D 2471

Designation: D 2471 ± 99

Standard Test Method for

Gel Time and Peak Exothermic Temperature of Reacting Thermosetting Resins

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This standard is issued under the ®xed designation D 2471; 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 (e) indicates an editorial change since the last revision or reapproval. 1 This   test   method   is   under   the   jurisdiction   of   ASTM Committee D­20 on Plastics and is the direct responsibility of 1. Scope * Subcommittee D20.16 on Thermosetting Materi­als. Current edition approved Nov. 10, 1999. Published February 1.1 This   test   method   covers   the 2000.  Originally  published  as   D  2471  ±   66  T.  Last  previous determination   of   the   time   from   the   initial edition D 2471 ± 94. 2 mixing   of   the   reactants   of   a   thermosetting Annual Book of ASTM Standards, Vol 08.01. 3 Annual Book of ASTM Standards, Vol 14.03. plastic   composition   to   the   time   when

solidi®cation   com­mences,   under   conditions approximating the conditions of use. This test method also provides a means for measuring the maximum   temperature   reached   by   a   reacting thermosetting   plastic   composition,   as   well   as the time from initial mixing to the time when this   peak   exothermic   temperature   is   reached. This test method is limited to reacting mixtures exhibiting gel times greater than 5 min. 1.2 The   values   stated   in   either   SI   units   or inch­pound units are to be regarded separately as standard. The values stated in each system may   not   be   exact   equivalents;   therefore,   each system shall be used independently of the other. Combining   values   from   the   two  systems   may result in nonconformance with this test method. 1.3 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   appro­ priate   safety   and   health   practices   and determine   the   applica­bility   of   regulatory limitations prior to use. 1.4 This   test   method   applies   to   adhesives, caulks,   sealants,   encapsulating   and   potting compounds, and similar materials, as described in Table 1. NOTE  1ÐThere is no similar or equivalent ISO  standard.

2. Referenced Documents 2.1  ASTM Standards: D 883  Terminology Relating to Plastics2 E 1  Speci®cation for ASTM Thermometers3 3. Termonology 3.1  De®nitions: 3.1.1 GeneralÐDe®nitions of plastics terms  used in this test method are in accordance with  Terminology D 883.

4. Signi®cance and Use 4.1 Since   the   gel   time   and   the   peak exothermic   temperature   of   a   reacting thermosetting plastic composition vary with the volume   of   material   mixed   at   one   time,   it   is essential   that   the   volume   be   speci®ed   in   any determination.   By   selection   of   an   appropriate volume, gel time and peak exothermic data may be   obtained   in   sufficiently   precise   and reproducible   form   or   application   evaluation, quality control, and material character­ization of a   thermosetting   plastic   composition.   For   most meaningful results, the cross sectional  area of the material  being examined, as well  as other conditions   of   testing,   should   approximate   as closely as possible the conditions of use of the material. 4.2 This   test   method   is   operator­dependent since it is simple to perform. It is of value for determining conditions required to produce an end product. 5. Apparatus 5.1 Sample Containers, to contain a volume of   reacting  thermosetting   plastic   in   a   cross sectional area representative of the conditions of application   of   the   material.   Suggested   con­ tainers are the following:

5.1.1  Aluminum  Foil   Dish,   approximately   7 cm (2.75 in.) in diameter and 1.4 cm (0.56 in.) deep. 5.1.2  Paint   Can,   open­top,  1¤4­pt, approximately 6.00 cm (2.375 in.) in diameter by 5.00 cm (2 in.) deep. 5.1.3  Paint   Can,   open­top,   1­pt, approximately 8.2 cm (3.25 in.) in diameter by 9.5 cm (3.75 in.) deep. 5.2 Wooden   ProbeÐApplicator   sticks approximately 0.24 cm (0.09 in.) in diameter by 15.2   cm   (6.00   in.)   long   have   been   found satisfactory. 5.3 Nonconducting   Surface,   such   as   dry wood or corrugated casing. 5.4 Temperature Measuring Devices: 5.4.1  Any  temperature  recorder   or  indicator utilizing   ex­pendable   thermocouples   and accurate   to   approximately  61   %   of   scale   is adequate   for   all   but   the   most   precise characterizing tests. NOTE  2ÐPrevious   versions   of   this   test   method   have contained   a   paragraph   detailing   the   possible   use   of   a thermometer   for   temperature   determination.   Use   of   a thermometer is no longer recommended due to potential hazard of breakage as well as loss of the thermometer due to imbedment in the curing mass.

*A Summary of Changes section appears at the end of this standard. Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.

