出路的意思
Designation:D955–08
不稂不莠Standard Test Method of
Measuring Shrinkage from Mold Dimensions of Thermoplastics1
This standard is issued under thefixed designation D955;the number immediately following the designation indicates the year of original adoption or,in the ca of revision,the year of last revision.A number in parenthes indicates the year of last reapproval.A superscript epsilon(´)indicates an editorial change since the last revision or reapproval.
1.Scope*
1.1This test method is intended to measure shrinkage from mold cavity to molded dimensions of thermoplastics when molded by compression or injection process with specified process conditions.
1.2This test method covers shrinkage measurements at24 and48h.
1.3This method will give comparable data bad on stan-dard specimens and can not predict absolute values in actual molded parts with varyingflow paths,wall thickness,pres-sure and temperature gradients and process conditions.Differ-ences in mold shrinkage may also be obrved among the three specimen geometries described in this test method.
1.4The values stated in SI units are to be regarded as the standard.The values given in parenthes are given for information only.
1.5This standard does not purport to address all of the safety concerns,if any,associated with its u.It is the responsibility of the ur of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to u.
N OTE1—This standard and ISO294-3are equivalent in the design of specimen D2.This test method is equivalent to ISO294-4where Type D2 specimens and the procedure in Appendix X2are ud.
2.Referenced Documents
2.1ASTM Standards:2
D618Practice for Conditioning Plastics for Testing
水浒传好句D788Classification System for Poly(Methyl Methacrylate) (PMMA)Molding and Extrusion Compounds
D883Terminology Relating to Plastics
D3641Practice for Injection Molding Test Specimens of Thermoplastic Molding and Extrusion Materials
D4066Classification System for Nylon Injection and Ex-trusion Materials(PA)
D4549Specification for Polystyrene and Rubber-Modified Polystyrene Molding and Extrusion Materials(PS)
D4703Practice for Compression Molding Thermoplastic Materials into Test Specimens,Plaques,or Sheets
D4976Specification for Polyethylene Plastics Molding and Extrusion Materials
D5947Test Methods for Physical Dimensions of Solid Plastics Specimens
D6778Classification for Polyoxymethylene(POM,Acetal) Molding and Extrusion Materials
D6779Classification System for Polyamide Molding and Extrusion Materials(PA)
E691Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
2.2ISO Standards:3
ISO293Plastics—Compression Moulding Test Specimens of Thermoplastic Materials
ISO294-1Plastics—Injection Moulding of Test Specimens of Thermoplastic Materials—Part1:General Principles, and Moulding of Multipurpo and Bar Test specimens ISO294-3Plastics—Injection Moulding of Test Specimens of Thermoplastic Materials—Part3:Small Plates
ISO294-4Plastics—Injection Moulding of Test Specimens—Part4:Determination of Moulding Shrink-age
3.Terminology怎么种植蔬菜
3.1Definitions—General definitions of terms applying to this test method appear in Terminology D883.
3.2Definitions of Terms Specific to This Standard:
3.2.1jetting,n—non-uniform multi-directionalflow front apparent on the surface of the mold due to rapidfilling of the mold cavity.
1This test method is under the jurisdiction of ASTM Committee D20on Plastics and is the direct responsibility of Subcommittee D20.09on Specimen Preparation.
Current edition approved Nov.1,2008.Published December2008.Originally approved in1948.Last previous edition approved in2000as D955-00.
2For referenced ASTM standards,visit the ASTM website,www.astm,or contact ASTM Customer Service at rvice@astm.For Annual Book of ASTM
Standards volume information,refer to the standard’s Document Summary page on the ASTM website.
3Available from American National Standards Institute(ANSI),25W.43rd St., 4th Floor,New York,NY10036,www.ansi.
*A Summary of Changes ction appears at the end of this standard. Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States.
4.Summary of Test Method
4.1The principle of this test method is to compare mold cavity dimensions with specimen dimensions and report the differences in percent.
5.Significance and U
5.1Injection Molding—In injection molding,the difference between the dimensions of a mold cavity and of the molded specimen may vary according to the design of the mold and operation of the molding process.Factors such as mold and melt temperature,fill times,and packing conditions are known to affect shrinkage significantly.Adherence to the specified mold design(e7.1)and specifications outlined in Practice D3641or ISO294-4or the appropriate material specification will improve the reproducibility of the test.
5.2Compression Molding—In compression molding,the difference between the dimensions of a mold cavity and of the molded specimen may vary according to the design of the mold and operation of the molding process.Factors,such as the amount of material in charge,cooling time,and pressure application are known to affect shrinkage significantly.Adher-ence to the specified mold design(e7.2)and specifications outlined in Practice D4703or ISO293or the appropriate material specifications will improve the reproducibility of the test.传染病的分类
6.Sample Preparation
6.1Some materials require special treatment before they are molded.For example,thermoplastics,which absorb moisture must be dried before molding.For required conditions for sample preparation,refer to the appropriate material specifica-tion or the manufacturer’s recommendations if no specification is available.The preparation given to the material prior to molding shall be recorded and reported.
