1、Designation: D6289 08D6289 13Standard Test Method forMeasuring Shrinkage from Mold Dimensions of MoldedThermosetting Plastics1This standard is issued under the fixed designation D6289; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, 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.1. Scope*1.1 This test method is intended to measure shrinkage from mold cavity to molded dimensions of thermosettin
3、g plastics whenmolded by compression, injection, or transfer under specified conditions.1.2 This test method provides for the measurement of shrinkage of thermosetting plastics from their molds both initially (within16 to 72 h of molding) and as they age after aging (postshrinkage at elevated temper
4、atures).1.3 This method will give comparable data based on standard specimens and can not predict absolute values in actual moldedparts with varying flow paths, wall thicknesses, pressure gradiants and process conditions. Differences in mold shrinkage generallyis observed between the specimen geomet
5、ries described in this test method.1.4 Knowledge of the initial shrinkage of plastics is important for the construction of molds and knowledge of post moldingshrinkage is important for determining the suitability of the molding material for manufacturing thermosetting plastic componentswith accurate
6、 dimensions.1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to es
7、tablish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.NOTE 1This test method and ISO 2577-1984 are equivalent when bars of 120 mm length, 15 mm width, and 10 mm thickness are used forcompression molding; or flat, square plaques approxim
8、ately 120 by 120 by 4 mm are used for injection molding.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD796 Practice for Compression Molding Test Specimens of Phenolic Molding Compounds (Withdrawn 1992)3D883 Terminology Relating to PlasticsD1896 Practic
9、e for Transfer Molding Test Specimens of Thermosetting CompoundsD3419 Practice for In-Line Screw-Injection Molding Test Specimens From Thermosetting CompoundsD5224 Practice for Compression Molding Test Specimens of Thermosetting Molding CompoundsE691 Practice for Conducting an Interlaboratory Study
10、to Determine the Precision of a Test Method2.2 ISO Standards:4ISO 291 PlasticsStandard Atmospheres for Conditioning and TestingISO 295 PlasticsCompression Molding Test Specimens of Thermosetting MaterialsISO 10724 PlasticsThermosetting Molding MaterialsInjection Molding of Multipurpose Test Specimen
11、sISO 2577-1984 PlasticsThermosetting Moulding MaterialsDetermination of Shrinkage1 This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.09 on Specimen Preparation.Current edition approved April 15, 2008April 1, 2013. Publis
12、hed May 2008April 2013. Originally approved in 1998. Last previous edition approved in 20032008 asD6289 - 03.D6289 - 08. DOI: 10.1520/D6289-08.10.1520/D6289-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of
13、ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 The last approved version of this historical standard is referenced on www.astm.org.4 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:
14、/www.ansi.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users con
15、sult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken
16、, PA 19428-2959. United States13. Terminology3.1 GeneralDefinitions of terms applying to this test method appear in Terminology D883.3.2 Definitions:3.2.1 For the purpose of this test method, the following definitions apply:3.2.2 molding shrinkagethe difference in dimensions between a molding and th
17、e mold cavity in which it was molded, boththe mold and the molding being at 23 6 2C when measured.3.2.3 post-shrinkageshrinkage of a plastic product after molding, during post-treatment, storage or use.4. Significance and Use4.1 Compression MoldingIn compression molding, the difference between the d
18、imensions of a mold and of the molded articleproduced therein from a given material vary according to the design and operation of the mold. It is probable that shrinkage willapproach a minimum where design and operation are such that a maximum of material is forced solidly into the mold cavity orsom
19、e part of it, or where the molded article is hardened to a maximum while still under pressure, particularly by cooling. Incontrast, shrinkages are higher where the charge must flow in the mold cavity but does not receive and transmit enough pressureto be forced firmly into all its recesses, or where
