1、Designation: D1238 10Standard Test Method forMelt Flow Rates of Thermoplastics by ExtrusionPlastometer1This standard is issued under the fixed designation D1238; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revi
2、sion. 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 covers the determination of the rate ofextrusion of molten thermoplastic resins using an extrusionplastometer
3、.After a specified preheating time, resin is extrudedthrough a die with a specified length and orifice diameter underprescribed conditions of temperature, load, and piston positionin the barrel. Four procedures are described. Comparableresults have been obtained by these procedures in interlabora-to
4、ry round-robin measurements of several materials and aredescribed in Section 15.1.2 Procedure A is used to determine the melt flow rate(MFR) of a thermoplastic material. The units of measure aregrams of material/10 minutes (g/10 min). It is based on themeasurement of the mass of material that extrud
5、es from the dieover a given period of time. It is generally used for materialshaving melt flow rates that fall between 0.15 and 50 g/10 min(see Note 1).1.3 Procedure B is an automatically timed measurementused to determine the melt flow rate (MFR) as well as the meltvolume rate (MVR) of thermoplasti
6、c materials. MFR measure-ments made with Procedure B are reported in g/10 minutes.MVR measurements are reported in cubic centimetres/tenminutes (cm3/10 min). Procedure B measurements are basedon the determination of the volume of material extruded fromthe die over a given period of time. The volume
7、is converted toa mass measurement by multiplying the result by the meltdensity value for the material (see Note 2). Procedure B isgenerally used with materials having melt flow rates from 0.50to 1500 g/10 min.1.4 Procedure C is an automatically timed measurementused to determine the melt flow rate (
8、MFR) of polyolefinmaterials. It is generally used as an alternative to Procedure Bon samples having melt flow rates greater than 75 g/10 min.Procedure C involves the use of a modified die, commonlyreferred to as a “half-die,” which has half the height and halfthe internal diameter of the standard di
9、e specified for use inProcedures A and B thus maintaining the same length todiameter ratio. The test procedure is similar to Procedure B, butthe results obtained with Procedure C shall not be assumed tobe half of those results produced with Procedure B.1.5 Procedure D is a multi-weight test commonly
10、 referred toas a “Flow Rate Ratio” (FRR) test. Procedure D is designed toallow MFR determinations to be made using two or threedifferent test loads (either increasing or decreasing the loadduring the test) on one charge of material. The FRR is adimensionless number derived by dividing the MFR at the
11、higher test load by the MFR at the lower test load. Resultsgenerated from multi-weight tests shall not be directly com-pared with results derived from Procedure A or Procedure B.NOTE 1Polymers having melt flow rates less than 0.15 or greater than900 g/10 min may be tested by the procedures in this t
12、est method;however, precision data have not been developed.NOTE 2Melt density is the density of the material in it molten state.It is not to be confused with the standard density value of the material. SeeTable 1.NOTE 3This test method and ISO 1133 address the same subjectmatter, but differ in techn
13、ical content.1.6 This standard does not purport to address the safetyconcerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2. Referenced
14、 Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD3364 Test Method for Flow Rates for Poly(Vinyl Chlo-ride) with Molecular Structural ImplicationsD4000 Classification System for Specifying Plastic Materi-alsE691 Practice for Conduc
15、ting an Interlaboratory Study toDetermine the Precision of a Test Method1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.30 on Thermal Properties(Section D20.30.08).Current edition approved Feb. 1, 2010. Published March
16、 2010. Originallyapproved in 1965. Last previous edition approved in 2004 as D1238 - 04c. DOI:10.1520/D1238-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the s
17、tandards Document Summary page onthe ASTM website.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.2.2 ANSI Standard:B46.1 on Surface Texture32.3 ISO Standard:ISO 1133
18、Determination of the Melt-Mass Flow Rate(MFR) and the Melt Volume-Flow Rate (MVR) of Ther-moplastics33. Terminology3.1 General:3.1.1 Definitions are in accordance with Terminology D883unless otherwise specified.4. Significance and Use4.1 This test method is particularly useful for quality controltes
