1、Designation: D4502 92 (Reapproved 2011)Standard Test Method forHeat and Moisture Resistance of Wood-Adhesive Joints1This standard is issued under the fixed designation D4502; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 The purpose of this test method is to estimate theresistance of adhesive-bonded joints to thermal and hydrolyticde
3、gradation.1.2 This test method is primarily for wood-to-wood jointsbut may be applied to joints of wood to other materials.1.3 The effects of chemicals such as fire retardants, preser-vatives, and extractives in the wood upon joint degradationresistance can be estimated.1.4 This test method does not
4、 account for the effects ofstress, the other principal degrading factor, nor does it accountfor cyclic or variable temperature or moisture levels.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this stan
5、dard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D897 Test Method for Tensile Properties of AdhesiveBondsD905 Test Method for Strength Properties of AdhesiveBonds in Shear by
6、Compression LoadingD907 Terminology of AdhesivesD2304 Test Method for Thermal Endurance of Rigid Elec-trical Insulating MaterialsD2307 Test Method for Thermal Endurance of Film-Insulated Round Magnet WireD2339 Test Method for Strength Properties of Adhesives inTwo-Ply Wood Construction in Shear by T
7、ension Loading2.2 IEEE Standard:IEEE No. 1 General Principles for Temperature Limits inthe Rating of Electrical Equipment33. Terminology3.1 Definitions3.1.1 For definitions of terms used in this test method, referto Terminology D907.3.2 shear strength, nin an adhesive joint, the maximumaverage stres
8、s when a force is applied parallel to the joint.3.2.1 DiscussionIn most adhesive test methods, the shearstrength is actually the maximum average stress at failure ofthe specimen, not necessarily the true maximum stress in thematerial.4. Summary of Test Method4.1 The degradation of adhesive joints is
9、 a physicochemicalprocess. The speed of degradation is related to the levels oftemperature, moisture (and other chemicals), and physicalstress to which the joint is exposed. This test method is basedon the principles of chemical kinetics and uses the Arreheniustemperature dependence relationship to
10、estimate the long-termeffects of heat and moisture at the service temperature.4.2 Specimens whose unaged properties have been esti-mated by control tests are subjected to an accelerated thermalor hydrolytic aging environment in groups. Aging is acceler-ated by using elevated temperature. Periodicall
11、y, a group ofspecimens is removed from the aging environment and tested.The estimated property after aging and the time of aging arerecorded.After several groups have been tested in this manner,the rate of property loss in the aging environment can beestimated. This basic experiment is repeated at s
12、everal otherelevated temperatures, and the rates of property loss at thosetemperatures estimated. The rate of property loss relationshipto temperature is estimated. This relationship can be extrapo-lated to lower service temperatures for estimating service life.4.3 This test method employs a smaller
13、 version of the TestMethod D905 block shear specimen, but other shear strength ortensile strength specimens may also be used.1This test method is under the jurisdiction of ASTM Committee D14 onAdhesives and is the direct responsibility of Subcommittee D14.70 on ConstructionAdhesives.Current edition
14、approved Jan. 1, 2011. Published January 2011. Originallyapproved in 1985. Last previous edition approved in 2004 as D4502 92 (2004).DOI: 10.1520/D4502-92R11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of A
15、STMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Institute of Electrical and Electronics Engineers, Inc. (IEEE),445 Hoes Ln., P.O. Box 1331, Piscataway, NJ 08854-1331, http:/www.ieee.org.1Copyright ASTM International, 100 Barr Harbor Dr
16、ive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5. Significance and Use5.1 This test method can serve as a useful tool for durabilityassessment and service life forecasting.5.1.1 This test method can be used to measure the effects ofheat and moisture and the effect of their interac
17、tion onadhesives and bonded joints. Knowledge of these effects isuseful to an adhesive formulator or manufacturer. Moist heataging is particularly useful for determining the effects of acidicadhesive systems on the hydrolysis of wood adherends.5.1.2 This test method provides a means of comparing the
18、rate of degradation of an unknown adhesive-adherend combi-nation to the rate of degradation of a known combination inthermal or hydrolytic aging environments. Such a comparisoncan be useful to adhesive manufacturers for introducing a newproduct to the market and for helping designers selectingadhesi
