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Polyurethaneurea aqueous dispersions prepared with diethyltoluenediamine as chain extender.

Abstract A series of polyurethaneurea (PUU) aqueous dispersions either with diethyltoluenediamine (DETDA) or ethylenediamine (EDA) as chain extender were prepared with polyester polyol, isophorone disocyanate and dimethylol propionic acid (DMPA), and characterized. It was found that the physical properties of the PUU aqueous dispersions prepared with DETDA were similar to or better than those prepared with EDA. Compared with the EDA- extended waterborne PUU films, the water resistance and the mechanical properties of the DETDA-extended waterborne PUU films were enhanced appreciably; these enhancements are attributed to the strong hydrogen bonding in urea carbonyl groups and the ordered structure of hard segments in the systems. The DETDA-extended PUU film with 40 wt.% of hard segment and 4.0 wt.% of DMPA unit showed the lowest water-absorbing amount (2.6 wt.%) over all PUU films studied. The hydrophobic surface of the DETDA-extended PUU film modified with a small amount of aminoethylaminopropyl polydimethylsiloxane (AEAPS) was observed and its hydrophobicity was enhanced by increasing the AEAPS content further.

Keywords Waterborne polyurethaneurea, Diethyltoluenediamine, Water resistance, Chain extender, Hard segment

Introduction

Recently, for environmental protection the waterborne polyurethane (PU) and polyurethanurea-acrylate (PUA) have gained greater attention,(1-3) and are widely used to prepare some coatings, adhesives, and surface finishes for textiles. These PU and PUA have the advantages of low volatile compound and excellent mechanical properties. Many works have been carried out to study the effects of soft segment, hard segment, neutralizing agent and hydrophilic monomer on the physical properties of the waterborne PU and PUA, which are often prepared with ethlenediamine (EDA) as chain extender. (2),(4),(5) Chen et al. (6) prepared a series of waterborne PUs with L-lysine, EDA, and L-lysine/ EDA mixture as extenders, respectively. It was found that the water absorption of PU film prepared with the L-lysine was higher than those of other films, but it showed the smallest hydrolysis weight loss among the three samples. Yen et al. (7) Studied the mechanical properties of several waterborne PUs prepared with different diamines or diols as chain extenders, such as EDA, diethyltriamine, and 1,4-butanediol, and found that the mechanical properties of the PUs prepared with diamine as chain extender were better than those prepared with 1,4-butanediol. Delpech and Coutinho (8) also studied the influence of various chain extenders on the properties of the waterborne PUs and found that the EDA-extended PU film exhibited better mechanical propertied than the hydrazine-extended one.

Diethltoluenediamine (DETDA) has been used as a chain extender in reaction injection molding of PU system resulting from its low reactivity, (9) but it has not been used in preparing the waterborne PU or PUA. In this article, a series of DETDA-extended polyurethaneurea (PUU) aqueous dispersions with different hard segment contents were prepared, and the effect of hard segment on the physical properties of PUU aqueous dispersions and their films was observed. Compared with the EDA-extended waterborne PUU, the physical properties of the DETDA-extended PUU aqueous dispersion only slightly changed, but for this kind of PUU film the mechanical properties were enhanced and the water-absorbing amount decreased appreciably. Furthermore, the DETDA-extended PUU aqueous dispersions were modified with aminoethylaminopropyl polydimethylsioxane (AEAPS), and it was found that the water resistance of their films was enhanced further.

Experimental

Materials

Polyester polyol (P756, hydroxyl number = 56 mg KOH [g.sup.-1]) provided by Qingdao Yutian Chemical Plant was dried under vacuum at 110[degrees]C for 1 h. Dimethylol propionic acid (DMPA, Perstop Co.) was dried at 60[degrees]C for 24 h under vaccum. DETDA (Huntsman Co.), N-methylpyrrolidone (NMP, Shanghai Feida Co.), and tertiary amine (TEA. Shanghai Chemical Reagent Plant) were dried with 4 [Angstrom] molecular sieves for 1 week before use. Isophorone diisocyanate (IPDI, Degussa Co), AEAPS emulsion (2-8168, Dow Corning, particle sizeL: 37 nm, solid content: 20 wt.%) and other standard laboratory reagents were used as received.

