1、Designation:D955-00INTERNATIONALStandard Test Method ofMeasuring Shrinkage from Mold Dimensions ofThermoplastics1This standard is issued under the fixed designation D 955;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of la
2、st 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*D 883 Terminology Relating to Plastics31.1 This test method is intended to measure shrinkage fromD 3641 Practice for Injection
3、Molding of Test Specimens ofmold cavity to molded dimensions of thermoplastics whenThermoplastic Molding and Extrusion Materialsmolded by compression or injection processes with specifiedD4066 Specification for Nylon Injection and Extrusionprocess conditions.Materials41.2 This test method covers ini
4、tial shrinkage measurements.D 4181 Specification for Acetal(POM)Molding and Extru-The method also accommodates shrinkage at 24 and 48 h,sion Materials4which may be critical for some materials.D 4549 Specification for Polystyrene Molding and Extru-1.3 This method will give comparable data based on st
5、an-sion Materials(PS)5dard specimens and can not predict absolute values in actualD 4703 Practice for Compression Molding of Thermoplas-molded parts with varying flow paths,wall thicknesses,pres-tic Materials into Test Specimens,Plaques,Sheetssure gradients and process conditions.Differences in mold
6、D 4976 Specification for Polyethylene Plastics Molding andshrinkage may also be observed between the three specimenExtension Materials5geometries described in this test method.D 5947 Test Methods for Physical Dimensions of Solid1.4 The values stated in SI units are to be regarded as thePlastics Spec
7、imensstandard.The values given in parentheses are given forE691 Practice for Conducting an Interlaboratory Study toinformation only.Determine the Precision of a Test Method61.5 This standard does not purport to address all of the2.2 ISO Standards:safety concerns,if any,associated with its use.It is
8、theISO 293 Plastics-Compression Moulding Test Specimensresponsibility of the user of this standard to establish appro-of Thermoplastic Materials?priate safety and health practices and determine the applica-ISO 294-3 Plastics-Injection Moulding of Test Specimensbility of regulatory limitations prior
9、to use.of Thermoplastic Materials-Part 3:Small PlatesISO 294-4 Plastics-Injection Moulding of TestNoTE 1-This test method is technically identical to ISO 294-4 whereSpecimens-Part 4:Determination of Moulding Shrink-Type D2 specimens are used except that pressure transducers are an optionin this test
10、 method and required in ISO 294-4.age?2.Referenced Documents3.Terminology2.1 ASTM Standards:3.1 Definitions-General definitions of terms applying toD 374 Test Methods for Thickness of Solid Electrical Insu-this test method appear in Terminology D 883.lation23.2 Definitions of Terms Specific to This
11、Standard:D618 Practice for Conditioning Plastics and Electrical3.2.1 demolding,n-removing the specimens from theInsulating Materials for Testingmold.D 788 Classification System for Poly(Methyl Methacrylate)(PMMA)Molding and Extension Compounds3 This test method is under the jurisdiction of ASTM Comm
12、ittee D20 on Plasticsand is the direct responsibility of Subcommittee D20.09 on Specimen Preparation.Annual Book of ASTM Standards,Vol 08.02.Current edition approved Noy.10,2000.Published January 2001.Originally Annual Book of ASTM Standards,Vol 08.03.published as D 955-48T.Last previous edition D 9
13、55-89(1996).6 Annual Book of ASTM Standards,Vol 14.02.2 Annual Book of ASTM Standards,Vol 10.01.Available from Americar.National Standards Institute,11 W.42nd St.,13th3 Annual Book of ASTM Standards,Vol 08.01.Floor,New York,NY 10036.*A Summary of Changes section appears at the end of this standard.C
14、opynght ASTM internatonal,100 Barr Harbor Dnve,PO Box C700,West Conshohocken,PA 19428-2959,United States201D955-004.Summary of Test Method4.1 The principle of this test method is to compare moldcavity dimensions with specimen dimensions and report thedifferences in percent.5.Significance and Use5.1
15、Injection Molding-In injection molding,the differencebetween the dimensions of a mold cavity and of the moldedspecimen may vary according to the design of the mold andoperation of the molding process.Factors such as mold andmelt temperature,fill times,and packing conditions are knownto affect shrink
