Synthesis and characterization of novel phosphorus-containing polyurethane elastomers

Article abstract of DOI:10.14233/ajchem.2014.17223

Bis(4-aminophenoxy)phenyl phosphine oxide (BAPPO) was synthesized based on phenyl phosphonic dichloride and 4-nitrophenol and characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). Then BAPPO was used to prepare a series of phosphorus-containing polyurethane elastomers (PPUEs) with different phosphorus contents by changing the soft segments. Combustion behaviours and thermal degradation behaviours of the PPUEs and polyurethane elastomer (PUE) were investigated by thermogravimetric analysis (TGA) and microscale combustion calorimetry (MCC). Thermogravimetric analysis result shows that the thermal degradation of polyurethane elastomers is divided into two stages and the thermal stability of PPUE-1 is poorer than that of PUE. The MCC result reveals that the values of the peak heat release rate and total heat release of PPUE-1 are lower than that of PUE made by 3,3'-dichloro-4,4'- diaminodiphenylmethane (MOCA) when they are obtained from the same soft segment.

Full text of DOI:10.14233/ajchem.2014.17223

Asian Journal of Chemistry; Vol. 26, No. 5 (2014), 1331-1333
ASIAN JOURNAL OF CHEMISTRY
http://dx.doi.org/10.14233/ajchem.2014.17223
Synthesis and Characterization of Novel Phosphorus-Containing Polyurethane Elastomers†
*
WENZONG XU , MINGYUAN REN and LIANG LIU
School of Materials Science and Chemical Engineering, Anhui Jianzhu University, 856 Jinzai Road, Hefei 230022, Anhui Province, P.R. China
*Corresponding author: E-mail: wenzongxu@sohu.com
Published online: 1 March 2014;
AJC-14764
Bis(4-aminophenoxy)phenyl phosphine oxide (BAPPO) was synthesized based on phenyl phosphonic dichloride and 4-nitrophenol and
characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). Then BAPPO was used to
prepare a series of phosphorus-containing polyurethane elastomers (PPUEs) with different phosphorus contents by changing the soft
segments. Combustion behaviours and thermal degradation behaviours of the PPUEs and polyurethane elastomer (PUE) were investigated
by thermogravimetric analysis (TGA) and microscale combustion calorimetry (MCC). Thermogravimetric analysis result shows that the
thermal degradation of polyurethane elastomers is divided into two stages and the thermal stability of PPUE-1 is poorer than that of PUE.
The MCC result reveals that the values of the peak heat release rate and total heat release of PPUE-1 are lower than that of PUE made by
3,3’-dichloro-4,4’-diaminodiphenylmethane (MOCA) when they are obtained from the same soft segment.
Keywords: Phosphorus-containing diamine, Polyurethane, Flame retardant.
were synthesized. The synthesis route of BAPPO is given in
Scheme-I.
INTRODUCTION
Polyurethane elastomers are widely used in various
industries because they have excellent chemical, physical and
mechanical properties such as antioxidation, low-temperature
stability and abrasion resistance. But their flammability
restricts the expansion of the scope of their application1-3.
In this paper, we report the synthesis of a novel phosphorus-
containing chain extender bis(4-aminophenoxy)phenyl
phosphine oxide (BAPPO) and a series of phosphorus-containing
polyurethane elastomers (PPUEs) that were synthesized by
adjusting the types of soft segments. The structure of BAPPO
was characterized and the thermal stability and flame retar-
dancy of the PPUEs were investigated.
Characterization: Infrared data were obtained with a
Spectrum 100 FTIR Spectrometer (Perkin Elmer) between
4000 and 500 cm-1 at the resolution of 4 cm-1. 1H nuclear magnetic
resonance (1H NMR) and 31P NMR spectra were obtained with
a Bruker AV400. A Govmark microscale combustion calori-
meter (MCC-2; Farmingdale, NY, USA) was used to investigate
the combustion of the PPUEs.
RESULTS AND DISCUSSION
Characterization of BAPPO: The nitro absorption peaks
at 1518 and 1348 cm-1 from -NO2 asymmetric and symmetric
stretching vibration absorption are found in BNPPO and
disappear in BAPPO. In BAPPO, the typical asymmetric and
symmetric stretching vibration absorption peaks of primary
amine are distinctly observed at 3443 and 3349 cm-1 in BAPPO.
All the above results indicate that BNPPO successfully converts
into BAPPO (Scheme-I, Fig. 1).
The 1H and 31P NMR spectra of BAPPO are shown in Figs.
2 and 3, respectively. In the 1H NMR of BAPPO (Fig. 2), the
electron-donating effect of amino group and proton-donating
effect of phosphine oxide group are demonstrated by the six
groups of peaks: 6.43-6.52 ppm (doublet, 4H, He), 6.78-6.83
EXPERIMENTAL
Synthesis of phosphorus-containing polyurethane
elastomers (PPUEs): Polyester diol was heated to 110-120 ºC,
stirred and vacuumed for 2 h to remove trace water. When the
temperature was reduced to 70 ºC, TDI was added and reacted
for 2 h. The prepolymer was prepared.
The molten chain extender and prepolymer were mixed
and stirred fully. Then the mixture was put into a Teflon mould
at 75 ºC for 2 h and 115 ºC for another 2 h. Finally, the PPUEs
†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

