1、Designation: D3929 03 (Reapproved 2010)1Standard Test Method forEvaluating Stress Cracking of Plastics by Adhesives Usingthe Bent-Beam Method1This standard is issued under the fixed designation D3929; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、case of revision, the year 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.1NOTECaptions of Figures 3, 4, 5, and 6 were corrected editorially in April 2010.1. Scope1.1 This te
3、st method describes a procedure for determiningthe compatibility of adhesives with plastics based on whetherthe adhesive causes cracking of stressed samples.1.2 Specimen configurations and test fixture designs aregiven.1.3 This test method is suitable for products in the form ofsheet or strip. It ca
4、n also be used on injection molded tensilespecimens or flexural bars.1.4 The values stated in SI units are to be regarded as thestandard. The inch-pound units given in parentheses are forinformation only.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with
5、 its use. It is theresponsibility of the user of this standard 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:2D638 Test Method for Tensile Properties of PlasticsD790 Test Methods
6、 for Flexural Properties of Unreinforcedand Reinforced Plastics and Electrical Insulating MaterialsD907 Terminology of Adhesives3. Terminology3.1 DefinitionsMany of the terms in this test method aredefined in Terminology D907.3.2 Definitions of Terms Specific to This Standard:3.2.1 cracking, na cont
7、inuous localized failure of theplastic, leading to loss of structural integrity.3.2.2 crazing, napparent fine cracks at or under thesurface of a plastic.3.2.2.1 DiscussionThis is a form of localized yielding ofthe plastic due to the combined action of stress and an attackingmedium. Initial crazing m
8、ay be detectable only by inspectionunder magnification.3.2.3 failure, nan arbitrary point defined by the initialdetection of cracks or crazes.4. Summary of Test Method4.1 This test method involves the qualitative determinationof the compatibility of adhesives with plastics by observing theeffect of
9、adhesives applied in the liquid state on stressed plasticspecimens. Bars of plastic are bent in a three-point loadingfixture to cause a predetermined initial tensile stress on thesurface of the bar. The liquid adhesive is then applied to thearea of maximum stress which is checked periodically forcra
10、zing or cracking.4.1.1 Due to the stress relaxation behavior of certain plas-tics, initial stress only can be determined and the stress levelmay decrease significantly during the course of the test.5. Significance and Use5.1 This test method is designed for obtaining a qualitativeestimate of the com
11、patibility of plastics and adhesives. Due tothe many process variables associated with the fabrication ofplastic parts, it is not possible to use this test as a substitute forcompatibility tests on actual parts.1This test method is under the jurisdiction of ASTM Committee D14 onAdhesives and is the
12、direct responsibility of Subcommittee D14.40 onAdhesives forPlastics.Current edition approved April 1, 2010. Published April 2010. Originallyapproved in 1980. Last previous edition approved in 2003 as D3929 03. DOI:10.1520/D3929-03R10E01.2For referenced ASTM standards, visit the ASTM website, www.as
13、tm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 The
14、detection of cracks or crazes may be determinedwith or without optical aid. Make comparisons only amongtests employing crack detection methods of equivalent sensi-tivity.6. Apparatus6.1 Test FixturesBent beam test fixtures (see Fig. 1)3aredesigned to place the specimen in three-point bending. Theamo
15、unt of deflection is adjustable as well as the loading span.Other fixtures may be used as long as specimen deflection isknown.6.2 The amount of deflection on the specimen is measuredby use of a dial gage indicator or a vernier caliper having adepth indicator (see Fig. 2). Use a measuring device capa
16、ble ofreading to 0.025 mm (0.001 in.).7. Test Specimen7.1 The preferred specimen is a flexural bar designed inaccordance with Test Methods D790.Depth 6.4 mm (14 in.)Width 13 mm (12 in.)Length 130 mm (5 in.)Loading Span 100 mm (4 in.)L/d 16/1Tensile bars, such as Type I in Test Method D638, can alsob
17、e used. Specimens of rectangular section may also be cut fromsheets or molded plastic articles.7.2 Mold specimens in a low-stress condition or anneal sothat molded-in stresses will not have a significant effect.7.3 Carefully cut or machine specimens in accordance withthe plastic manufacturers recomm
18、ended procedures to avoidintroducing stresses at machined surfaces.8. Procedure8.1 Place the plastic test specimen in the test fixture at therequired loading (see Fig. 6).8.2 Apply adhesive to be tested to the center point on thelength of the loaded specimen. Cover a specimen length ofapproximately
19、25 mm (1 in.). In general, apply the adhesiveonly once, as would be the case in an actual end-use applica-tion.8.2.1 If the adhesive contains a solvent, allow it to evaporateat a normal rate.8.2.2 If the adhesive is a curing type, cure in a normalfashion.8.2.3 If the adhesive is a hot melt, apply at
