ThreeBond Technical News
Published on April 1, 200973

NEW PRODUCTS
ThreeBond 7700 Gold Label series
Introduction ________________________________________________
The advent of instant adhesive dates back to 1949, when Goodrich Co. of the US discoveredalpha-cyanoacrylate synthesis method. Since 1959, when the world’s first instant adhesive “Eastman910” appeared in the market, practical applications are going on around the world and improvements
on cyanoacrylate adhesive are under way night and day seeking for higher functionality.
Instant adhesive means an adhesive which can stick adherends in seconds, as understood by thename. It is one-part non-solvent and can be used at ordinary temperature without any emission ofenvironmental burdens, whose pro-environmental nature is widely supported. However, it has morethan a few weak points to overcome as an adhesive and many trials have been made for better
cyanoacrylate monomer synthesis method, additive compositions, etc.
ThreeBond started production of instant adhesive in 1969 and placed various products on the market
known as “ThreeBond 1700” series with different features. In 2006, we also launched “ThreeBond
7780 Gold Label” series, the ultra-fast curing instant adhesives focusing on “INSTANT”, the raisond'etre of the products.
In this issue, we introduce two products of “ThreeBond 7700 Gold Label” series, developed byThreeBond to realize high peeling- and impact-resistance and greater adhesion capabilities for difficult
adherends, which were weak points of conventional instant adhesives.

Contents
Introduction .......................................................1
1 Reaction mechanism of instant adhesive .....2
2 Advantages and disadvantages of instantadhesive .......................................................2
3 Ultrahigh peeling- and impact-resistant instantadhesive “ThreeBond 7737 / 7738” ..............3
3-1 Outline ....................................................3
3-2 Properties and features ..........................3
3-3 Main applications....................................4

4 Exclusive multi-primer “ThreeBond 7797” forinstant adhesives.......................................... 5
4-1 About primers ......................................... 5
4-2 Properties and characteristics ................ 5
4-3 Applications ............................................ 7
5 Product line of ThreeBond 7700 Gold Labelseries............................................................ 7
Conclusion ........................................................ 81

1

Reaction mechanism of instantadhesive

The principal component of instant adhesive isalpha-cyanoacrylate, which has strong electrophilicgroups such as cyano group, carbonyl group, etc. in
its molecules, causing great charge imbalance tokeep polarity in the molecules. Therefore basecomponent such as moisture in the air works as
nucleophilic agent to proceed to anionicpolymerization as shown in Figure-1.
Instant adhesiveness by instant adhesives comesfrom its extremely sensitive, momentarily
progressing reaction to anionic polymerization.

2-cyanoacrylicacid ester

Cyanoacrylate polymer
N = ca. 20000
Nu-: nucleophilic agent – water on adherend surface, amine compound in hardening accelerator, etc.

Figure-1 Reaction mechanism of instantadhesive (Cyanoacrylate)
Curing mechanism of instant adhesive iscontrolled almost by this sensitive anionicpolymerization and radical polymerization by heator light is negligibly-small, allowing traces ofvarious acidic substances to be added to improve
preservative property. Curing starts when both of
the whole surface reached alkalinity by least bit ofwater (alkaline component) absorbed in adherends
having neutralized the acidic substances. Typically,
radical polymerization inhibitors are added to avoid
the progress of radical polymerization, be it ever so
slow, during preserving period.

2

Advantages and disadvantages of
instant adhesive
Major advantages of instant adhesive are:(1) Rapid curing at ordinary temperature(2) Good workability brought by “one-part andnon-solvent”(3) Shear-resistant adhesion capability(4) Applicable to a wide variety of adherends(5) Clear and colorless curing adhesion layer
Typical disadvantages are:(1) Blooming(2) Low heat resistance (up to 80°C)(3) Hard curing with less flexibility and impact
resistance(4) Moisture and water resistance to be improved(5) Filling adhesion to be improved

Instant adhesive can be used for almost alladherends to give strong adhesion as well as rapid
curing. This advantage has found various
applications in the market of home consumer,
industrials and medical services.
Disadvantages described above are being
improved gradually by selecting monomer types
and investigating additives, especially for
insufficient impact-, peeling-, and thermal cycleresistance due to hard and brittle curing of instantadhesive.
These disadvantages are gradually improved by
selecting monomers and investigating additives.
Some examples:(1) To improve impact-, and peeling-resistanceToughening components or additives such aselastomer has been formulated to ThreeBond1730
series for a great improvement.
(2) To improve resistance for humidity, heat andheatcycle
Bridged structure has been introduced intoThreeBond1757 by adding additives to enable heatand heatcycle resistance over 100°C, whichconventional instant adhesives could not realize.
Now let us introduce our new products toimprove weak points of instant adhesive.

