Aliphatic thermoplastic polyurethane-ureas and polyureas synthesized through a non-isocyanate route

Article abstract of DOI:10.1039/c4ra12195c

A simple non-isocyanate route for synthesizing aliphatic thermoplastic polyurethane-ureas (TPUUs) and thermoplastic polyureas (TPUreas) is presented. Melt transurethane polycondensation of isophorone diamine or diethylene glycol bis(3-aminopropyl) ether with bis(hydroxyethyl) hexanediurethane, bis(hydroxyethyl) isophoronediurethane or bis(hydroxyethyl) piperazinediurethane was conducted at 170?°C under a reduced pressure of 3 mmHg. A series of thermoplastic TPUUs and TPUreas were prepared, and were characterized by gel permeation chromatography, FT-IR, ¹H-NMR, differential scanning calorimetry, thermogravimetric analysis, and tensile testing. The TPUUs and TPUreas have an M_n up to 14 900 g mol^-1, an M_w up to 43 700 g mol^-1, T_g between -18.6?°C and 116.8?°C, and an initial decomposition temperature of over 222.3?°C. A flexible TPUU exhibits a melting temperature of 77.7?°C, a tensile strength of 6.46 MPa, and an elongation at break of 180.20%.

Full text of DOI:10.1039/c4ra12195c

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PAPER
Aliphatic thermoplastic polyurethane-ureas and
polyureas synthesized through a non-isocyanate
route†
Cite this: RSC Adv., 2015, 5, 6843
Suqing Li, Jingbo Zhao,* Zhiyuan Zhang, Junying Zhang and Wantai Yang
A simple non-isocyanate route for synthesizing aliphatic thermoplastic polyurethane-ureas (TPUUs) and
thermoplastic polyureas (TPUreas) is presented. Melt transurethane polycondensation of isophorone
diamine or diethylene glycol bis(3-aminopropyl) ether with bis(hydroxyethyl) hexanediurethane,
bis(hydroxyethyl) isophoronediurethane or bis(hydroxyethyl) piperazinediurethane was conducted at
ꢀ
1
70 C under a reduced pressure of 3 mmHg. A series of thermoplastic TPUUs and TPUreas were
1
prepared, and were characterized by gel permeation chromatography, FT-IR, H-NMR, differential
Received 11th October 2014
Accepted 15th December 2014
scanning calorimetry, thermogravimetric analysis, and tensile testing. The TPUUs and TPUreas have an
ꢁ
1
ꢁ1
ꢀ
ꢀ
M
n
up to 14 900 g mol , an M
w
up to 43 700 g mol , T
g
between ꢁ18.6 C and 116.8 C, and an initial
DOI: 10.1039/c4ra12195c
ꢀ
ꢀ
decomposition temperature of over 222.3 C. A flexible TPUU exhibits a melting temperature of 77.7 C,
www.rsc.org/advances
a tensile strength of 6.46 MPa, and an elongation at break of 180.20%.
polyurethanes (NIPUs) are currently focused on cross-linked
PUs prepared from cyclic carbonates and diamines or multi-
Introduction
15–22
Polyurethanes (PUs) are important commercial polymers that amines.
Meanwhile, Loontjens et al. synthesized NIPUs
23–25
are widely used as foams, bers, adhesives, coatings, and from carbonyl biscaprolactamate.
medical materials because of their outstanding mechanical
properties, abrasion resistance, and good biocompatibility.
Transurethane polycondensation of diurethanes has been
developed to synthesize linear or thermoplastic polyurethanes
1
Almost all the commercial polyurethanes are currently prepared (TPUs). Deepa et al. synthesized a series of amorphous TPUs
from diisocyanates and polyols with low molecular-weight diols from the transurethane polycondensation of dimethyl 1,6-
or diamines as chain extenders. Polyurethane-ureas (PUUs) are hexamethylene dicarbamate and dimethyl isophorone dicar-
2
–7
prepared when diamines are used as the chain extenders.
