1、Designation: D 1238 04cStandard Test Method forMelt Flow Rates of Thermoplastics by ExtrusionPlastometer1This standard is issued under the fixed designation D 1238; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last r
2、evision. 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 covers measurement of the rate ofextrusion of molten resins through a die of a specified lengthand diamet
3、er under prescribed conditions of temperature, load,and piston position in the barrel as the timed measurement isbeing made.1.2 Procedure A is a manual cutoff operation based on timeused for materials having flow rates that fall generally between0.15 and 50 g/10 min. Procedure B is an automatically
4、timedflow rate measurement used for materials having flows from0.50 to 900 g/10 min. By both procedures, the piston travel isgenerally the same during the timed measurement; the pistonfoot is about 46 and 20.6 mm above the die. Comparable flowrates have been obtained by these procedures in interlabo
5、ratoryround-robin measurements of several materials described in14.1. Provision is made for calculation of melt volume-flowrate as well as melt mass-flow rate.NOTE 1Round-robin testing indicates this test method may be suit-able at flow rates up to 1500 g/10 min if the timing clock resolves theelaps
6、ed time to the nearest 0.01 s.NOTE 2This test method and ISO 1133-1991 are technically equiva-lent.1.3 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 practic
7、es and determine the applicability of regulatorylimitations prior to use. Specific precautionary statements aregiven in 5.7, 10.2.12, and 15.1.2.2. Referenced Documents2.1 ASTM Standards:2D 618 Practice for Conditioning Plastics for TestingD 883 Terminology Relating to PlasticsD 3364 Test Method for
8、 Flow Rates for Poly Vinyl Chloridewith Molecular Structural ImplicationsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ANSI Standard:B46.1 on Surface Texture32.3 ISO Standard:ISO 1133-1991 Determination of the Melt-Mass Flow Rate(MFR) and the Me
9、lt Volume-Flow Rate (MVR) of Ther-moplastics33. Terminology3.1 General:3.1.1 For definition of some of the technical terms used inthis test method refer to Terminology D 883.4. Significance and Use4.1 This test method is particularly useful for quality controltests on thermoplastics.NOTE 3Polymers h
10、aving flow rates less than 0.15 or greater than 900g/10 min may be tested by the procedures in this test method; however,precision data have not been developed.4.2 This test method serves to indicate the uniformity of theflow rate of the polymer as made by an individual process and,in this case, may
11、 be indicative of uniformity of other proper-ties. However, uniformity of flow rate among various polymersas made by various processes does not, in the absence of othertests, indicate uniformity of other properties.4.3 The flow rate obtained with the extrusion plastometer isnot a fundamental polymer
12、 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 number of variables. Since the values ofthese variables occurring in
13、 this test may differ substantiallyfrom those in large-scale processes, test results may notcorrelate directly with processing behavior.4.4 The flow rate of a material may be measured under anyof the conditions listed for it in 8.2.Additional characterizationof a material can be obtained if more tha
14、n one condition is1This test method is under the jurisdiction ofASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.30 on Thermal Properties(Section D20.30.08).Current edition approved December 1, 2004. Published December 2004. Origi-nally approved in 1965. Last previo
15、us edition approved in 2004 as D 1238 - 04b.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 standards Document Summary page onthe ASTM website.3Available from A
16、merican 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 Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.used. In case two conditions
17、are employed, a Flow Rate Ratio(FRR) may be obtained by dividing the flow rate at onecondition by the flow rate at the other condition.5. Apparatus5.1 Plastometer:5.1.1 The apparatus shall be a dead-weight piston plastom-eter consisting of a thermostatically controlled heated steelcylinder with a di
18、e at the lower end and a weighted pistonoperating within the cylinder. The essential features of theplastometer, illustrated in Figs. 1 and 2, are described in5.2-5.8.All dimensional measurements shall be made when thearticle being measured is at 23 6 5C.5.1.2 Relatively minor changes in the design
19、and arrange-ment of the component parts have been shown to causedifferences in results among laboratories. It is important,therefore, for the best interlaboratory agreement that the designadhere closely to the description herein; otherwise, it should bedetermined that modifications do not influence
20、the results.5.2 CylinderThe steel cylinder shall be 50.8 mm indiameter, 162 mm in length with a smooth, straight hole9.5504 6 0.0076 mm in diameter, displaced 4.8 mm from thecylinder axis. Wells for a thermal sensor (thermoregulator,thermistor, etc.) and thermometer shall be provided as shownin Fig.
