Three Bond Technical News
Issued July 1, 2008

71

Three Bond’s Evaluation Technologies
Introduction ________________________________________________
Given the importance of accurately assessing the performance of various products, evaluation
technologies play an essential role in manufacturing. Three Bond strives to establish measurement
methods and to build the facilities required for various products, drawing on its own unique concepts.
This issue provides a summary of our evaluation technologies.
Contents
Introduction................................................................. 1
1. Observation ........................................................... 2
1-1. Optical microscope observation..................... 2
1-2. Scanning electron microscope (SEM)
observation .................................................... 2
1-3. Surface roughness measurement.................. 2
1-4. Dimension measurement (non-contact
three-dimensional measurement device)....... 2
2. Physical Measurement .......................................... 2
2-1. Strength measurement using the universal
testing machine.............................................. 2
2-2. Torque measurement..................................... 2
2-3. Pressure resistance tests............................... 2
3. Characteristics....................................................... 2
3-1. Workability investigation ................................ 2
3-1-1. Flow property analysis with rheometer ...... 2
3-1-2. Sedimentation velocity analysis ................. 3
3-2. Curing behavior ............................................. 3
3-2-1. Analysis of the curing process
for sealants and adhesives ........................ 3
3-2-2. Curing rate measurement .......................... 3
3-2-3. Reaction rate analysis................................ 3
3-3. Modulus measurement .................................. 3
3-4. Physical property study.................................. 3
3-4-1. Thermal analysis........................................ 3
3-4-1-1. Dynamic mechanical analysis (dynamic
thermomechanical measurement) ................ 3
3-4-1-2. Differential scanning calorimeter(DSC) ...................................................... 4
3-4-1-3. Thermal gravimetric analyzer (TGA) ....... 4

3-4-1-4. Thermal mechanical analyzer (TMA) .......4
3-4-2. Measurement of the glass transition
temperature (Tg) by various measuring
instruments .................................................4
3-4-3. Thermal conductivity measurements..........5
3-4-4. Wettability ...................................................5
3-4-5. Electrical insulation property
measurements ............................................5
3-4-5-1. Volume and surface resistivities...............5
3-4-5-2. Dielectric properties .................................5
3-4-5-3. Insulation degradation test.......................5
3-4-5-4. Dielectric pressure resistance test ...........5
4. Qualitative and Quantitative Analysis.....................5
4-1. Compositional qualification.............................5
4-2. Analysis of the generated gas ........................6
4-3. Pretreatment for quantitative compositional
analysis of specific components .....................6
4-3-1. Measurement of impurity ion
concentrations ............................................6
4-3-2. Quantification of low molecular weightsiloxane ......................................................6
4-3-3. Water vapor permeability measurement.....6
4-3-4. Molecular weight distribution
measurement..............................................6
4-3-5. Elemental analysis......................................7
4-3-6. Trace water content measurement .............7
4-3-7. Measurement of solid content
and ash content ..........................................7
4-3-8. Trace component analysis..........................7
4-3-9. Total halogen analysis ................................71

1.

Observation

Observation constitutes the basis for all analysis.
Various observations involve not just visuallyinspecting the subject being observed, but
magnifying it. Observations with an optical
microscope provide more information than simple
visual observations. However, optical microscopes
often suffer from shallow depth of field. In suchcases, we use scanning electron microscopes (SEM).
We may also need to measure minute contact
surface areas; if so, we draw on surface roughness
and three-dimensional profile measurement
techniques.
1-1. Optical microscope observation
Subjects measuring from several cm to100 µm
are generally observed using digital microscopes.
Digitalmicroscopic
observations
allow
observations in relatively natural conditions,making it possible to reduce both brightness andreflected light and to perform integrated imaging of
natural light over relatively longer integration times.
Other optical microscope observation methods
include the following:• Profile magnification in 3-D mode
• Confirmation of dispersion characteristics using
phase-contrast microscope
1-2.