Polyureas (PUreas), which are usually used as two-component cyclohexanediol and isosorbide.
systems in protective coating/lining industry, are prepared two a,u-bis(hydroxyethyloxy carbonyl amino)alkanes and
bamate with glycol oligomers, 1,4-cyclohexanedimethanol, 1,4-
26,27
Rokicki et al. synthesized
8–11
normally from diisocyanates and polyamines.
The urea studied their solution polycondensation with 1,6-hexanediol or
28
linkages introduced provide many hydrogen bonds, and 1,10-decanediol. Ochiai studied the self-polycondensation of
improve the mechanical properties of PUUs and PUreas 1,6-bis(hydroxyethyloxy carbonyl amino)hexane and used the
evidently compared to those of common PUs. However, in the obtained polyurethane to synthesize methacrylate macromo-
29
preparation of PUs including PUUs and PUreas, the starting raw lecular monomers. Sharma et al. synthesized a series of
materials, diisocyanates, are highly toxic, and the major a-hydroxy-u-amino-amides and transformed them into
synthesis precursor of them is the extremely toxic phosgene. a-hydroxy-u-O-phenyl urethanes or a-hydroxy-u-O-hydroxyethyl
Non-isocyanate synthesis is becoming a promising alternative urethanes, from which several alternating poly(amide urethane)
30–32
for the isocyanate route, and is attracting increasing attention s were prepared.
In our previous work, we synthesized
from academic and industrial researchers who are working on aliphatic thermoplastic poly(amide urethane)s having short
12–14
33
polyurethanes.
Most investigations on non-isocyanate nylon-6 segments, poly(ether amide urethane)s having short
Key Laboratory of Carbon Fiber and Functional Polymers(Beijing University of
Chemical Technology), Ministry of Education, State Key Laboratory of Chemical
Resource Engineering, College of Materials Science and Engineering, Beijing
University of Chemical Technology, Beijing 100029, China. E-mail: zhaojb@mail.
buct.edu.cn; Tel: +86-10-6443-4864
†
Electronic supplementary information (ESI) available. See DOI:
0.1039/c4ra12195c
Scheme 1 Synthesis of BHPDU through the ring-opening reaction of
EC with PIP.
1
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Table 1 Synthesis of TPUUs
a
b
c
ꢁ1
c
ꢁ1
c
ꢀ
ꢀ
T
i
TPUUs
Diamine
IPDA
Diurethanediol
Reaction time (h)
M
n
(g mol ) (GPC)
M
w
(g mol ) (GPC)
PDI (GPC)
T
g
( C)
( C)
TPUU-1
TPUU-2
TPUU-3d
TPUU-4
TPUU-5
TPUU-6
BHHDU
BHIDU
BHPDU
BHHDU
BHIDU
BHPDU
5.0
2.5
5.5
2.1
2.5
6000
4800
3300
—
14 900
12 100
7100
5500
4400
—
43 700
25 000
1.17
1.13
1.34
—
2.93
2.07
75.3
116.8
113.3
222.3
232.3
239.1
—
297.6
274.0
DGBAE
—
51.5
ꢁ18.6
11.0
a
ꢀ
b
Reaction conditions: diamine–diurethanediol ¼ 1 : 1 (molar ratio); reaction temperature, 170 C; 30 mmHg, 0.5 h. Reaction time under a
c
d
reduced pressure of 3 mmHg. GPC data detected in DMF containing 10 mM LiBr with PS as the standard. TPUU-4 is in solid state up to
ꢀ
2
20 C and cannot dissolve in DMF.
Scheme 2 Synthesis of TPUUs from the polycondensation of IPDA or DGBAE with BHHDU or BHIDU.