7.Apparatus
7.1Injection Mold—Specimens shall be molded in a two cavity mold conforming with dimensions as shown in Figs.1 and2for the60360-mm plaque specimen(Type D2),Fig.3 for the12.7by127-mm bar s
pecimen(Type A)and Fig.4for the100mm by3.2-mm disk specimen(Type B).Pressure transducers for monitoring the pressure in at least one cavity are mandatory for Type D2.Mold shrinkage measurements shall be made on specimens that have been molded at one of the following cavity pressures63%from the lected pressure:20MPa,40MPa,60MPa,80MPa,100MPa,or as specified in the appropriate material specification.Pressure transducers are recommended,but not mandatory for speci-mens Type A and Type B.
7.2Compression Mold—A single cavity positive mold hav-ing cavity dimensions conforming to the dimensions of Fig.2 for the60360-mm plaque(Type D2)Fig.3for the12.73 127-mm bar specimen(Type A)and Fig.4for the100-mm3 3.2-mm disk specimen(Type B),not including the sprue, runner or gate.
N OTE2—Although scribe marks are not required,if they are ud for injection or compression molded specimens for the measurement of shrinkage,the scribe marks shall be1.0mm long by0.1mm wide located 4.0mm from each edge on one side of the mold.
7.3Injection Press—A suitable injection molding machine that shallfill the test molds when it is operated in the range from20to80%of its rated shot capacity at the
molding Sp|sprue
G|gate
L c=distance between the lines along which the test specimens are cut from the runners
Molding volume=20000mm3
Projected area=11000mm2
FIG.1Type D2(Mold
10086查流量
Layout)
parameters specified in Practice D 3641,ISO 294-3or the appropriate material specification.
N OTE 3—If the injection machines of appropriate capacity are not available,the requirements of 7.3may be met in machines of larger capacities by providing test molds with multiple cavities (maximum of four)to be filled from a common sprue and having a balanced filling
pattern,so that the total weight of the shot,including sprue and runner will fall within the specified limits.
7.4Compression Press —A suitable hydraulic press that shall deliver a pressure of 20to 35MPa (3000to 5000psi)to the material in the
mold.
Sp sprue G gate R runner
P pressure nsor l length of plate 6062mm b width of plate 6062mm h thickness of plate 2.060.1mm l G length of gate 4.060.1mm h G height of gate (0.7560.05)3h l R length of runner 25to 40mm b R width of runner
$(b +6)mm h g depth of runner at gate l*unspecified distance
...
l p distance of pressure nsor from gate
562mm
FIG.2Type D2(Cavity
Details)
孕妇吃什么补钙最快最好w =12.760.2mm t =3.260.05mm l =12762mm G =Gate
P =Pressure Transducer
FIG.3Bar
Specimen
7.5Measuring Tools —Measuring tools (micrometers,ver-nier calipers,etc.)accurate to 0.025mm (0.001in.)for measuring the molds and test specimens conforming to the measuring tool requirements in Test Methods D 5947.8.Test Specimen
8.1The following specimen dimensions are applicable for both compression and injection molding.Orientation effects due to flow direction do not generally pertain to compression molding.
8.1.1Specimen Type D2—For mold shrinkage in both flow and cross flow the preferred specimen shall be 60by 60by 2mm depth conforming to the dimensions of Fig.2.
8.1.2Specimen Type A —For shrinkage parallel to flow,a bar mold having a cavity of 12.7by 127mm shall be ud as shown in Fig.3.The thickness shall be 3.2mm unless otherwi agreed upon by the ller and the purchar.The mold shall have at one end a gate 6.4mm in width by 3.2mm in depth.
8.1.3Specimen Type B —A disc shaped specimen,as shown in Fig.4,having a cavity 100mm in diameter by 3.2mm in thickness with a gate 12.7mm in width by 3.2mm in depth,placed radially at the edge,shall be ud.
N OTE 4—Although this specimen may be ud to determine mold shrinkage in both the flow and cross flow directions,the filling pattern does not produce uniform flow lengths and orientation.Conquently,there may be significant differences when measuring the specimen at different points around the circumference.Values would not be expected to be in agreement with tho obtained using the specimens described in 8.1.1and 8.1.2.
9.Conditioning
9.1Conditioning —Conditioning of molded specimens shall be done in the Standard Laboratory Atmosphere,2362°C and 50%610RH,if not otherwi specified in the appropriate materials standard.
9.2Test Conditions —Conduct measurement in the standard laboratory atmosphere of 2362°C and 50%610RH,if not otherwi specified in the appropriate materials standard.10.Procedure
10.1Measure the length and width of the mold cavity at the center of each edge or at the molded scribe marks,to the nearest 0.025mm at 2362°C and 50%610RH.Record the values as l and w ,respectively.
10.2Mold at least five flat test specimens from the sample to be tested.
N OTE 5—Flat is reprented by a specimen with less than 3%warp.Three percent warp is defined as 3mm depth deflection,positive or negative,per 100mm in length.
