NEW DEVELOPMENTS IN POLYETHERAMINE CURING AGENTS

NEW DEVELOPMENTS IN
POLYETHERAMINE CURING AGENTS
David C. Alexander, Bruce L. Burton, Howard P. Klein
Huntsman Petrochemical Corporation
8600 Gosling Rd.
The Woodlands, Texas 77381
281-719-7492
david_alexander@huntsman.com
November 14, 2005
This paper is presented by invitation of TRFA. It is publicly distributed upon request by
the TRFA to assist in the communication of information and viewpoints relevant to the
thermoset industry. The paper and its contents have not been reviewed or evaluated by
the TRFA and should not be construed as having been adopted or endorsed by the
TRFA.

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NEW DEVELOPMENTS IN POLYETHERAMINE CURING AGENTS
1. INTRODUCTION
David C. Alexander, Bruce L. Burton, Howard P. Klein
Huntsman Corporation – Performance Products
Polyetheramines (PEAs) have been used in many applications since their introduction some
thirty-five years ago. Their value in curing epoxy resins was quickly realized, and this continues
to be a very important market for these materials. 1 At the same time, their uses in other
applications, such as nylon and polyurea modification, continue to grow at a rapid pace. In
recent years we have undertaken to modify their structures in order to expand the scope of their
utility both in epoxy curing and in the newer applications. These modifications include changes
in the amine environment as well as in the backbone structures. In this paper we will describe
some of these structural changes and their effects on the amines’ epoxy curing behavior.
2.0 MODIFICATIONS OF END GROUPS
The reactivity of the primary PEAs is influenced strongly by the steric environment of the
primary amine group. Most members of this family are made by reductive amination of
poly(propylene glycol)-based secondary alcohols and thus have a methyl group adjacent to the
primary amine. The presence of this methyl group moderates the amine reactivity, which results
in relatively slow cure of epoxy resins. In epoxy curing, with a standard liquid resin, the room
temperature pot life is on the order of 4-8 hours for the most commonly used members of this
series (230-400 molecular weight diamines and triamines). While this is advantageous for some
applications, for others a shorter cure time is desirable. Accelerators can, of course, be used for
this purpose, but we sought to expand the product line with amines that are inherently more
reactive to simplify formulation. This can be done by reducing the hindrance around the amine
group.
On the other hand, by increasing the hindrance around the amine group, slower curing agents
can be prepared. Such materials would be of particular use in situations where a longer pot life
is required, such as in fabrication of large composite parts. These new amines differ structurally
from the conventional PEAs in that an ethyl group, rather than a methyl group, is adjacent to the
primary amine. The resulting increased steric hindrance inhibits the approach of the amine to
epoxy resins and slows the reactions.
2.1 FASTER AMINES
The conventional route to production of PEAs is reductive amination of a secondary alcohol,
which leads to very little formation of secondary amine, an undesirable structure in this
application. Reductive amination of a primary alcohol, however, generally results in the
formation of a significant amount of secondary amine, since the primary amine that is formed
reacts with the primary alcohol starting material. With proper conditions and processing pure
primary amines (such as triethylene glycol diamine, XTJ-504) can be prepared by reductive
amination. We are, however, also using other routes to prepare reactive amines.

3
1, XTJ-504
2, XTJ-590
3, XTJ-548
4, BAPDEG
viscosity, cps
flexural strength, ksi
2.1.1 FASTER AMINES – BASIC CURING DATA
[
H 2N O
H2N
H 2N O
H2N N
O 8
x O 8
750
650
550
450
350
250
150
50
25
20
15
10
5
0
( ) ] (
Viscosity
XTJ-504 XTJ-590 BAPDEG D-230
amine
Flexural Strength
XTJ-504 XTJ-590 BAPDEG D-230
amine
Figure 1. Structures of reactive amines
Figure 2. Epoxy curing properties of faster amines
H
gel time, min
Tg, °C
80
75
70
65
60
55
50
100
95
90
85
80
75
70
65
60
55
50
O
O
Gel Time
O
XTJ-504 XTJ-590 BAPDEG
amine
Glass Transition Temperature
XTJ-504 XTJ-590 BAPDEG D-230
amine
NH2
O NH 2
)
NH 2
O NH 2