Preparation of PUU aqueous dispersions

P756, DMPA, NMP, and IPDI were charged into a 250-ml foru-necked, round-bottom flask equipped with a mechanical stirrer, an inlet of dry nitrogen, a condenser, and a thermometer. It was then heated to 80[degrees]C for 3-4 h until the theoretical NCO content was reached, which was tested with a standard dibutylamine back titration method. This NCO-terminated prepolymer was neutralized by adding TEA at 50[degrees]C, then it was dispersed into deionized water and chain-extended at 50[degrees]C using DETDA or EDA as a chain extender to prepare the PUU aqueous dispersions were prepared at 33wt.% solid content. For simplicity, the PUUs chain-extended by DETDA and EDA were called PU-D-X and PU-E-X, respectively, in which X represented the hard segment content.

Under vigorous stirring, AEAPS emulsion was dispersed into the PUU aqueous dispersion chain-extended by DETDA to prepare a modified PUU aqueous dispersion. For simplicity, the modified PUU aqueous dispersion was called M-Y, in which Y represented the AEAPS content.

PUU films were prepared by casting the aqueous dispersions into a poly(tetrafluoraethylene) mold under ambient conditions. The films were dried at ambient temperature for 1 week and then dried to a constant weight under vacuum at 60[degrees]C.

Measurements

The particle size of the PUU aqueous dispersion was determined by a Mastersizer 2000 particls size analyzer. The viscosity of the aqueous dispersion was measured by NDJ--79 rotation viscometer at a shear rate of 2000 [s.sup.-1]. The surface tension of the PUU aqueous dispersion was tested using the drop volume method. Above measurements were all performed at 25[degrees]C. The high-temperature stability of the aqueous dispersion was determined by observing whether the aqueous dispersion precipitated or not after heating to 60[degrees]C for 40 h in an oven. For measuring the freeze-thaw stability of the aqueous dispersion, the PUU aqueous dispersion was cooled to -20[degrees]C for 18 h and kept at ambient temperature for 6 h. This cycle was repeated five times to observe whether the aqueous dispersion precipitated or not. FTIR spectra of the PUU films were measured with a Nicolet 5DXC FTIR spectrometer at ambient temperature. Differential scanning calorimetry (DSC) was measured with a TA Instruments 2910 modulated DSC analyzer at a heating rate of 10[degrees]C [min.sup.-1] under a nitrogen atmosphere. The mechanical properties for all the specimens were conducted on an Instron 4465 testin machine at a crosshead rate of 50 mm [min.sup.-1], and the specimens were made in accrodance with GB1040-79. The hardness of PUU film was tested according to GB/G170393. The contact angle of water on the surface of the film was measured by using a JC2000A Contact Angle Measuring Apparatus at ambient temperature.

The water absorption of the PUU film was determined by immersing a film (20 x 20 x 1 mm) in deionize water at 25[degrees]C for 24 h, then the sample was blotted dry and weighed. The water absorption was calculated as follows:

Water absorption (%) = ([W.sub.2] - [W.sub.1])/[W.sub.1]/[W.sub.1] x 100% (1)

where [W.sub.1] is the weight of original film and [W.sub.2] is the weight of the film after swelling.

The surface energy of the PUU film was evaluated by the static contact angle measurement on the surface of the sample with two liquids (water and ethyleneglycol), (10) and was calculated as follows:

(1 + cos[[upsilon].sub.1])[[gamma].sub.1] = 4([[[[gamma].sub.1.sup.d][[gamma].sub.s.sup.d]]/[[[gamma].sub.1.sup.d] + [[gamma].sub.s.sup.d]]] + [[[[gamma].sub.1.sup.p][[gamma].sub.s.sup.p]]/[[[gamma].sub.1.sup.p] + [[gamma].sub.s.sup.p]]]) (2)