Scanning electron microscope (SEM)
observation
Although scanning electron microscopes do notprovide color information, they do provide
three-dimensional imaging information. The test
specimens used in SEM observations range fromseveral cm to 0.1 µm in size. At Three Bond, we use
a compact low-vacuum SEM unit, which permits
observations of a sample as-is under a vacuum
without the vapor deposition process. Observations
can easily be made to magnifications ranging up to
3,000x. For cases requiring higher-resolution
imaging, magnification of 50,000x can be achieved
after spattering with osmium oxide. For samples
measuring approximately 30 mm square, several
images can be superimposed to obtain a single
panoramic image. In addition, the characteristics ofthe electron beam can be applied to perform
elemental analysis.
1-3. Surface roughness measurement
This instrument measures various parameters
representing the surface roughness of processedsurfaces, expressing the unevenness of the surface
in accordance with Japanese Industrial Standards(JIS).

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1-4.

Dimension measurement (non-contact
three-dimensional measurement device)
This instrument measures surface morphology atvertical resolutions of 0.01 µm. This device isnormally used to measure specific points, but canalso be used to map and draw the contours of themeasured surface.

2.

Physical Measurement

2-1.

Strength measurement using theuniversal testing machine
The universal testing machine measures the stressgenerated in a test specimen by applying
displacement at constant rates. The jigs can beswitched to change the direction of the stress placedon the sample to measure tensile, compressional,
bending, and peeling stress. The machine can also
be used to measure resin adhesive force, resin
strength, elongation percentage, Young’s modulus,
and other parameters. If the measured values are to
be used as standards, care is required to select theappropriate specimen shape (dimensions).
2-2. Torque measurement
A torque wrench is used to manually measure thetightening, breaking, and residual torque of bolt
sealants such as anaerobic sealants and sealants for
MEC (precoated) bolts.
2-3. Pressure resistance tests
This test measures the pressure resistance ofliquid gaskets and pipe sealants. The procedure
involves assembling the jigs and applying pressure,then visually inspecting for leaks while monitoring
the pressure gauge. Pressure-proof flanges fortesting are used to evaluate the pressure resistanceof liquid gaskets. Pipe sealant pressure resistance isevaluated using assembled pipe components.

3.

Characteristics

3-1.

Workability investigation

3-1-1. Flow property analysis with rheometer
One parameter assessed to evaluate the flow
properties of liquid samples is viscosity. Since mostadhesives and sealants are non-Newtonian fluids,
we must evaluate the flow behavior of samples
based on flow curves obtained by changing theshear velocity (or shear stress) applied to the sample.
Stress controlled rheometers can control stressthrough torque control and can be used to evaluate
highly viscous samples—for example, in paste form.
Additionally, we can evaluate sagging and levelingbehavior for specific intended applications based on
viscoelastic properties.

3-2.

Curing behavior

3-2-1.

Analysis of the curing process forsealants and adhesives
Identifying the curing state for sealants andadhesives is a common requirement. However,results can differ, depending on whether the curing
process is observed as a chemical reaction or amechanical process. Three Bond approaches the
problem from both perspectives, drawing on bothchemical and physical measurement techniques.
Recent years have seen advances in techniques formaking continuous measurements of the reaction
process. However, the curing process is extremely
difficult to define precisely. For this reason,
evaluations are currently based on assessments ofthe state of the sealant/adhesive at various points inthe curing process.
• Measurement of time course of reaction using
real-time FT-IR (fourier transform infrared
spectrometer)• Observation of exothermic reaction using DSC(differential scanning calorimeter)• Observation of change in viscosity withrheometer
3-2-2. Curing rate measurement
This method for evaluating the status of curing
materials includes observations of the heat value ofthe unreacted material and of the rate of change offunctional groups based on infrared absorption
spectrum measurement.
• DSC• Photo-DSC• FT-IR
3-2-3. Reaction rate analysis
Activation energy is analyzed using DSC. Kinetic
analysis is performed with software based on an
equation of state; theoretical reaction rates can bevisualized in graphs. (Figure 1)

50% reacted
90% reacted

Curing time (min)3-1-2. Sedimentation velocity analysis
We can evaluate the stability of particles
contained in a liquid sample by observing lighttransmitted through or scattered by a liquid sample
placed in a transparent vessel in the near-infrared
range. When particles settle, the intensity oftransmitted light in the upper part of the vesselincreases, while light scattering increases in thelower portion. The effects of inter-particle
interactions (e.g., coagulation) can be evaluatedbased on the charts obtained.