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3

Ultrahigh peeling- andimpact-resistant instant adhesive“ThreeBond 7737 / 7738”

3-1. Outline
To overcome above mentioned weak points ofless impact-, peeling-resistance, ThreeBond 7737 /7738 have been developed for ultrahigh peelingand impact-resistance, which has been realized byadding and alloying a special toughening
component (elastomer) for
ethyl-alpha-cyanoacrylate, the main component of
instant adhesive.
These adhesives also have high adhesion underhigh heat and heatcycle environment. (Hereafter
ThreeBond 7737 / 7738 are shown TB7737 / 7738.)

Table-2. Lap shear strength on various
adherends
Lap shear strength [MPa]Adherends

Our

TB7737 TB7738 conventional
products

Iron
Aluminum
Stainless steel
Brass
CopperNickelZinc chromate
Rigid PVC
PC (Polycarbonate)
Phenol6-Nylon
6,6-Nylon

3-2. Properties and features
Basic properties of TB7737 / 7738 are shown in
Table-1. “Curing promoter combined” in “Set time”
row shows the value got when our promoter
TB1796 is applied to one of the two surfaces, and
30 seconds later, the other being stuck with theadhesive applied.

ABS (Acrylonitrilbutadiene-styrene resin)
Glass epoxy
PBT (Polybutylene terephthalate)
PET (Polyethylene terephthalate)
PPO (Polyphenylene oxide)
PPS (Polyphenylene sulfide)
HIPS (Impact-resistant polystyrene)
Acrylic

Table-1. Basic properties of TB7737 / 7738
Test items

Adherend

Unit

TB7737

TB7738 Test method

Polyacetal
NR (Natural rubber)
CR (Chloroprene rubber)
NBR (Nitrile rubber)Appearance

Pale yellow Pale yellow
clear
clear

Viscosity

SBR (Styrene-butadiene rubber)
EPDM (Ethylene-propylenediene terpolymer)

Structural viscosity ratio

Note: * in the table indicates material failure of adherends.

Specific gravity 25

Table-2 shows high shearing adhesion strength
especially on metals and good adhesion on a wide
variety of things regardless of material.

Adhesive only
Set time
25
50
Accelerator
combined

Table-2 shows the adhesion strength on various
adherends in comparison with our old products. Lap
shear strength was tested with sandblasting process
for metals, and without it for non-metals. The
measurement was carried out at ordinary
temperature after 24 hours’ curing of adhesion
under 25°C and 50%RH.

Table-3 shows peeling-, and impact-resistantadhesion strength, Figure-2: heat-resistant adhesion
at various temperatures, Figure-3: heatcycle
adhesion.
Peeling adhesion strength was tested for 2
L-shaped metal plates stuck by the surface of 25 x
100mm under 25°C, 50%RH. The strength wasmeasured for 25mm width at the speed of
50mm/min, at ordinary temperature after 24 hours’
curing of adhesion under the same environment.
Iron and aluminum are degreased.

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Table-3. Peeling-, and impact-resistingadhesion strength
Test items Adherend Unit

TB7737

Our

Test method
TB7738 conventional
product

TB773830
Our conventional
product

25

Lap shear strength (MPa)

Impact resisting adhesion strength was tested for
2 blocks of iron stuck by the surface of 3cm2 under
25°C, 50%RH. The strength was measured by
Charpy impact test after 24 hours’ curing ofadhesion under the same environment.

20
15
10
5
0

Peelingadhesionstrength

0

100

200

300

400

500

Number of cycles

Figure-3. Heatcycle resistance
Impact-resistingadhesionstrength

Heat resisting adhesion was tested for two ironplates stuck under 25°C, 50%RH. The strength wasmeasured after 24 hours’ curing of adhesion under
the same environment for lap shear strength by 2hours’ exposure at various temperatures.
TB773830
Our conventional
product

Lap shear strength (MPa)25

3-3. Main applications
TB7737 / 7738 series have ultrahigh peeling andimpact-resisting strength that could not be realized
by conventional products. Therefore, they can beused in more harsh environments where instantadhesives have not been applied. The appearance isin semi-gel state, not drippy but fluid enough toapply to bonding small parts of electronics.