19、ves.5.1.3 This test method does not duplicate any naturalservice environment, but it does provide a means of estimatingthe service life of joints in similar environments. Service-lifeestimates are useful to designers of bonded structures orstructures using bonded products.5.2 Service-life estimates
20、rely on the assumption that thechemical degradation mechanism is the same at the elevatedaging temperatures as at the service temperature. However, thismay not be true in every case. This possibility, together withthe variability in specimen preparation, in the aging exposures,and in the strength me
21、asurements, require that caution be usedin accepting the estimate of service life.6. Apparatus6.1 Aging OvensOvens are required that are capable ofcontrol within 62 % of specified exposure temperaturethroughout the chamber for extended periods of time (60.5Ccontrol is desirable).4The ovens must be c
22、apable of operatingat temperatures from 60 to 175C. The oven must have aninternal capacity for up to 100 specimens well-spaced andsupported on racks to allow free air flow.6.2 Environmental ChambersChambers for moist-heataging must be capable of 60.5C temperature and 0.5 %relative humidity control u
23、niformly throughout the chamber.The chamber must be capable of operating at temperaturesfrom 60 to 90C and relative humidity from 60 to 80 %. Thechamber must have the capacity for up to 100 specimenswell-spaced and supported on racks to allow free air flow.6.3 Moist Aging JarsHeat-resistant glass ja
24、rs are requiredto expose specimens to constant relative humidity and tem-perature over saturated salt solutions. Wide-neck canning jarswith volumes of 312 L (1 gal), rubber gaskets, and clamp lidshave proven satisfactory at temperatures of 100C (212F) andbelow. The jars must have a platform inside (
25、without legs) tosupport specimens above the saturated salt solution. A 6-mm(14-in.) diameter bead of silicone sealant around the insidesurface of the jar and about 5 cm (2 in.) above the bottomprovides a ledge to support the platform. The platform must beperforated to permit free-flow of water vapor
26、. It may be cutfrom any material that is resistant to corrosion, heat, andmoisture. Perforated high-density hardboard has proven satis-factory. The platform must be cut in half to pass through theneck of the jar. An aging jar with platform is shown in Fig. 1.The jars must be placed in an aging oven,
27、 such as described in5.1, to achieve the required temperature.6.4 Water BathsConstant-level water baths capable ofcontrol to within 0.5C of the desired temperature are required.The baths must be able to contain 100 specimens.6.5 Testing MachineThe testing machine shall have acapacity of not less tha
28、n 3000 kg (6210 lbf) in compression.The machine shall be capable of maintaining a uniform rate ofloading such that the load may be applied with a continuousmotion of the movable head to the maximum load at a rate of10.0 6 5 mm/min (0.40 in./min) with a permissible variationof + 0.5 %.6.6 Shearing To
29、olA shearing tool similar to the toolpictured in Test Method D905 is satisfactory. The tool musthave a self-aligning seat to ensure uniform lateral distributionof the load.7. Materials7.1 Adhesive to Be Tested:7.2 JointsWood for wood-to-wood joints or joints ofwood to metal or plastic shall be free
30、of defects such as knots,cracks, short-grain and sharp-grain deviations, or any discol-orations or soft spots indicative of decay. Generally, a high-density uniform-textured wood is desirable so that the maxi-mum stress will be placed on the adhesive joint during testing.The standard shall be hard m
31、aple (Acer saccharum or Acernigrum) having a minimum specific gravity of 0.65 (based onoven-dry weight and volume). Other species may be usedwhere evaluation of the adhesives performance in contact withthat species is a specific requirement.7.3 Saturated Salt SolutionsA constant relative humidityat
32、a given temperature can be maintained in sealed aging jarsby a saturated aqueous solution in contact with an excess of thesolid phase of a specific salt. Tables are available that showrelative humidities at given temperatures for many salts.5Sodium chloride is recommended. A saturated solution ofsod
33、ium chloride will produce a relative humidity of 73 to 76 %over the temperature range from 40 to 100C. This translates towood moisture content in the approximate range from 9 to13 %.8. Test Specimens8.1 A modified block shear specimen (Fig. 2) is suggested.The specimen is similar to the specimen of
34、Test Method D905,but its smaller size allows more specimens to fit in the agingchambers. Other specimens such as used in Test Method D897or Test Method D2339 are also satisfactory. If a type from TestMethod D2339 is selected, then use 6.5-mm (14-in.) lumber foreach lamina, and increase the specimen