19、ts on thermoplastics.4.2 The data produced by this test method serves to indicatethe uniformity of the flow rate of the polymer as made by anindividual process. It is not to be used as an indication ofuniformity of other properties without valid correlation withdata from other tests.4.3 The flow rat
20、e obtained with the extrusion plastometer isnot a fundamental polymer property. It is an empiricallydefined parameter critically influenced by the physical proper-ties and molecular structure of the polymer and the conditionsof measurement. The rheological characteristics of polymermelts depend on a
21、 number of variables. It is possible that thevalues of these variables occurring in this test will differsubstantially from those in large-scale processes, which wouldresult in data that does not correlate directly with processingbehavior.4.4 Measure the flow rate of a material using any of thecondi
22、tions listed for the material in 8.2. For many materials,there are specifications that require the use of this test method,but with some procedural modifications that take precedencewhen adhering to the specification. Therefore, it is advisable torefer to that material specification before using thi
23、s testmethod. Table 1 in Classification D4000 lists the ASTMmaterials standards that currently exist. An alternative testmethod for poly (vinyl chloride) (PVC) compounds is found inD3364.4.5 Additional characterization of a material can be ob-tained if more than one condition is used. In the case th
24、at twoor more conditions are employed, a Flow Rate Ratio (FRR) isobtained by dividing the flow rate at one condition by the flowrate at another condition. Procedure D provides one method tomeasure more than one condition in a single charge.4.6 Frequently, variations in test technique, apparatus ge-o
25、metry, or test conditions, which defy all but the most carefulscrutiny, exist, causing discrepancies in flow rate determina-tions. A troubleshooting guide is found in Appendix X2 and itis a resource to be used to identify sources of test error.5. Apparatus5.1 Extrusion Plastometer (Alternative Names
26、Melt In-dexer, Melt Flow Indexer):NOTE 4Older plastometers that were manufactured in accordancewith “design specifications” detailed in previous revisions of this testmethod (pre D1238 - 04c) are deemed to be acceptable, as long as theymeet the dimensional and performance specifications stated in th
27、is section.NOTE 5Relatively minor changes in the design and arrangement ofthe component parts have been shown to cause differences in resultsamong laboratories. For the best interlaboratory agreement, it is importantthat the design adhere closely to the description herein; otherwise, itshould be det
28、ermined that modifications do not influence the results. Referto Fig. 1.5.1.1 The apparatus shall be a dead-weight piston plastom-eter consisting of a thermostatically controlled heated steelcylinder with a bore that contains a die at the lower end, and aweighted piston operating within the cylinder
29、. The essentialfeatures of the plastometer, illustrated in Figs. 1 and 2, aredescribed in 5.2-5.12. The bore of the extrusion plastometershall be properly aligned in the vertical direction (seeAppendixX1). All dimensional measurements shall be made when thearticle being measured is at 23 6 5C.5.2 Cy
30、linderThe cylinder shall be 50 mm 6 10 mm indiameter, 115 to 180 mm in length with a smooth, straight bore9.5504 6 0.0076 mm in diameter. The cylinder bore shall bemanufactured in a way that produces a finish approximately 12rms or better in accordance with ANSI B46.1. Means shall beprovided to moni
31、tor the temperature inside the bore.5.3 Die (Orifice):5.3.1 Standard DieThe outside diameter of the die shallbe such that it will fall freely to the bottom of the hole in thecylinder. The orifice of the die shall have a smooth straight bore2.095 6 0.005 mm in diameter and shall be 8.000 6 0.025 mmin
32、 length (see Fig. 2). The bore of the orifice and its finish arecritical. It shall have no visible drill or other tool marks and nodetectable eccentricity. The bore of the orifice shall be manu-factured by techniques known to produce finishes approxi-mately 12 rms or better in accordance with ANSI B
33、46.1.5.3.2 “Half” DieUsed for Procedure C. When testingpolyolefins with a MFR of 75 or greater (using the standard3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.TABLE 1 Standard Test Conditions, Sample Mass,Aand TestingT
34、imeBFlow Range,g/10 minSuggested Mass ofSample in Cylinder,gTime Inter-val, minFactor forObtaining FlowRateing/10min0.15 to 1.0 2.5 to 3.0 6.00 1.671.0 to 3.5 3.0 to 5.0 3.00 3.333.5 to 10 4.0 to 8.0 1.00 10.0010 to 25 4.0 to 8.0 0.50 20.0025 4.0 to 8.0 0.25 40.00AThis is a suggested mass for materi