20
15
10
5
0
25

50

75
Temperature (

100

125

)

Figure-2. Heat resisting adhesion at various
temperatures
Thermal cycle resistance was tested for two irontest specimens stuck under 25°C, 50%RH. The
strength was measured after 72 hours’ curing ofadhesion under the same environment for lap shear
strength back in ordinary temperatures frompredefined exposure to heat cycles alternating
between – 40°C x 1 hour and 120°C x 1 hour.

4

Table-3 shows that the new products have far
more improved peeling and impact adhesion
strength compared to old improved ones. Figure-3
and 4 also shows that they keep lap shear strength
over 10MPa for 120°C aging and 500 thermal
cycles between -40°C and 120°C.
TB7737 / 7738 are so high-functional that keepadhesion strength and impact resistance under these
extremely harsh environments.

<Main applications>(1) Bonding general parts requring high strengthand impact resistance(2) Dripping-free sticking such as on verticalsurface(3) Bonding various electronics parts on
printed-circuit board such as IC chips,
condensers, etc.
(4) Bonding speaker parts such as cone paper andmagnets(5) Bonding weather-strip for cars, etc.

4.

Exclusive multi-primer “ThreeBond7797” for instant adhesives

4-1. About primers
High-polymer materials such as polypropylene,
polyethylene, polyacetal, polytetrafluoroethylene(teflon®), silicone rubber are very commonly used
for consumer and industrial uses. However thesematerials are known difficult to adhere generally,
which have required very much effort to solve theproblem of insufficient adhesion when stuck withusual adhesives.
The main characteristics causing the insufficiency
can be interpreted as due to little surface energy ofthe materials and little wettability of adhesives on
the surface of adherends which should contribute toadhesion, that is, little conformity of adhesives withadherends.
Cyanoacrylate, the adhesive material of instantadhesives, is a polar material whereas difficult
adherends such as polypropylene are nonpolar,
which explains the difference of SP (solubility
parameter) value telling the difficult onset ofadhesion.

4-2. Properties and characteristics
Properties and general characteristics of TB7797
are shown in Table-4. Lap shear strength was tested
for difficult adherends, both of whose surfaces tostick were applied with TB7797 by absorbent cottonand left 2 minutes for solvent sublimation, then oneof the surfaces was applied with TB7784 (seeTable-8 at the end) and stuck, and the strength wasmeasured after 24 hours’ curing of adhesion under
25°C, 50%RH.
Table-4. Properties and general characteristics
of TB7797

Test items

Adherend Unit Characteristic
Test method
value
Clear andcolorlessAppearance
Specific gravity
25

Lap shear strength
25

50%RH 24hrs

TB7784

Existing typical solution to this problem has been
improving the surface wettability of adherends foradhesion onset by applying and interposing
pretreatment material (primer) comprised ofcomponents such as amine and solvent. However, it
is difficult to get stable onset of adhesion for thewide variety of adherends.
ThreeBond has now developed high-reliability
multi-primer which deliver stable onset of adhesion
for a wide variety of adherends after its research forprimers to solve the problem of adhesion difficulty.

deformed

SiliconerubberNote: * in the table indicates material failure of adherends.

Tables 5, 6 and 7 show lap shear strengths andenvironmental durabilities (heat resistance, thermal
cycle resistance, and chemical resistance) of various
adherends when stuck using TB7797 and TB7784.
Lap shear strengths of various adherends aremeasured at 50mm/min tension rate for gum
elastomer, 10mm/min for others.

Exclusive multi-primer “ThreeBond 7797” forinstant adhesives specialized to be used with instantadhesive has excellent quick drying and workability
in addition to good adhesion for difficult adherends.
Details are described below.
(Hereafter ThreeBond 7797 is referred to as
TB7797.)

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Table-5. Lap shear strengths of various
adherends
Lap shear strength [MPa]Adherends

TB7784
TB7784
TB7797 combined No primer combined

Iron
Aluminum
SUS304

As for chemical resistance, lap shear strength wasmeasured back in ordinary temperature after 250
hours’ immersion in various chemicals.
Table-7. Lap shear strength after immersion invarious chemicals
TB7784

Brass
CopperLap shear strength [MPa]SiliconerubberChemicals Immersion

Nickeltemp.

Zinc chromate
Rigid PVC

Tap water

PC (Polycarbonate)(*: deformed)

Phenol6-NylonEngine oil(*: deformed)

6,6-Nylon

Gasoline(*: deformed)

ABS (Acrylonitrilbutadiene-styrene resin)
Glass epoxy

Heating oil(*: deformed)

Methanol(*: deformed)

PBT (Polybutylene terephthalate)Note: * in the table indicates material failure of adherends.
** in the table indicates material failure by swelling of silicone rubber itself.

