ASTM D4502-92(2004)
(Test Method)Standard Test Method for Heat and Moisture Resistance of Wood-Adhesive Joints
Standard Test Method for Heat and Moisture Resistance of Wood-Adhesive Joints
SIGNIFICANCE AND USE
This test method can serve as a useful tool for durability assessment and service life forecasting.
5.1.1 This test method can be used to measure the effects of heat and moisture and the effect of their interaction on adhesives and bonded joints. Knowledge of these effects is useful to an adhesive formulator or manufacturer. Moist heat aging is particularly useful for determining the effects of acidic adhesive systems on the hydrolysis of wood adherends.
5.1.2 This test method provides a means of comparing the rate of degradation of an unknown adhesive-adherend combination to the rate of degradation of a known combination in thermal or hydrolytic aging environments. Such a comparison can be useful to adhesive manufacturers for introducing a new product to the market and for helping designers selecting adhesives.
5.1.3 This test method does not duplicate any natural service environment, but it does provide a means of estimating the service life of joints in similar environments. Service-life estimates are useful to designers of bonded structures or structures using bonded products.
Service-life estimates rely on the assumption that the chemical degradation mechanism is the same at the elevated aging temperatures as at the service temperature. However, this may not be true in every case. This possibility, together with the variability in specimen preparation, in the aging exposures, and in the strength measurements, require that caution be used in accepting the estimate of service life.
SCOPE
1.1 The purpose of this test method is to estimate the resistance of adhesive-bonded joints to thermal and hydrolytic degradation.
1.2 This test method is primarily for wood-to-wood joints but may be applied to joints of wood to other materials.
1.3 The effects of chemicals such as fire retardants, preservatives, and extractives in the wood upon joint degradation resistance can be estimated.
1.4 This test method does not account for the effects of stress, the other principal degrading factor, nor does it account for cyclic or variable temperature or moisture levels.
1.5 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 regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D4502 – 92 (Reapproved 2004)
Standard Test Method for
Heat and Moisture Resistance of Wood-Adhesive Joints
This standard is issued under the fixed designation D4502; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope IEEE No. 1, General Principles for Temperature Limits in
the Rating of Electrical Equipment
1.1 The purpose of this test method is to estimate the
resistance of adhesive-bonded joints to thermal and hydrolytic
3. Terminology
degradation.
3.1 Definitions
1.2 This test method is primarily for wood-to-wood joints
3.1.1 For definitions of terms used in this test method, refer
but may be applied to joints of wood to other materials.
to Terminology D907.
1.3 The effects of chemicals such as fire retardants, preser-
3.2 shear strength, n—in an adhesive joint, the maximum
vatives, and extractives in the wood upon joint degradation
average stress when a force is applied parallel to the joint.
resistance can be estimated.
3.2.1 Discussion—In most adhesive test methods, the shear
1.4 This test method does not account for the effects of
strength is actually the maximum average stress at failure of
stress, the other principal degrading factor, nor does it account
the specimen, not necessarily the true maximum stress in the
for cyclic or variable temperature or moisture levels.
material.
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Summary of Test Method
responsibility of the user of this standard to establish appro-
4.1 The degradation of adhesive joints is a physicochemical
priate safety and health practices and determine the applica-
process. The speed of degradation is related to the levels of
bility of regulatory limitations prior to use.
temperature, moisture (and other chemicals), and physical
2. Referenced Documents stress to which the joint is exposed. This test method is based
2 on the principles of chemical kinetics and uses theArrehenius
2.1 ASTM Standards:
temperature dependence relationship to estimate the long-term
D897 Test Method for Tensile Properties of Adhesive
effects of heat and moisture at the service temperature.
Bonds
4.2 Specimens whose unaged properties have been esti-
D905 Test Method for Strength Properties of Adhesive
mated by control tests are subjected to an accelerated thermal
Bonds in Shear by Compression Loading
or hydrolytic aging environment in groups. Aging is acceler-
D907 Terminology of Adhesives
ated by using elevated temperature. Periodically, a group of
D2304 Test Method for Thermal Endurance of Rigid Elec-
specimens is removed from the aging environment and tested.
trical Insulating Materials
The estimated property after aging and the time of aging are
D2307 Test Method for Thermal Endurance of Film-
recorded.Afterseveralgroupshavebeentestedinthismanner,
Insulated Round Magnet Wire
the rate of property loss in the aging environment can be
D2339 Test Method for Strength Properties ofAdhesives in
estimated. This basic experiment is repeated at several other
Two-Ply Wood Construction in Shear by Tension Loading
elevated temperatures, and the rates of property loss at those
2.2 IEEE Standard:
temperatures estimated. The rate of property loss relationship
to temperature is estimated. This relationship can be extrapo-
This test method is under the jurisdiction of ASTM Committee D14 on
lated to lower service temperatures for estimating service life.
Adhesives and is the direct responsibility of Subcommittee D14.70 on Construction
4.3 This test method employs a smaller version of the Test
Adhesives.
MethodD905blockshearspecimen,butothershearstrengthor
Current edition approved April 1, 2004. Published April 2004. Originally
´1
approved in 1985. Last previous edition approved in 1998 as D4502–92(1998) .
tensile strength specimens may also be used.