3
4
5
nylon-6 segments and poly(ethylene glycol) (PEG) sequences,
and poly(ether urethane)s having short PEG segments.
the transurethane polycondensation of diamines with different
diurethanediols. Melt transurethane polycondensation of iso-
3
Meanwhile, Tang et al. synthesized thermoplastic polyureas phorone
TPUreas) from solution polycondensation of the dimethyl bis(3-aminopropyl) ether (DGBAE) with bis(hydroxyethyl) hex-
dicarbamates, which contained different multi-urea segments, anediurethane (BHHDU), bis(hydroxyethyl) isophoronediur-
diamine
(IPDA)
and
diethylene
glycol
(
3
6
with amino-terminated poly(propylene glycol).
ethane (BHIDU) or bis(hydroxyethyl) piperazinediurethane
ꢀ
In this paper, several aliphatic thermoplastic polyurethane- (BHPDU) were conducted at 170 C under reduced pressure.
ureas (TPUUs) and TPUreas were directly prepared through The obtained TPUUs or TPUreas were characterized by gel
Scheme 3 Synthesis of TPUUs from the polycondensation of IPDA or DGBAE with BHPDU.
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a
Table 2 Different vibration modes in the FT-IR spectra of TPUUs
TPUUs
nN–H
nC–H
nC]O
dN–H
nC–O
nC–N
nC–O–C
TPUU-1
TPUU-2
TPUU-3
TPUU-5
TPUU-6
3340.3 (s, b)
3359.1 (s, b)
3368.8 (s, b)
3363.5 (s, b)
3327.5 (s, b)
2931.1 (s), 2857.5 (s)
2951.4 (s), 2915.3 (s)
2950.5 (s), 2914.4 (s)
2930.2 (s), 2868.7 (s)
2924.9 (sh), 2873.0 (s)
1707.3 (s), 1627.4 (vs)
1702.0 (s), 1644.8 (s)
1643.6 (vs)
1639.6 (vs)
1747.5 (m, sh), 1618.0 (vs)
1568.7 (vs)
1557.6 (vs)
1556.4 (vs)
1567.4 (vs)
1566.1 (s)
1253.2 (s)
1242.5 (s)
1241.1 (s)
1253.0 (s)
1261.4 (s)
1143.9 (w)
1143.9 (w)
1132.8 (w)
—
—
—
—
1113.1 (s)
1118.3 (vs)
—
a
(sh) shoulder, (b) broad, (vs) very strong, (s) strong, (m) medium, (w) weak.
1
28,33
ꢀ
1
permeation chromatography (GPC), FT-IR, H-NMR, differential literatures.
Its melting point was 94 C. BHIDU ( H-NMR
scanning calorimetry (DSC), thermogravimetric analysis (TGA), spectrum, Fig. S2†) was prepared similarly from the reaction
and tensile test.
of EC with IPDA.
Synthesis of BHPDU
Experiment section
Materials
1
1
7.76 g (0.21 mol) PIP and 38.16 g (0.42 mol) EC were added to a
00 mL 3-necked ask. The mixture was mechanically stirred
ꢀ
IPDA and DGBAE were purchased from TCI Japan. Piperazine and heated under N
2
atmosphere to 80 C for 7 h. The resulting
hexahydrate (PIP) and ethylene carbonate (EC) were purchased solution was cooled to room temperature. White crystals were
from Alfa Aesar UK. 1,6-Hexanediamine (HAD) was purchased obtained and recrystallized with ethanol. Aer ltration and
from Shanghai Reagent Plant, China. Other materials, such as drying, 41.86 g BHPDU (yield: 78.95%) was obtained. Its melting
0
ꢀ
ethanol, N,N -dimethyl formamide (DMF) and dimethyl sulf- point is 105 C.
ꢁ1
oxide (DMSO), were all obtained as reagent grades and used
directly. BHHDU ( H-NMR spectrum, Fig. S1†) was prepared (–O–C]O), 1661.7 (amide I), 1445.3 (–CH –), 1243.9 (–C–O in
FT-IR, cm
(KBr): 3375.2 (–OH), 2876.2 (–CH –), 1699.1
2
1
2
2
from the reaction of EC with HAD according to the carbamate group), 1075.2 (–C–O in –CH –OH).
1
Fig. 1 H-NMR spectrum of TPUU-1.
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1
Fig. 2 H-NMR spectrum of TPUU-2.