Temperature (°C)

Figure 1. Curing rate of liquid epoxy resins
3-3. Modulus measurement
Modulus measurement is one method forexpressing the viscoelastic properties of solid
high-polymer materials. Modulus is either static ordynamic. Static modulus is measured using theuniversal testing machine, while dynamic modulus
is measured using the dynamic mechanical analysis(DMA) unit. The measured parameters are
generally temperature and change in the modulus ofelasticity. The changes in adhesive strength andelectrical characteristics with temperature are
known to correlate with temperature dispersion ofviscoelastic properties. By determining the thermal
dispersion of modulus of elasticity, we can estimate
the applicable temperature range of thesealant/adhesive in question.
Modulus measurements entail applying stress to atest specimen to create displacement and observing
the amount of displacement and the phase lag. Thus,
the shape (dimensions) of the test specimen is an
important element.
Additionally, a change in elasticity (recovery) canbe evaluated by creep & recovery observations todetermine changes in the curing material over time.
3-4.

Physical property study

3-4-1.

Thermal analysis

3-4-1-1.

Dynamic mechanical analysis(dynamic thermomechanicalmeasurement)
In dynamic mechanical analysis (DMA),
temperature is changed continuously while applying
stress to the test specimen. The generated
displacement and phase lag are measured toevaluate mechanical characteristics. This approachis used primarily to study changes in modulus ofelasticity with temperature. As stated previously, the3temperature dispersion of hot strength correlateswith the temperature dispersion of the modulus ofelasticity measured by DMA.
3-4-1-2.

Differential scanning calorimeter(DSC)
The DSC controls and changes the temperatureinside the sample chamber to measure differences inheat flux between the test specimen and reference
specimen as a function of temperature, permitting
measurements of the heat of reaction, specific heat,reaction initiation temperature, and varioustransition points (e.g., melting point) of the resin.
3-4-1-3. Thermal gravimetric analyzer (TGA)The TGA measures changes in the weight of thesample with changing temperature and over time.
The TGA can be used to identify the decomposition
temperature, melting point, and boiling point ofliquids and solids, as well as changes in weight
upon heating (e.g., loss on heat, total outgassing).
3-4-1-4. Thermal mechanical analyzer (TMA)
The TMA lets us measure the coefficient of linear
expansion of a test specimen. It is important toknow the difference in the coefficients of linear
expansion of the adhesive and the adherend, sincesuch differences, where present, can generate strain,
resulting in undesirable effects, such as thedestruction or exfoliation of the adherend or
adhesive.
3-4-2.

Measurement of the glass transition
temperature (Tg) by various measuring
instruments
While high-polymer materials such as sealants
and adhesives may seem solid, their molecular
structure is in motion at the atomic level. Whilemost parts are stationary and hard as glass at low
temperatures, they begin to move above a certain
temperature, displaying rubber elasticity. Thistemperature is known as the glass transition
temperature (Tg). In addition to hardness, changes
in the kinetic state of the molecular structure also
cause changes in the coefficient of thermal
expansion, specific heat, electrical characteristics,
adhesive strength, resin strength, and chemical
resistance.
If we define the criteria for thermal resistance of atest specimen as the retention of physical properties
at the same level as specimens measured at room
temperature, we can estimate thermal resistance
simply by measuring Tg. No other evaluation
method would be needed. However, sincehigh-polymer materials have a range of molecularweight distributions, Tg will be a range oftemperatures, not a specific point. For high-polymer

