Study on fluorine-containing polyurethane elastomers based on 2,2-Bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane

Article abstract of DOI:10.14233/ajchem.2014.17222

A series of fluorine-containing polyurethane elastomers (FPUEs) were synthesized from 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)- phenyl]hexafluoropropane (BAFPF6P), which was made from 2-chlorobenzotrifluoride and 2,2-bis(4-hydroxyphenyl) hexafluoropropane and characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, thermogravimetric analysis, microscale combustion colorimeter and contact angle measurement. The results show that the fluorine-containing polyurethane elastomers prepared from BAFPF6P have good thermal stability and low surface tension. Furthermore, fluorine-containing polyurethane elastomers also exhibit good flame retardance and the peak heat release rate and total heat released of fluorine-containing polyurethane elastomer based on BAFPF6P are much lower than those of polyurethane elastomer without the fluorine element.

Full text of DOI:10.14233/ajchem.2014.17222

Asian Journal of Chemistry; Vol. 26, No. 5 (2014), 1324-1326
ASIAN JOURNAL OF CHEMISTRY
http://dx.doi.org/10.14233/ajchem.2014.17222
Study on Fluorine-Containing Polyurethane Elastomers Based on
2,2-Bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane†
1
1
2,*
WENZONG XU1,2,*, LIANG LIU , SHAOQING WANG and YUAN HU
1School of Materials Science and Chemical Engineering, Anhui Jianzhu University, 856 Jinzai Road, Hefei 230022, Anhui Province, P.R. China
2State Key Lab of Fire Science, University of Science and Technology of China, Hefei 230026, Anhui Province, P.R. China
*Corresponding author: E-mail: wenzongxu@sohu.com; yuanhu@ustc.edu.cn
Published online: 1 March 2014;
AJC-14762
A series of fluorine-containing polyurethane elastomers (FPUEs) were synthesized from 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)-
phenyl]hexafluoropropane (BAFPF6P), which was made from 2-chlorobenzotrifluoride and 2,2-bis(4-hydroxyphenyl) hexafluoropropane
and characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, thermogravimetric analysis, microscale
combustion colorimeter and contact angle measurement. The results show that the fluorine-containing polyurethane elastomers prepared
from BAFPF6P have good thermal stability and low surface tension. Furthermore, fluorine-containing polyurethane elastomers also
exhibit good flame retardance and the peak heat release rate and total heat released of fluorine-containing polyurethane elastomer based
on BAFPF6P are much lower than those of polyurethane elastomer without the fluorine element.
Keywords: Fluorinated diamine, Fluorinated polyurethane elastomer, Surface properties, Flame retardancy.
to 70 ºC, TDI was added and reacted for 2 h. The prepolymer
was prepared. The synthesis route of BAFPF6P is given in
Scheme-I.
INTRODUCTION
Polyurethane (PU) is widely applied in synthetic leathers,
coatings, foams, adhesives, sealants, etc. due to its excellent
properties. Fluorinated polyurethane (FPU) not only maintains
the excellent properties of polyurethane but is also noted for
some outstanding features such as low surface tension, low
water absorption and good thermal stability; consequently, since
the first patent about fluorinated polyurethane was published,
it has attracted many scientists to do research in this area1-4.
In this study, a series of fluorine-containing polyurethane
elastomers (FPUEs) were synthesized from 2,2-bis[4-(4-
amino-2-trifluoromethylphenoxy)phenyl] hexafluoropropane
(BAFPF6P) which was made from 2-chlorobenzotrifluoride
and 2,2-bis(4-hydroxyphenyl)hexafluoropropane. The structure
of BAFPF6P was characterized by Fourier transform infrared
(FTIR) and nuclear magnetic resonance (NMR) and the surface
tension, thermostability and flame retardancy of FPUEs were
investigated.
The molten chain extender (BAFPF6P or MOCA) and
prepolymer were fully mixed, then the mixture was casted on
a Teflon plate at 70 ºC for 2 h and 115 ºC for another 2 h.
Thus, the FPUEs were synthesized. Table-1 provides a descrip-
tion of the FPUEs and polyurethane elastomer.
Characterization: The contact angles of water and
ethylene glycol on FPUE were measured with a JCZ 2000
contact angle goniometer at room temperature by the sessile
drop method. The surface tension is calculated through the
following equations:
γs = γsd + γsp
2
cosθ =
[(γdLγsd )1/2 + (γLp γsp )1/ 2 ]−1
γL
where γs is the elastomer surface tension, γd is the dispersion
component, γp is the polar component, θ is the contact angle
of polymer with liquid(water or ethylene glycol in this test),
γH2Od = 21.8 × 10-3 N/m, γH2OP = 51 × 10-3 N/m, γEGd = 29.3 × 10-3
N/m, γEGP =19.0 × 10-3 N/m.
EXPERIMENTAL
Synthesis of fluorinated polyurethane elastomers:
Polyester diol was heated to 110 ºC, stirred and vacuumed for
2 h to remove trace water. When the temperature was reduced
†Presented at The 7th International Conference on Multi-functional Materials and Applications, held on 22-24 November 2013, Anhui
University of Science & Technology, Huainan, Anhui Province, P.R. China