1332 Xu et al.
Asian J. Chem.
O
O
O2N
OH
Cl P Cl
O2N
O
NO2
O P
O
O
Fe/HCl
O2N
O
NO2
O P
H2N
O
NH2
O P
(
)
(
)
BAPPO
BNPPO
Scheme-I: Synthesis route of BAPPO
BAPPO
3349
3443
BNPPO
1518
1348
30
20
10
0
-10
3500
3000
2500
2000
1500
1000
500
ppm
Fig. 3. 31P NMR spectrum of BAPPO
Wavenumbers(cm-1)
Fig. 1. FTIR spectra of BNPPO and BAPPO
Thermal property of PPUEs: T5, T50 and Tmax are the
temperature of 5 %, 50 % and max weight loss of the sample,
respectively. The TGA curves of the PPUEs and PUE have
two distinct regions of weight loss, implying at least two stages
of degradation occur in these samples (Fig. 4). The T5, T50 and
Tmax of PPUE-1 are 279.0, 386.6 and 397.5 ºC and those of
PPUE-2 are higher and reach 281.4, 405.9 and 410.9 ºC; that
is to say, PPUE-2 shows better thermal stability. PPUE-1 and
PUE have the same soft segement, R and chain extender
coefficient, but PPUE-1 shows poorer thermal stability than
polyurethane elastomer. The possible reason is that the thermal
stability of phosphorus-containing extender is poor.
e
e
f
d
O
P
H2
N
O
O
NH2
d
c
b
a
f
b
C
a
Flame retardant property of PPUEs: The PHRR and
THR of PUE are 212 W/g and 15.9 KJ/g, respectively, but the
values of PPUE-1 are 174.2 W/g and 14 KJ/g; evidently, both
PHRR and THR of PPUE-1 are lower than those of PUE. PUE
and PPUE-1 have the same soft segment, R and chain extension
coefficient, with the only difference in the types of chain
extender. It means that PPUE-1 based on chain extender BAPPO
shows better flame retardation than PUE based on conventional
chain extender MOCA; in other words, the introduction of
phosphorus-containing chain extender enhances the flame
retardation. All the PPUEs contain BAPPO, but the molecular
weight of soft segments increases in the order of PPUE-1,
PPUE-2 and PPUE-3 and as a result, the contents of BAPPO
8
7
6
5
4
3
ppm
Fig. 2. 1H NMR spectrum of BAPPO
ppm (doublet, 4H, Hd), 7.52-7.57 ppm (triplet. 2H, Hb), 7.62-
7.67 ppm (triplet, 1H, Ha), 7.79-7.87 ppm (triplet, 2H, Hc) and
4.85-5.11 ppm (singlet, 4H, Hf). Furthermore, the single peak
at 12.14 ppm in 31P NMR spectrum (Fig. 3) indicates the high
purity of BAPPO.