10.2.1Thermoplastics Molded by Injection —Molding of thermoplastic materials shall be conducted in accordance with the appropriate material standard,Practice D 3641or ISO 294-3.The temperature of the heating cylinder and the mold shall be maintained at a point which,on a cycle lected,will produce temperature within the range recommended by the material molding standard.Begin with a short shot to ensure the flow front is straight and not radial and that the flow is laminar and does not exhibit melt fracture (jetting).Collect samples after the machine is at
equilibrium.
t =3.260.05mm D =10062mm G =Gate
P =Pressure Transducer
FIG.4Disk
Specimen
10.2.2Thermoplastics Molded by Compression—For ther-moplastics,molding shall be conducted in accordance with the appropriate material standard or D4703.
10.3Treatment of Specimens after Removal from the Mold: 10.3.1In order to minimize warpage,parate the test specimens from the runners in the gate area immediately after removal from the mold.Do not modify or alter the edges ud for the measurement of dimensions.It is recommended to cool specimens in a horizontal position at room temperature by placing them on a
material of low thermal conductivity to minimize warpage.After thefirst hour,condition the speci-mens at2362°C and50%65RH,unless otherwi specified in the material standard.
10.3.2Specification of Measurement Time:
10.3.2.1Twenty four hour shrinkage measurements shall be made2460.5h after the specimen has been removed from the mold.
10.3.2.2Forty eight hour shrinkage measurements shall be made4860.5h after the specimen has been removed from the mold.
11.Calculation and Report
11.1
S w5~W m2W s!3100/Wm(1) where:
S w=the shrinkage perpendicular toflow,%,
W m=the mold dimension perpendicular toflow,
W s=the specimen dimension perpendicular toflow,and
S15~L m2L s!3100/Lm(2) where:
S1=the shrinkage parallel toflow,%,
L m=the mold dimension parallel toflow,and,
L s=the specimen dimension parallel toflow.
Report mold shrinkage in bothflow and cross direction to two significantfigures.
11.2The report shall include the following:
集合教案11.2.1Details of any special material preparation,such as drying,which the material received before molding;
11.2.2The molding procedure ud,following the report as outlined in Practice D3641for injection molding and Practice D4703for compression molding.
11.2.3The24-hour shrinkage and the48-hour shrinkage shall be expresd in percent(mm/mm)with e
ach value reprenting the mean of determinations obtained onfive or more specimens.
12.Precision and Bias
12.1Precision:
12.1.1Tables1-3summarize data from a round robin4 conducted in1988,using specimens Type A and Type B, involvingfive thermoplastics materials tested by eight labora-tories.Each material was supplied in granular form to each of the testing laboratories by a single supplier.The resins were handled in accordance with the supplier’s instructions and were molded in accordance with Practice D3641.Each test result is the average offive individual determinations from successive injection molding cycles.Each laboratory obtained one test result for each material.8
N OTE6—A repeatability study was conducted in Europe using speci-men Type D2.The results,including suggested cavity hold pressure for various materials,are shown in Appendix X1.
12.1.2Repeatability estimates S r and r were made by treating thefive individual determinations from successive injection molding cycles as test results.Poorer precision(larger values of S r and r)would be expected if the same operator were to shutdown and then restart the injection molding machine o
n the same day with the same mold,material and operating t points.Repeatability under such circumstances was not evalu-ated.
12.1.3The following explanations of r and R only are intended to prent a meaningful way of considering the
4Supporting data are available from ASTM Headquarters.Request RR:D-20-1158.
TABLE1Shrinkage from Mold Dimensions of I.M.Bars A Material B Average S r S R r R
10.005130.000080.001240.000220.00347
20.041080.000220.007540.000620.02111
30.004740.000210.001270.000590.00356
40.021070.000130.002800.000360.00784
50.017310.000170.003890.000480.01089
A Values expresd in mm/mm(in./in.).
B1=Polystyrene Specification D4549PS110B56152
2=Polyethylene Specification D4976PE235
3=PMMA Specification D788PMMA0131V0
4=Acetal Specification D6778POM0213
5=Nylon(Polyamide)Specification D6779PA0111
TABLE2Shrinkage from Mold Dimensions of I.M.Disks Flow
Direction A
Material B Average S r S R r R
10.004630.000080.001240.000220.00347
20.037990.000350.009230.000980.02584
30.004200.000180.001700.000500.00476
40.023270.000210.002940.000590.00823
50.019410.000280.003480.000780.00974
A Values expresd in mm/mm(in./in.).
B1=Polystyrene Specification D4549PS110B56152
2=Polyethylene Specification D4976PE235
3=PMMA Specification D788PMMA0131V0
4=Acetal Specification D6778POM0213
5=Nylon(Polyamide)Specification D6779PA0111
TABLE3Shrinkage from Mold Dimensions of I.M.Disks Cross
Direction A
Material B Average S r S R r R
10.004030.000100.001620.000280.00454
20.020400.000190.002470.000530.00692
30.004270.000130.001420.000360.00398
40.025280.000370.004710.001040.01319
50.020680.000470.005060.001320.01417
A Values expresd in mm/mm(in./in.).
B1=Polystyrene Specification D4549PS110B56152
2=Polyethylene Specification D4976PE235
3=PMMA Specification D788PMMA0131V0
4=Acetal Specification D6778POM0213
5=Nylon(Polyamide)Specification D6779
PA0111
