1、Designation: D 6289 08Standard Test Method forMeasuring Shrinkage from Mold Dimensions of MoldedThermosetting Plastics1This standard is issued under the fixed designation D 6289; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、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 frommold cavity to molded dimensions of thermosetting plast
3、icswhen molded by compression, injection, or transfer underspecified conditions.1.2 This test method provides for the measurement ofshrinkage of thermosetting plastics from their molds bothinitially (within 16 to 72 h of molding) and as they age(postshrinkage at elevated temperatures).1.3 This metho
4、d will give comparable data based on stan-dard specimens and can not predict absolute values in actualmolded parts with varying flow paths, wall thicknesses, pres-sure gradiants and process conditions. Differences in moldshrinkage generally is observed between the specimen geom-etries described in t
5、his test method.1.4 Knowledge of the initial shrinkage of plastics is impor-tant for the construction of molds and knowledge of postmolding shrinkage is important for determining the suitabilityof the molding material for manufacturing thermosetting plas-tic components with accurate dimensions.1.5 T
6、he values stated in SI units are to be regarded asstandard. The values given in parentheses are for informationonly.1.6 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 standard to establish appro-priate
7、 safety and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE 1This test method and ISO 2577-1984 are equivalent whenbars of 120 mm length, 15 mm width, and 10 mm thickness are used forcompression molding; or flat, square plaques approximately 120 by 120by
8、 4 mm are used for injection molding.2. Referenced Documents2.1 ASTM Standards:2D 618 Practice for Conditioning Plastics for TestingD 796 Practice for Compression Molding Test Specimens ofPhenolic Molding Compounds3D 883 Terminology Relating to PlasticsD 1896 Practice for Transfer Molding Test Speci
9、mens ofThermosetting CompoundsD 3419 Practice for In-Line Screw-Injection Molding TestSpecimens From Thermosetting CompoundsD 5224 Practice for Compression Molding Test Specimensof Thermosetting Molding CompoundsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Te
10、st Method2.2 ISO Standards:4ISO 291 PlasticsStandard Atmospheres for Conditioningand TestingISO 295 PlasticsCompression Molding Test Specimensof Thermosetting MaterialsISO 10724 PlasticsThermosetting Molding MaterialsInjection Molding of Multipurpose Test SpecimensISO 2577-1984 PlasticsThermosetting
11、 MouldingMaterialsDetermination of Shrinkage3. Terminology3.1 GeneralDefinitions of terms applying to this testmethod appear in Terminology D 883.3.2 DefinitionsFor the purpose of this test method, thefollowing definitions apply:1This test method is under the jurisdiction of ASTM Committee D20 on Pl
12、asticsand is the direct responsibility of Subcommittee D20.09 on Specimen Preparation.Current edition approved April 15, 2008. Published May 2008. Originallyapproved in 1998. Last previous edition approved in 2003 as D 6289 - 03.2For referenced ASTM standards, visit the ASTM website, www.astm.org, o
13、rcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi
14、.org.1*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.3.2.1 molding shrinkagethe difference in dimensions be-tween a molding and the mold cavity in which it was molded,
15、both the mold and the molding being at 23 6 2C whenmeasured.3.2.2 post-shrinkageshrinkage of a plastic product aftermolding, during post-treatment, storage or use.4. Significance and Use4.1 Compression MoldingIn compression molding, thedifference between the dimensions of a mold and of the moldedart
16、icle produced therein from a given material vary accordingto the design and operation of the mold. It is probable thatshrinkage will approach a minimum where design and opera-tion are such that a maximum of material is forced solidly intothe mold cavity or some part of it, or where the molded articl
17、eis hardened to a maximum while still under pressure, particu-larly by cooling. In contrast, shrinkages are higher where thecharge must flow in the mold cavity but does not receive andtransmit enough pressure to be forced firmly into all itsrecesses, or where the molded article is not fully hardened