1
1
H-NMR, ppm (400 MHz, DCCl
3
): 2.51 (2H, –OH), 3.52 (8H,
Polymer samples for FT-IR and H-NMR characterization
were puried thrice through dissolution–precipitation cycles by
using 20 mL DMSO as solvent and 200 mL ether as non-solvent.
FT-IR spectra were acquired on a NICOLET 60SXB FTIR spec-
4
ꢂ ring CH ), 3.84 (4H, 2 ꢂ –CH OH), 4.29 (4H, 2 ꢂ –OCH ).
2
2
2
Synthesis of TPUUs
.40 g (0.02 mol) IPDA and 5.84 g BHHDU (0.02 mol) were added
to a 100 mL 3-necked ask equipped with a distilling adapter, a
condenser, and a receiver. The mixture was melt and stirred at
1
trometer (Nicolet Analytical Instruments, USA). H-NMR spectra
of the polymers were obtained in deuterated DMSO on a Bruker
00 AVANCE (Bruker Corporation, USA) by using tetrame-
3
4
thylsilane as the internal standard.
ꢀ
1
70 C under a nitrogen atmosphere, and was reacted under a
The second heating DSC spectra were measured with a TA
Q200 differential scanning calorimeter (TA Instruments, USA) in
N atmosphere. Samples were rst heated from room tempera-
ture to 200 C at a heating rate of 40 C min and maintained for
min to eliminate thermal history. The samples were then
reduced pressure of 30 mmHg for 0.5 h. Then, the pressure in
the ask was gradually reduced to 3 mmHg for different periods
until no further increase of viscosity was observed. The obtained
TPUU-1 was poured and cooled at room temperature.
Similarly, TPUU-2 and TPUU-3 were prepared from the melt
polycondensation of IPDA with BHIDU and BHPDU at a
diamine–diurethanediol molar ratio of 1 : 1, respectively.
TPUU-4, TPUU-5 and TPUU-6 were prepared from the melt
polycondensation of DGBAE with BHHDU, BHIDU or BHPDU at
a diamine–diurethanediol molar ratio of 1 : 1.
2
ꢀ
ꢀ
ꢁ1
5
ꢀ
ꢀ
ꢁ1
ꢀ
ꢁ1
cooled to ꢁ80 C at a rate of 40 C min or 10 C min . In the
ꢀ
second heating scans, the samples were heated from ꢁ80 C to
ꢀ ꢀ
ꢁ1
2
00 C at a rate of 10 C min . TGA was performed on a TGA Q50
ꢀ
ꢁ1
analyzer (TA Instruments, USA) with a heating rate of 10 C min
from 25 C to 600 C in N atmosphere.
Samples for tensile testing were processed by a heating
compression molding method which was similar to that reported
in the literature. Polymer lms (50 mm ꢂ 50 mm ꢂ 1 mm) were
ꢀ
ꢀ
2
Characterization
6
n w
The M , M
and polydispersity index (PDI) of TPUUs were prepared by using a 70911-24B powder press machine (Tianjin
determined via GPC by using an Agilent-2600 system (Agilent New Technical Instrument Co. Ltd., China). Samples were heated
ꢀ
˚
to temperature 30 C higher than their T or T , maintained for 5
Technologies, Inc., USA) equipped with a PLgel 5 mm 1000 A
g
m
ꢀ
column and a refractive index detector at 25 C. The DMF min under 10 MPa, naturally cooled to room temperature with
containing 10 mM LiBr was used as an eluent with a ow rate of the pressure unchanged, and then cut into dumbbell-shaped
ꢁ1
1
mL min , and polystyrene (PS) was used as the standard.
bars (50 mm ꢂ 4 mm ꢂ 1 mm). Mechanical analysis was
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Fig. 3 H-NMR spectrum of TPUU-3.
conducted on a LLOYD LR30K tensile testing machine (Lloyd vacuum up to 3 mmHg favored the removal of by-product
ꢁ1
Materials Testing, UK) at a crosshead speed of 200 mm min at ethylene glycol, and led to the increase of molecular weight.