35、als with melt densities of about 0.7 g/cm3.Correspondingly, greater quantities are suggested for materials of greater meltdensities. Density of the molten resin (without filler) may be obtained using theprocedure described by Terry, B. W., and Yang, K., “ANew Method for DeterminingMelt Density as a
36、Function of Pressure and Temperature,” SPE Journal, SPEJA,Vol. 20, No. 6, June 1964, p. 540 or the procedure described by Zoller, Paul, “ThePressure-Volume-Temperature Properties of Polyolefins,” Journal of Applied Poly-mer Science, Vol 23, 1979, p. 1051. It may also be obtained from the weight of a
37、nextruded known volume of resin at the desired temperature. For example, 25.4 mm(1 in.) of piston movement extrudes 1.804 cm3of resin. An estimate of the densityof the material can be calculated from the following equation:resin density at test temperature 5 M/1.804where:M = mass of extruded resin.B
38、See 9.13.D1238 102die), an alternate die has shown to improve the reproducibilityof results by reducing the flow rate of these materials. Theoutside diameter of the die shall be such that it will fall freelyto the bottom of the hole in the cylinder. The orifice shall havea smooth straight bore 1.048
39、 6 0.005 mm in diameter and shallbe 4.000 6 0.025 mm in length (see Fig. 2A). The bore of theorifice and its finish are critical. It shall have no visible drill orother tool marks and no detectable eccentricity. The bore of theorifice shall be manufactured by techniques known to producefinishes appr
40、oximately 12 rms or better in accordance withANSI B46.1 (Note Note 6). No spacer shall be used with thisdie.NOTE 6Recommended die material is tungsten carbide. Also satisfac-tory are steel, synthetic sapphire, and cobalt-chromium-tungsten alloy.When softer materials are used, it will be necessary to
41、 conduct criticaldimensional checks and visual inspections on the die more often.5.4 Piston:5.4.1 The piston shall be made of steel. There shall beinsulation at the top as a barrier to heat transfer from the pistonto the weight. The piston shall be prevented from rubbing onthe bore. Most commerciall
42、y available instruments use a loosefitting metal guide sleeve, but other methods are acceptable.The weight of the sleeve shall not be considered as part of thetest load. The land (foot) of the piston shall be9.4742 6 0.0076 mm in diameter and 6.35 6 0.10 mm inlength. Above the land, the piston shall
43、 be relieved to # 9.0FIG. 1 General Arrangement of Extrusion Plastometer (SeeSection 5.)FIG. 2 Details of Extrusion PlastometerD1238 103mm in diameter (see Fig. 2). The piston land shall bemanufactured by techniques known to produce finishes ap-proximately 12 rms in accordance with ANSI B46.1.Ifcorr
44、osion is a problem, the piston or piston land, if removable,shall be made of corrosion resistant material.5.4.2 For procedure A, the piston shall be scribed with tworeference marks 4 mm apart in such fashion that when thelower mark coincides with the top of the cylinder, guide sleeveor other suitabl
45、e reference point, the bottom of the piston is 48mm above the top of the die (see Fig. 1) and the timed test runshall start within these two reference marks. The targetedstarting point shall be 46 6 2mm above the upper face of thedie. (see Fig. 1).5.4.3 The combined weight of piston and load shall b
46、ewithin a tolerance of 60.5 % of the selected load.5.5 Temperature Control System:5.5.1 The equipment shall have the capability of heating andmaintaining the temperature inside the bore of the cylinder inaccordance with the requirements specified in Table 2 through-out the duration of the test.5.5.2
47、 The preferred method for calibrating the temperatureis to use a temperature sensor assembly having a sensor with atleast an accuracy of 60.08C at 200C and a 20 6 0.5-mmlong brass tip press fit on the end of the sensor. The diameterof the brass tip shall closely match the diameter of the die andthe
48、length of the active measuring length of the temperaturesensor (see Appendix X3).5.5.3 Temperatures shall be verified with the bottom of thetemperature sensor at 10 and 75 6 1 mm above the upper faceof the die and at each test temperature, without touching thedie. Allow at least four minutes for equ
49、ilibrium of temperatureto be reached for each position. Temperature variation shall bedetermined over a minimum of 15 minutes. When using the“half” die, the temperature indicating device shall be calibratedas stated in Table 2 except temperatures are measured at79 6 1 mm and 14 6 1 mm above the upper surface of the die.5.5.4 An alternative method is to insert the temperaturesensor without a brass tip into the melt from the top of thecylinder so that it is 10 and 75 6 1 mm above the upper faceof the die.5.5.5 The temperature sensor and readout equipment usedfor calibrat
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