18、when discharged. The plasticity of the material used affectsshrinkage insofar as it affects the retention and compression ofthe charge.4.2 Injection MoldingIn injection molding, as in com-pression molding, the differences between the dimensions ofthe mold and of the molded article produced therein f
19、rom agiven material vary according to the design and operation ofthe mold. The differences vary with the type and size ofmolding machine, the thickness of molded sections, the degreeand direction of flow or movement of material in the mold, thesize of the nozzle, sprue, runner, and gate, the cycle o
20、n whichthe machine is operated, the temperature of the mold, and thelength of time that follow-up pressure is maintained. As in thecase of compression molding, shrinkages will approach aminimum where design and operation are such that a maximumof material is forced solidly into the mold cavity and w
21、here themolded article is hardened to a maximum while still underpressure as a result of the use of a runner, sprue, and nozzle ofproper size, along with proper dwell. As in compressionmolding, shrinkages are higher where the charge must flow inthe mold cavity but does not receive and transmit enoug
22、hpressure 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 molding, as in compres-sion or injection molding,
23、the difference between the dimen-sions of the mold and of the molded article produced thereinfrom a given material vary according to the design andoperation of the mold. It is affected by the size and temperatureof the pot or cylinder and the pressure on it, as well as on moldtemperature and molding
24、 cycle. Direction of flow is not asimportant a factor.4.4 Materials StandardsAlways refer to material stan-dards for special treatment prior to molding, molding condi-tions and special handling of the test specimens after molding.In the event the material standard is unavailable, contact themanufact
25、urer for these recommendations.4.5 UtilityMeasurement of batch-to-batch consistency ininitial shrinkage from mold to molded dimensions is useful forevaluating the quality of thermosetting plastics.5. Sample Preparation5.1 Some materials require special treatment before they aremolded. Materials to b
26、e tested shall be prepared for molding inaccordance with the relevant material standard or the manu-facturers recommendations. The preparation given to thematerial prior to molding shall be recorded and reported.6. Apparatus6.1 Mold, Press, etc., suitable for molding the test speci-mens specified in
27、 Section 8. For transfer or compressionmolding, a positive or a semi-positive mold with single ormultiple cavities shall be used. For injection molding, the typeof mold is defined.6.1.1 If required, marks are engraved in the mold nearopposite ends of the specimen to facilitate the accuratemeasuremen
28、t of the length of the cavity and the specimens.NOTE 2If multiple cavities are used with a positive mold, resultingvariations in test specimen density may be sufficient to produce inconsis-tent shrinkage.6.2 Equipment, suitable for measuring the lengths of the testspecimen and the corresponding cavi
29、ty of the mold to within0.02 mm.6.3 Oven, for post-shrinkage only, a forced draft type isrecommended.7. Sampling7.1 Arepresentative sample shall be taken from the moldingmaterial and be kept at room temperature in airtight containers,without any conditioning, until molded into test specimens.8. Test
30、 Specimen8.1 Compression-Molding MaterialsFor mold shrinkageof compression-molding materials, the test specimens shall bebars 120 by 15 by 10 mm, bars 12.7 by 12.7 by 127 mm (12 by12 by 5 in.), or disks 3.2 mm (18 in.) in thickness and 102 mm(4 in.) in diameter made in a positive mold in such a way
31、as tominimize lateral movement of the plastic during the molding.8.2 Injection-Molding MaterialsFor mold shrinkage ofinjection-molding materials, the test specimens shall be bars12.7 by 3.2 by 127 mm (12 by18 by 5 in.) gated at the end, bars12.7 by 12.7 by 127 mm (12 by12 by 5 in.) disks 3.2 mm (18i
32、n.) in thickness and 102 mm (4 in.) in diameter gated radiallyat a single point in the edge, plaques 120 by 120 by 4 mm orplaques 60 by 60 by 2 mm gated with a full edge gate.8.3 Transfer-Molding MaterialsFor shrinkage of transfer-molding materials, specimens 12.7 by 12.7 by 127 mm (12 by12 by 5 in.