ꢀ
ꢁ1
2
5 C. Five measurements were performed for each sample, and TPUUs or TPUreas with M up to 14 900 g mol and M up to
n
w
ꢁ1
the results were averaged to obtain a mean value.
43 700 g mol were prepared (Table 1). Scheme 2 shows the
synthesis reaction of TPUU-1, TPUU-2, TPUU-4 and TPUU-5
from IPDA or DGBAE with BHHDU or BHIDU, respectively.
Co-polycondensation of IPDA or DGBAE with BHHDU or BHIDU
forms urea linkages. Meanwhile, self-polycondensation of
BHHDU or BHIDU also occurs, resulting in the possible
urethane units. Similarly, TPUU-3 and TPUU-6 were prepared
from the co-polycondensation of IPDA or DGBAE with BHPDU
Results and discussion
Synthesis of BHPDU
Huang et al. synthesized BHPDU from the reaction of EC with
PIP under the catalysis of cesium carbonate. Li et al. had
synthesized BHHDU from direct melt reaction of EC with HAD.
37
33
(
Scheme 3). TPUU-1 is an opaque polyurethane-urea. Other
TPUUs such as TPUU-2, TPUU-3, TPUU-5, and TPUU-6 are all
transparent polyurethane-ureas or polyureas.
In this article, direct reaction of EC with PIP was conducted at
ꢀ
8
7
0 C without any catalyst, and BHPDU with a yield of about
8.95% was prepared (Scheme 1). Its structure was veried by
FT-IR and H-NMR spectrum (Fig. S3†).
1
1
FT-IR and H-NMR characterization
Synthesis of TPUUs
1
The structures of TPUUs were characterized by FT-IR and H-
Melt transurethane polycondensation of IPDA or DGBAE with NMR spectra. The major vibrations in the FT-IR spectra of
ꢀ
BHHDU, BHIDU or BHPDU was conducted at 170 C under TPUUs are listed in Table 2. Based on the characteristic vibra-
reduced pressure. A series of TPUUs were prepared. Higher tions in FT-IR spectrum and the chemical shis of different
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1
Fig. 4 H-NMR spectrum of TPUU-5.
1
hydrogens in H-NMR spectrum (Fig. 1), the structure of TPUU- BHIDU was little inuenced because of lower steric interac-
1
is described. TPUU-1 is mainly constructed with isophorone tion, with higher amount of urethane units (i.e. -EIPDU-
hexanediurea (-IP-HDU-) segments and ethylene hexanediur- segments) formed in TPUU-2 than in TPUU-1. Some
ethane (-EHDU) segments, which were formed from the co- hydroxyethyl isophorone urethane (HEIPU) groups were le
polycondensation of IPDA with BHHDU and the self- as terminal groups due to low molecular weight of TPUU-2.
polycondensation of BHHDU, respectively. Urea formation is The -IP-IPDU- segments may also contains -IP-IPDU-(1) and
the major reaction in TPUU-1 synthesis. Some hydroxyethyl -IP-IPDU-(2) segments, which derive from different connec-
urethane (HEU) or –HNCOOCH CH OH groups were le as tions between IPDA with BHIDU, i.e. head-to-tail connec-
2
2
terminal groups, because the molecular weight of TPUU-1 was tions and head-to-head connections. As H N– terminal
2
not too high. Meanwhile, some urea units were formed due to groups are sensitive to the solvents used in NMR detection,
tail-biting side reaction of the –HNCOOCH
groups.
2
CH
2
OH terminal and TPUU-2 has not very low molecular weight, the signal
corresponding to H N– terminal groups was not found in
TPUU-2 shows almost the same intensities of FT-IR peaks Fig. 2.