(1 + cos[[upsilon].sub.2])[[gamma].sub.2] = 4([[[[gamma].sub.2.sup.d][[gamma].sub.s.sup.d]]/[[[gamma].sub.2.sup.d] + [[gamma].sub.s.sup.d]]] + [[[gamma].sub.2.sup.p][[gamma].sub.s.sup.p]]/[[[gamma].sub.2.sup.p] + [[gamma].sub.s.sup.p]]]]) (3)

[[gamma].sub.s] = [[gamma].sub.s.sup.d] + [[gamma].sub.s.sup.p] (4)

where, [[gamma].sub.s], [[gamma].sub.s.sup.d], and [[gamma].sub.s.sup.P] are the surface energy, the dispersion component of the surface energy and the polar component of the surface energy for PUU film, respectively; [[gamma].sub.1], [[gamma].sub.1.sup.d], and [[gamma].sub.1.sup.p] are the surface tension, the dispersion component of the surface tension and the polar component of the surface tension for water, respectively ([[gamma].sub.1.sup.d] = 51.0 mN [m.sup.-1], [[gamma].sub.1.sup.p] = 21.8 mN [m.sup.-1]); [[gamma].sub.2], [[gamma].sub.2.sup.d], and [[gamma].sub.2.sup.p] are the surface tension, the dispersion component of the surface tension and the polar component of the surface for ethylene glycol, respectively ([[gamma].sub.2.sup.d] = 19.0 mN [m.sup.-1], [[gamma].sub.2.sup.p] = 29.3 mN [m.sup.-1]).

Results and discussion

PUU aqueous dispersions

In general, [NCO]/[OH] (molar ratio) calculated mainly from the isocyanate and polyol in the initial system has great effect on the structure morphology, and property of PU synthesized. Xu et al. (11) found that the PUA aqueous dispersion tended to gel if the [NCO]/[OH] was less than 1.3, and the aqueous dispersion was not stable with wide particle size distribution, if the [NCO]/[OH] was more than 2.0. Thus, for preparing waterborne PUU it is appropriate to control the [NCO]/[OH] from 1.3 to 2.0. A series of PUU aqueous dispersions with different hard segment structures and contents were prepared by adjusting the DMPA content and the value of [NCO]/[OH] from 1.3 to 2.0, as shown in Table 1. In order to prepare the PUU aqueous dispersions with different hard segment contents but at a constant DMPA content, the value of [NCO]/[OH] was varied accordingly. To keep a 4.0 wt.% concentration of DMPA in PUU, the hard segment content could be varied within a narrow range, and the highest hard segment content for PU-D or PU-E system was only at 40% or 35%. In this case, to increase the hard segment content in PUU aqueous dispersion, the DMPA concentration should also increase, as [NCO]/[OH] keeps 2.0. Table 1 shows that all the physical properties,. i.e., the particle size, polydispersity index, viscosity, and surface tension, for PU-D aqueous dispersions are similar to and/or even better than those for PU-E aqueous dispersions. This means that the PU-D aqueous dispersions were successfully prepared with DETDA as chain extender. It was also found that within the experimental conditions the physical properties, except the viscosity, only slightly changed for both PU-D and PU-E aqueous dispersions, although a great difference between the hard segment (HS) contents as well as the DMPA contents for both systems was set up. It should be pointed out that this experimental behavior could be further attributed to a broad tolerance of experimental conditions for preparing the waterborne PU-D with DETDA as chain extender.
Table 1: Some physical properties of PUU aqueous dispersions prepared
with different chain extenders (a)

Samples Hard segment [NCO]/ DMPA/ Particle size
 content (%) [OH] prepolymer (%) (nm)

PU-D-28 28 1.35 4.0 100
PU-D-34 34 1.7 4.0 104
PU-D-40 40 2.0 4.0 108
PU-D-47 47 2.0 6.2 105
PU-D-54 54 2.0 8.0 101
PU-E-25 25 1.35 4.0 103
PU-E-31 31 1.7 4.0 108
PU-E-35 35 2.0 4.0 111
PU-E-43 43 2.0 6.2 106
PU-E-50 50 2.0 8.0 103

Samples Polydispersity Viscosity Surface tension
 index (mPa.s) (mN [m.sup.-1])