21、 1.A3.2-mm plate shall be attached to the bottom of thecylinder to retain the die. A hole in this plate, centered underthe die and countersunk from below, allows free passage of theextrudate. The cylinder may be supported by at least two6.4-mm high-strength screws at the top (radially positioned atr
22、ight angles to the applied load) or by at least two 10-mmdiameter rods screwed into the side of the cylinder forattaching to a vertical support. The essential dimensions of asatisfactory cylinder of this type are shown in Fig. 1 (Note 4).The cylinder bore should be finished by techniques known topro
23、duce approximately 12 rms or better in accordance withANSI B46.1.NOTE 4Cylinders made of SAE 52100 or other equivalent steelheat-hardened to 6065 Rockwell Hardness Scale C give good servicewhen used at temperatures below 200C. Cylinder liners of cobalt-chromium-tungsten alloy are also satisfactory t
24、o 300C.5.3 DieThe outside of the steel die shall be such diameterthat it will fall freely to the bottom of the 9.5504 6 0.0076 mmdiameter hole in the cylinder (Note 5). The die shall have asmooth straight bore 2.0955 6 0.0051 mm in diameter andshall be 8.000 6 0.025 mm in length. The bore and its fi
25、nishare critical. It shall have no visible drill or other tool marks andno detectable eccentricity. The die bore shall be finished bytechniques known to produce approximately 12 rms or better inaccordance with ANSI B46.1.NOTE 5Recommended die material is tungsten carbide.Also satisfac-tory are steel
26、, synthetic sapphire, and cobalt-chromium-tungsten alloy.5.4 Piston:FIG. 1 General Arrangement of Extrusion PlastometerFIG. 2 Details of Extrusion PlastometerD 1238 04c25.4.1 The piston shall be made of steel with an insulatingbushing at the top as a barrier to heat transfer from the pistonto the we
27、ight. The land of the piston shall be 9.4742 6 0.0076mm in diameter and 6.35 6 0.13 mm in length. The pistondesign may incorporate means for land replacement, forexample, having threads and flats immediately above the land.Above the land, the piston shall be no larger than 8.915 mm indiameter (Note
28、6). The finish of the piston foot shall be 12 rmsin accordance with ANSI B46.1. If wear or corrosion is aproblem, the piston should be of stainless steel and equippedwith a detachable foot for ease of replacement.NOTE 6To improve standardization it is preferable that the piston beguided with a loose
29、-fitting metal sleeve at the top of the cylinder.NOTE 7Pistons of SAE 52100 steel with the bottom 25 mm, includingthe foot, hardened to a Rockwell hardness, C scale, of 55 to 59 have beenfound to give good service when used at temperatures below 200C.5.4.2 The piston shall be scribed with two refere
30、nce marks4 mm apart in such fashion that when the lower mark coincideswith the top of the cylinder or other suitable reference point,the bottom of the piston is 48 mm above the top of the die (seeFig. 1).5.4.3 The combined weight of piston and load shall bewithin a tolerance of 60.5 % of the selecte
31、d load.5.5 Heater:5.5.1 The equipment must have a heater capable of heatingthe apparatus so that the temperature at 10 mm above the diecan be maintained within 60.2C of the desired temperatureduring the test. The temperature of the barrel, from 10 mm to75 mm above the top of the die, must be maintai
32、ned within61 % of the set temperature (C).NOTE 8At temperatures higher than 200C this degree of temperaturecontrol may be more difficult to obtain.5.5.2 Calibrate the temperature-indicating device by meansof a light-gage probe-type thermocouple or a platinum-resistance temperature sensor having a sh
33、ort sensing length.4The thermocouple should be encased in a metallic sheathhaving a diameter of approximately 1.6 mm with its hotjunction grounded to the end of the sheath. Insert the tempera-ture sensor into the melt from the top of the cylinder so that itis 10 6 1 mm above the upper face of the di
34、e. The temperaturesensors shall be used with a potentiometer having a sensitivityof at least 0.005 mV, or a temperature readout having asensitivity of at least 0.1C. Calibration should also be verifiedat 75 mm above the upper face of the die. An alternatetechnique for calibration is to use a sheathe
35、d thermocouple orplatinum-resistance temperature sensor with tip diameter of9.4 6 0.1 mm for insertion in the bore without materialpresent. An example of this is shown in Fig. 3. Calibration ofthe temperature-indicating device shall be verified at each runtemperature.NOTE 9The response of the temper
