ThreeBond Technical News
Issued January 1, 201789

Developing MEKO-Free Silicone FIPG
Introduction
Silicone FIPG are used for a variety of sealing and adhesion applications such as in automotiveengines, transmissions, etc., areas thanks to their flexibility when cured and excellent heat andchemical resistance, and ThreeBond has been developing products using them to meet customer
needs.
Meanwhile, environmental regulations have been growing more and more strict across the world,with chemical substance risk assessments and other mandates being required in Japan, as well, toprevent occupational risk. European nations are particularly conscious of the work environment,
establishing environmental regulations and chemical substance registration/management systems
well ahead of the rest of the world.
The silicone FIPG currently in extensive use releases methyl ethyl ketoxime (hereafter, abbreviatedas MEKO) as a by-product of the curing reaction, and this has been designated a hazardous
substance in Europe (Legal Reference 1, 2, 3). In this document, we will introduce MEKO-freesilicone FIPG made in response to these European working environment regulations.

Table of Contents

Introduction.................................................1
1. Background.............................................2
2. FIPG........................................................2
3. Required Characteristics........................3

4. Product Lineup........................................5
5. ThreeBond 1217M Evaluations...............6
6. ThreeBond 1217P Evaluations................7
Closing........................................................81

1.

Background

1-1 Environmental Regulations
Recent years have seen stricter and stricter regulations
related to chemical substances. These are a part of a global
effort to appropriately manage chemical substances in orderto improve the working environment and save the earth.
European Union, in particular, has been ahead of the restof the word in terms of management and implementationof environmental regulations, continuing revisions overtime to create a global standard for chemical substances.
Automobile and other manufacturing industries must comply
with a variety of countries’ environmental regulations, andeven chemical industry manufacturers are required to move
forward on product development that complies with theseregulations.
1-2 Automotive Industry Efforts
In order to both reduce CO2 emissions and use renewable
petroleum substitutes within automobile and othermanufacturing industries, hybrid (HV/PHV), electric (EV),fuel cell (FCV) and other eco-friendly vehicles have beenreleased one after another, and their market share continues
to grow. Along with this, competition continues to increasein terms of reduction in fuel consumption and otherenvironmental considerations.

Compliance with conservation efforts applies not only
to completed vehicles (products), but also to continuing
workload reduction and simplification across the
manufacturing line. There has been considerable focus onenvironmentally regulated substances, including organic
solvents.

2.

FIPG

2-1 FIPG
FIPG are liquid gaskets (FIPG: Formed-In-Place Gaskets)
are used in the process where liquid materials are used forcoating/applying to the flange where these than cure toperfectly shaped sealing/adhesive. Currently, RTV silicone(RTV: Room Temperature Valcanizing) is the mostly widelyused type of material for FIPG, which includes considerable
use of oxime types which release MEKO during the curing
reaction.
2-2 FIPG Seal Theory
While solid gaskets maintain a seal through repulsive force,
FIPG seal oily mediums mainly through bonding, adhesion,
viscoelasticity and cohesive force. These characteristics
must be tuned excellent in order to maintain a fully sealed
component (Figs. 2-1, 2-2).

Applications: Adhesive sealant for oil pans, chain cases, etc.

Fig. 1 Parts Where FIPG are Used

2

Solid Gaskets

Permeation (inner surface) Leakage
Leaky where the interior of the gasket is penetrated
Mainly due to the gasket having insufficient chemical
resistance

FlangeSeal Medium Pressure

Repulsive Force

GasketBurst Leakage
Fig. 2-1 Solid Gasket Seal Theory

Leaky from the broken surface of the gasket
Mainly due to gasket deformation ability, flange vibration

Liquid Gaskets (FIPG)

Seal Medium Pressure

FlangeGasketBonding/Adhesion
Viscoelasticity/
Cohesive Force

Junction Leakage

Bonding/Adhesion

Leaky from the interface of the gasket and the flange
Mainly due to insufficient bonding/adhesion*Adhesion for each part is vitalFig. 2-2 Liquid Gasket (FIPG) Seal Theory

2-3 Types of Leaks
The three main types of leaks are permeation (inner layer)leakage, where the inside of the gasket is penetrated by themedium, burst leakage, where the gasket itself breaks, andjunction leakage, where leakage occurs at the interface ofthe gasket and the flange (Fig. 3).
There are various causes of leakage, and FIPG are importantin prevention because of their durability for the sealed
medium, ability to follow flange vibrations and opening
deviations and their ability to adhere to the flange.