PU-D-28 1.07 20.5 47.3
PU-D-34 1.06 9.8 46.3
PU-D-40 1.06 9.0 45.5
PU-D-47 1.06 14.6 44.3
PU-D-54 1.06 15.2 43.4
PU-E-25 1.07 25.0 47.6
PU-E-31 1.07 17.0 46.7
PU-E-35 1.08 11.5 46.0
PU-E-43 1.07 24.9 45.7
PU-E-50 1.07 36.8 44.2

(a) All PUU aqueous dispersion do not precipitate after the tests of
freeze-thaw and high-temperature stability


Table 1 shows that the surface tension of both aqueous dispersion systems (PU-D and PU-E) decreases with increasing the HS content, and is independent of the DMPA concentration. This behavior can be attributed to the microphase separation between the hard and soft segments. The microphase separation degree or PUU should increase with increasing the HS content in the system (see the following part), and the surface of the aqueous dispersion could be occupied by more hydrophobic soft segment resulting in the lowering of the surface tension. The particle size for both kinds of PUU aqueous dispersions does not change obviously and the particle size distribution nearly remains constant with increasing the HS content and the DMPA concentration, as listed in Table 1. IN this case, the microphase separation morphologies of these particles seemed to have no significant effect on the particle size. The hydrophilic DMPA salt unit (for simplicity, it is called DMPA unit) easily migrates to the surface of the particles during the formation process of the aqueous dispersions resulting in similar particle size.

The viscosities for both PU-D and PU-E aqueous dispersions are complicated, as shown in Table 1, but they may be attributed to the rigidity and the surface charge density of the particles, and should be studied further. However, the viscosity of PU-D system is lower than that of PU-E system with similar hard segment content. This experimental result is of benefit for PU-D to further prepare the line chemical products, such as adhesives and coatings.

For enhancing the water resistance of waterborne PUU farther, the DETDA-extended PUU aqueous dispersions were modified with AEAPS and their physical properties are listed in Table 2. Compared with the unmodified dispersions, the particle size and the viscosity of AEAPS-modified PUU aqueous dispersions increase, and the particle size distribution is still quite narrow, indicating that most of the hydrophobic AEAPS particles may be wrapped by the PUU macromolecular chains in the systems. (12) The surface tension of the modified PUU aqueous dispersions is much higher than that of AEAPS emulsion (26.3 mN [m.sup.-1]) and decreases gradually with the increase of AEAPS content. When the AEAPS content increases from 5.0% to 7.0%, the surface tension levels off. Thus, the surface of the dispersed particles in M-7 system may be saturated with the emulsifying agents present in the original AEAPS emulsion giving rise to the low surface tension. This behavior may further confirm that most of the hydrophobic AEAPS particles were wrapped by the PUU macromolecular chains. The viscosity of the modified PUU aqueous dispersions increases with increasing the particle size which may also result from the emulsifying agents existing on the surface of the particles.
Table 2: Some physical properties of PUU aqueous dispersions modified
with AEAPS (a)

Sample AESPS Particle Polydispersity Viscosity Surface
 content size index (mPa.s) tension
 (wt.%) (nm) (mN
 [m.sup.-1])

PU-D-40 0 108 1.06 9.0 45.5
M-1 1.0 115 1.09 10.5 44.0
M-3 3.0 122 1.15 12.0 40.8
M-5 5.0 130 1.18 18.3 37.4
M-7 7.0 142 1.20 21.5 37.2

(a) All PUU aqueous dispersions do not precipitate after the tests of
freeze-thaw and high-temperature stability


Tables 1 and 2 show that all the PUU aqueous dispersions are very stable at ambient temperature and they do not precipitate after low- and high-temperature stability tests. This phenomenon is obviously significant for further application of these aqueous dispersions in industry.