20、 the molded article is not fully hardened when discharged. The plasticity of thematerial used affects shrinkage insofar as it affects the retention and compression of the charge.4.2 Injection MoldingIn injection molding, as in compression molding, the differences between the dimensions of the moldan
21、d of the molded article produced therein from a given material vary according to the design and operation of the mold. Thedifferences vary with the type and size of molding machine, the thickness of molded sections, the degree and direction of flow ormovement of material in the mold, the size of the
22、 nozzle, sprue, runner, and gate, the cycle on which the machine is operated, thetemperature of the mold, and the length of time that follow-up pressure is maintained. As in the case of compression molding,shrinkages will approach a minimum where design and operation are such that a maximum of mater
23、ial is forced solidly into themold cavity and where the molded article is hardened to a maximum while still under pressure as a result of the use of a runner,sprue, and nozzle of proper size, along with proper dwell.As in compression molding, shrinkages are higher where the charge mustflow in the mo
24、ld cavity but does not receive and transmit enough pressure to be forced firmly into all of the recesses of the mold.The plasticity of the material used affects shrinkage indirectly, in that the more readily plasticized material will require a lowermolding temperature.4.3 Transfer MoldingIn transfer
25、 molding, as in compression or injection molding, the difference between the dimensions ofthe mold and of the molded article produced therein from a given material vary according to the design and operation of the mold.It is affected by the size and temperature of the pot or cylinder and the pressur
26、e on it, as well as on mold temperature and moldingcycle. Direction of flow is not as important a factor.4.4 Materials StandardsAlways refer to material standards for special treatment prior to molding, molding conditions andspecial handling of the test specimens after molding. In the event the mate
27、rial standard is unavailable, contact the manufacturerfor these recommendations.4.5 UtilityMeasurement of batch-to-batch consistency in initial shrinkage from mold to molded dimensions is useful forevaluating the quality of thermosetting plastics.5. Sample Preparation5.1 Some materials require speci
28、al treatment before they are molded. Materials to be tested shall be prepared for molding inaccordance with the relevant material standard or the manufacturers recommendations. The preparation given to the material priorto molding shall be recorded and reported.6. Apparatus6.1 Mold, Press, etc., sui
29、table for molding the test specimens specified in Section 8. For transfer or compression molding, apositive or a semi-positive mold with single or multiple cavities shall be used. For injection molding, the type of mold is defined.6.1.1 If required, marks are engraved in the mold near opposite ends
30、of the specimen to facilitate the accurate measurement ofthe length of the cavity and the specimens.NOTE 2If multiple cavities are used with a positive mold, it is possible that resulting variations in test specimen density maycan be sufficient toproduce inconsistent shrinkage.6.2 Equipment, suitabl
31、e for measuring the lengths of the test specimen and the corresponding cavity of the mold to within 0.02mm.6.3 Oven, for post-shrinkage only, a forced draft type is recommended.7. Sampling7.1 A representative sample shall be taken from the molding material and be kept at room temperature in airtight
32、 containers,without any conditioning, until molded into test specimens.D6289 1328. Test Specimen8.1 Compression-Molding MaterialsFor mold shrinkage of compression-molding materials, the test specimens shall be bars120 by 15 by 10 mm, bars 12.7 by 12.7 by 127 mm (12 by 12 by 5 in.), or disks 3.2 mm (
33、18 in.) in thickness and 102 mm (4 in.)in diameter made in a positive mold in such a way as to minimize lateral movement of the plastic during the molding.8.2 Injection-Molding MaterialsFor mold shrinkage of injection-molding materials, the test specimens shall be bars 12.7 by3.2 by 127 mm (12 by 18
34、 by 5 in.) gated at the end, bars 12.7 by 12.7 by 127 mm (12 by 12 by 5 in.) disks 3.2 mm (18 in.) inthickness and 102 mm (4 in.) in diameter gated radially at a single point in the edge, plaques 120 by 120 by 4 mm or plaques 60by 60 by 2 mm gated with a full edge gate.8.3 Transfer-Molding Materials
35、For shrinkage of transfer-molding materials, specimens 12.7 by 12.7 by 127 mm (12 by 12 by5 in.) gated at the end or at the top near one end, so as to provide flow throughout their entire length or disk specimen 3.2 mm(18 in.) in thickness and 102 mm (4 in.) in diameter gated radically at a single p