The low molecular weight reactive diamines include the previously mentioned TEGDA (1, XTJ-
504) and the similar diamine BAPEG [(bis(aminopropyl)ethylene glycol, 2, XTJ-590)]. A third
amine, PTMEGA-1700 (3, XTJ-548), is a blend of diamine and triamine prepared from a
PTMEG [poly(tetramethylene ether glycol)]. The PTMEGA-1700 blend is much higher in
molecular weight (ca. 1700 average). With its higher equivalent weight, its reactivity will still be
low, but it would be higher than that of a more hindered amine of comparable equivalent weight,
and it may be useful as a flexibilizing blend component.
Some of the basic epoxy curing and cured resin data are shown in Figure 2 for 1 and 2, along
with comparative data for JEFFAMINE ® D-230 amine and bis(aminopropyl) diethylene glycol
(BAPDEG, 4, another commercially available diamine). The gel time for the D-230 amine is not
shown, because this curing agent is too slow to give a discrete gel point with a standard epoxy
resin. For the three reactive amines, the trend is toward lower Tg and lower flexural strength
values with increasing molecular weight. The D-230 amine, however, gives higher Tg and
flexural strength because of the higher rigidity of the poly(propylene glycol) backbone.
Formulated viscosities for the four diamines are similar and are in the 550-750 cps range; they
decrease with increasing molecular weight for the three reactive amines.
As would be expected, these amines are useful in many epoxy adhesive formulations. Lap
shear strengths, with a heat cure, are in the 3000-3500 psi range (acid-etched aluminum).
The structure 3 is obviously very different, with a much higher amine hydrogen equivalent
weight (AHEW); furthermore, it consists mainly of two components, with x = 0 and 1. Since the
backbone structure would probably be considered the most significant feature of this amine
blend, it will be described in the “New Backbones” section.
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2.1.2 FASTER AMINES – COATINGS DATA
The highest volume commercial use for epoxy resins remains today in the paints and coatings
sector. The PEA products have found a wide variety of applications in coatings, but have some
restrictions due to reduced chemical resistance for industrial and maintenance coatings.
However, in some of these areas, smaller amounts of PEA materials may be used in these
formulations to provide benefits in processing and properties. The PEA products have found
wide applications in high-build, 100 % solids coatings for decorative or decoupage coatings,
floor coatings and some architectural coatings.
The clear coating formulations in Table 5 are examples of high-build clear coatings, which find
uses in decoupage epoxy systems for decorative coatings, labels, costume jewelry and other
items, such as synthetic water in floral displays. Use of the PEA as sole curing agents in these
systems will result in a highly clear, colorless epoxy coating, but these may cure too slowly
when using JEFFAMINE ® D-230 or T-403 amines. Also, these coatings may show a tendency
to blush slightly under low temperature and high humidity conditions.
Addition of an alkylphenol, such as p-nonylphenol (MNP), will sufficiently speed the curing
reaction and reduce any tendency for blushing with these products. However, the coating may
be too soft at typically used levels of MNP (around 30%). The addition of smaller amounts of an
aliphatic amine, such as AEP, will help to both harden the coating and further speed their drying
times without any signs of blushing or surface imperfections.

