Three Bond Technical News
Issued Jan. 1, 2006

66

Development Trend of Epoxy Resins 2006
Introduction
We have developed and sold a wide variety of adhesives and sealants using epoxy resins as materials so far. Their supply is increasing
year by year, and their deployment to new fields is expected by providing new characteristics.
However, development to comply with the regulations of substances of environmental concern is required so that it is clear that raw
materials used for manufacturing are restricted and the option of resin design is narrower than before.
Under these circumstances, we have marketed products provided with various characteristics with curing properties, whichcharacterize epoxy resins, and physical properties of cured objects are retained the balance.
There are examples of the value-added products that are added to light-curing property, anaerobic curing property, or high purity.
Many of these products have been used for specific fields and places, making their application deployment difficult. As the result,small-lot production causes high cost, which is a factor to narrow further deployment.
To break through the current status, we have developed products from the view of general-purpose deployment. We will introduce
development concept, characteristics, and future direction of our development products in this issue.

Contents
Introduction . ...................................................... 1

2-1. About ThreeBond 2249G....................... 4

1. About Low-temperature Fast-curing One-part
Epoxy Resins ................................................ 2

2-2. Development Trend in Future................. 5

1-1. About ThreeBond 2277 . ....................... 2
1-2. Comparison of Physical Properties........ 2
1-3. Development Trend in Future................. 3
2. About Structural Adhesives............................. 4

3. About Frozen Epoxy Resin............................. 6
3-1. About Status of Development................ 6
3-2. Development Trend in Future................. 6
Conclusion............................................................ 8

Temperature [℃]

On one hand, thermal curing one-part epoxy resins (hereinafterreferred to one-part epoxy resins) are relatively low cost andprovided with good workability. On the other hand, there aresome cases where they cannot be used for adherends with lowheat resistance because heating up to as high as 100 to 150°C or so is required during curing. In addition to our release of
low-temperature-curing type one-part epoxy resins: ThreeBond
2200 Series and 2210 Series, we have developed ThreeBond
2277 that faster curing is enabled by using newly developed
fast-curing epoxy resin and fast-curing agent this time.

TB2277 has the great characteristics of high tensile shearing
adhesive strength and no development of uncured part due
to separation compared with TB2202 and the competitors'
products.

Viscosity [Pa・s]

1. About Low-temperature Fast-curing Onepart Epoxy Resins

TB2277
TB2202Competitor's low-temperature
fast-curing product1-1. About ThreeBond 2277

Time [min.]Low-temperature fast curing (80°C×10min. or 60°C×15min.)

2)

High adhesive strength (tensile shearing adhesive strength:15MPa)

3)

TB2277
TB2202

Phenomenon of uncuring due to separation of curing agent
during curing of interstice does not occur

Competitor's low-temperature
fast-curing product1-2. Comparison of Physical Properties

Characteristics/
physicalproperties

Competitor's
lowUnit temperature
fast-curing
product

TB2277

TB2202 Test method

Color and– Creamy-white BlackBlack 3TS-201-02
appearance
Viscosity
Pa•s
23
30
13
3TS-208-03
Specific gravity
–
–
1.14
1.14
3TS-213-02
Hardness–
88
85
88
3TS-215-01
Tensile shearing
MPa
18
21
10
3TS-301-11
adhesive strength
Peeling adhesive
N/m
1,000
1,200
160
3TS-304-21
strength
Glass transition
°C
42
80
105
3TS-501-05
pointLinear expansion/°C
40×10-6
50×10-6 74×10-6 3TS-501-05
coefficient α1
Linear expansion
Not/°C
125×10-6
138×10-6
3TS-501-05
coefficient α2measured
Uncured part due
Not–
ExistedExisted–to separation
ExistedFreezerFreezer
Cold
Storage condition ––storagestorage storage
Curing condition–
80°C×30min.
←←–of test piece

Figure-1. Comparison of curing behavior (Upper: curing
at 80°C; Lower: curing at 60°C)
As shown in Figure-1, the curing reaction of TB2277 is so
fast that it reaches the almost ultimate viscosity in 8 min. at
80°C and in 15 min. at 60°C. In addition, since no viscosity
reduction occurs during heating with TB2277, the phenomenonof uncuring due to separation does not occur.