PUU films

Table 3 shows that for both kinds of PUU films with 4.0 wt.% concentration of DMPA the water-absorbing amount decreases remarkably with increasing the HS content, but the contact angle only increases slightly. When the HS content in either PU-D or PU-E system is higher than 40% or 35%, the DMPA concentration in these specimens increases with increasing the HS content, giving rise to increase the water-absorbing amount and decrease the contact angle. However, it should be pointed out that in all cases the water-absorbing amount of PU-D films is much lower than that of PU-E films and the PU-D-40 him shows the lowest water-absorption behavior (2.6 wt.%) and the highest contact angle of water over all specimens studied here. In other words, this sample exhibits the excellent waterproof performance.
Table 3: Some physical properties of PUU films prepared with different
chain extenders

Samples Hard segment DEPA/prepolymer (%) Water absorption
 content (%) (wt.%)

PU-D-28 28 4.0 9.6
PU-D-34 34 4.0 3.2
PU-D-40 40 4.0 2.6
PU-D-47 47 6.2 4.1
PU-D-54 54 8.0 6.5
PU-E-25 25 4.0 18.5
PU-E-31 31 4.0 13.7
PU-E-35 35 4.0 9.2
PU-E-43 43 6.2 15.8
PU-E-50 50 8.0 22.3

Samples Contact angle [[gamma].sub.2]
 of water (degree) (mN [m.sup.-1])

PU-D-28 85 28.1
PU-D-34 86 27.5
PU-D-40 87 26.7
PU-D-47 83 28.6
PU-D-54 78 31.7
PU-E-25 83 28.7
PU-E-31 84 28.1
PU-E-35 85 27.5
PU-E-43 81 30.4
PU-E-50 76 32.9


It is well known that PUU is a typical multi-block copolymer consisting of alternating soft and hard segments along the macromolecular chain. Thus, the strong hydrogen bonding should be formed not only between the hard segments but also between the soft and hard segments in the copolymer. The hydrogen bonding directly affects the ordered structure of hard segments in PUU (3) and was measured by using FTIR spectrometer, as shown in Fig. 1. The N-H stretching region in FTIR spectra is too complicated to be analyzed for both PU-D and PU-E films, so that earlyzed for both PU-D and PU-E films, so the carbonyl stretching region was chosen for investigation. The multiple absorption bands are observed in the carbonyl region in Fig. 1, which imply different kinds of hydrogen bonding for urethane carbonyl and urea carbonyl groups. Thus, the hydrogen bonding between the urea linkages in PUU was observed, as the absorption peaks for urethane groups would be affected by the carbonyl absorption peaks of polyester soft segment. It should be pointed out that the carbonyl absorption peak of DMPA units present in the PUU macromolecular chains is located at 1550 [cm.sup.-1], which would not influence the study of hydrogen bonding for urea groups. (3) The iteration procedure of damping least squares was used to separate the absorption peaks in the carbonyl region (13) (Fig. 1) corresponding to different hydrogen bondings (see Table 4), and the curvefitting results are shown Fig. 2 and Table 5. The degree of hydrogen bonding for urea groups ([X.sub.b,UA]), the percentage of ordered urea-urea hydrogen bonds ([X.sub.o,UA]), and the percentage of disordered urea-urea hydrogen bonds ([X.sub.d.UA]) in Table 5 were defined as follows:

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]
Table 4: Assignment of absorption band in urea carbonyl region of FTIR
spectra for PUUs

Wave number ([cm.sub.-1] Assignment

1960-1680 Free urea carbonyl
1670-1660 Disordered I hydrogen-bonded urea carbonyl
1660-1650 Disordered II hydrogen-bonded urea carbonyl
1650-1640 Ordered I hydrogen-bonded urea carbonyl
1640-1632 Ordered II hydrogen-bonded urea carbonyl

Table 5: Least-square curve fitting FTIR spectra in urea carbonyl
region for different PUUs

Samples Wave number (c[m.sup.-1]) Peak area (%)