28,29
2
ꢁ
1
ꢁ1
at 1702.0 cm and 1644.8 cm , which correspond to the
TPUU-3 exhibits a very strong peak corresponding to urea
ꢁ
1
C]O stretching vibration of urethane groups and that of linkage at 1643.6 cm in FT-IR spectrum. Fig. 3 shows the
urea groups, respectively. The amount of urea groups is
1
H-NMR spectrum, the chemical shis of different hydrogen
slightly higher. Combined the chemical shis of different atoms, and the major structural units in TPUU-3. TPUU-3 is
1
hydrogens in H-NMR spectrum (Fig. 2), the structure of mainly constructed with isophorone piperazinediurea (-IP-PDU-)
TPUU-2 is described. TPUU-2 is constructed with isophorone segments, because of less steric interaction in the co-
isophorone diurea (-IP-IPDU-) segments and ethylene iso- polycondensation of IPDA with BHPDU. As TPUU-3 had very
phoronediurethane (-EIPDU-) segments, which were formed low molecular weight, some hydroxyethyl piperazine urethane
from the co-polycondensation of IPDA with BHIDU and the (HEPU) groups and amino isophorone (AIP) groups were le as
self-polycondensation of BHIDU. Large steric hindrance terminal groups.
between IPDA and BHIDU leads to lower amount of urea
linkages (i.e. -IP-IPDU- segments) formed than TPUU-1, to urea linkages at 1639.6 cm in FT-IR spectrum. Based on the
because IPDA and BHIDU all contain bulky trimethyl- chemical shis of different hydrogens in H-NMR spectrum, the
TPUU-5 also merely shows a very strong peak corresponding
ꢁ
1
1
substituted cyclohexylene units. Self-polycondensation of structure of TPUU-5 is described in Fig. 4. TPUU-5 is mainly
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Fig. 5 H-NMR spectrum of TPUU-6.
ꢁ
1
constructed with DGBAE isophorone diurea (-DGBAE-IPDU-)
TPUU-6 shows a medium shoulder peak at 1747.5 cm and
ꢁ
1
segments, which were formed from the co-polycondensation a very strong peak at 1618.0 cm in FT-IR spectrum, which
of DGBAE with BHIDU. Some HEIPU groups were le as correspond to the urethane groups and urea groups, respec-
1
terminal groups.
tively. Combined the chemical shis in H-NMR spectrum, the
Table 3 Urea/urethane ratios in TPUUs
Urea/urethane
TPUUs
Peak
Area
Calculation equation
Ratio
1.60
Urea (%)
61.54
Urethane (%)
38.46
TPUU-1
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
17
1.00
13.42
2.53
1.66
1.00
1.82
1.46
0.63
0.52
1.00
5.86
7.43
1.00
28.07
0.34
1.00
5.70
36.73
ðA1þ18Þ=2
Urea=urethane ¼
Urea=urethane ¼
1+18
12
A12 þ A14
14
TPUU-2
15
ðA1þ10 þ A9þ90 Þ=2
A10 þ A11
1.43
58.85
41.15
0
0
1+1
9+9
10
11
13
1
TPUU-3
TPUU-5
TPUU-6
A1 þ A9
13.29
82.56
25.78
93.00
98.80
96.27
7.00
1.20
3.73
Urea=urethane ¼
Urea=urethane ¼
Urea=urethane ¼
A13
9
A10
A15
18
10
15
10
7
A2
A7
4
2
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structure TPUU-6 is described in Fig. 5. TPUU-6 is constructed through melt transurethane polycondensation of diamines
with the major DGBAE piperazinediurea (-DGBAE-PDU-) with diurethanediols.
segments and the minor ethylene piperazinediurethane
TPUUs resist common organic solvents. They are soluble in
(-EPDU-) segments, which were formed from the co- high polar solvents like DMF or DMSO, and are insoluble in
polycondensation of DGBAE with BHPDU and the self- common solvents such as ether, alcohol, ethyl acetate, acetone,
polycondensation of BHPDU, respectively. Some HEPU groups and tetrahydrofuran. TPUU-1, TPUU-2 and TPUU-3 are inert to
derived from BHPDU and amino propyl (AP) groups from water and dilute HCl solution or NaOH solution in short time
DGBAE were le as terminal groups.