Temperature [℃]

Table-1. Physical property table

Time [min. ]Viscosity [Pa・s]

A comparison of physical properties of our current lowtemperature-curing grade (TB2202) and the competitor's lowtemperature fast-curing product is shown in Table-1 and acomparison of curing behavior, which indicates fast-curing
property, is shown in Figure-1.

Temperature [℃]1)Viscosity [Pa・s]

ThreeBond 2277 (hereinafter ThreeBond is abbreviated as TB)
has the following characteristics:

Time [min.]Curing at 60℃

Curing at 80℃

Curing at 100℃

Curing at 120℃

Curing at 150℃

Figure-2. Comparison of curing behavior (TB2277)
Figure-2 shows the curing behavior of TB2277 for each curing
temperature. It is confirmed that it has been cured within 10
minutes at temperature of above 80°C. Especially at temperatureof above 100°C, it is confirmed that it has been cured before
reaching the processing temperature.
This is a great feature of this newly developed fast-curing epoxy
resin.

We will improve the followings.

Viscosity [Pa・s]

1)
2)
3)
4)
5)

Figure-3 shows data of storage stability (viscosity change) at
each temperature. At room temperature (25°C), the viscosity
almost doubled in 10 elapsed days.

1-3. Development Trend in Future
Although TB2277 is the product designed to place the highest
priority on the fast-curing property using unprecedented fastcuring epoxy resin and fast-curing agent, it has the following
disadvantages:
Freezer storage
High cost

General one-partepoxy resin
TB2277
improved

Fast

Figure-3. Storage data (TB2277)

Curing time

Slow

Figure-4 shows the position of the improved product.

Storage period [days]

1)
2)

Cost reduction
Storage condition (cold storage)
Tensile shearing adhesive strength (20MPa or more)Tg (120°C or more)Curing condition (within 60 min. at 60°C)

Low

Curing temperatureHigh

We are planning to improve TB2277 for more general use in the
future. Table-2 shows the target specifications.

Figure-4. Positioning map of current product group (lowtemperature-curing one-part epoxy)

Table-2. Target specifications

Although it is inferior to TB2277 in fast-curing property at
low temperature, we believe that there are enough advantagesof workability and the like by developing products with cold
storage capability. We are planning further cost reduction andimprovement in specifications.

TB2277
improved
product
Good–(Within 60
min.)Pa•s 10 ～ 100
10°C– 4 months or
more
Unit

Curingcondition(60°C)
Viscosity
Storagestability

TB2277

TB2202

Test method

Excellent(15min.)Fair(180min.)

–

30
–20°C
3 months or
more

13
10°C

Glass
Excellent
Fair°Ctransition(120 or more)
(80)
point
Tensileshearing
Excellent
ExcellentMPaadhesive(20 or more)(21)
strength
Uncuring due– Not Existed Not Existed
to separation
Price (/kg)
–
Good
Fair

7 months

3TS-208-03

Besides them, we are examining UV-curing property added
types and repairability added types as well.

–

Good
(105)

3TS-501-05

Fair
(10)

3TS-301-11

Existed–Excellent–2. About Structural Adhesives
It is generally known that epoxy resins have excellent shearing
adhesive strength to adherends such as metal, glass, concrete,
and wood, and they are used in various fields. In recent years,
as the demand for additional applications increases, highperformance in peeling adhesive strength, heat resistance,
creeping property, and durability against time degradation isrequired as well as shearing adhesive strength.
The application of structural adhesives, which bondconventionally physically fastened parts by welding, bolt
screwing, and the like is especially requested. For structural
adhesives, improvement in not only shearing adhesive strength
but also peeling adhesive strength is required.
However, in general, as the cured objects harden, although
the shearing adhesive strength of the adhesives increases,
the peeling adhesive strength tends to decrease inversely
proportional to it. It is not easy to improve both adhesivestrengths at the same time. Therefore although general epoxy
resin based adhesives have high shearing adhesive strength,
they do not satisfy the high peeling adhesive strength andflexibility of absorbing vibration and shock required forstructural adhesives and the like. To satisfy these requirements,
the methods to bind with chemical reaction, blend, or alloy 1
thermoplastic resins to epoxy resins are employed.