Vol. 26, No. 5 (2014)
Study on Fluorine-Containing Polyurethane Elastomers 1325
CF3
Cl
HO
C
OH
CF3
Cl
HNO3/H2SO4
CF3
CF3
DMF/K2CO3
NO2
F3C
O
CF3
F3C
O
CF3
C
NO2
O2N
O
C
H2N
O
NH2
CF3
CF3
CF3
CF3
(BNFPF6P)
(BAFPF6P)
Scheme-I: Synthesis route of BAFPF6P
b
TABLE-1
DESCRIPTION OF THE FPUES AND PUE
a
1
2
3
4
Chain
extension
coefficient*
Fluorine
content
wt.(%)
F3C
O
Sample
Soft segment
R*
CF3
C
N
H2
H2N
O
PUE
Polyester diol 1975 2.0
Polyester diol 1975 1.8
Polyester diol 1975 2.0
Polyester diol 1975 2.4
0.9
0.9
0.9
0.9
0
CF3
FPUE1
FPUE2
FPUE3
6.1
7.2
9.1
CF3
6
5
*R is the molar ratios of NCO of TDI and OH of soft segment. *Chain
extension coefficient is the molar ratios of NH2 of chain extender and
NCO of prepolymer.
3
5
6
1
2
RESULTS AND DISCUSSION
Characterization of BAFPF6P: The chemical structures
of BNFPF6P and BAFPF6P were identified by FTIR (Fig. 1),
1H NMR (Fig. 2) and 19F NMR (Fig. 3).
4
BNFPF6P
7
6
5
ppm
Fig. 2. 1H NMR spectrum of BAFPF6P
1538
1353
BAFPF6P
3222
3483
a
3396
4000
3500
3000
2500
2000
1500
1000
500
Wavenumbers (cm–1)
Fig. 1. FTIR spectra of BNFPF6P and BAFPF6P
b
The FTIR of BNFPF6P in Fig. 1 shows that there are nitro
absorption peaks at 1538 cm-1 which is from -NO2 asymmetric
stretching and 1353 cm-1 which is from symmetric stretching.
But the two peaks disappear in the FTIR of BAFPF6P, which
shows that the reduction of -NO2 has happened; In the
meantime, the typical N-H stretching absorptions at 3483 and
3396 cm-1, N-H bending absorption at 1634 cm-1 are found in
the FTIR of BAFPF6P, which indicates the -NH2 has arisen.
-50
-60
-70
ppm
Fig. 3. 19F NMR spectrum of BAFPF6P