4materials, it would be more appropriate to refer to
Tg as the glass transition range, not the glasstransition temperature.
Several techniques exist for measuring Tg. Three
Bond measures Tg via DSC, TMA, or DMA (DMS).
Note that differences in measuring instrument,
technique, and curing conditions, even for the sameadhesive/sealant, will result in differences inmeasured Tg. This means comparisons using Tgvalues provided in catalogs and technical references
are meaningless without specific information on thetechniques/conditions under which the values wereobtained.
(1) DSC: With DSC, Tg is determined by measuring
the change in specific heat associated with thephase transition in the molecular structure
occurring near the temperature. In general, thetemperature at which the phase change begins isregarded as Tg. Thermodynamically, Tg
measured by DSC is considered most reliable.
(2) TMA: The Tg measured by TMA corresponds tothe point of discontinuity (point of inflection) in
the curve of the coefficient of linear expansion.
The intersection of the extrapolated lines below
and above the point of inflection is defined as
Tg. In curing materials for which reaction
remains incomplete, initial measurements will
indicate shrinkage on curing. Reactions must be
given time to complete before measurement isperformed to determine Tg.
(3) DMA (DMS): E” (loss elastic modulus)
represents the component of the applied stressabsorbed by the sample and lost. Since thefreedom of molecular motion is large in the Tg
range, E” will also be large. The Tg (glasstransition temperature) measured by DMA
corresponds to the peak of E”. Since the peakvalue of tan δ is larger than that of E”, theformer is sometimes used as Tg. However,strictly speaking, this has been judged
academically inappropriate, and is now used lessoften. However, the peak tan δ values tends togive values that coincide with those found in
actual applications and are sometimes used asapparent glass transition temperatures. Since Tg
measurements can be made by DMA byobserving changes in the state of the curing
material, the curing reaction need not becomplete. This method is often used to measure
Tg under a range of curing conditions.

3-4-3. Thermal conductivity measurements
Two types of thermal conductivity measurements
are used: the hot wire method and the steady-statemethod. In general, test specimens with a thicknessof 2 cm or more are used for measurements. The
hot-wire method is used for thin films. Other
techniques include those entailing visualization
schemes.
• Measurement either by the hot-wire or
steady-state method• Observations of heat transfer by thermography
3-4-4. Wettability
Measuring the contact angle of a liquid on a solid
surface using the contact angle meter lets us
measure the wettability between a resin and aparticular adherend, an important factor in adhesion.
Measuring the contact angle of a liquid whose
interfacial tension component for a given solid
surface is known also makes it possible todetermine the surface free energy of the solid
surface (surface tension of the solid).
3-4-5.

Electrical insulation property
measurements

3-4-5-1. Volume and surface resistivities
Volume resistivity and surface resistivity refer,respectively, to electrical resistance per unit volume
and per unit surface area. High-resistivity
measuring units are used to measure these values.
However, accurate measurement of volume andsurface resistivities requires resin and electrode to
be in contact. The measurement methods provided
in ASTM and JIS recommend forming the resin into
thin plates and pressing these plates onto theelectrode. However, this does not guarantee contact
with the electrode, which can impair measurement
accuracy. Additionally, mercury, the material
recommended for the electrode to avoid the above
problem, is increasingly falling out of favor due toenvironmental considerations. For these reasons,Three Bond has developed an electrode patternusing a copper-lined glass epoxy plate. The test
specimen is sandwiched between this plate and acopper plate, with any air bubbles carefully
removed, and cured for measurements. Test
specimens prepared in this way are characterized bysolid contact between the resin and electrode.
3-4-5-2. Dielectric properties
Materials displaying small values in both thedielectric constant and dielectric dissipation factor
are regarded to have good electrical insulation
properties.
Aswithelectricalresistivity
measurements, test specimens for measurement are

