ASTM D411-1998(2003) Standard Test Methods for Shellac Used for Electrical Insulation《电绝缘试验用紫胶片的标准试验方法》.pdf

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1、Designation: D 411 98 (Reapproved 2003)An American National StandardStandard Test Methods forShellac Used for Electrical Insulation1This standard is issued under the fixed designation D 411; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re

2、vision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover tests for shellac in the drybutton or powder form to be used for electri

3、cal insulatingpurposes. Typically, shellac is used as a bonding agent for micasplittings and reconstituted mica paper products, or as a coatingor adhesive for other material.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibil

4、ity 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.NOTE 1There is no similar or equivalent IEC standard.2. Referenced Documents2.1 ASTM Standards:2D 29 Test Methods for Sampling and Testing La

5、c ResinsD 1711 Terminology Relating to Electrical InsulationD 5032 Practice for Maintaining Constant Relative Humid-ity by Means of Aqueous Glycerine SolutionsD 6054 Practice for Conditioning Electrical Insulating Ma-terials for TestingE 104 Practice for Maintaining Constant Relative Humidityby Mean

6、s of Aqueous Solutions3. Terminology3.1 Definitions: For definitions of terms used in this stan-dard, refer to Terminology D 1711.4. General Tests4.1 Each of the following tests shall be made in accordancewith the procedures described in Test Methods D 29:4.2 Sampling,4.3 Insoluble Matter,4.4 Iodine

7、 Number,4.5 Moisture Content,4.6 Wax,4.7 Ash, and4.8 Orpiment (Native arsenic trisulfide).POLYMERIZATION TIME5. Significance and Use5.1 Polymerization time provides a measure of time duringwhich shellac retains its plasticity and flow properties at thespecified temperature before gelling or polymeri

8、zing to thetough rubbery insoluble form. This test is important in deter-mining the quality of different lots, useful shelf-life, batchuniformity, and processing characteristics of shellac.6. Apparatus6.1 Test Tubes and Wire RackTwo 18-mm outside diam-eter glass test tubes, supported by a wire rack

9、to a depth of 100mm when placed in an oil bath. The test tubes must besupported and maintained in a vertical position. The rack shallbe constructed so as to permit free circulation of oil around thetest tubes.6.2 Oil BathThe oil bath shall be constructed with heat-ers, temperature control, and means

10、 of circulation to maintainthe oil or other liquid at a temperature of 150 6 1C at allpoints within the bath. The oil or other liquid used shall beappropriate for the design of the bath and for safety at the testtemperature. The bath shall be equipped with a thermometer, orother indicator or recorde

11、r, to indicate the oil temperaturewithin 61C.6.3 Glass RodA smooth glass rod about 3 mm in diameterand approximately 200 mm long. The end of the glass rodwhich is to be immersed in the shellac shall be fire polished toa smooth round end.NOTE 2A smooth glass rod about 5 mm in diameter and approxi-mat

12、ely 200 mm long with an indicator mark at the top to indicatemovement may be used. Flatten slightly the diameter of the glass rod forapproximately 3 mm length at the end which is immersed in the shellac.The purpose of the flattened rod is to provide a more positive feel of thetwist back and rubbery

13、character at the end point. If this alternative isused, it must be specified in the report.1These methods are under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and are the direct responsibility ofSubcommittee D09.01 on Electrical Insulating Varnishes, Powd

14、ers, and Encapsu-lating Compounds.Current edition approved Nov. 10, 1998. Published January 1999. Originallyapproved in 1935. Last previous edition approved in 1998 as D 411 98.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. F

15、or 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.6.4 Timer, for indicating elapsed time in minutes andseconds.7. Test

16、Specimens7.1 For each test specimen use 4.00 6 0.01 g of shellac,dried as specified in 8.2.7.2 Prepare two specimens from each sample.8. Conditioning8.1 Crush samples of shellac on clean paper, mix well, andthen dry as described in 8.2.8.2 For each sample to be tested, evenly spread 9 to 10 g ofthe

17、sample in a flat-bottom dish about 50 mm in diameter.Desiccate over anhydrous calcium chloride for at least 24 h atroom temperature, or dry in a forced-convection oven at atemperature of 40 6 2C for 16 to 20 h.8.3 After drying, immediately transfer the sample to a clean,dry, tightly stoppered bottle