PET (Polyethylene terephthalate)

PPO (Polyphenylene oxide)
PPS (Polyphenylene sulfide)

Figure-4 shows the status after lap shear strength
test of PE (polyethylene) test specimen, on which
TB7797 was applied and stuck with TB7784. The
figure tells how adhesion strength for difficult
adherends improves with TB7797.

HIPS (Impact-resistant polystyrene)

Acrylic
Liquid crystalline polymer
Polyacetal
PP (Polypropylene)
PE (Polyethylene)
PTFE (Polytetrafluoroethylene)

deformed

Silicone rubber
NR (Natural rubber)
CR (Chloroprene rubber)
NBR (Nitrile rubber)
SBR (Styrene-butadiene rubber)
EPDM (Ethylene-propylenediene terpolymer)

Note: * in the table indicates material failure of adherends.

Table-5 shows high lap shear strength onset forplastics hard to bond such as polyethylene.
As for exposure test, lap shear strength wasmeasured back in ordinary temperature after
exposing for predetermined time.
Table-6. Lap shear strength after exposure
TB7784Lap shear strength [MPa]Exposurecondition

Siliconerubber(*: deformed)(*: deformed)(*: deformed)

Heat cycle
60 cyclesto(*: deformed)

Note: * in the table indicates material failure of adherends.

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Before test

TB7784
only

TB7784/

TB7797

Figure-4. Polyethylene test specimen after
lap shear strength testAs seen above, TB7797 is a multi-primer which
dramatically improves adhesion for various difficult
adherends, and delivers onset of stable adhesion
under exposure environment by heat and chemicals.
Main features of TB7797 are:(1) Far improved adhesion for difficult adherends(2) Quick drying and good workability(3) Brush, absorbent cotton, cotton swab, etc. canbe used for easy application(4) Usable for all ThreeBond instant adhesive
series (TB1700 and 7700 series)

5.

4-3. Applications
TB7797 is an exclusive primer specialized ininstant adhesive. It is recommended to be used as
pretreatment material for instant adhesive whenbonding parts comprising of various difficult
adherends (polypropylene, polyethylene, polyacetal,
polytetrafluoroethylene, silicone rubber).

Product line of ThreeBond 7700 Gold Label series

We launched “ThreeBond 7780 Gold Label” series, the ultra-fast curing instant adhesives focusing on“INSTANT”, the raison d'etre of the products, in the course of development. We are also seeking a way to more
multi-potent products by adding higher functionalities in this series. Please see Table-8 below for the product lineof ThreeBond 7700 Gold Label series since 2006 launch.
We continue to develop and improve product line of ThreeBond 7700.

Table-8. The product line of ThreeBond 7700 Gold Label series (as of January, 2009)
Category

Application
Ultrahigh peeling-,
impact-resistance type
Standard typeThreeBond
7700
Gold LabelseriesTB grade

Viscosity [mPa s]

Features- Excellent peeling strength and impact resistance- Good heat and humidity resistance- General purpose type for various materials- Good for ultra-fast curing

Ultra-fast curing type

- Good for porous materials and acid paper- Good adhesion for difficult adherends(POM, PPS, etc.)

Multi-primer specialized ininstant adhesive- Adhesion brought to the extent of material
failure for PP, PE, PTFE, POM, etc.

Note: TB is referred to as ThreeBond

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Conclusion
It has been 60 years since the development and penetration of alpha-cyanoacrylate adhesive and a wide variety
of products has been delivered until now through repeated improvements by many researchers. They haveadvantages of one-part and non-solvent, and instant curing, however, they also have disadvantages of blooming,
less heat-resistant and less impact-resistant; the latter having been big issues for ages to overcome.
The two products introduced here are supposed to have shown the possibilities of instant adhesives for
multifaceted applications by not only overcoming disadvantages of instant adhesives and improving peeling- andimpact-resistance, but solving the issues of adhesion of difficult adherends which has been generally thought very
difficult for any types of adhesives.
We appreciate your continued support as we strive to meet the needs of customers and develop new products.
We are also going to focus on improving preservative quality of instant adhesive itself and developing completely
new high functionality never found in existing ones.
Shigekazu Motoki
Koji Yamada
Industrial Market Department
Product Development Division
R&D Group
ThreeBond Co., Ltd.

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

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