because they contain hydrophobic alkylenes. Their surface did
Melt polycondensation of IPDA or DGBAE with BHHDU, not change aer contact with drops of water, 0.1 M HCl solution
BHIDU or BHPDU was conducted at a diamine–diurethanediol or 0.1 M NaOH solution for 48 h. Drops of water, 0.1 M HCl
molar ratio of 1 : 1. In addition to the co-polycondensation solution or 0.1 M NaOH solution on the surface of TPUU-5 or
between diamine and diurethanediol, which resulted in urea TPUU-6 were absorbed in 48 h, and the surface became viscous,
units, some self-polycondensation of diurethanediols also maybe because some hydrolysis took place. TPUU-5 and TPUU-6
occurred, with some urethane units formed. Table 3 shows the exhibit poor resistance to water and dilute HCl solution or
urea/urethane ratios in TPUUs. The urea linkages are the major NaOH solution, because they contain hydrophilic short PEG
units, with urethane linkages ranging from 1.20% to 41.15% segments.
formed. Although the self-polycondensation of diurethanediols
effects the stoichiometric reaction between diamines and diu-
rethanediols, the molecular weight of TPUUs was not inu-
Thermal and mechanical properties
Fig. 6 shows the second heating DSC curves of TPUUs. Their
enced, because the self-polycondensation of diurethanediols
33,35
glass transition temperature (T ) is listed in Table 1. As TPUUs
also results in high molecular polyurethanes.
All poly-
g
from TPUU-1 to TPUU-5 are random polyurethane-ureas or
condensations were conducted until Weissenberg effect took
place, i.e. the polymers formed nally climbed onto the stirrer
blades.
ꢀ
ꢀ
polyureas, they merely exhibit a T
g
from ꢁ18.6 C to 116.8 C.
TPUU-2 and TPUU-3, which were prepared from the co-
polycondensation of IPDA with BHIDU or BHPDU, have
n
Table 4 shows the degree of polymerization (X ) calculated
higher stiff structural units and higher T than TPUU-1 that was
prepared from IPDA and BHHDU with exible structure. TPUU-
based on structural units, and the extent of reaction (P) in
TPUU synthesis. TPUUs with P of above 86.38% were
prepared. From FT-IR and H-NMR characterization, the
g
1
6
was prepared from the co-polycondensation of DGBAE with
BHPDU, and had symmetrical structural units. TPUU-6 is a
TPUU-1 and TPUU-2 are veried as polyurethane-ureas, and
the TPUU-3, TPUU-5 and TPUU-6 are nearly polyureas.
Polyurethane-ureas and polyureas are prepared directly
Table 4 Extent of reaction in TPUU synthesis
a
n
X
b
TPUUs
Peak Area
Calculation equation
Value P (%)
TPUU-1
A
A
A
17
1.00
25.49
53.26
A10
4
A4þ7
24.58 95.93
7.92 87.37
7.34 86.38
þ
1
10
9
Xn ¼
Xn ¼
Xn ¼
¼
¼
¼
1 ꢁ P
A17
4+7
2
TPUU-2
TPUU-3
A
A
15
1.00
35.66
A4þ7
9
A15
2
A10
8
1
4+7
1
ꢁ P
A
A
A
A
A
A
A
13
1.00
103.92
7.53
4.81
1.00
A4þ7
9
þ
1
4+7
10
1 ꢁ P A13 þ A14=2
2
14
TPUU-5
TPUU-6
18
A11
4
A4þ7
61.34 98.37
56.73 98.24
þ
1
4+7
11
146.58
57.53
9
Xn ¼
Xn ¼
¼
¼
1 ꢁ P
A18
2
A
A
A
A
10
1.00
5.91
37.38
0.74
A7
4
A2 þ
1
7
1 ꢁ P A10 þ A11=2
2
2
11
a
Degree of polymerization calculated based on structural units in
b
TPUUs. Extent of reaction in TPUU synthesis.
ꢀ
Fig. 6 Second heating DSC scans of TPUUs (cooling rate: 40
min ; heating rate: 10 C min ).