prepared by sandwiching the resin between asubstrate having an electrode pattern and a substratethat acts as a common electrode, then curing theassembly. This eliminates error factors such as airlayers from the test specimen. While the applicablefrequency range of the measuring device is 20 Hz to
1 MHz, the range for the test specimen assemblyused at Three Bond is 100 Hz to 1 MHz. In general,
the term dielectric constant corresponds to relative
dielectric constant.
* Dielectric constant (ε): Degree of polarization
generated within a test specimen in analternating field* Relative dielectric constant (ε γ): Ratio of thematerial’s dielectric constant to that of avacuum* Dielectric dissipation factor: Degree of electric
power loss; losses via the electrical insulationmaterial can generate heat or oscillations.
3-4-5-3. Insulation degradation test
Resin is coated onto a comb-teeth electrode andcured, after which resin degradation is evaluated byapplying a direct voltage under specific conditions.
Using materials that experience migration such as
silver for the comb-teeth electrode allows migration
performance testing.
3-4-5-4. Dielectric pressure resistance test
When an electrically insulating material issandwiched between electrodes and subjected to a
voltage, a minute leakage current is produced at low
voltages. When a certain voltage is exceeded, thecurrent rapidly increases, resulting in electric
discharge, and the insulating property between theelectrodes is lost. This phenomenon is known as
dielectric breakdown. Although conventionallyexpressed in units of (kV/mm), where measured
voltage is divided by sample thickness (mm), thedielectric breakdown voltage in practice is notproportional to sample thickness, corresponding
instead to the power approximation of sample
thickness. Three Bond has created test substrates
with different gap widths to make it possible toobtain results for four or more points, which canthen be plotted on a graph for approximations todetermine dielectric breakdown voltage.

4.

Qualitative and Quantitative Analysis

4-1. Compositional qualification
Compositional qualification refers to the roughclassification of the primary ingredient of the test
specimen—for example, whether it belongs to an
epoxy or a silicone system. The sample can be

5

Observation: Digital microscope, SEM
Solid

LiquidElemental analysis: EDX

Centrifuge

Confirmation of functional groups: FT-IR

Confirmation of functional groups: FT-IR

Structural analysis: Thermal decomposition GC-MS

Confirmation of the number of components: LC, GC
Dispensing
GC-MS

Structural analysis: FT-IR, NMR

Figure 2. Analysis method for major components of unknown materials
analyzed as-is or chemically separated to thespecified extent before analysis. (Figure 2)
4-2. Analysis of the generated gas
The gas generated when using adhesives may
pose problems in certain cases. To investigate thisproblem, Three Bond used a total outgas volume
measurement system and the GC-MS (gaschromatography mass spectrometry) system forcompositional analysis.
• Total outgas volume measurement with TGA• Compositional analysis using GC-MS
4-3.

4-3-1.

Pretreatment for quantitative
compositional analysis of specificcomponents

Measurement of impurity ion
concentrations
Impurity ions refer to the free ions present on thesurface of or within the solid adhesive/sealant.
Impurity ions contained within the resin trigger
corrosion in the presence of water. In general, fewer
impurity ions are believed to enhanceadhesive/sealant performance. The method forevaluating impurity ions depends on which ions areto be captured. For example, rinsing with purewater will capture ions adhering to the surface ofthe solid adhesive, while extraction at hightemperatures and pressures will permit the captureof ions present at relatively deeper portions of theadhesive. The extraction method affects measured
ion concentrations.
To perform a quantitative analysis of ion
concentrations, we can measure the electricalconductivity of the extraction solution obtained toevaluate total ion concentrations, or separately
quantify ion species via ion chromatography (IC)6analysis.
4-3-2.

Quantification of low molecular weightsiloxane
Low molecular weight siloxane is relatively
volatile and a known causative factor leading tocontact faults. Low molecular weight siloxane canbe extracted using solvents such as n-hexane oracetone and quantitatively measured by GC (gaschromatography).
4-3-3.