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5.5 Temperature­Controlled Bath, capable of holding the temperature within 60.1°C. 5.6 Stop Watch. D 2471 TABLE 1 Sampl e Volum es Relate d to Applic ation Application Thin-section applications, adhesives, tooling surface coats, dip coatings, laminating materials, impregnants, caulking and sealing compounds, small-volume encapsulating, and potting compounds Surface-casting systems, larger-volume encapsulating, and potting compounds Laminating materials, surface-casting systems Mass-casting systems, potting compounds, quality control of any material normally mixed and used in this quantity

6. Conditioning 6.1 Place   all   components   in   suitable containers in the temperature­controlled bath at the test temperature for at least 4 h prior to being tested, or for however much longer time is needed for all parts of the sample to   reach   the   test   temperature   within   0.5°C (1.0°F). Condition all containers and probes to be used in the test at the test temperature at the same time. 6.2 If experience has shown that less than 4 h conditioning   is   required   for   all   parts   of   the sample to reach the test temperature, report the time of conditioning. 7. Procedure 7.1 When   all   components   have   reached   the test   temperature   (Note   2),   agitate   each component slowly and separately with a stirring rod or mixing paddle for at least 3 min, avoiding the entrapment of air. NOTE 3ÐThe test temperature shall be 23.0 6 1.0°C  (73.4 6 1.8°F), unless otherwise speci®ed.

7.2   Combine   the   components   in   the recommended   ratio   to   provide   a   convenient working quantity. NOTE  4ÐFor  accurate  measurements of  quantities  of components,   the   individual   components   should   be weighed, using the speci®c gravities of the respective components to determine the weights needed to make up the required volume. NOTE  5ÐTable   1   lists   suggested   test   volumes   and working   volumes   for   materials   to   be   used   in   various applications.

7.3 Start   the   stop   watch,   and   mix   the components thor­oughly for 3 min, avoiding air entrapment by slow agitation with a stirring rod or mixing paddle. To avoid transfer of heat, do not   hold   the   container   by   hand   during   the mixing operation. Record the start of mixing as the ªstarting time.º 7.4 Transfer the appropriate test volume (see Note 4) of the mixed components immediately to   an   appropriate   sample   container   which   has been   previously   conditioned   at   the   test temperature. 7.5 Place   the   sample   container   on   a nonconducting   surface   in   still   air   at   the   test temperature. NOTE  6ÐIf   it  is  desirable,  because   of   the   nature  of   the application,   to   use   a   conducting   surface   of   high   heat capacity   instead   of   a   nonconducting   surface,   include   a description of the surface in the report. If, because of the

nature of an application, it becomes desirable to measure gel   time   and   peak   exothermic   temperature   in   a temperature­controlled   bath,   the   condi­tions   used  must be  noted  in  the   report.  WarningÐGel   times  and  peak exothermic   temperatures   observed   in   a   temperature­ controlled   bath   are   functions   of   the   total   system, including the quantity and nature of the coolant, as well as the nature of all components inserted into the bath. These   properties   are  not  functions   of   the   resincuring agent system alone.

7.6 Insert   a   thermocouple,   or   other temperature­measuring   device,   into   the geometric   center   of   the   reacting   mass,   and record the observed temperature changes to the end of the test. 7.7 Every 15 s, probe  the  center surface of the   reacting  mass,   with   the   applicator   stick perpendicular to the material surface. NOTE 7ÐUse of a mechanical gel time meter is feasible in the larger sample sizes. However, the results obtained with  the  various  mechanical  gel  time  meters  have not been consistent with results obtained with hand probing. If   a   mechanical   gel   time   meter   is   used,   include   this information in the report.

7.8 When   the   reacting   material   no   longer adheres to the end of a clean probe, record the ªgel timeº as the elapsed time from the start of mixing. 7.9 Continue   recording   the   time   and temperature until the temperature starts to drop. Record the highest temperature reached as the ªpeak   exothermic   temperature.º   Record   the ªpeak exothermic timeº as the elapsed time from the start of mixing. 8. Report 8.1 Report the following information: 8.1.1 Identi®cation   of   the   thermosetting plastic composition being tested, 8.1.2 Time of conditioning, if less than 4 h, 8.1.3 Method   of   mixing   (by   hand   or mechanical mixer), 8.1.4 Volume of sample tested, 8.1.5 Thickness of sample tested, 8.1.6 Test temperature, to the nearest 1°C (or 2°F). 8.1.7 Gel time, to the nearest 0.5 min, 8.1.8 Peak   exothermic   temperature,   to   the nearest 1°C (or 2°F), and 8.1.9 Peak exothermic time, to the nearest 1 min. 9. Precision and Bias 9.1 The operator­dependent nature of this test  method does not lend itself to a meaningful  development of a precision

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D 2471

state ment. In additi on, the small numb er   of labor atorie s using this test meth od also precl udes attem pting to devel op such a state ment. 9.2 Ther e   are no stand ard refer ence mater ials upon whic h   to base an estim ate of bias for this test meth od.

10. K e y w o r d s

10.1 cau lks; gel time; peak exoth ermic temp eratur e; resin, therm osetti ng; seala nts

SUMMARY OF CHANGES This section identi ®es the

locatio n   of selecte d change s   to this test metho d.   For the conven ience of   the user, Comm ittee D­20 has highlig hted those change s   that may impact the use of   this test metho d. This section also may includ e descrip tions of   the change s   or reason s   for the change s,   or both. D 2471±99: (2) Added  summary of  changes  section. (1) Editorially  changed scope  for  clari®cation. (3) Changed SI  units statement. A S T M

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