Test items
Unit
Color and–appearance
Specific gravity–
ViscosityPa•sHardness–
Tensile shearing
adhesiveMPastrengthT-type peelingadhesivekN/mstrength
Glass transition°C
temperature
Linear expansion/°C
coefficient*Curing condition: 160°C×30min.

Characteristics

Test methodGray3TS-201-02

1.59
75
D90

3TS-213-02
3TS-210-02
3TS-215-01

39

3TS-301-11

8

3TS-304-21

104

3TS-501-05

42×10-6

3TS-501-05

It has been confirmed that TB2249G is an epoxy resin provided
with excellent adhesive strength that tensile shearing adhesivestrength (SPCC-SD steel plate: 1.6×25×100mm) is 39.0MPa
and T-type peeling adhesive strength (SPCC-SD: 0.5×25×150mm) is 8.0kN/m.
Figure-5 shows S-S chart 2 of tensile shearing adhesive strengthof TB2249G and S-S chart of general epoxy resin (TB2252) as
reference.

Load [N]However, although it was possible to improve both shearing
adhesive strength and peeling adhesive strength with thesemethods in a balanced manner, the obtained strength was stillinsufficient and it was in lack of reliability for use as structural
adhesives. The development of resins excellent in both shearing
adhesive strength and peeling adhesive strength is required.

Table-3. Characteristics and properties of TB2249G

2-1. About ThreeBond 2249G
So we have developed one-part heat-curing epoxy resin
provided with both shearing adhesive strength and peelingadhesive strength.
Table-3 shows data of TB2249G, extra-strength one-part heatcuring epoxy resin.

Elongation [mm]Figure-5. Shear S-S chart of TB2249G and TB2252
From the S-S chart above, it is recognized that TB2249G isprovided with excellent toughness. During measurement oftensile shearing adhesive strength, resins with insufficient
toughness will fracture before reaching the equilibrium stateon the S-S chart due to elongation of the test piece. However,thanks to excellent toughness, TB2249G tolerates elongationof the test piece and has excellent tensile shearing adhesivestrength. For this reason, after the tensile shearing adhesivestrength test, elongation of the test piece was observed as shownin Photo-1.

In proportion to this toughness, it is provided with excellent
adhesive strength at T-type peeling adhesive strength test
as well. Photo-2 shows the appearance of the measurementof T-type peeling adhesive strength test. As shown in thephotograph, it is recognized that cohesive failure has occurred,
which indicates it is provided with high adhesion and bonding
strength.

Table-5. T-type peeling adhesive strength of various
adherends
TP type
SPCC-SDSUS430A1050P
SPCC-SB (Ni plating)
SPCC-SB (hexavalent chromium plating)
SPCC-SB (trivalent chromium plating)* Test method: 3TS-301-11

T-type peeling adhesivestrength (kN/m)
TB2249G
TB2252
8.0
4.5
3.6
0.6
4.5
3.0
4.0
2.0
5.0
2.0
2.7
1.0

Although inferior to the SPCC-SD steel plate, it has been
confirmed that it is provided with excellent bonding strength tovarious adherends.
TB2249G has the following features:
Photo-1. Test piece for tensile shear test
Left: After the test, Right: Before the test

• Includes modified epoxy resin to improve toughness andadhesion.
• Selects fillers to eliminate brittleness of the resin.
• Selects curing agent to provide toughness to the resin andeliminate brittleness.

