ASTM D7998-15
(Test Method)Standard Test Method for Measuring the Effect of Temperature on the Cohesive Strength Development of Adhesives using Lap Shear Bonds under Tensile Loading
Standard Test Method for Measuring the Effect of Temperature on the Cohesive Strength Development of Adhesives using Lap Shear Bonds under Tensile Loading
SIGNIFICANCE AND USE
4.1 The test method enables strength values for wood and other materials bonded with an adhesive under a range of controlled bonding temperature, time, and pressure conditions to be evaluated. Bond formation and subsequent testing is affected in a coordinated fashion, and this enables transient strength values of sets of similar bond types to be explored with diverse parameters as independent variables. Principal among these variables is the temperature at which bonds are formed and the time that selected temperatures are maintained prior to testing. The use of controlled methods of adhesive application, the rapid attainment of stable bond formation conditions, and the rapid transition to the bond testing mode enables snapshots of bond strength to be attained as bonds progress from limited strength (or initial tack) to maximum strength. Derived data may be used to evaluate and compare the strength development characteristics of diverse types and formulations of adhesive. The method may thus be used to aid in tailoring and matching adhesives to the manufacture of diverse bonded products that involve heating.
4.2 The method may also be used to evaluate the co-dependent effect of temperature and time on the degradation of sample bonds. Pressing temperatures up to 265°C (509°F) may be necessary for such investigations of thermal degradation. Specimens are pressed for a range of times and temperatures and very shortly thereafter tested either at elevated temperature or immediately following rapid forced air cooling. Alternatively, thermal damage of pre-formed bond samples may be evaluated by subjecting them to controlled temperature and time sequences prior to testing.
4.3 The method may also be used to evaluate the effect of wood type and variability, or of non-wood materials, on bond strength development.
4.4 By hermetically sealing the overlap region of sample bonds during their formation, the method may also be used to evaluate the effect of moisture and oth...
SCOPE
1.1 This test method concerns bonding and testing of wood adhesives and related adhesives using small scale tensile lap-shear samples in a manner that emphasizes transient cohesive strength as a function of bonding time and temperature.
1.2 Use of thin adherends enables bondlines to be rapidly heated to elevated temperatures and maintained at those temperatures for a range of times at a controlled pressure before testing.
1.3 Optional rapid forced air cooling of bonds after pressing and immediately before testing enables the effect of testing temperature on transient strength to be evaluated.
1.4 Bond overlap distance is specified to ensure that failure occurs in the bondline rather than in unbonded portions of adherend strips, and also to minimize the effect of shear stress non-uniformity along the overlap during tensile testing.
1.5 Standard wood or alternative non-standard materials must be of specified high quality and uniformity of structure and dimension to minimize variability of bonding and maximize stress transfer into the bonds during testing.
1.6 The effect of wood variability and type, or of the properties of alternative non-wood materials, on bond strength development may be explored using the method.
1.7 Optional hermetic sealing of bond overlaps during their heated pressing enables the effect of moisture on bonding to be evaluated.
1.8 Thermal damage, either of pre-formed bonds or by prolonging bond forming times, may be evaluated as a function of time and elevated temperature using this test method.
1.9 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.10 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulator...
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Designation: D7998 − 15
Standard Test Method for
Measuring the Effect of Temperature on the Cohesive
Strength Development of Adhesives using Lap Shear Bonds
1
under Tensile Loading
This standard is issued under the fixed designation D7998; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.10 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This test method concerns bonding and testing of wood
responsibility of the user of this standard to establish appro-
adhesives and related adhesives using small scale tensile
priate safety and health practices and determine the applica-
lap-shear samples in a manner that emphasizes transient
bility of regulatory limitations prior to use. Some specific
cohesive strength as a function of bonding time and tempera-
hazards statements are given in Section 10 on Hazards.
ture.
1.2 Use of thin adherends enables bondlines to be rapidly
2. Referenced Documents
heated to elevated temperatures and maintained at those
2
2.1 ASTM Standards:
temperatures for a range of times at a controlled pressure
D907 Terminology of Adhesives
before testing.
1.3 Optional rapid forced air cooling of bonds after pressing
3. Terminology
and immediately before testing enables the effect of testing
3.1 Definitions of Terms Specific to This Standard:
temperature on transient strength to be evaluated.
3.1.1 adherend strip, n—one of two adherend pieces that
1.4 Bond overlap distance is specified to ensure that failure
constitute a test specimen.
occurs in the bondline rather than in unbonded portions of
3.2 adhesive spread rate, n—the mass of adhesive applied
adherend strips, and also to minimize the effect of shear stress
per unit surface area of the overlap region of the adherend.
non-uniformity along the overlap during tensile testing.
3.3 contact heating, n—thetransferofheatenergytothetest
1.5 Standard wood or alternative non-standard materials
specimen by the application of precisely temperature-
must be of specified high quality and uniformity of structure
controlled heads pressing on the test specimen’s surfaces with
and dimension to minimize variability of bonding and maxi-
controlled force.
mize stress transfer into the bonds during testing.
3.4 forced air cooling, n—the rapid cooling of the overlap
1.6 The effect of wood variability and type, or of the
region of a test specimen after bonding at elevated temperature
properties of alternative non-wood materials, on bond strength
by the controlled application of air jets onto both external faces
development may be explored using the method.
of the overlap portion of the specimen.
1.7 Optional hermetic sealing of bond overlaps during their
3.5 test specimen, n—the lap shear sample made up of an
heated pressing enables the effect of moisture on bonding to be
adhesive between two pieces of adherend.
evaluated.
3.6 thermal damage, n—the decrease in measured bond
1.8 Thermal damage, either of pre-formed bonds or by
strength due to exposure to a specified elevated temperature for
prolongingbondformingtimes,maybeevaluatedasafunction
a specified time.
of time and elevated temperature using this test method.
3.7 transient bond strength, n—the strength of a partially
1.9 The values stated in SI units are to be regarded as
formed test specimen bond (sometimes referred to as “green
standard. No other units of measurement are included in this
strength”) upon being tested.
standard.
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This test method is under the jurisdiction of ASTM Committee D14 on
2
Adhesives and is the direct responsibility of Subcommittee D14.30 on Wood For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Adhesives. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved Sept. 15, 2015. Published November 2015. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D7998-15. the ASTM website.
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D7998 − 15
4. Significance and Use
4.1 The test method enables strength values for wood and
other materials bonded with an adhesive under a range of
controlled bonding temperature, time, and pressure conditions
to be evaluated. Bond formation and subsequent testing is
affected in a coordinated fashion, and this enables transient
strength values of sets of similar bond types to be explored
with diverse parameters as independent variables. Principal
among t
...
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