If the more reactive PEA products, such as XTJ-504 and XTJ-590, are used by themselves to
cure clear coatings, these would blush under most ambient conditions. Therefore the use of
MNP is necessary for blush prevention, though it significantly reduces working time of the
formulations. In all cases for the coatings in Table 5, the epoxy resin is mixed well with the
hardener formulation, prior to the draw down of the coating. Some people may choose to add
more or less MNP to create formulations having convenient mix ratios. Although a slight excess
of epoxy resin or amine, away from a 1:1 stoichiometry may give properties sufficient for some
applications, the best properties, having the most consistent, long-term performance will be
obtained near a 1:1 ratio of amine-hydrogen to epoxide groups. In some commercial
applications these systems are poured onto the wood, ceramic or metal substrates and allowed
to self-level during curing. Pigments, fillers and other additives may be included to achieve the
desired appearance.
During this work we saw that (data not shown) increasing the MNP level from 31 to 35 weight
percent in a XTJ-590 formulation (similar to that in table 1) produced much softer coatings,
reducing their pendulum hardness by 66%. Also, in those coatings formulated with the XTJ-504
and XTJ-590 the greatly increased curing speed of these already fast systems caused systems
warmed to 50°C to gel in fifteen minutes or less in a forty gram mass. Blending with the less
reactive amines can be used to slow these reactions, as desired.
The amount of MNP may be adjusted to control reactivity, flexibility, and adjust mix ratios for the
formulator. Mix ratios of resin to hardener will often vary somewhere within the range of 2/1 to
1/1 by volume, depending on the resulting application. For decorative coatings the 1/1 ratio is
most popular, while 2/1 is more popular in self-leveling, seamless flooring systems. Because
the densities of the components involved differ from one another, volume ratios and weight
ratios may not be interchanged without affecting processing and performance.
In seamless flooring systems, working times may be adjusted for use in summer and in winter
applications, where faster curing is needed at lower temperatures. When using the more
reactive PEA products in wintertime epoxy flooring systems, we recommend that derivatives,
such as epoxy adducts or Mannich bases of the XTJ-504 or XTJ-590, be prepared and added to
the epoxy system, along with a suitable diluent to compensate for their higher viscosity. Such
diluents may be products like JEFFAMINE ® D-230 amine (reactive diluent) or benzyl alcohol
(non-reactive diluent). Using such epoxy adducts or Mannich base hardeners, blushing
tendencies can be significantly reduced when curing is done at cold temperatures.
Amines having a wide range of reactivity are available to the formulator and may be combined
to provide an optimum balance of processing speed and final cured properties. Amines like
XTJ-504 and XTJ-590 are particularly fast compared to well-known PEAs like JEFFAMINE ® D-
230 and T-403 amines. The use of MNP (mono-nonyl phenol) in conjunction with the fastest
amines can suppress the blushing that occurs when they are used as the sole curing agent.
Increasing MNP levels can greatly decrease the hardness of these formulations however some
hardness may be regained by using some AEP or other cycloaliphatic amines in the formulation.
The coatings formulations containing TEGDA and BAPEG amines gave significantly faster
drying times, excellent gloss, and excellent conical mandrel bend values. Though they also
showed lower impact and crosshatch adhesion strengths than the JEFFAMINE ® products, they
may still be used to adjust reactivity and other properties in some applications. Maintaining an
amine-epoxy mix ratio near a 1:1 stoichiometry is desirable for the optimization of some
properties such as Tg, hardness, and surface appearance.
5

6
Curing agent components concentrations, phr, in standard liquid resin
Liquid Epoxy Resin 100 100 100
XTJ-504 15.7
XTJ-590 19.3
JEFFAMINE ® -230 26.2
Decoupage Monononylphenol
(MNP), 31.0 Wt. % 53.8 55.4 58.5
Aminoethylpiperazine (AEP) 4 4 4
Coatings properties, 3 mil
Film Thickness, mil.
Dry Time, hours
3 3.3 3.3
a) Set to touch 2.3 1.8 3.8
b) Surface Dry 3.3 2.3 5.3
c) Through Dry
Pendulum Hardness, Koenig, 20ºC
4.1 3.4 6.8
1 day 39 34 22
7 days 68 51 63
Crosscut Adhesion, 7 days, ASTM D 3359-95
Method B: Rating / % Removed with tape
0 / 90 0 / 100 5/0
Gloss, 20º, 1 day / 7 days 108 / 109 106 / 108 109 / 111
Gloss, 60º, 1 day / 7 days 123 / 123 116 / 121 123 / 124
Gardner Impact, direct, 7 days > 160 110 > 160
Gardner Impact, reverse, 7 days 140 120 > 160
Conical Mandrel Bend Pass Pass Pass
Appearance
2.2 SLOWER AMINES
High gloss, no
blushing
Table 1. Coatings properties with faster amines
High gloss, no
blushing
High gloss, no
blushing
In this paper we are focusing on two examples of the slower curing agents, a butylene oxideterminated
diamine (XTJ-568) and a butylene oxide-terminated triamine (XTJ-566) 2 . The amine
end groups of these two products are identical and are shown in Figure 3; the conventional PEA
termination is also shown for comparison.

