the loss of the
plasticizer in D-1 in four different solvents was more than the
others. The resistance performance of migration for D-1 in
distilled water, 30% (w/v) acetic acid, 10% (v/v) ethanol and
petroleum ether was 1.40, 1.54, 1.55 and 3.45%, respectively. The
degree of migration decreased obviously with the addition of
THEIC–MR-phosphate. The resistance performance of migration
for N-3 in distilled water, 30% (w/v) acetic acid, 10% (v/v) ethanol
and petroleum ether was 0.97, 0.87, 0.92 and 1.91%, respectively.
This data illustrated that the resistance performance of migration
for the THEIC–MR-phosphate was better than that of the DOP.
The reason is that the large molecular weight and high degree of
branching make THEIC–MR-phosphate harder to migrate in the
PVC matrix. The better resistance performance of migration can
help stabilize the properties of PVC materials.
Fig. 11 THR curves of PVC blends.
the other PVC materials for the whole combustion process. The
results indicated that the THEIC–MR-phosphate decreased the
THR of the PVC materials.
Fig. 12 shows the TSR curves of the PVC materials. The MLR
data illustrated that the THEIC–MR-phosphate had a smoke
suppression effect during the whole combustion process. The
TSR curves further proved that conclusion. As seen in Fig. 12,
the TSR value was the highest aer 60 s. The time occurred just
aer cyclization of conjugated polyene sequences to form
aromatic compounds. The results indicated that the smoke
released aer the cyclization process of the conjugated polyene
sequences. An interesting phenomenon could be found by
comparing the TSR curves and THR curves. The trend of the
THR curves is similar to the TSR curves but always lagged
behind the TSR curves. We can infer that the burning of the PVC
materials was in fact the burning of the char residue.
3.2.6 Anti-aging tests. The plasticized PVC materials were
put into a thermal aging oven. The temperature was kept at
ꢁ
185 C. Anti-aging properties were evaluated by observing the
change of color with time. The results showed that the time for
the color change was prolonged from 8 min to 78 min with the
addition of THEIC–MR-phosphate. The color change for D-1, N-
1, N-2 and N-3 was 8, 26, 57 and 78 min, respectively. The time
was extended nearly four times. In addition, the TGA tests
showed that the thermal stability of the PVC materials was
enhanced with the addition of THEIC–MR-phosphate. These
Table 3 The mechanical properties of the PVC blends
Tensile strength
(MPa)
Elongation at
break (%)
Modulus of
elasticity (MPa)
Sample
PVC
D-1
N-1
N-2
N-3
26.60
13.08
14.12
14.78
15.20
167.21
605.35
527.10
482.04
391.98
197.11
56.93
76.23
96.12
115.81
Fig. 12 TSR curves of PVC blends.
902 | RSC Adv., 2017, 7, 897–903
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In this study, we designed and synthesized a novel ne chemical
product based on castor oil containing THEIC and diethyl phos-
phate groups. The product was used as a ame retardant plasti-
cizer for preparing ame PVC materials. FT-IR spectra and 1H
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Acknowledgements
This work was supported by Jiangsu Key Lab of Biomass-based
Green Fuels and Chemicals; the Fundamental Research Funds
from Jiangsu Province Biomass and Materials Laboratory
(JSBEM-S-2017010); National Natural Science Foundation of
China (Grant No. 31670578); the President of the Chinese
Academy of Forestry Foundation (Grant No. CAFYBB2014QB021).
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