DOI: 10.1520/D4502-92R04.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available from Institute of Electrical and Electronics Engineers, Inc. (IEEE),
the ASTM website. 445 Hoes Ln., P.O. Box 1331, Piscataway, NJ 08854-1331, http://www.ieee.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D4502 – 92 (2004)
5. Significance and Use perforated to permit free-flow of water vapor. It may be cut
from any material that is resistant to corrosion, heat, and
5.1 Thistestmethodcanserveasausefultoolfordurability
moisture. Perforated high-density hardboard has proven satis-
assessment and service life forecasting.
factory. The platform must be cut in half to pass through the
5.1.1 This test method can be used to measure the effects of
neck of the jar.An aging jar with platform is shown in Fig. 1.
heat and moisture and the effect of their interaction on
The jars must be placed in an aging oven, such as described in
adhesives and bonded joints. Knowledge of these effects is
5.1, to achieve the required temperature.
useful to an adhesive formulator or manufacturer. Moist heat
6.4 Water Baths—Constant-level water baths capable of
agingisparticularlyusefulfordeterminingtheeffectsofacidic
controltowithin0.5°Cofthedesiredtemperaturearerequired.
adhesive systems on the hydrolysis of wood adherends.
The baths must be able to contain 100 specimens.
5.1.2 This test method provides a means of comparing the
6.5 Testing Machine—The testing machine shall have a
rate of degradation of an unknown adhesive-adherend combi-
capacity of not less than 3000 kg (6210 lbf) in compression.
nation to the rate of degradation of a known combination in
The machine shall be capable of maintaining a uniform rate of
thermal or hydrolytic aging environments. Such a comparison
loading such that the load may be applied with a continuous
can be useful to adhesive manufacturers for introducing a new
motion of the movable head to the maximum load at a rate of
product to the market and for helping designers selecting
10.0 6 5 mm/min (0.40 in./min) with a permissible variation
adhesives.
of+0.5%.
5.1.3 This test method does not duplicate any natural
6.6 Shearing Tool—A shearing tool similar to the tool
service environment, but it does provide a means of estimating
pictured in Test Method D905 is satisfactory. The tool must
the service life of joints in similar environments. Service-life
have a self-aligning seat to ensure uniform lateral distribution
estimates are useful to designers of bonded structures or
of the load.
structures using bonded products.
5.2 Service-life estimates rely on the assumption that the
7. Materials
chemical degradation mechanism is the same at the elevated
7.1 Adhesive to Be Tested:
agingtemperaturesasattheservicetemperature.However,this
7.2 Joints—Wood for wood-to-wood joints or joints of
may not be true in every case. This possibility, together with
wood to metal or plastic shall be free of defects such as knots,
thevariabilityinspecimenpreparation,intheagingexposures,
cracks, short-grain and sharp-grain deviations, or any discol-
and in the strength measurements, require that caution be used
orations or soft spots indicative of decay. Generally, a high-
in accepting the estimate of service life.
density uniform-textured wood is desirable so that the maxi-
6. Apparatus mum stress will be placed on the adhesive joint during testing.
The standard shall be hard maple (Acer saccharum or Acer
6.1 Aging Ovens—Ovens are required that are capable of
nigrum) having a minimum specific gravity of 0.65 (based on
control within 62 % of specified exposure temperature
oven-dry weight and volume). Other species may be used
throughout the chamber for extended periods of time (60.5°C
whereevaluationoftheadhesive’sperformanceincontactwith
control is desirable). The ovens must be capable of operating
that species is a specific requirement.
at temperatures from 60 to 175°C. The oven must have an
7.3 Saturated Salt Solutions—A constant relative humidity
internal capacity for up to 100 specimens well-spaced and
at a given temperature can be maintained in sealed aging jars
supported on racks to allow free air flow.
byasaturatedaqueoussolutionincontactwithanexcessofthe
6.2 Environmental Chambers—Chambers for moist-heat
solid phase of a specific salt. Tables are available that show
aging must be capable of 60.5°C temperature and 0.5%
relative humidities at given temperatures for many salts.
relative humidity control uniformly throughout the chamber.
Sodium chloride is recommended. A saturated solution of
The chamber must be capable of operating at temperatures
sodiumchloridewillproducearelativehumidityof73to76%
from 60 to 90°C and relative humidity from 60 to 80%. The
overthetemperaturerangefrom40to100°C.Thistranslatesto
chamber must have the capacity for up to 100 specimens
wood moisture content in the approximate range from 9 to
well-spaced and supported on racks to allow free air flow.
13%.