36、ature sensing device may beaffected by immersion level. Take care to ensure adequate insulation of thedevice sensor and stabilization of the barrel temperature.5.5.3 Heat shall be supplied by electric band heater(s)covering the entire length of the cylinder. The heater(s) may be4Round-robin data sho
37、wing flow rate and corresponding temperature profile ofthe melt obtained using probe-type thermocouples and platinum resistance tempera-ture sensors can be obtained from ASTM Headquarters. Request RR:D20-1094.FIG. 3 Example of a Temperature Calibration DeviceNote AMineral glass insulation or equival
38、ent spacer shall be bonded to tip and SS tube. Bond material shall be lowconductivity type, 400C minimum rating. Insulation jacket material shall be low conductivity type (400C minimum ratingpreferred, see Note 5).Note BThe RTD shall be inserted into bronze tip and bonded using high conductivity, 40
39、0C rated material. Tip of RTDelement shall touch the bronze tip. Minimum insertion depth of 11.2 mm clearance between RTD and tip wall shall be minimized.D 1238 04c3single- or multi-element, depending upon the manufacturerscontrol means. The heater(s) plus control system must becapable of maintainin
40、g the temperature within the required60.2C of the set point. The temperature sensor and readoutequipment must be calibrated to a traceable national standard(that is, NIST) at least once per year. The cylinder with theheater(s) shall be lagged with 38 mm of foamed-glass insula-tion. An insulating pla
41、te 3.2 mm in thickness shall be attachedto the bottom of the cylinder to minimize heat loss at this point.5.6 Temperature ControllerThe type of controller andsensor must be capable of meeting the required controltolerance specified in 5.5.1.5.7 Thermometer Thermometers having a range of 4Cgraduated
42、in 0.2C divisions may be used to indicate tempera-ture. The temperature at this point may not necessarily be thetemperature of the material 10 mm above the die. Thethermometer may be used to monitor indirectly the temperatureof the material 10 mm above the die and may be calibrated byreference to a
43、thermocouple or platinum resistance temperaturesensor inserted in the material 10 mm above the die. See 5.5.2for a description of a method for measuring temperature.(WarningCaution should be observed with the use of amercury-filled thermometer. Mercury vaporization occurs ifthe thermometer is broken
44、. Mercury thermometers are not to beused at or above the boiling point of mercury, which is 357C.)5.8 LevelProvision shall be made for vertical alignmentof the bore of the extrusion plastometer. This is necessary tominimize subtractive loads resulting from rubbing or frictionbetween the piston tip a
45、nd sidewall. Means of alignment arediscussed in Appendix X1.5.9 Accessory EquipmentNecessary accessories includeequipment for charging samples to the cylinder, a funnel, a dieplug, a tool for cutting off the extruded sample, a timer or stopwatch, cleaning equipment, go/no-go gages, a balance accurat
46、eto 60.001 g, and, when required, a weight or weight-pistonsupport.NOTE 10Satisfactory operation of the apparatus for polyethylenes canbe ascertained by making measurements on NIST Standard ReferenceMaterials (SRMs) certified for melt flow rate. The four SRMs certifiedunder condition 190/2.16 are SR
47、M 1473 with a flow rate of 1.29 g/min,SRM 1474 with a flow rate of 5.03 g/10 min, SRM 1496 with a flow rateof 0.26 g/10 min, and SRM 1497 with a flow rate of 0.19 g/10 min. SRM1475a is certified under condition 190/3.25 with a flow rate of 2.20 g/10min.56. Test Specimen6.1 The test specimen may be i
48、n any form that can beintroduced into the bore of the cylinder, for example, powder,granules, strips of film, or molded slugs. It may be desirable topreform or pelletize a powder.7. Conditioning7.1 Many thermoplastic materials do not require condition-ing prior to testing. Materials which contain vo
49、latile compo-nents, are chemically reactive, or have other special character-istics most probably require appropriate conditioningprocedures. Moisture not only affects reproducibility of flowrate measurement but, in some types of materials, degradationis accelerated by moisture at the high temperatures used intesting. Check the applicable material specification for anyconditioning requirements before using this test. See PracticeD 618 for appropriate conditioning practices.8. Procedural Conditions8.1 Standard conditions of test are given in Table 1