2-2. Development Trend in Future
At present, we are examining various grades of TB2249G.
• Low-temperature-curing type (curing time: 100°C×60min. orso)• High Tg type (glass transition temperature: about 150°C)
Photo-2. Appearance of T-type peeling test
Since it was proved that it is provided with excellent adhesivestrength to the SPCC-SD steel plate, adhesive properties tovarious adherends (metal) have been examined. The results oftensile shearing adhesive strength are shown in Table-4 and theresults of T-type peeling adhesive strength are shown in Table-5.
The data of TB2252 is listed as reference.

By developing these grades, one-part heat-curing epoxy resins
with very high reliability for various fields and applications canbe provided.
1) Alloy type2) Elongation – load chart

Table-4. Tensile shearing adhesive strength of various
adherends
TP type
SPCC-SDSUS430A1050P
SPCC-SB (Ni plating)
SPCC-SB(hexavalent chromium
plating)
SPCC-SB(trivalent chromium plating)* Test method: 3TS-301-11

Tensile shearing
adhesive strength (MPa) Length of test
piece (mm)TB2249G
TB225239
26
1.6×25×100
36
19
1.5×25×100
22
19
2.0×25×100
35
23
2.0×25×100
38

24

1.6×25×100

31

20

1.6×25×100

3. About Frozen Epoxy Resin

They have the following advantages compared withconventional one-part epoxy resins.
(1) Uncuring due to separation does not occur.
Since the curing agent is liquid component, there is no uncuring
due to separation. With conventional one-part epoxy resins, theissue of uncuring due to separation has not been completely
solved, but there is no problem with the frozen epoxy resins.
(2) Low viscosity (5Pa•s or less) can be achieved.
Since many of the curing agents of conventional one-part epoxy
resins have been solid, there was a limit to the effort to makethe resin with low viscosity; however, since the curing agents offrozen epoxy resin are liquid, it is possible to make it with low
viscosity.
(3) Curing temperature can be controlled.
Since curing agent for two-part epoxy resin is used, curing
temperature can be set widely to range from 25 to 150°C.
Furthermore, since the curing agents, which could not be usedconventionally for one-part type, can be used, unprecedented
chemical resistance and heat resistance can be achieved.

Moreover, compared with conventional two-part epoxy resins,
since the operation of mixing and stirring is not required, they
can be used easily without worrying of uncuring caused bymeasuring mistakes and insufficient stirring.
On the other hand, disadvantages are that they must be frozen(−40 to −20°C) when storing and transporting and they cannot
be restored once they have been used at room temperature.
Therefore the quantity is required to use up at one time.

3-1. About Status of Development
Prototype 20X-343 is the first frozen epoxy resin manufactured
in our company. The characteristics are shown in Table-6.

Unit
Measured value
Color andTransparent light–appearance
brown
ViscosityPa•s2
Specific gravity–
1.14
Pot life
min.
60
Tensile shearingMPa
20
adhesive strength
Volume shrinkage
%
2.54
ratio
Glass transition point °C
111
Storage modulus
Pa
2.5×109
Linear expansion/°C
63×10–6
coefficient*1. Until the viscosity increase of up to 40% (25°C)* Curing condition: 150°C×5min.

Test method
3TS-201-02
3TS-210-05
3TS-213-02*1
3TS-301-11
3TS-228-01
3TS-501-05
3TS-501-04
3TS-501-05

Figure-6 shows the viscosity change by freezer storage.
Although small amount of viscosity increase was observed
during freezer storage, it has a slight effect on the pot life.

Viscosity [mPa・s]

Frozen epoxy resin are new type adhesives, which are provided
to users in the retained temperature of −20°C after mixing andstirring of main agent and curing agent, which are sold as twopart epoxy resin conventionally.

Table-6. Characteristics and physical properties ofprototype 20X-343

Elapsed time after thawing [min.]Figure-6. Viscosity change of prototype 20X-343 byfreezer storage

As mentioned above, to use its own low viscosity and highreliability, which one-part epoxy resins cannot perform, we
have considered it for use to adhere small areas, where heat
resistance and chemical resistance are required.