1326 Xu et al.
Asian J. Chem.
300
250
200
150
100
50
All the above results indicate that BNFPF6P completely
converts into BAFPF6P. The peaks at 1502 cm-1 is a charac-
teristic absorption peak of the benzene ring. The C-F multiple
stretch bending absorptions from -CF3 are observed between
1300 and 1100 cm-1.
The 1H and 19F NMR of BAFPF6P are shown in Figs. 2 and
3, respectively. The structure of BAFPF6P molecule is symme-
trical and all the hydrogen can be divided into six types for
different chemical environments. The ratio of the integral height
of H1:H2:H3:H4:H5:H6 is 4:4:2:2:2:4, which is identical with
the number of hydrogen atoms of BAFPF6P. In Fig. 3, two
peaks are found at -60.28 and -63.44 ppm, indicating that the
fluorine atoms are in two different chemical environments.
The ratio of the integral height Fa and Fb is equal to 1, which
is in accordance with that of the designed product.
PUE
FPUE1
FPUE2
FPUE3
0
-50
200
300
400
Temperature (°C)
500
600
Thermal property of FPUEs: T10, T50 and Tmax are the
temperature of 10 %, 50 % and max weight loss of the sample,
respectively. The T10 and T50 of FPUE2 are higher than those
of polyurethane elastomer, meanwhile the char yield of FPUE2
(19.6 %) is higher than that of PUE (14.9 %). It can be concluded
that FPUE2 has a better thermal stability than PUE (Table-2).
Fig. 4. MCC curves of FPUEs
TABLE-3
SURFACE PROPERTIES OF FPUES AND PU
Contact angle (º)
Surface tension (× 10-3 N/m)
Sample
γd
γp
γ
Water Ethylene glycol
PUE
66.2
89.7
51.1
70
10.07
15.45
17.64
17.12
25.71
6.52
2.47
1.06
35.77
21.97
20.11
18.18
TABLE-2
TGA DATA OF FPUES AND PUE
FPUE1
FPUE2
FPUE3
98.8
77
T10
(ºC)
T50
(ºC)
Tmax1
(ºC)
Tmax2
(ºC)
Char yield
(%)
105.5
83.5
Sample
PUE
329
350.6
349
429.2
431.6
430.2
430.2
308.4
307.4
303
439.7
438.4
433
14.9
17.3
19.6
21.2
Conclusion
FPUE1
FPUE2
FPUE3
2,2-Bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]-
hexafluoropropane (BAFPF6P) was synthesized from 2-chloro-
benzotrifluoride and 2,2-bis(4-hydroxyphenyl)hexafluoro-
propane and it was utilized as a chain extender to prepare a
series of FPUEs. Through the FTIR and NMR analysis, the
results demonstrate the structure of synthetic product is in
accord with that of the expected design. The influence of
fluorine on thermal stability, flammability and surface properties
of the FPUE were investigated. The results show that the
introduction of fluorinated chain extender can improve the
surface properties efficiently. The surface tension of FPUE3
is almost reduced by 50 % compared with that of PUE. The
results from TGA show that the introduction of fluorinated
chain extender to the PUE improves the thermal stabilities;
the THR and PHRR of FPUE2 are 15 KJ/g and 179.5 W/g,
respectively, which indicates that the fluorinated chain extender
incorporated contributes to improved flame-retardant prop-
erties. These properties should make these FPUEs attractive
for practical applications.
333.4
298.6
433
Flame retardant property of FPUEs: The THR and
PHRR of FPUE2 are 15 KJ/g and 179.5 W/g, respectively.
They are both lower than those of PUE which are 17.1 KJ/g
and 275.6 W/g. FPUE2 and PUE have the same soft segment,
R and Chain extension coefficient, with the only difference in
the types of chain extender. It means that FPUE2 based on
BAFPF6P shows better flame retardation than PUE based on
MOCA; in other words, the introduction of fluorinated chain
extender improves the flame retardation.
From FPUE1 to FPUE3, the THR and PHRR decrease
from 15.3 KJ/g and 244.4 W/g to 11 KJ/g and 119.1 W/g,
respectively. The main reason for this is that, from FPUE1 to
FPUE3, they all contain the same soft segment and chain
extender, but the R increases from 1.8-2.4, so the increase in
the fluorinated chain extender content gradually results in an
increase in flame retardation (Fig. 4).
Surface property of FPUEs: The contact angle of PUE
with water and ethylene glycol are 66.2 and 51.1º and the
surface tension is 35.77 mN/m, while the surface tension of
FPUE1, FPUE2 and FPUE3 is obviously lower. The surface
tension of FPUE3 is just 18.18 mN/m, almost reduced 50 %
compared with PUE. It shows that the introduction of fluorine
to the polyurethane elastomer reduces the surface tension. The
main reasons for this is that the CF3 bears relatively low surface
energy, so it is easy to migrate to and enrich on the surface,
which results in the higher concentration of CF3 groups on the
surface than in bulk and then the FPUEs show excellent low
surface energy (Table-3).
ACKNOWLEDGEMENTS
The authors thank the National Natural Science Founda-
tion of China (No. 21004001/B040601) and the National Key
Technology R&D Program (No. 2013BAJ01B05) for their
financial support.
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