 1 2 3 4 5 1 2 3 4 5

PU-D-28 1653 1647 1653 1664 1686 23.0 3.6 8.6 12.9 51.9
PU-D-34 1653 1645 1653 1664 1689 35.1 3.3 7.0 16.2 38.4
PU-D-40 1653 1647 1653 1664 1685 42.6 3.6 4.7 22.5 26.6
PU-D-47 1635 1645 1653 1664 1689 43.4 3.8 7.3 20.8 24.7
PU-D-54 1635 1645 1653 1664 1690 46.4 4.5 12.2 15.8 21.1
PU-E-25 1635 1647 1653 1664 1686 9.6 4.3 13.9 19.1 53.1
PU-E-31 1635 1647 1653 1664 1686 13.9 10.3 9.1 27.1 39.6
PU-E-35 1635 1647 1653 1664 1685 21.5 7.3 10.5 28.8 31.9
PU-E-43 1635 1645 1653 1664 1685 21.9 7.2 11.4 29.0 30.5
PU-E-50 1635 1645 1653 1664 1684 22.1 7.4 12.7 28.5 29.3

Samples [X.sub.o,UA] [X.sub.d,UA] [X.sub.h,UA]

PU-D-28 26.6 21.5 48.1
PU-D-34 38.4 23.2 61.6
PU-D-40 46.2 27.2 73.4
PU-D-47 47.2 28.1 75.3
PU-D-54 50.9 28.0 78.9
PU-E-25 13.9 33.0 46.9
PU-E-31 24.2 36.2 60.4
PU-E-35 28.8 39.3 68.1
PU-E-43 29.1 40.4 69.5
PU-E-50 29.5 41.2 70.7


[X.sub.b.UA] = [[SIGMA]Area(bonded)]/[Area(1690 - 1680[cm.sup.-1]) + [SIGMA]Area(bonded)]] (5)

[X.sub.b,UA] = [[[SIGMA]Area(1650 - 1630[cm.sup.-1])]/[Area(1690 - 1680[cm.sup.-1]) + [SIGMA]Area(bonded)]] (6)

[X.sub.d,UA] = [[[SIGMA]Area(1670 - 1650[cm.sup.-1])]/[Area(1690 - 1680[cm.sup.-1]) + [SIGMA]Area(bonded)]] (7)

Table 5 shows that both the hydrogen bonding degree of urea groups ([X.sub.b,UA]) AND THE VALUE OF [x.sub.o,UA] for PU-D systems are higher than those of PU-E systems containing nearly the same HS content. Furthermore, the value of [X.sub.b,UA] for both kinds of PUU films increases with increasing the HS content. It is clear that the PU-D films should have better ordered structure of hard segments than the PU-E films, which is beneficial for protecting the hydrophilic DMPA unit, so as to decrease the amount of water absorption of the film. It is of interest to note that the surfaces of these films are not affected by the ordered structure of the hard segments appreciably, so that the values of the water contact angle measured and the surface energy estimated only slightly change. While the HS content in either PU-D or PU-E system is higher than 40% or 34%, the values of [X.sub.b,UA] and [X.sub.o,UA] increase a bit with increasing the HS content, because the DMPA units in HS interfere with the formation of the hydrogen bonding. Thus, the water-resistance ability for both kinds of PUU films decreases when the HS content in PU-D or PU-E film is higher than 40% or 35%, mainly because the hydrophilicity of PUU films increase with increasing the concentration of hydrophilic DMPA unit.

Figure 3 shows the DSC scan curves for DETDA-extended PUU films with different HS contents, and the DSC scan results are listed in Table 6. Table 6 shows that the glass transition temperatures ([T.sub.gs]) of the PUU films shift to high temperature, as compared with that of polyester polyol used. It indicates some compatibility between the soft segment and the hard segment in these PUU films. A small endothermic peak was observed in Fig. 3 at 134[degree]C or 150[degree]C ([T.sub.a]) for PU-D-34 or PU-D-40 specimen, which should be attributed to the disruption of some domains and/or crystallites composed of the ordered hard segments. (14) There is no endothermic peak for the PU-D-28 film with low HS content and low value of [X.sub.b,UA]. These experimental data further confirm that the ordered structure of hard segments is enhanced with increasing the HS content, and coincide with the FTIR observation.