Vol. 26, No. 5 (2014)
Synthesis and Characterization of Novel Phosphorus-Containing Polyurethane Elastomers 1333
TABLE-1
DESCRIPTION OF THE PPUES AND PUE
Chain extension
coefficient*
Hard segment
content wt. (%)
P/Cl content
wt. (%)
Samples
Soft segment
R*
Chain extender
PPUE-1
PPUE-2
PPUE-3
PUE
Polyester diol 1213
Polyester diol 1975
Polyester diol 2600
Polyester diol 1213
2
2
2
2
0.9
0.9
0.9
0.9
BAPPO
BAPPO
BAPPO
MOCA
35.4
25.3
19.9
32.7
1.5
1.1
0.8
3.5
*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.
Conclusion
100
Bis(4-aminophenoxy)phenyl phosphine oxide (BAPPO)
PPUE-2
was synthesized from phenyl phosphonic dichloride and
PPUE-3
80
60
40
20
0
1
4-nitrophenol and characterized by FTIR, H and 31P NMR.
Phosphorus-containing polyurethane elastomers were synthe-
sized with BAPPO by two steps.
PUE
PPUE-1
1
The results of FTIR, H and 31P NMR demonstrate that
the molecular structure of BAPPO absolutely corresponds to
anticipation. The flame retardant properties of PPUEs and PUE
are evaluated by microscale combustion calorimetry experi-
ments. The PHRR and THR of FPUE-1 are 174.2 W/g and 14
KJ/g and the results show the flame retardancy of PPUE-1 is
better than that of PUE. The TGA results indicate that the thermal
stability of phosphorus-containing polyurethane is lower than
that of common polyurethane. However, the incorporation of
BAPPO into polyurethane increases the char yield and a glass
coating and a protective carbonized skin may be formed on
the pyrolyzing phosphorus-containing polyurethanes, thus
possibly leading to fire protection.
100
200
300
400
500
600
700
Temperature (°C)
Fig. 4. TGA curves of PPUEs
in PPUEs become gradually less from PPUE-1 to PPUE-3; in
other words, the phosphorus-containing contents are gradually
less from PPUE-1 to PPUE-3, as we see in Table-1, from 1.5-
0.8 %. From PPUE-1 to PPUE-3, the PHRR and THR increase
from 174.2 W/g and 14 KJ/g to 270.9 W/g and 16.2 KJ/g,
respectively. Thus, it can be seen that the increase in the BAPPO
content gradually results in an increase in flame retardation.
The ignition temperature corresponds to the temperature
of the maximum heat release rate. The ignition temperature
for PPUE-1 is lower than that for PUE and with the BAPPO
content increasing from PPUE-3 to PPUE-1, the ignition tem-
perature decreases from 445-428.9 ºC. It indicates the PPUEs
have inferior thermal stability, which corresponds to the TGA
result (Fig. 5).
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.
REFERENCES
1. G.B. Huang, J.R. Gao, Y.J. Li, L. Han and X. Wang, Polym. Degrad.
Stabil., 95, 245 (2010).
2. D.K. Chattopadhyay and D.C. Webster, Progr. Polym. Sci., 34, 1068
(2009).
3. H. Singh, A.K. Jain and T.P. Sharma, J. Appl. Polym. Sci., 109, 2718
(2008);
300
PPUE-3
250
PPUE-2
PUE
200
PPUE-1
150
100
50
0
-50
100
200
300
Temperature (°C)
Fig. 5. Specific heat release rate curves of the PUE and PPUEs
400
500
600
700