C
ꢁ1
ꢀ
ꢁ1
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ꢀ
crystallizable polyurethane–urea with a T
m
at 77.7 C and a T
c
at
ꢀ
6
0.5 C. A T meant that TPUU-6 did not crystallize fast enough
c
to complete crystallization just aer fast cooling period before
the second heating started. Crystallization still progressed in
the second DSC scan.
The second heating DSC scans in Fig. 6 were recorded via a
ꢀ
heating–cooling–heating process: i.e. fast heating to 200 C and
ꢀ
maintaining for 5 min, fast cooling to ꢁ80 C at a rate of
ꢀ
ꢁ1
ꢀ
ꢀ
ꢁ1
4
0 C min , and slow heating to 200 C at 10 C min . Fast
cooling in the second period is oen adopted to evaluate the
crystallization behavior of the crystallized polymers. If a poly-
mer crystallizes very fast, its crystallization may have nished
before the fast cooling period ends. A T of TPUU-6 in the
c
second heating DSC curve meant that it did not crystallize fast
enough and the crystallization did not nish aer fast cooling.
ꢀ
ꢁ1
A slow cooling mode at 10 C min was also adopted, and the
related second heating DSC curve of TPUU-6 is showed in
ꢀ
ꢁ1
Fig. 8 TGA curves of TPUUs (heating rate: 10 C min ; atmosphere:
N ).
2
Fig. 7(a). A weak T peak in this mode meant that the crystalli-
c
zation was nearly complete aer the melt sample was cooled at a
ꢀ
ꢁ1
slow rate of 10 C min
.
The initial decomposition temperature (T
i
) of TPUUs or
TPUreas is summarized in Table 1. All TPUUs or TPUreas
ꢀ
exhibit T
i
above 222.3 C (Fig. 8), which is not too high because
carbamate and urea linkages are only moderately thermally
stable. TPUUs are thermoplastics still suitable for processing
with normal thermal processing machines. TPUU-1, TPUU-2,
TPUU-3 and TPUU-5 are very brittle polymers, and their
tensile testing cannot be conducted. They lack any exibility
and elasticity. TPUU-6 exhibits an elongation at break of
180.20% and a tensile strength of 6.46 MPa (Fig. 9). TPUU-6 is a
thermoplastic polyurethane-urea with appropriate tensile
strength and good exibility, but it has no elasticity. TPUU-6
shows similar tensile strength and elongation at break to the
TPUUs prepared from poly(oxytetramethylene) glycol with 1,6-
5
hexanediisocyanate, but shows obviously lower tensile strength
and elongation at break than the TPUUs prepared from
Fig. 9 Stress–strain curve of TPUU-6.
polyester glycols with 1,6-hexanediisocyanate or 1,4-butane
2,6
diisocyanate. Maybe TPUUs with high tensile strength and
long elongation at break can be prepared through the copoly-
merization of diurethanediols with long polyester glycols.
TPUU-1, TPUU-2 and TPUU-3 have low molecular weight.
Their strength, exibility and elasticity are poor. These prop-
erties are also inuenced by the structural units in their main
chains. TPUU-5 and TPUU-6 have similar molecular weight. As
TPUU-5 is constructed with irregular trimethyl-substituted
cyclohexylene units, it is a brittle polymer, and its tensile
strength cannot be detected. Otherwise, TPUU-6 is composed of
symmetric structural units, it is a polyurethane-urea with
appropriate tensile strength and good exibility.
Conclusion
This method provides a simple method to synthesize thermo-
plastic polyurethane-ureas and polyureas directly from melt
transurethane polycondensation of diamines with simple
Fig. 7 Second heating DSC scans of TPUU-6 detected after different
ꢀ
ꢁ1
ꢀ
ꢁ1
cooling period (cooling rate: (a) 10 C min ; (b) 40 C min ) (heating
ꢀ
ꢁ1
rate: 10 C min ).
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0 B. Moritz, B. Alexandro and M. Rolf, Green Chem., 2012, 14,
The authors acknowledge the nancial support from the
1447–1454.
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