[FIGURE 3 OMITTED]
Table 6: DSC scan results for PU-D films with different hard segment
contents (a)

Samples Hard segment [T.sub.g] [T.sub.a] [DELTA][H.sub.a]
 content (%) ([degrees]C) ([degrees]C) (J[g.sub.-1])

PU-D-28 28 -31 - -
PU-D-34 34 -31 134 0.6
PU-D-40 40 -32 150 1.3

(a) [T.sub.g] of polyester polyol (P756) is -44[degrees]C


Table 7 lists the surface properties and the water-absorbing amounts of the DETDA-extended PUU films modified with AEAPS. For these modifies samples, the contact angle increases and the [[gamma].sub.s] decreases with increasing the AEAPS content. The surface of modified PUU film shows the hydrophobic capacity when the AEAPS content is more than 1 wt.%. This means that the hydrophobic AEAPS units may enrich on the surface of the modified PUU film during the film formation process. (12) The water-absorbing amount of these modified PUU films only increasing a little, which may be also attributed to the emulsifying agent existed in the AEAPS emulsion, as discussed before.
Table 7: Some physical properties of PUU films modified with AEAPS

Samples AEAPS Water Contact [[gamma].sup.s]
 content absorption angle of water (mN [m.sup.-1])
 (wt. %) (wt. %) (degree)

PU-D-40 0 2.6 87 26.7
M-1 1.0 2.6 90 25.8
M-3 3.0 2.8 95 23.5
M-5 5.0 3.0 97 22.4
M-7 7.0 3.3 99 21.3


The mechanical properties for different PUU films were measured, as listed in Tables 8 and 9. Table 8 shows that the introduction of the rigid phenyl ring from DETDA in the PUU macromolecular chain gives rise to increase the hardness and tensile strength for PU-D films compared to those for PU-E films. For both kinds of PUU films, the hardness and the tensile strength increase and the elongation at break decreases with increasing the HS content. Table 9 shows that the hardness and tensile strength of AEAPS-modified PUU films decrease due to the introduction of flexible AEAPS units in the systems.
Table 8: Mechanical properties of PUU films prepared with
different chain extenders

Samples Hard Hardness Tensile Elongation
 segment strength at break
 content (%) (MPa) (%)

PU-D-28 28 0.18 7.8 879
PU-D-34 34 0.24 17.7 520
PU-D-40 40 0.40 28.8 450
PU-D-47 47 0.59 38.5 327
PU-D-54 54 0.65 - (a) - (a)
PU-E-25 25 0.12 6.3 904
PU-E-31 31 0.20 12.1 707
PU-E-35 35 0.26 17.3 582
PU-E-43 43 0.42 26.7 521
PU-E-50 50 0.51 35.2 492

(a) The film is too frangible to be measured for tensile property

Table 9: Mechanical properties of AEAPS modified PU-D-40 films

Samples AEAPS Hardness Tensile Elongation
 content strength at break
 (wt.%) (MPa) (%)

PU-D-40 0 0.40 28.8 450
M-1 1.0 0.39 26.7 488
M-3 3.0 0.37 23.2 521
M-5 5.0 0.35 20.8 582
M-7 7.0 0.32 16.7 640


In conclusion, a series of PUU aqueous dispersions with DETDA as chain extender were prepared and characterized. The experimental results showed that these PUU aqueous dispersions had excellent freeze-thaw and high-temperature stability, and exhibited similar particle size and surface tension, but low viscosity, compared to those prepared with EDA as chain extender. The particle size of AEAPS-modified PUU aqueous dispersions increases compared with the unmodified one. The water resistance and the mechanical properties of the DETDA-extended PUU films were enhanced appreciably. The DETDA-extended PUU film with 40 wt.% of HS and 4.0 wt.% of DMPA unit showed the lowest water-absorbing amount (2.6 wt.%) over all PUU films studied. The hydrophobicity of the DETDA-extended PUU films modified with AEAPS was enhanced further.

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L. Jiang, Y. L. Chen, C. P. Hu

Key Laboratory for Ultrafine Materials, Ministry of Education, Shanghai 200237, PR China

L. Jiang, Y. L. Chen, C. P. Hu ([??])

School of Materials Science and Engineering, East China

University of Science and Technology, Shanghai 200237, PR China

e-mail: cphu@guomai.sh.cn
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Author:Jiang, Lin; Lin Chen, Yong; Pu Hu, Chun
Publication:JCT Research
Date:Mar 1, 2007
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