18、, and allow to cool. Do not open thebottle except when a specimen is being removed for test.9. Procedure9.1 Transfer a specimen of shellac from the stoppered bottleto the 18-mm glass test tube. Insert the tube and hold securelyin a vertical position in the test rack. Place the rack in the oilbath ha

19、ving a test temperature of 150 6 1C maintainedthroughout the test.9.2 Start the timer when the test tube enters the oil bath.9.3 Using the glass rod, stir the specimen gently until thespecimen melts, but not for more than 3 min. Do not stir after3 min.9.4 Beginning 4 min after immersion of the test

20、tube, and atthe end of each subsequent minute, give the glass rod a slighttwist, turning approximately 90 each time. In the early stagesof the test, and before the polymerization point is reached, theglass rod will remain in the position to which it has beenturned. When, however, the shellac takes o

21、n a rubbery set,there will be a definite turning or twisting back of the rodfollowing the 90 twist. This is the end point.NOTE 3In the early stages of the test there may be a tendency for theglass rod to move back slowly after twisting with the fingers. This slightmovement should not be confused wit

22、h the definite “twist-back” observedwhen the end point is reached.10. Polymerization Time10.1 Record as the polymerization time, the elapsed time inminutes, from the time of entry of the specimen into the bathand including the 3-min stirring period, until the first “twist-back” of the glass rod is n

23、oted.11. Report11.1 Report the following information:11.1.1 The polymerization time in minutes for each speci-men, and11.1.2 The average of the values in 11.1.1.12. Precision and Bias12.1 This test method has been in use for many years, andno determination of precision has been made, and no work isp

24、lanned to develop such information.12.2 This test method has no bias, because the test valuesare defined solely in terms of this method.FLOW TEST13. Summary of Test Methods13.1 These tests determine the flow of shellac when sub-jected to 1006 1C under the conditions of test specifiedherein. These me

25、thods consist of melting a specimen of groundshellac in a graduated test tube and then tilting the tube to aspecified angle while maintained at 1006 1C in order topermit the shellac to flow down the tube.13.2 Two methods are provided as follows:13.2.1 Method AIn this method the time required for the

26、shellac to flow specified distances along the test tube ismeasured, and13.2.2 Method BIn this method the total distance theshellac flows along the test tube in a specified time ismeasured.14. Significance and Use14.1 The rate at which shellac flows down an inclined planeunder standard conditions can

27、 be used to determine the flowvariation that occurs between different types, grades, or lots ofshellac.14.2 Flow tests are sensitive to atmospheric conditions, theflow being greater under humid conditions, and less with lowhumidity. It is essential to carry out the tests in a conditionedatmosphere o

28、r as quickly as possible after removal from theconditioning atmosphere so as to minimize errors due to theeffects of atmospheric conditions.15. Apparatus15.1 Suitable apparatus for both Methods A and B aredescribed in Annex A1.15.2 Any apparatus that will provide for accurate tempera-ture control, c

29、orrect positioning of the test tubes, and for visualobservation of flow when required may be used.16. Conditioning16.1 For each specimen use 2.0 6 0.1 g of shellac, groundto pass a No. 20 sieve. Prepare two specimens from eachsample.16.2 Spread the specimens out in shallow vessels. Conditionfor at l

30、east 24 h in a standard laboratory atmosphere inaccordance with Practice D 6054. Alternatively, condition forthe same time in a desiccator over an aqueous glycerinesolution adjusted to give 50 % relative humidity, in accordancewith Practice D 5032, or over a saturated solution of magne-sium nitrate

31、(52.9 % relative humidity), in accordance withPractice E 104.16.3 Test, in accordance with Section 18 or Section 21, inthe standard atmosphere, or immediately upon removal of thespecimens from the conditioned atmosphere specified in 16.2.17. Preparation of Specimens17.1 Place the two specimens of sh

32、ellac in separate glasstest tubes with care being taken that the specimen in each tubeis at the bottom and that none of the powdered shellac adheresD 411 98 (2003)2to the walls of the glass tube. Read the top level of the dryshellac in each tube on the millimetre graduated scale. Clampthe tubes cont

33、aining the specimens in place in the testingfixture (see Section 15 and Fig. A1.1).17.2 Insert the testing fixture, with the glass test tubes in avertical position, into the oil bath maintained at the testtemperature of 100 6 1C.17.3 The top surface of the specimen in each tube should belevel and at

34、 right angles to the walls of the tube.17.4 Allow the specimens to melt for 3 min.METHOD A18. Procedure18.1 At the end of the 3-min melting period, place each testtube at an angle of 15 from the horizontal, with the corkedends down (see 15.1 and Fig. A1.2), and with the breather tubeextending above