FlangeGasketFig. 3 Types of Leaks

3.

Required Characteristics

3-1 MEKO Positioning in Europe
European union is ahead of the word in terms of enforcement
and management standards of environmental regulations,and this management and these standards are strict. In
Europe, MEKO is designated as a category 2 carcinogen(Legal Reference 3). MEKO is released as a gaseouscomponent in the condensation reaction during curing of
the FIPG (MEKO-releasing types) used most extensively
throughout the world.

3

3-4 Adhesion to Oily or Dirty Parts
Engine blocks, transmission casings and similar parts areusually produced by molding and cutting iron or aluminum
die cast. A certain amount of the cutting oil used for thisremains on the flange even after cleaning. Additionally,various industrial equipment in operation within an engine
manufacturing plant scatter lubricant oil, creating a mist
(oil becomes small particles that float through the air)that attaches to adherends and causes dirt to remain. This
negatively impacts FIPG adhesion, even leading to leakage.

Therefore, an FIPG which does not release gaseous MEKO
during condensation is vital in order to conform to European
standards.

3-2. Durability versus Oil
Silicone FIPG is mainly used as an oil sealant in engines,
transmissions, etc. This means it is important that strengthand elasticity do not suffer with high temperatures (120 °C
or more), while also ensuring effective adhesion (bonding)to the part is maintained in order to ensure proper sealantapplication.

Currently, degreasing processes using organic solventsare used to remove oil attached to adherends, but as theseprocesses are reduced due to environmental concerns, thispreviously removed oil and dirt remains on those surfaces.

3-3 High Elongation
FIPG are mainly used in vehicle parts (such as engines ortransmissions) that vibrate or are subjected to impact, so
the ability to follow vibrations and deviations in openings
in those parts is required in addition to good adhesion. Oilleaks occur due to FIPG fractures when deformation ability
is insufficient even if adhesion is sufficient.

Oil or dirt on an adherend are commonly known tosignificantly reduce adhesive strength, which may also leadto market defects such as oil bleed. This means that FIPG
require robust improvement of adhesion to prevent theseissues (see Figure 4 for determination of adhesion criteria).

Cohesive Fracture (CF)Side(side a)Front(side a)Sealant on
both sides

Application
Test(side b)Adhesive Fracture (AF)Side

Shear Test Piece
Side View* Cohesive fracture indicates thatadhesion is maintained in terms of thepart, which is desirable for the sealantin terms of adherend leakage(side a)(side b)

Firmly bonded

Front(side a)Sealant on asingle side
(side b)Fig. 4 Cohesive and Adhesive Fractures

4(side b)4.

Product Lineup

Here, we explore the features and properties of our new
products, ThreeBond 1227H and ThreeBond 1217P (hereafter
abbreviated to TB1227H and TB1217P, respectively), which
overcome the issues presented above (Table 1 & 2).

4-1 TB1227H (Alcohol-Releasing)
Instead of MEKO classified as a carcinogen in Europe, thisFIPG releases gaseous alcohol during the condensation. Itfeatures improved curing speed, which has been an issue
in alcohol-releasing types. Compared to conventional
FIPG, it features oil resistance and oily surface adhesionthat make it excellent for sealing and adhesion applications
where conventional FIPG products do not produce sufficientadhesion to oil and dirt which are the result of changes todegreasing processes.