35、length to 130 mm (5.1in.) while maintaining the 25.4-mm (1-in.) overlap. Other4Millett, M.A., Western, L. J., and Booth, J. J., “AcceleratedAging of CellulosicMaterials: Design and Application of a Heating Chamber,” TAPPI, Vol 50, No. 11,1967, pp 74A80A.5Dean, J. A., ed., Langes Handbook of Chemistr
36、y, 12th ed., McGraw-HillBook Co., Inc., 1978.D4502 92 (2011)2bonded joints or products may also be tested if a suitablespecimen can be devised.8.2 Condition the wood at 23 6 2C (73.4 + 3.6F) andrelative humidity of either 30 or 65 %, or other conditions,depending on the adhesive manufacturers requir
37、ement.8.3 Prepare modified shear block specimens as described inTest Method D905 with the following exceptions:8.3.1 Cut rough 25.4-mm (1-in.) lumber into 127 or 63 by305-mm (5 or 212 by 12-in.) billets as required by Section 9.Saw each billet in half through the thickness using a bandsaw.Joint the
38、surface of each half that is to be bonded and plane to8-mm (516-in.) thickness. (Note 1) Bond the billets as describedin Test Method D905.NOTE 1If during strength testing specimens fail in compressionparallel to the grain at the ends, the laminae thickness should be increasedfrom8mm(516 in.) to 9.5
39、mm (38 in.) or greater, as necessary.8.3.2 After bonding, trim one edge and one end of eachpanel. Then cut two rows of five specimens each from the 63by 305-mm (212 by 12-in.) panels, as shown in Fig. 3, or fourrows of five specimens each from the 127 by 305-mm (5 by12-in.) panels.NOTE 2The adhesive
40、 should be thoroughly cured by hot pressing,oven heating, high-frequency heating, or whatever method is appropriate.Undercured adhesives cause unwanted results in the early stages ofelevated temperature aging.8.4 Mark each specimen using a template before cutting toindicate the panel and position in
41、 the panel.9. Sampling9.1 Sample Size:9.1.1 If using the modified block shear specimen, preparethe following numbers and sizes of panels, depending on theFIG. 1 Moist Aging Jar with a Shelf for Aging Specimens Over a Saturated Salt SolutionD4502 92 (2011)3type of experiment to be performed (service
42、life, rate compari-son, or quality control):Service life estimation 10 panels,127 by 305 mmRate comparison:One adhesive/different exposures(10 panels, 127 by 305 mm)Two adhesives/same exposure(10 panels, 63 by 305 mm)(for each adhesive)Quality control (10 panels,63 by 305 mm)9.1.2 If using some othe
43、r specimen, prepare 10 panels, eachpanel large enough to yield the following minimum number ofspecimens depending on the type of experiments to be per-formed:Service life 26Rate comparison:One adhesive/different exposure 22Two adhesives/same exposure 12Quality control 39.2 Sampling Method:9.2.1 In a
44、 given experiment (service life, rate comparison, orquality control) pair the 6.5 by 127 (or 63) by 305-mm billetsrandomly for bonding into panels.9.2.2 Distribute the specimens from each panel according tothe plan shown in the appropriate table for the experiment.Service-life estimation Table 1Rate
45、 comparison Table 2Quality control Table 39.2.3 The distribution of specimens for subsequent dataanalysis is summarized by the block experimental designsshown in Table 4 for each of the experiments.10. Procedure10.1 Initial Strength:10.1.1 Condition the control specimens to equilibriummoisture conte
46、nt (EMC) at 23 + 2C and 50 6 2 % relativehumidity or other conditions as agreed upon by the partiesinvolved. 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 theshear tool with the universal test machine cr
47、osshead moving at10 + 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 theconditioned environment during testing. Record the strengthand estimated percentage of wood failure for each specimen.10.2 Service Life Estimate:10.2.1 Aging tempera
48、tures are given in Table 4. For a giventemperature/moisture condition, mount five groups (10 speci-mens per group) on suitable racks for dry aging, place in jarsfor moist aging, or string each group on stainless steel wire forwet aging.10.2.2 Estimate five aging intervals that will produce ap-proxim
49、ately equal strength decrements to a total strength lossof 25 to 30 % from the initial strength for each of the five agingtemperatures. Previous aging experience may not be available,especially for new adhesives. If this is the case, use theapproximate times given in Table 5.NOTE 3Twenty-five percent strength loss is a convenient level. Anyamount of loss can be defined as failure as long as it is agreeable to theparties requiring this test and it is defined in the report. Higher percentagesof loss require longer exposure times.10.2.3 Place the