35、the level of the oil bath. Make the changefrom the vertical position to the flow position as quickly aspossible. With the oil bath maintained at the test temperature of100 6 1C, record the total time required for the shellac ineach tube to flow from the initial level of the shellac to eachcentimetre

36、 marking along the tube. Discontinue the test in eachtube when the flow is 9 cm or the total time is 20 min.19. Report19.1 Report the following information, for tests usingMethod A:19.1.1 The elapsed time for each centimetre of flow for eachspecimen;19.1.2 A plot of the data reported in 19.1.1, with

37、 time as theabcissa and flow as the ordinate;19.1.3 The angle of the test tubes during the test; and19.1.4 The temperature and relative humidity of the atmo-sphere within which the test was conducted.20. Precision and Bias20.1 This test method has been in use for many years, andno determination of p

38、recision has been made, and no work isplanned to develop such information.20.2 This test method has no bias, because the test valuesare defined solely in terms of this method.METHOD B21. Procedure21.1 At the end of the 3-min melting period, place each testtube at an angle of 15 from the horizontal,

39、with the corkedends down (see 21.2 and Fig. A1.2) and with the breather tubeextending above the level of the oil bath. Make the changefrom the vertical position to the flow position as quickly aspossible. With the oil bath maintained at the test temperature of100 6 1C, allow the test tubes to remain

40、 in the bath in thisposition for 12.0 6 0.1 min.21.2 Remove the test tubes immediately, place in a verticalposition, cool, wipe, and measure the flow of the shellac ineach tube by reading the distance between the initial point andthe end of the flow tongue. Disregard the “feather” at the verytip of

41、the tongue.NOTE 4This “feather,” caused by separation of wax from the shellac,is more noticeable with some shellacs than with others. It can readily bedistinguished from the main body of shellac as it is always of a differentcolor.22. Report22.1 Report the following information for tests usingMethod

42、 B:22.1.1 Flow, expressed in millimetres, for each specimen;22.1.2 The average of the values in 22.1.1;22.1.3 The angle of the test tubes during the test period; and22.1.4 The temperature and relative humidity of the atmo-sphere within which the test was conducted.23. Precision and Bias23.1 This tes

43、t method has been in use for many years, andno determination of precision has been made, and no work isplanned to develop such information.23.2 This test method has no bias, because the test valuesare defined solely in terms of this method.24. Keywords24.1 bonded mica; electrical insulation; flow; p

44、olymeriza-tion time; shellacD 411 98 (2003)3ANNEX(Mandatory Information)A1. DESCRIPTION OF APPARATUS FOR DETERMINING THE FLOW OF SHELLACA1.1 The apparatus shown in Fig. A1.1 and Fig. A1.2 isillustrative of what may be used to determine the flow ofshellac. Other apparatus, differing in detail from th

45、at shown inthe figures, may be used, but must include the followingfeatures and capabilities:A1.1.1 Test Tubes Two test tubes, A, 120 to 130 mm inlength, 25 mm outside diameter, preferably graduated in 5 mmdivisions, beginning 11 mm from the outside bottom andextending upward to 100 mm from the bott

46、om.A1.1.1.1 The test tubes shall be equipped with tightly-fittingstoppers, through which extend breather tubes, B.A1.1.2 SupportA fixture, C, for holding the test tubes inthe correct position, and allowing for insertion into andremoval from the bath and for accurate rotation of the axes ofthe tubes

47、to the proper angle.A1.1.3 Oil BathA bath of the proper size to accommodatethe fixture with the test tubes, and capable of maintaining atemperature of 100 6 1C at all points in the bath during theperiod of the test.A1.1.3.1 The bath shall be equipped with a temperatureindicator or recorder calibrate

48、d to the precision specifiedabove.A1.1.3.2 The liquid used shall have a sufficiently high flashpoint to operate safely at the test temperature.A1.1.3.3 If Method A is to be used, the construction of thebath and the selection of the liquid in the bath shall be such asto permit the required visual obs

49、ervations.FIG. A1.1 Flow Test Fixture Showing Essential Parts with TestTubes in Vertical PositionFIG. A1.2 Apparatus Arranged with Tubes in Inclined Position forImmersion in Bath for Flow TestD 411 98 (2003)4ASTM 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 riskof infringement of such rights, are entirely their own responsibility.This standard is