4-2 TB1217P (MIBKO-Releasing)
Instead of MEKO classified as a carcinogen in European
union, this FIPG releases MIBKO (methyl isobutyl ketoxime)
as a gaseous component generated in condensation. It has
better curability than alcohol-releasing type and cures atthe same speed as MEKO-releasing FIPG. Additionally,
it features oily surface adhesion that make it excellent for
sealing and adhesion applications where conventional FIPG
products do not produce sufficient adhesion to oil and dirt
which are the result of changes to degreasing processes.
* Effectiveness varies depending on oil type. Effectivenessfor the oil type, concentration and other factors must be
checked before use after degreasing.

Table 1 Properties
Property

Unit

Conventional
Product A

TB1227H

Conventional
Product B

TB1217P

Testing Method

Remarks

Curing Method—

AlcoholReleasing

AlcoholReleasing

MEKOReleasing

MIBKOReleasing——

Appearance

—

Black

Black

Gray

Black

3TS-2100-002—

Viscosity

Pa·s

200

230

330

260

3TS-2F30-001

SOD

Specific gravity

—

1.47

1.39

1.36

1.36

3TS-2500-002—

Tack free time

min

90

10

5

6

3TS-3130-003—

Thick film curingperformance

min

1.7

2.3

3.0

2.9

3TS-3160-005

1 Day

Curing conditions: 23°C, 50% RH

Table 2 Cured Material Characteristics
Property

Unit

Conventional
Product A

TB1227H

Conventional
Product B

TB1217P

Testing Method

Remarks

Hardness

—

A30

A58

A51

A57

3TS-2B00-004—

Elongation Rate

%

420

280

470

430

3TS-4190-005—

Tensile Strength

MPa

2.1

2.3

2.6

2.4

3TS-4190-005—

Tensile Shear
Bond Strength

MPa

1.7

1.8

2.6

1.9

3TS-4100-023

Al/Al

Curing conditions: 23°C, 50% RH×168h
Al: Aluminum55.

ThreeBond 1227H Evaluations

5-1 Chemical Resistance
The test specimen were cured at standard conditions (23°C,
50% RH×168 h), immersed in 120°C engine oil or coolant
for 4 days, then checked for changes in physical properties.
TB1227H maintained better characteristics than conventional
FIPG (Fig. 5-1).
TB1227H showed excellent engine oil resistance, maintain
incredible adhesion after the long-term immersion test (Fig.
5-2).
3.0

Engine Oil Resistance
Coolant Resistance

2.0

The above study results indicate that TB1227H
demonstrates better adhesive performance on oily surfaces
than conventional FIPG products. The below study results
indicate that TB1227H demonstrates better adhesive
performance on oily surfaces than conventional FIPG
products.

1.5

Conventional Product A

Conventional
Product A,
Alcohol-Releasing

TB1227H

Conventional
Product B,
MEKO-Releasing

Fig. 5-1 TB1227H Chemical Resistance Test (AI/AI)
2.0

100

1.6

80

1.2

60

0.8

40

Cohesive Fracture
Ratio
Tensile Shear Bond
Strength

0

250

500
750
1000
Immersion Time (h)

1500

20

1.5

1.0

0.5

0.0
Cohesive Fracture Ratio (%)

0.4

Tensile Shear Bond Strength (MPa)

0.5

0.0

TB1227H

2.0

1.0

0.0

Tensile Shear Bond Strength (MPa)■■TB1227H
Highly robust adhesive performance was maintained, withalmost no reduction in shear bond strength or the cohesive
fracture ratio until reaching an oily surface concentration of
10% (Figs. 6-1, 6-2).

0.0

Fig. 5-2 TB1227H Long-Term Engine Oil
Resistance Test (AI/AI)

5-2 Oily Surface Adhesion
To check adhesion to oily or otherwise dirty parts, engine
oil was diluted to a specific concentration using a solvent,applied to an aluminum plate which was used as the test
piece, then the tensile shear bond strength was checked.

Control

1%

3%
5%
7%
Oily Surface Concentration

10%

Fig. 6-1 Oily Surface Adhesion Test (Al/Al)
Conventional Product A

TB1227H

100.0

Cohesive Fracture Ratio (%)

Al Shear Bond Strength (MPa)

Initial
2.5■■Conventional FIPG
Shear bond strength did not decrease significantly, though
the state of cohesive failure gradually decreased, becoming
almost entirely adhesive fractures (AF) at around 5% (Fig.
6-1, 6-2).