3-2. Development Trend in Future
At present, we are developing some types with extended pot
life with the same curing conditions. They enable us to makeavailable operating time elongated and increase in the quantity
used at once is possible.
In addition, we are examining reduction in curing time, lowtemperature curing, improvement in various characteristics, andthe like as well. As a development example, the characteristics
of prototype 20X-382B are listed below.

Table-7. Properties of prototype 20X-382B
Test method
3TS-201-02
3TS-210-05
3TS-213-02*1
3TS-301-11
3TS-228-01
3TS-501-05
3TS-501-04
3TS-501-05

Viscosity［Pa･s］

Unit
Measured value
Color and appearance–
Light yellow
ViscosityPa•s
8.0
Specific gravity–
1.15
Pot lifeh10 or more
Tensile shearingMPa25
adhesive strength
Volume shrinkage ratio%
3.15
Glass transition point°C
113
Storage modulus
Pa
2.9×109
Linear expansion/°C
74×10–6
coefficient*1. Until the viscosity increase of up to 40% (25°C)* Curing condition: 100°C×1h

Here, we introduce a special prototype for low viscosity.
Prototype 20X-343-20 has been developed as an underfill agent.
Basic characteristics and physical properties are as follows:

Tensile shearing adhesive strength［MPa］

Elapsed time after thawing［h］

Figure-9. Viscosity change at 25°C of prototype
20X-343-20 after thawing
Prototype 20X-343-20 has achieved low viscosity of 1 Pa•s orless, and it has also high permeability even at room temperature.

Table-9. Physical property of prototype 20X-343-20
Time [min.]Viscosity［Pa･s］

Table-7. Low-temperature-curing property of prototype
20X-382B

Time［h］

Figure-8. Viscosity change at room temperature
As listed above, low-temperature curing, pot life of 10 hours or
more, high adhesive strength, and the like have been achieved.
Table-8. Comparison with prototype 20X-382B andgeneral products

20X-382B
General-purpose
one-part epoxy
resin
General-purpose
two-part epoxy
resin

Separation

Pot life

Good

Good

Low-temperature
curing
Good

Fair

Good

Fair

Fair

Good

Poor

Good

Good

Unit
Measured value Test method
3TS-301-11
Tensile shearing
MPa
14
SPCC SDadhesive strength
Glass transition°C
104
3TS-501-05
point (TMA method)
Storage modulus°C
102(DMA method: E”)
Loss modulus
3TS-501-04(DMA method:
°C
122
tanδ)
Storage modulus
Pa
1.5×109
Linear expansion
3TS-501-05/°C
83×10–6
coefficient
25°C ～ 80°C
* Curing condition: 150°C×10min.
Furthermore, prototype 20X-343-20 is so excellent adhesivestrength and heat resistance that it can be cured in a short time
curing.
Utilizing these features, frozen epoxy resins are expected for
applications in a variety of fields including small relays, andadhesion of various parts of HDD as well as underfill agents.

Storage
PoorConclusion
The history of epoxy resins goes back a long way and our products have been used for various fields.
We are considering what kinds of features should be provided to epoxy resins, which have high performance as raw materials.
In this issue, we have introduced some characteristics of epoxy resins: low-temperature curing, extra strength, and frozen technology.
Regarding above mentioned development products, we are now taking the long view of product lineups not only for specific fields
but also for general use.
We will comply the regulations of substances of environmental concern and continue to develop products, which can be widely used
for you by advancing further reform and improvement in the future as well.
In addition, we are planning to market products, which match your needs, timely.

Three Bond Co., Ltd. Research Laboratory
Development Department
Okayama Development Division
Akihiko Okamura
Manabu Inoue
Masaki Takayama
Hisayasu Onuma
Yasutoshi Nogami
Tatsuhiro Kiryu

1456 Hazama-cho, Hachioji-shi, Tokyo 193-8533, Japan
Tel: 81-426-61-1333