16、age significantly.Adherence to the specifiedmold design(see 7.1)and specifications outlined in PracticeD 3641 or ISO 294-4 or the appropriate material will improvethe reproducibility of the test.5.2 Compression Molding-In compression molding,thedifference between the dimensions of a mold cavity and
17、of themolded specimen may vary according to the design of the moldand operation of the molding process.Factors,such as theamount of material in charge,cooling time,and pressureapplication are known to affect shrinkage significantly.Adher-ence to the specified mold design(see 7.2)and specificationsSp
18、sprueoutlined in Practice D 4703 or ISO 293 or the appropriateGgatematerial specifications will improve the reproducibility of theRrunnerpressure sensordimensions in mmtest.length of plate602bwidth of plate6026.Sample Preparationthickness of plate2.00.1length of gate4.00.16.1 Some materials require
19、special treatment before they arehaheight of gate(0.750.05)x hmolded.For example,thermoplastics,which absorb moisturelength of runner25to40must be dried before molding.Refer to the manufacturersDRwidth of runner(b+6)h。depth of runner at gateh+(1.50.5)recommendations for required conditions or approp
20、riate mate-unspecified distancerial specification.The preparation given to the material prior todistance of pressure sensor from gate5=2molding shall be recorded and reported.FIG.2 Type D27.Apparatus7.1 Injection Mold-Specimens shall be molded in a twohave scribe marks included for the measurement o
21、f shrinkage.cavity mold conforming with dimensions as shown in Figs.1The scribe marks shall be 1.0 mm long by.01 mm wide locatedand 2 for the 60 60-mm plaque specimen(Type D2),Fig.31.0 mm from each edge on one side of the mold.Pressurefor the 12.7 127-mm bar specimen(Type A)and Fig.4 fortransducers
22、for monitoring the pressure in at least one cavitythe 100mm 3.2-mm disk specimen(Type B).The mold mayare mandatory for Type D2.Mold shrinkage measurementsshould be made on specimens that have been molded at one ofXthe following cavity pressures 3%from the selectedX-Ypressure:20 MPa,40 MPa,60 MPa,80
23、MPa,100 MPa,or asspecified in the appropriate material specification.Pressuretransducers are recommended,but not mandatory for speci-mens Type A and Type B.7.2 Compression Mold-A single cavity positive mold hav-ing cavity dimensions conforming to the dimensions of Fig.2for the 60 60-mm plaque(Type D
24、2)Fig.3 for the 12.7 X127-mm bar specimen(Type A)and Fig.4 for the 100-mm X3.2-mm disk specimen(Type B),not including the sprue,runner or gate.The mold may have scribe marks included forthe measurement of shrinkage.The scribe marks shall be 1.0mm long by 0.1 mm wide located 1.0 mm from each edge onS
25、pspruemolding volume=30 000 mm3Gone side of the mold.gateprojected area=11 000 mmic=distance between the lines along which the test specimens are cut from7.3 Injection Press-A suitable injection molding machinethe runnersthat will fill the test molds when it is operated in the range fromFIG.1 Type D
26、220 to 80%of its rated shot capacity at the molding parameters202D955-0012.7+-0.2 mm=3.2+/-0.05mum1=127+/-2mmG=GateP=Pressure TransducerFIG.3 Bar Speciment=3.2+/-0.05mmD-100+/-2mmGatePessure TrnsducerFIG.4 Disk Specimenspecified in Practice D 3641,ISO 294-3 or the appropriate8.3 Specimen Type B-A di
27、sc shaped specimen,as shown inmaterial specification.Fig.4,having a cavity 100 mm in diameter by 3.2 mm inNorE 2-If the injection machines of appropriate capacity are notthickness with a gate 12.7 mm in width by 3.2 mm in depth,available,the requirements of 7.3 may be met in machines of largerplaced
28、 radially at the edge,may also be used.capacities by providing test molds with multiple cavities(maximum ofNoTE 3-Although this specimen may be used to determine moldfour)to be filled from a common sprue and having a balanced fillingshrinkage in both the flow and cross flow directions,the filling pa
29、tternpattern,so that the total weight of the shot,including sprue and runner willdoes not produce uniform flow lengths and orientation.Consequently,fall within the specified limits.there may be significant differences when measuring the specimen at7.4 Compression Press-A suitable hydraulic press tha
30、t willdifferent points around the circumference.Values would not be expecteddeliver a pressure of 20 to 35 MPa(3000 to 5000 psi)to theto be in agreement with those obtained using the specimens described inmaterial in the mold.clauses 8.1 and 8.2.7.5 Measuring Tools-Measuring tools(micrometers,ver-9.