80.0

60.0

40.0

20.0

0.0

Control

1%

3%
5%
7%
Oily Surface Concentration

10%

Fig. 6-2 Conventional Product (Alcohol-Releasing)
Oily Surface Adhesion Test (Al/Al)

6

6.

ThreeBond 1217P Evaluations

6-1 Oily Surface Adhesion
Engine oil was diluted to a specific concentration using asolvent, applied to an aluminum plate which was used as thetest piece, then the tensile shear bond strength was checked.
■■Conventional FIPG
Shear bond strength and the cohesive fracture ratio all began
to drop from an oily surface concentration of around 1%,
becoming almost entirely adhesive fractures (AF) at around
5% (Fig. 7-1, 7-2).
3.0

TB1217P

Test results (Fig. 7-1, 7-2 and 7-3) showed that TB1217P
demonstrates better adhesive performance on oily surfaces
than conventional FIPG products.

6-2 Long-Term Durability
The test specimen was cured at standard conditions (23°C,
50% RH×168 h), immersed in 150°C engine oil over a longtime period, then checked for changes in physical properties.
Shear bond strength equal or better than conventional FIPG
was maintained, even after long-term immersion (Fig. 8-1).

2.0

Additionally, changes in physical characteristics due to longterm heat exposure were checked in a 150°C heat resistancetest. Shear bond strength equal or better than conventional
FIPG was maintained, even after long-term immersion (Fig.
8-2), just as in the engine oil immersion test.

1.5
1.0
0.5
0.0

3.0
Conventional Product B
Control

1%

3%
5%
7%
Oily Surface Concentration

10%

Fig. 7-1 TB1217P Oily Surface Adhesion
Evaluations (AI/AI)
Degreased
Surfacen=1

Oily Surface(*)

Tensile Shear Bond Strength (MPa)Tensile Shear Bond Strength (MPa)Conventional Product B
2.5■■TB1217P
Adhesive performance was maintained, with no reduction intensile shear bond strength, shear elongation or the cohesive
fracture ratio until reaching around a 7% oily surface (Fig.
7-1, 7-3).

2.5

TB1217P

2.0
1.5
1.0
0.5

n=2
0.0

0

200

400

n=3

1%

3%

5%

7%

Oily Surface

n=2

n=3

5%

7%

10%

Fig. 7-3 TB1217P Cohesive Fracture Ratio* See Fig. 4, page 4

4.0
Tensile Shear Bond Strength (MPa)

Absorbent
Cotton

3%

1200

4.5

Fig. 7-2 Conventional FIPG Cohesive Fracture Ratio

1%

1000

Fig. 8-1 TB1217P Long-Term Engine Oil Resistance
Test

10%

n=1

600
800
Endurance (h)

3.5
3.0
2.5
2.0
1.5
1.0

Conventional Product B

0.5
0.0

TB1217P
0

200

400

600
800
Endurance (h)

1000

1200

Fig. 8-2 TB1217P Long-Term Heat Resistance Test

7

Closing

Here, we have explored the superior oily surface adhesion of our MEKO-free TB1227H and TB1217P, which meet European
chemical management standards. These products contribute to the reduction of both manufacturing processes and organic
solvents used in those processes, thereby contributing to environmental conservation efforts. At ThreeBond, we will continue
to develop products that meet customer needs while also taking work environment concerns into consideration.
<Legal References>
1) Dangerous Substances Directive” / Substance Directive 67/548/EEC
2) Dangerous Products Directive” / Preparation Directive 1999/45/EC
3) Classification Labelling and Packaging of substances and mixtures” / Regulation (EU) 1272/2008

ThreeBond Co., Ltd. R&D Headquarters
Transport Development Division, Development Section
Masao Inoue
Akihiro Koyama

ThreeBond Co., Ltd.
8

4-3-3 Minamiosawa, Hachioji,
Tokyo 192-0398
Tel: +81-42-670-5333