Figure 4 provides an illustration of the effect of replacing methyl groups with ethyl groups. It is
clear that the pot life for formulations with these amines will be significantly longer. The AHEW
for the XTJ-568 amine is similar to that of the JEFFAMINE ® D-230 amine (55 vs. 60), but a little
lower, so any concentration effect would tend to favor a faster reaction. Likewise, the AHEW for
the XTJ-566 amine is similar to, but slightly lower than, that of the T-403 amine. The rate of
viscosity increase for T-403 amine-based formulations is not shown here, but it is similar to that
of D-230 amine/epoxy formulations.
As far as other epoxy curing and cured resin properties are concerned, the behavior of the new
slower curing agents is quite similar to that of existing PEA products. Comparative plots for
several properties are shown in Figure 5. It can be seen that mix ratios, viscosities, and cured
resin flexural strengths are similar; the glass transition temperatures of the slow amines are
slightly higher. Variations in starting polyol structure, somewhat lower AHEW, and higher
rigidity in the terminal groups are responsible for the higher values. Elongation values, like
7
Conventional
polyetheramine
termination
Viscosity - centipoise
10000
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
Figure 3. Comparison of amine environments
Viscosity vs. Time - Cure at 40°C
JEFFAMINE D-230
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00
Time - hours
Figure 4. Comparison of epoxy curing rates
XTJ-566
More hindered
polyetheramine
termination
XTJ-568

those given by conventional PEAs, are in the 8-12% range. These data suggest that, for those
applications which would benefit from longer pot life, these new, more hindered curing agents
provide a good alternative to existing PEAs. They may be of particular value in slowing the
cure of formulations based on faster amines; variations in the fast amine/slow amine ratio would
allow the formulator to tailor a basic formulation according to conditions such as working
temperature or required working time.
8
mix ratio, phr
T g , °C
45
40
35
30
25
20
15
10
5
0
110
100
90
80
70
60
50
Mix Ratio
XTJ-568 D-230 XTJ-566 T-403
amine
Glass Transition Temperature
XTJ-568 D-230 XTJ-566 T-403
amine
3.0 MODIFICATIONS IN BACKBONE STRUCTURES
viscosity, cps
1800
1600
1400
1200
1000
800
600
400
200
0
Viscosity
XTJ-568 D-230 XTJ-566 T-403
amine
Flexural Strength
The other significant expansion to the PEA family includes amines with different backbone
segments. Although the amines based on poly(propylene glycol) and poly(ethylene glycol) are
suitable for a variety of applications, others would benefit from a backbone that is more
hydrophobic or that gives better mechanical properties. To address these needs we now have
several developmental products that contain varying levels of backbone substitution by
poly(tetramethylene ether glycol) (PTMEG) segments.
As discussed previously, most of the PEA products are made by amination of secondary
alcohols. Since the PTMEGs contain primary alcohol termination, in most cases they are
propoxylated to provide secondary alcohol end groups. Amination of these diols gives the
flexural strength, ksi
19
17
15
13
11
9
7
5
XTJ-568 D-230 XTJ-566 T-403
amine