31、Conditioningnier calipers,etc.)accurate to 0.025 mm(0.001 in.)formeasuring the molds and test specimens conforming to the9.1 Conditioning-Conditioning of molded specimens shallmeasuring tool requirements in Test Methods D 374.be done in the Standard Laboratory Atmosphere,232C and50%5 RH,if not other
32、wise specified in the appropriate8.Test Specimenmaterials standard.8.1 Specimen Type D2-For mold shrinkage in both flow9.2 Test Conditions-Conduct measurement in the standardand cross flow of compression and injection molding materialslaboratory atmosphere of 23 2C and 50%5 RH,if notthe preferred sp
33、ecimen shall be 60 60 2 mm depthotherwise specified in the appropriate materials standard.conforming to the dimensions of Fig.2.8.2 Specimen Type A-For shrinkage parallel to flow,a bar10.Proceduremold having a cavity of 12.7 127 mm may be used as shown10.1 Measure the length and width of the mold ca
34、vity at thein Fig.3.The thickness shall be 3.2 mm unless otherwisecenter of each edge or at the molded scribe marks,to theagreed upon by the selier and the purchaser.The mold shallnearest 0.025 mm at 23 2C and 50%5 RH.Record thesehave at one end a gate 6.4 mm in width by 3.2 mm in depth.values as I
35、and w,respectively.203D955-00TABLE 2 Shrinkage from Mold Dimensions of I.M.Disks Flow12.1.4 Concept of r and R-If S,and SR(standard devia-Directiontions)have been calculated from a large enough body of data,MaterialeAverageSrSRRand for test results that were averages from testing five10.004630.00008
36、0.001240.000220.00347specimens:20.037990.000350.009230.000980.025840.0042012.1.4.1 Repeatability,r(Comparing Two Test Results,as0.000180.001700.000500.004760.023270.000210.002940.000590.00823Defined in 12.1.2,for the Same Material Obtained by the Same50.019410.000280.003480.000780.00974Operator Usin
37、g the Same Equipment on the Same Day)-The Values expressed in mm/mm(in./in.).two test results should be judged not equivalent if they differ byB1=PolystyreneSpecification D 4549PS110B56152more than the r value for that material.2=PolyethyleneSpecification D 4976PE23512.1.4.2 Reproducibility,R(Compar
38、ing Two Test Results for3=PMMASpecification D 788PMMA0131V04=AcetalSpecification D 4181POM213the Same Material Obtained by Different Operators Using5=Nylon(Polyamide)Specification D 4066PA111Different Equipment on Different Days)-The two test resultsshould be judged not equivalent of they differ by
39、more than theR value for that material.TABLE 3 Shrinkage from Mold Dimensions of I.M.Disks Cross12.1.4.3 Any judgment made in accordance with 12.4.1 andDirection12.4.2 has an approximate 95%probability of being correct.MaterialeAverageS,SRR12.1.4.4 Results-The r and R values are obviously a0.004030.
40、000100.001620.000280.00454function of each material and its molding characteristics.It20.020400.000190.002470.000530.0069230.004270.000130.001420.000360.00398would be incorrect to assume values form Tables 1-3 for any0.025280.000370.004710.001040.01319new material.50.020680.000470.005060.001320.0141
41、712.2 Bias-It is known that the test result is as dependent inA Values expressed in mm/mm(in./in.).the experimental conditions as on the material itself.It is theB1=PolystyreneSpecification D 4549PS110B56152intent of this method to control and document as many of these2=PolyethyleneSpecification D 4
42、976PE2353=PMMASpecification D 788PMMA0131V0variables as possible.There are no recognized standards by4=AcetalSpecification D 4181POM213which to estimate the bias of this test method.5=Nylon(Polyamide)Specification D 4066PA11113.Keywords13.1 mold shrinkage;shrinkage;thermoplasticsSUMMARY OF CHANGESTh
43、is section identifies the location of selected changes to this test method.For the convenience of the user,Committee D20 has highlighted those changes that may impact the use of this test method.This section may alsoinclude descriptions of the changes or reasons for the changes,or both.D955-00:Test
44、Method for Measuring Shrinkage from Mold Dimensions(I)This is a complete revision of Test Method D 955 andof Molded Thermosetting Plastics,was developed for thermo-harmonization with ISO 294-3,-4.After several ballots,thesetting plastics.negatives and comments that were accepted have been incor-(3)6
45、0 by 60 mm Type D2 specimens were added.porated in this edition.The following changes have been made:(4)Drawings of specimens were added.(2)Title and Scope were changed to reflect that the test(5)ISO equivalency statement was added.method is for thermoplastics only.New Test Method D 6289,(6)Keywords
46、 were added.ASTM 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 r
47、ights,are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised,either reapproved or withdrawn.Your comments are invited either for revision of this standard or for additional
48、standardsand should be addressed to ASTM International Headquarters.Your comments will receive careful consideration at a meeting of theresponsible technical committee,which you may attend.If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Com
49、mittee on Standards,at the address shown below.This standard is copyrighted by ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.Individual reprints(single or multiple copies)of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585(phone),610-832-9555(fax),or serviceastm.org(e-mail);or through the ASTM website(www.astm.org).205
