1、Designation: D 6289 03Standard 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 (e) 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 plas
3、ticswhen 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 meth
4、od 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
5、this 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
6、The values stated in SI units are to be regarded as thestandard. The values given in brackets are for information only.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-pri
7、ate 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 12
8、0by 4 mm are used for injection molding.2. Referenced Documents2.1 ASTM Standards:2D 618 Practice for Conditioning Plastics and ElectricalInsulating Materials for TestingD 796 Practice for Compression Molding Test Specimens ofPhenolic Molding CompoundsD 883 Terminology Relating to PlasticsD 1896 Pra
9、ctice for Transfer Molding Test Specimens ofThermosetting CompoundsD 3419 Practice for In-line Screw-Injection Molding of TestSpecimens from Thermosetting CompoundsD 5224 Practice for Compression Molding Test Specimensof Thermosetting Molding CompoundsE 691 Practice for Conducting an Interlaboratory
10、 Study toDetermine the Precision of a Test Method2.2 ISO Standards:3ISO 291 PlasticsStandard Atmospheres for Conditioningand TestingISO 295 PlasticsCompression Molding Test Specimensof Thermosetting MaterialsISO 10724 PlasticsThermosetting Molding MaterialsInjection Molding of Multipurpose Test Spec
11、imensISO 2577-1984 PlasticsThermosetting 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:3.2.1 molding shrinkagethe diff
12、erence in dimensions be-tween a molding and the mold cavity in which it was molded,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 compr
13、ession molding, thedifference between the dimensions of a mold and of the moldedarticle produced therein from a given material vary according1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.09 on Specimen Preparation.Cu
14、rrent edition approved November 1, 2003. Published January 2004. Originallyapproved in 1998. Last previous edition approved in 1998 as D 6289 - 98.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandard
15、s volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr H
16、arbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.to 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 t
17、he molded articleis 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 no
18、t fully hardenedwhen 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 pr
19、oduced therein from 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 g
20、ate, the cycle on 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 m
21、old cavity and where 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 an
22、d transmit enoughpressure 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 inj
23、ection molding, 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 moldtempera
24、ture and molding 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, con
25、tact themanufacturer for these recommendations.4.5 UtilityMeasurement of batch-to-batch uniformity 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.
26、 Materials to be 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-me
27、ns specified in 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 acc
28、uratemeasurement 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 cor
29、responding cavity of the mold to within0.02 mm.6.3 Oven, for post-shrinkage only, a forced draft type isrecommended.7. Sampling7.1 A representative sample shall be taken from the moldingmaterial and be kept at room temperature in airtight containers,without any conditioning, until molded into test s
30、pecimens.8. Test 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 mm4 in. in diameter made in a positive mold in s
31、uch a way 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 m
32、m 18in. in thickness and 102 mm 4 in. in diameter grated 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 i
33、n. 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 injection m
34、olding using a mold with single ormultiple cavities.NOTE 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 nearest 0.02
35、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 toD6289032measuring directly the lengths of the cold molds, the gauge for the moldsmay
36、 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., specifi
37、edin 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, ISO10724 or
38、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 th
39、econditions 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 lo
40、ad toavoid warping. Store them at a temperature of 23 6 2C and arelative humidity of 45 % to 55 % (ISO 291, Atmosphere 23/50or Practice D 618, Procedure F, Condition 23/50) for between16 and 72 h, or for such shorter time to be shown to give thesame test results.NOTE 6It is recommended that a minimu
41、m 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 hasa warp exceeding 1 % of its length shall be discarded.9.5 For t
42、he 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.Measure the plaque specimens at a distance of 20 mm from thecorners, two
43、 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 measurementsin the same direction) are measured and calculated ind
44、ependently.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 deformation and in sucha way that they are separated from each other.9.6.1
45、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 determination.NOTE 8Post shrinkage depends on the time of exposure for
46、somematerials. Note the exposure time (see 10.2 and 11f) and specify it in thematerial standard if necessary.9.7 At the end of the heating period, remove 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 3 h.
47、9.8 After the cooling period examine the specimens as in 9.4and then measure the 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 1
48、00 (1)where:L0= length of the dimension of the mold, determined as in9.1, mm, andL1= 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, m
49、easured 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 168 h, inaccordance with 9.6, mm.NOTE 10When post-shrinkage is being determined using injectionmolded plaques, L2is the average of two readings, measured in the samedirection, taken 20 mm from the corners