difunctional primary amines with minimal secondary amine content. Products with mixed
PTMEG/PPG backbones are available in molecular weights ranging from 1000 to 2000. Most of
the exploratory work in epoxy curing has been done with the 1000 mw product, XTJ-542.
One product, however, is made by direct amination of a PTMEG. This material, the XTJ-548
mentioned earlier, is a blend of a di(primary) amine (with relatively reactive amines) and a
triamine with two primary amines and one secondary amine.
Because these PTMEG/PPG- and PTMEG-based products range in molecular weight from
1000 to 2000, their main use would be as flexibilizing curing agents. Used in combination with
lower molecular weight curing agents, such as the conventional PEAs, they can be part of
formulations that give higher elongations than typical epoxy formulations for applications where
increased flexibility is an advantage.
It should be noted also that few PEAs with molecular weights around 1000 have previously
been available. (One exception is a very hydrophilic, PEG-based product of 900 molecular
weight.) Thus the XTJ-542, aside from being novel in its backbone structure, fills a gap that has
existed for less hydrophilic amines – no conventional, PPG-based diamine product of this
molecular weight has been available.
Table 1 shows examples of formulations that combine XTJ-542 with the JEFFAMINE ® D-230 or
D-400 amines; the data can be compared with literature formulations that combine the D-400
amine with the D-2000 amine. The XTJ-542, with a molecular weight half that of the D-2000
amine, gives much higher tensile strength values along with slightly higher elongations. The
glass transition temperatures for these formulations are around room temperature to slightly
above, and the formulated viscosities are typical of PEA formulations. Several of the
formulations give elongations greater than 100%, while those with T-403 are in the intermediate
range.
The other type of new amine with the PTMEG backbone is made by amination without
propoxylation, which leads to formation of a significant amount of secondary amine. This
product, XTJ-548, can be used in much the same way as XTJ-542, in combination with lower
molecular weight amines. Some of these formulations and their properties are shown in Table
2. Of particular note are the formulations that combine XTJ-548 and monoethanolamine (MEA)
or DGA ® Agent (N-aminoethyl ethanolamine); these curing agent blends combine relatively fast
cure (35-45 minute gel times) with high elongation values of 150-300% in the cured resins 3 .
These fast gel times are obtained without accelerators; the low molecular weight aminoalcohols
are themselves potent accelerators because of their low molecular weight and high amine and
alcohol content. Because they are monoamines they do not increase the crosslink density as is
typical of diamines, so the cured resins have a high degree of flexibility along with the rapid
cures. One minor drawback of using the aminoalcohols, however, is increased sensitivity to
polar solvents such as acetone.
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10
Curing agent components concentrations, phr, in standard liquid resin
XTJ-548 26 26 35 35 35 35
JEFFAMINE ® D-2000 25 25
JEFFAMINE D-400 52 52 50 50
DGA ® Agent 24 24
MEA 14 14
Accelerator 399 5 10
Properties
Viscosity, cps 800 600 950 1800
Gel time, min 46 35
Tg, °C 33 22 40
Cure conditions heat rt heat rt heat rt heat rt
Flexural strength, psi 6600
Flexural modulus, psi 180000
Tensile strength, psi 2150 2000 1700 1700 2150 5150 4300
Elongation at break, % 100 150 86 73 300 150 136
% Wt gain, 24 hr water boil 2.2 3.9 2.6 1.2 6.4 6.4 5.5 5.7
% Wt gain, 3 hr acetone boil 29 28 30 33 42 42 27 31
Curing agent components concentrations, phr, in standard liquid resin
XTJ-542 22 22 40 40 33 33
JEFFAMINE ® D-2000 25 25
JEFFAMINE D-400 44 44 50 50 40 40
JEFFAMINE T-403 33 33
Accelerator 399 10 10 10 5
Properties
Table 2. Epoxy curing with XTJ-548
Viscosity, cps 700 600 450 1800
Tg, °C 35 33 25 43
Cure conditions heat rt heat rt heat rt heat rt
Flexural strength, psi 5500 -- -- -- -- -- 11500 7600
Flexural modulus, psi 195000 -- -- -- -- -- 337000 230000
Tensile strength, psi 3500 2400 1700 1700 1250 570 6500 4100
Elongation at break, % 115 125 86 73 145 95 12 48
% Wt gain, 24 hr water boil 2.7 2.8 2.6 1.2 2.4 2.6 2.5 4.3
% Wt gain, 3 hr acetone boil 23 25 30 33 33 27 15 20
Table 3. Epoxy curing with XTJ-542

4.0 CONCLUSIONS
Through the structural changes to the PEAs described in this paper Huntsman has expanded
the range of reactivities provided by this family of curing agents. Although the more reactive
amines have been commercially available for some time, the slower ones are novel. A
considerable amount of control over cure rate can be achieved through control of the
environment around the amine, and we are exploring more new materials with such
modifications. Examples of applications for slower amines are fabrication of large composite
parts, where more working time is required, or wood consolidation, where longer times are
required for the curing epoxy to penetrate into a wooden structure.
Likewise, changes in the PEA backbone structure can be used to tailor the properties of cured
resins. The PTMEG diols are considered to be premium products for polyurethanes, and some
advantages in mechanical properties might be expected in cured epoxy resins as well.
REFERENCES
1. “Epoxy Formulations Using JEFFAMINE ® Polyetheramines” Huntsman Technical Publication, 2005
2. Klein, H. P. et al. World Patent App. WO2004/020506
3. This combination of high molecular weight polyetheramines and low molecular weight aminoalcohols was first reported by Lin, J.-
J., Tseng, F.-P., Chang, F.-C. Polymer International 2000, 49, 387-394
All information contained herein is provided "as is" without any warranties, express or implied, and under no circumstances shall the
authors or Huntsman be liable for any damages of any nature whatsoever resulting from the use or reliance upon such information.
Nothing contain in this publication should be construed as a license under any intellectual property right of any entity, or as a
suggestion, recommendation, or authorization to take any action that would infringe any patent. The term "Huntsman" is used herein
for convenience only, and refers to Huntsman Petrochemical Corporation, its direct and indirect affiliates, and their employees,
officers, and directors.
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