20、 the normalapplication temperature and then allow to cool. This is a lesssevere condition than would occur if the adhesive werecontinually applied, but is more consistent with situations thatoccur in actual adhesive use.8.3 Control SpecimensConcurrently run one controlspecimen with the test specimen
21、s in the same location. Exces-sive molded-in stresses or airborne solvent vapors may causestress cracking even without application of adhesive.9. Stress Calculations9.1 The equation given below is valid only for specimens ofrectangular cross section at stresses below the elastic limit ofthe material
22、. The deflection is based on initial stress only. Thelevel of stress will normally decrease with time as the plasticundergoes relaxation. Deflection is calculated based on thedesired stress level as follows:D 5 SL2/6 dE (1)where:D = deflection, m (in.),S = stress, Pa (psi),L = loading span, m (in.),
23、d = specimen depth, m (in.), andE = modulus of the plastic, Pa (psi).NOTE 1This equation holds for rectangular specimens only.9.2 If it is desired to run tests on the basis of constant strain,the following formula can be used:D 5rL26 d(2)where r = strain, m/m (in./in.).9.3 Tensile stress and strain
24、values represent the maximumlevel at the surface of the specimen in the area to whichadhesive is applied. This is mid-span in the three-point loadingarrangement.10. Choice of Test Conditions10.1 Suggested stress levels for testing are 7, 14, and 21MPa (1000, 2000, and 3000 psi). For initial screenin
25、g, 21 MPa(3000 psi) is recommended since incompatible adhesives willcause rapid crazing or cracking. Lower stress levels may beused for discerning finer differences in materials.3Detailed drawings are shown in Figs. 3-5. Also necessary to complete the testfixture are the following parts: 2 pieces at
26、 6 by 38 mm (14 by 112-in.) dowel pinsand 2 pieces of M40.7 (832 unc) by 32 mm (114-in.) socket head cap screws.FIG. 1 Test Fixture with Plastic Bar in PlaceD3929 03 (2010)1210.2 Testing can also be based on constant strain if this ismore meaningful for particular end-use applications.10.3 The test
27、duration is 5 days for adhesives that harden orcure. For adhesives that remain in the liquid state on thespecimens (for example, anaerobic adhesives), the test shouldbe extended to 10 days.10.4 Maintain environmental conditioning at 23 6 2C (736 3.5F), 50 6 5 % RH. Specify other conditions as agreed
28、 toby user and manufacturer.10.5 Since stress cracking is more likely to occur immedi-ately after application of the adhesive, it is desirable to observethe specimens at frequent intervals in the beginning of the test.A suggested observation schedule is as follows: 1 min, 5 min,1 h, 24 h, and daily
29、thereafter.11. Inspection of Specimens11.1 Determine the presence of cracks or crazes by carefulvisual observation.FIG. 2 Measurement of Test Bar Deflection with Depth Gage of Vernier CaliperFIG. 3 Test Fixture Frame(All dimensions in mm (in.) unless otherwise stated.)D3929 03 (2010)13NOTE 2Magnific
30、ation may be used upon agreement by user andmanufacturer.11.2 If adhesives are not transparent, remove sufficientadhesive to determine if cracks or crazes are present.12. Report12.1 Report the results of the test as the absence or presenceof cracks or crazes at a given stress level. If cracks or cra
31、zes arepresent, the time required for their occurrence is also reported.Report the following specific items:12.1.1 Specimen identification,12.1.2 Material name or specification code,12.1.3 Adhesive identification,12.1.4 Stress level,12.1.5 Type and orientation of specimen used and method offabricati
32、on (injection molded, tensile specimen, annealed, etc.),12.1.6 Detailed description of test environment (for ex-ample, temperature, humidity, exposure time), and12.1.7 Remarks concerning the size and appearance ofcracks or crazes may be included if significant.NOTE 3Indicate magnification techniques
33、 used for inspection, if any.13. Precision and Bias13.1 No information is presented about either the precisionor bias of Test Method D3929 for evaluating stress cracking ofplastics by adhesives since the test result is nonquantitative.14. Keywords14.1 adhesive compatibility; bent-beam; cracking; cra
34、zing;liquid adhesive; stress crackingASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the ri
35、skof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of th
36、is standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake
37、 your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by
38、 contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).FIG. 4 Test Fixture Center Loading Bar(All dimensions in mm (in.) unless otherwise stated.)FIG. 5 Test Fixture Top Plate(All dimensions in mm (in.) unless otherwise stated.)FIG. 6 Cut-Away View of Sample Mounted in Fixture(All dimensions in mm (in.) unless otherwise stated.)D3929 03 (2010)14