6.3 Moist Aging Jars—Heat-resistant glass jars are required
to expose specimens to constant relative humidity and tem-
8. Test Specimens
perature over saturated salt solutions. Wide-neck canning jars
1 8.1 A modified block shear specimen (Fig. 2) is suggested.
with volumes of 3 ⁄2 L (1 gal), rubber gaskets, and clamp lids
ThespecimenissimilartothespecimenofTestMethodD905,
haveprovensatisfactoryattemperaturesof100°C(212°F)and
but its smaller size allows more specimens to fit in the aging
below. The jars must have a platform inside (without legs) to
chambers. Other specimens such as used inTest Method D897
support specimens above the saturated salt solution. A 6-mm
1 orTest Method D2339 are also satisfactory. If a type fromTest
( ⁄4-in.) diameter bead of silicone sealant around the inside
MethodD2339isselected,thenuse6.5-mm( ⁄4-in.)lumberfor
surface of the jar and about 5 cm (2 in.) above the bottom
each lamina, and increase the specimen length to 130 mm (5.1
providesaledgetosupporttheplatform.Theplatformmustbe
in.) while maintaining the 25.4-mm (1-in.) overlap. Other
Millett,M.A.,Western,L.J.,andBooth,J.J.,“AcceleratedAgingofCellulosic
Materials: Design andApplication of a Heating Chamber,” TAPPI, Vol 50, No. 11, Dean, J. A., ed., Lange’s Handbook of Chemistry, 12th ed., McGraw-Hill
1967, pp 74A–80A. Book Co., Inc., 1978.
D4502 – 92 (2004)
FIG. 1 Moist Aging Jar with a Shelf for Aging Specimens Over a Saturated Salt Solution
bonded joints or products may also be tested if a suitable 8.3.2 After bonding, trim one edge and one end of each
specimen can be devised. panel. Then cut two rows of five specimens each from the 63
8.2 Condition the wood at 23 6 2°C (73.4+3.6°F) and by 305-mm (2 ⁄2 by 12-in.) panels, as shown in Fig. 3, or four
relative humidity of either 30 or 65%, or other conditions, rows of five specimens each from the 127 by 305-mm (5 by
depending on the adhesive manufacturer’s requirement. 12-in.) panels.
8.3 Prepare modified shear block specimens as described in
NOTE 2—The adhesive should be thoroughly cured by hot pressing,
Test Method D905 with the following exceptions:
oven heating, high-frequency heating, or whatever method is appropriate.
8.3.1 Cut rough 25.4-mm (1-in.) lumber into 127 or 63 by
Undercured adhesives cause unwanted results in the early stages of
305-mm (5 or 2 ⁄2 by 12-in.) billets as required by Section 9.
elevated temperature aging.
Saw each billet in half through the thickness using a bandsaw.
8.4 Mark each specimen using a templet before cutting to
Joint the surface of each half that is to be bonded and plane to
indicate the panel and position in the panel.
8-mm( ⁄16-in.)thickness.(Note1)Bondthebilletsasdescribed
9. Sampling
in Test Method D905.
9.1 Sample Size:
NOTE 1—If during strength testing specimens fail in compression
9.1.1 If using the modified block shear specimen, prepare
paralleltothegrainattheends,thelaminaethicknessshouldbeincreased
5 3
from8mm( ⁄16 in.) to 9.5 mm ( ⁄8 in.) or greater, as necessary. the following numbers and sizes of panels, depending on the
D4502 – 92 (2004)
9.2.3 The distribution of specimens for subsequent data
analysis is summarized by the block experimental designs
shown in Table 4 for each of the experiments.
10. Procedure
10.1 Initial Strength:
10.1.1 Condition the control specimens to equilibrium
moisture content (EMC) at 23+2°C and 50 6 2% relative
humidity or other conditions as agreed upon by the parties
involved. One to four weeks may be required to reach EMC,
depending on the beginning moisture content.
10.1.2 Test the specimens (after they reach EMC) in the
shear tool with the universal test machine crosshead moving at
10+0.05 mm/min (0.400 6 0.002 in./min). Store the speci-
mens in a plastic bag, or remove them one at a time from the
conditioned environment during testing. Record the strength
and estimated percentage of wood failure for each specimen.
10.2 Service Life Estimate:
10.2.1 Aging temperatures are given inTable 4. For a given
temperature/moisture condition, mount five groups (10 speci-
mens per group) on suitable racks for dry aging, place in jars
for moist aging, or string each group on stainless steel wire for
wet aging.
10.2.2 Estimate five aging intervals that will produce ap-
proximately equal strength decrements to a total strength loss
of25to30%fromtheinitialstrengthforeachofthefiveaging
temperatures. Previous aging experience may not be available,
FIG. 2 Modified Block Shear Specimen
especially for new adhesives. If this is the case, use the
approximate times given in Table 5.
NOTE 3—Twenty-five percent strength loss is a convenient level. Any
type of experiment to be performed (service life, rate compari-
amount of loss can be defined as failure as long as it is agreeable to the
son, or quality control):
partiesrequiringthistestanditisdefinedinthereport.Higherpercentages
Service life estimation 10 panels,
of loss require longer exposure times.
127 by 305 mm
Rate comparison:
10.2.3 Place the five groups (see Note 4) in the aging
One adhesive/different exposures
exposure. At the end of the first aging interval, withdraw the
(10 panels, 127 by 305 mm)
Two adhesives/same exposure
first group of specimens, recondition to EMC, and test as
(10 panels, 63 by 305 mm)
described in 10.1.1 and 10.1.2. Based on this test, project the
(for each adhesive)
time to reach 25% loss. If necessary,
...
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