Water vapor permeability
measurement
Water vapor permeability can be measured bymeasuring the water vapor permeability directly or
the water vapor transmission rate. The former is avalue characteristic of the resin itself, while thelatter represents the performance of the sample
formed into a film. At Three Bond, water vapor
permeabilityismeasuredusingadifferential-pressure gas permeability meter, while
the water vapor transmission rate is measured by
the cup method. Since results with the cup method
depend on film thickness, the water vapor
transmission rate is generally used for products
having specific dimensions, such as plastic
wrapping materials for food.
4-3-4.

Molecular weight distribution
measurement
The molecular weight distribution of highpolymers that dissolve in a solvent is often
measured. SEC (size-exclusion chromatography,
GPC), a liquid chromatography technique, is used
to measure molecular weight distributions. This
separation technique separates substances solely bymoleculesize,
unlikenormalHPLC(high-performance liquid chromatography), which
relies on interactions such as adsorption. In theactual analysis of adhesives and sealants, theseparation columns used are selected based on thetarget molecular weight, while THF, an effective
solvent when used with materials found inadhesives and sealants, is often used as the solvent.
The measurement results are converted values
based on the standard polystyrene sample.
4-3-5. Elemental analysis
This technique quantifies the composition ratio ofvarious elements. The samples are first decomposedby thermolysis in high-purity acids, and the solution
is used as samples for ICP-MS (inductively coupledplasma mass spectrometry) analysis or for atomic
absorption spectrometry analysis for qualitative andquantitative analysis of the elements contained in
the sample. Both analysis methods are capable ofmeasuring concentrations on the order of ppm to
ppb.
• Other methods• EDS (energy dispersive X-ray spectrometer)
Concentration analyzed on percent orders• ESCA (electron spectroscopy for chemical
analysis)
Concentrations analyzed as percent values• XRF (X-ray fluorescence analysis)
Concentration analyzed on the order of ppm forcertain elements

4-3-8. Trace component analysis
Trace components in the analyzed sample are
isolated based on differences in polarity and othercharacteristics in HPLC and GC analysis, thenqualitatively and quantitatively measured bycomparing retention times and detected amounts
against a reference standard. Samples that do notdecompose and gasify upon heating are measured
by GC. Samples displaying unstable behavior whenheated, samples that do not gasify, or samples
separated by components into different fractions formeasurement by other instruments are measured by
HPLC.
4-3-9. Total halogen analysis
The total halogen content (F, Cl, Br, I) of thesample can be measured quantitatively by theflask-combustion method. Note that the results
based on this method are susceptible to errors
involving technician skill or contamination from thelaboratory environment. At Three Bond, to prevent
errors attributable to laboratory and analyticalenvironments, we perform high-sensitivity halogen
quantification with an instrument that integrates a
pretreatment unit for combustion and absorption
and an analyzer unit (the ion chromatography
instrument).

4-3-6. Trace water content measurement
The Karl Fischer titration method is one method
for measuring the trace water content of a sample.
With the Karl Fischer method, selective reactions
between iodine and water are used to measure theabsolute volume of water in a given sample. The
instrument is equipped with a water vaporization
unit that makes it possible to handle solid samples
and samples that do not readily dissolve in the Karl
Fischer reagent. Trace water concentrations can bemeasured as percent values or on the order of ppm.
4-3-7.

Measurement of solid content and ash
content(1) Thermal decomposition by TGATGA is used to heat samples to 550°C innitrogen (900°C for silicone). The organic
components are thermally decomposed tomeasure the ratio of organic to inorganic
components in the resin.
(2) Solid content measuring device
Heated-air dried weight measurement lets us
measure moisture content, solid content, andvolatile content of resins.

7Conclusion
Analysis and evaluation technologies for R&D at Three Bond are based on the client’s perspective. This is why
we have more facilities dedicated to investigating the characteristics and physical properties of our products thanstructural analysis. In developing our measurement techniques, we go beyond the information required by JIS toobtain a range of other critical information.

Naoto Ichikawa
Takao Goto
Tatsuhiro Kiriu
Technical Service Department
Technical 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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