33、) gated at the end or at the top near one end, so asto provide flow throughout their entire length or disk specimen3.2 mm (18 in.) in thickness and 102 mm (4 in.) in diametergated radically at a single point in the edge.8.4 The specimens shall be molded to shape by compres-sion, transfer or injectio
34、n molding using a mold with single ormultiple cavities.D6289082NOTE 3Different specimens give differing shrinkage. For comparisonpurposes, use the same specimen.9. Procedure9.1 If not already known, measure the lengths of the cavities(or the distances between the engraved marks in the mold) tothe ne
35、arest 0.02 mm at a temperature of 23 6 2C (ISO 291,Atmosphere 23 or Practice D 618, T-23).9.1.1 Record these measurements for use in the calculationsof shrinkage.NOTE 4From time to time, check molds for wear. As an alternate tomeasuring directly the lengths of the cold molds, the gauge for the molds
36、may be obtained very precisely by cold-molding specimens from lead andmeasuring their lengths.9.2 Mold at least two specimens from the sample to betested, under the conditions given below.9.2.1 For Compression MoldingMold the specimens un-der the conditions of pressure, temperature, time, etc., spec
37、ifiedin the relevant standard for the material, in ISO 295, PracticeD 796, Practice D 5224, or at the recommendations of thematerial manufacturer if the standards are not available.9.2.2 For Injection MoldingMold the specimens underthe conditions outlined in the relevant material standard,ISO 10724
38、or Practice D 3419. If the material standards are notavailable, consult the manufacturer of the material for themolding conditions.NOTE 5In the case of those fibrous materials that are to be injection-molded as a plaque, test at least four specimens.9.2.3 For Transfer MoldingMold the specimens under
39、 theconditions outlined in the relevant material standard or PracticeD 1896 or at the recommendations of the material manufac-turer.9.3 After removal from the mold, allow the test specimensto cool to room temperature by placing them on a material withlow thermal conductivity and under an appropriate
40、 load toavoid warping. Unless otherwise specified in the appropriatematerial standard, store them at a temperature of 23 6 2C anda relative humidity of 45 % to 55 % (ISO 291, Atmosphere23/50 or Practice D 618, Procedure F, Condition 23/50) forbetween 16 and 72 h, or for such shorter time to be shown
41、 togive the same test results.NOTE 6It is recommended that a minimum of two specimens bemeasured and the average reported.9.4 Before measuring the lengths of the test specimens,place them on a flat surface or against a straight edge in orderto determine any warp or distortion.Any test specimen that
42、hasa warp exceeding 1 % of its length shall be discarded.9.5 For the determination of molding shrinkage, measure, tothe nearest 0.02 mm, the lengths of the bar specimens parallelto their major axis between opposite end faces or the distancesbetween the gauge marks, at a temperature of 23 6 2C.Measur
43、e the plaque specimens at a distance of 20 mm from thecorners, two measurements in the same direction.NOTE 7In order to measure the effect of orientation on the shrinkageof an injection-molded specimen, shrinkages in two directions at right-angles (each of which is calculated from an average of two
44、measurementsin the same direction) are measured and calculated independently.9.6 For the determination of post-shrinkage, place the testspecimens, measured as described in 9.5, in an oven main-tained at the temperature given below. Support the specimens(preferably on an open grid) to avoid deformati
45、on and in sucha way that they are separated from each other.9.6.1 The heating temperatures shall be: 80 6 2C forurea-formaldehyde molding materials; 110 6 3C for all otherthermosetting molding materials.9.6.2 The times of exposure shall be: 48 6 1 h for rapiddetermination; 168 6 2 h for normal deter
46、mination.NOTE 8Post shrinkage depends on the time of exposure for somematerials. If exposure times different from those noted in 10.2 are used,these shall be noted in the report in accordance with 11.1.6 and, ifappropriate, specified in the material standard.9.7 At the end of the heating period, rem
47、ove the testspecimens from the oven and allow them to cool in a standardatmosphere of 23 6 2C and a relative humidity of 45 % to55 % for at least three hours unless otherwise specified in theappropriate material standard.9.8 After the cooling period examine the specimens as in 9.4and then measure th
48、e test specimens again, at a temperature of23 6 2C to the nearest 0.02 mm, as specified in 9.5.10. Interpretation of Results10.1 The molding shrinkage (MS) is given, as a percentage,by the following formula:MS 5L0 L1L03 100 (1)where:L0= length of the dimension of the mold, determined as in9.1, mm, a
49、ndL1= length of the corresponding dimension measured onthe test specimen, in accordance with 9.5, mm.NOTE 9When shrinkage is being determined using injection-moldedplaques, L0and L1are each the averages of two readings, measured in thesame direction, taken 20 mm from the corners of the mold and the testspecimen respectively.10.2 Post-shrinkage (PS) is given, as a percentage, by thefollowing formula:PS48 hor PS168 h5L1 L2L13 100 (2)where:L2= length of the same dimension of the test specimen,measured after heat treatment at 48 h or 16