36、oint in the edge.8.4 The specimens shall be molded to shape by compression, transfer or injection molding using a mold with single or multiplecavities.D6289 133NOTE 3Different specimens give differing shrinkage. For comparison purposes, use the same specimen.9. Procedure9.1 If not already known, mea
37、sure the lengths of the cavities (or the distances between the engraved marks in the mold) to thenearest 0.02 mm at a temperature of 23 6 2C (ISO 291, Atmosphere 23 or Practice D618, T-23).9.1.1 Record these measurements for use in the calculations of shrinkage.NOTE 4From time to time, check molds f
38、or wear.As an alternate to measuring directly the lengths of the cold molds, the gauge for the molds maycanbe obtained very precisely by cold-molding specimens from lead and measuring their lengths.9.2 Mold at least two specimens from the sample to be tested, under the conditions given below.9.2.1 F
39、or Compression MoldingMold the specimens under the conditions of pressure, temperature, time, etc., specified in therelevant standard for the material, in ISO 295, Practice D796, Practice D5224, or at the recommendations of the materialmanufacturer if the standards are not available.9.2.2 For Inject
40、ion MoldingMold the specimens under the conditions outlined in the relevant material standard, ISO 10724or Practice D3419. If the material standards are not available, consult the manufacturer of the material for the molding conditions.NOTE 5In the case of those fibrous materials that are to be inje
41、ction-molded as a plaque, test at least four specimens.9.2.3 For Transfer MoldingMold the specimens under the conditions outlined in the relevant material standard or PracticeD1896 or at the recommendations of the material manufacturer.9.3 After removal from the mold, allow the test specimens to coo
42、l to room temperature by placing them on a material with lowthermal conductivity and under an appropriate load to avoid warping. Unless otherwise specified in the appropriate materialstandard, store them at a temperature of 23 6 2C and a relative humidity of 45 % to 55 % 50 6 10 % (ISO 291, Atmosphe
43、re23/50 or Practice D618, Procedure F, Condition 23/50) for between 16 and 72 h, or for such shorter time to be shown to give thesame test results.NOTE 6It is recommended that a minimum of two specimens be measured and the average reported.9.4 Before measuring the lengths of the test specimens, plac
44、e them on a flat surface or against a straight edge in order todetermine any warp or distortion. Any test specimen that has a warp exceeding 1 % of its length shall be discarded.9.5 For the determination of molding shrinkage, measure, to the nearest 0.02 mm, the lengths of the bar specimens parallel
45、 totheir major axis between opposite end faces or the distances between the gauge marks, at a temperature of 23 6 2C. Measurethe plaque specimens at a distance of 20 mm from the corners, two measurements in the same direction.NOTE 7In order to measure the effect of orientation on the shrinkage of an
46、 injection-molded specimen, shrinkages in two directions at right-angles(each of which is calculated from an average of two measurements in the same direction) are measured and calculated independently.9.6 For the determination of post-shrinkage, place the test specimens, measured as described in 9.
47、5, in an oven maintained atthe temperature given below. Support the specimens (preferably on an open grid) to avoid deformation and in such a way that theyare separated from each other.9.6.1 The heating temperatures shall be: 80 6 2C for urea-formaldehyde molding materials; 110 6 3C for all otherthe
48、rmosetting molding materials.9.6.2 The times of exposure shall be: 48 6 1 h for rapid determination; 168 6 2 h for normal determination.NOTE 8Post shrinkage depends on the time of exposure for some materials. If exposure times different from those noted in 10.2 are used, these shallbe noted in the r
49、eport in accordance with 11.1.6 and, if appropriate, specified in the material standard.9.7 At the end of the heating period, remove the test specimens from the oven and allow them to cool in a standard atmosphereof 23 6 2C and a relative humidity of 45 % to 55 % 50 6 10 % for at least three hours unless otherwise specified in theappropriate material standard.9.8 After the cooling period examine the specimens as in 9.4 and then measure the test specimens again, at a temperature of23 6 2C to the nearest 0.02 mm, as specified in 9.5.
