1、Designation: D 3835 08Standard Test Method forDetermination of Properties of Polymeric Materials byMeans of a Capillary Rheometer1This standard is issued under the fixed designation D 3835; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, the year of last revision. 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 measurement of the rheologicalproperties of polymeric materials at various
3、 temperatures andshear rates common to processing equipment. It covers mea-surement of melt viscosity, sensitivity, or stability of meltviscosity with respect to temperature and polymer dwell timein the rheometer, die swell ratio (polymer memory), and shearsensitivity when extruding under constant r
4、ate or stress. Thetechniques described permit the characterization of materialsthat exhibit both stable and unstable melt viscosity properties.1.2 This test method has been found useful for qualitycontrol tests on both reinforced and unreinforced thermoplas-tics, cure cycles of thermosetting materia
5、ls, and other poly-meric materials having a wide range of melt viscosities.1.3 The values stated in SI units are to be regarded asstandard. The inch-pound units given in parentheses are forinformation only.NOTE 1Although this test method and ISO 114431995, “PlasticDetermination of the Fluidity of Pl
6、astics Using Capillary and Slit-DieRheometers” differ in approach or detail, the data obtained using ISO11443, Method A is technically equivalent to this test method1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of th
7、e user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 618 Practice for Conditioning Plastics for TestingD 883 Terminology Relating to PlasticsD 1238 Test Metho
8、d for Melt Flow Rates of Thermoplasticsby Extrusion PlastometerE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ANSI Standard:B46.1 Surface Texture33. Terminology3.1 For definitions of general terms, see TerminologyD 883.3.2 Definitions of Terms Sp
9、ecific to This Standard:3.2.1 apparent valuesviscosity, shear rate, and shearstress values calculated assuming Newtonian behavior and thatall pressure drops occur within the capillary.3.2.2 critical shear ratethe shear rate corresponding tothe critical shear stress (1/s).3.2.3 critical shear stresst
10、he value of the shear stress atwhich there is a discontinuity in the slope of log shear stressversus log shear rate plot or periodic roughness of the polymerstrand occurs as it exits the rheometer die (MPa).3.2.4 delay timethe time delay between piston stop andstart when multiple data points are acq
11、uired from a singlecharge(s).3.2.5 melt densitythe density of the material in the moltenform expressed in g/mL.3.2.6 melt timethe time interval between the completionof polymer charge and beginning of piston travel(s).3.2.7 percent extrudate swellthe percentage change in theextrudate diameter relati
12、ve to the die diameter.3.2.8 shear raterate of shear strain or velocity gradient inthe melt, usually expressed as reciprocal time such assecond1(s1).3.2.9 shear stressforce per area, usually expressed inpascals (Pa).3.2.10 swell ratiothe ratio of the diameter of the extrudedstrand to the diameter of
13、 the capillary (die).3.2.11 viscosityratio of shear stress to shear rate at a givenshear rate or shear stress. It is usually expressed in pascalseconds (Pas).3.2.11.1 Viscosity determined on molten polymers is some-times referred to as melt viscosity.1This test method is under the jurisdiction ofAST
14、M Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.30 on Thermal Properties.Current edition approved Dec. 1, 2008. Published December 2008. Originallyapproved in 1979. Last previous edition approved in 2002 as D 3835 02.2For referenced ASTM standards, visit the ASTM webs
15、ite, 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 American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http
16、:/www.ansi.org.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.3.2.11.2 Viscosity determined on materials exhibiting non-Newtonian flow behavior is referred to as appa
17、rent viscosityunless corrections are made as specified in Section 11.3.2.12 zero shear viscosity, h0the limiting viscosity as theshear rate falls to zero.4. Significance and Use4.1 This test method is sensitive to polymer molecularweight and molecular weight distribution, polymer stabilityboth therm
18、al and rheological, shear instability, and additivessuch as plasticizers, lubricants, moisture reinforcements, orinert fillers, or combination thereof.4.2 The sensitivity of this test method makes the data usefulfor correlating with processing conditions and aids in predict-ing necessary changes in
19、processing conditions. Unlike TestMethod D 1238, which makes a one-point measure at a shearrate typically below processing conditions, this test methoddetermines the shear sensitivity and flow characteristics atprocessing shear rates, and therefore can be used to comparematerials of different compos
20、itions.5. Interferences5.1 Relatively minor changes in the design and arrangementof the component parts have not been shown to cause differ-ences in results between laboratories. However, it is importantfor the best interlaboratory agreement that the design adhereclosely to the description herein; o
21、therwise, it should bedetermined that modifications do not influence the results.5.1.1 TemperatureThe effect of temperature variation onoutput rate, Q, or resultant pressure, P, the other variablesremaining constant, is given approximately by:(A) For a constant-stress rheometer:% error in Q 5dQQ3 10
22、0 5E*RT2dT 3 100 (1)(B) For a constant-rate rheometer:% error in P 5dPP3 100 5E*RT2dT 3 100 (2)where:E* = energy of activation,R = gas constant (8.3 J/Kmol), andT = absolute temperature, K.For some thermoplastics dT = 0.2 K will produce up to 5 %error in Q or P. Therefore, the temperature control sh
23、ould meetthe requirements specified in 6.1.5.5.1.2 Force and Output RateThe output rate varies ap-proximately as the pressure, P, raised to some power, b, greaterthan unity. Over a range of output rates, b may not be constant.The effect of pressure variation on output rate, the othervariables remain
24、ing constant, is given by:% error in Q 5dQQ3 100 5 bdPP3 100 (3)Thus a 0.5 % error in pressure measurement implies an errorof b/2 % in output rate. As the value of b can range from 1 to3, a corresponding error in Q of 0.5 to 1.5 % could result fromthis 0.5 % error in P. It is therefore necessary tha
25、t the precisionof the force and output rate measurements be within 1.0 % ofthe absolute values.5.1.3 Capillary DimensionsThe output rate and forcevary with r3+ bL b, where b is as defined in 5.1.2, r is thecapillary radius, and L the length of land. The error that arisesin Q due to variations only i
26、n r and L is given by:% error in Q 5dQQ3 1005 bdPP3 1005 3 1 b!drr3 100 bdLL3 100 (4)As the value of b can range from 1 to 3, the resultant errorin Q due to a variation in r of 60.5 % can be 2 to 3 %, and theresultant error in Q due to variation in L of 60.5 % can be 0.5to 1.5 %. If Q is being held
27、constant, similar variations in r andL can result in an error of 1.0 to 2.0 % and 0.5 %, respectively,in P.6. Apparatus6.1 RheometerAny capillary rheometer is satisfactory inwhich molten thermoplastic can be forced from a reservoirthrough a capillary die and in which temperature, applied force,outpu
28、t rate, and barrel and die dimensions can be controlledand measured accurately as described as follows. Equipmentthat operates under constant stress or constant rate has beenshown to be equally useful.6.2 BarrelThe barrel (Note 1) shall have a smooth,straight bore between 6.35 and 19 mm in diameter.
29、 Well(s) fortemperature sensor(s) shall be provided as close to the barrelinside wall as possible. The barrel bore should be finished bytechniques known to produce approximately 12 rms or better inaccordance with ANSI B46.1.NOTE 2Cylinders with Rockwell hardness, C scale, greater than 50have shown g
30、ood service life when used at temperatures below 300C.6.3 The capillary (Note 3) shall have a smooth straightbore that is held to within 60.00762 mm (60.0003 in.) indiameter and shall be held to within 60.025 mm (60.001 in.)in length. The bore and its finish are critical. It shall have novisible dri
31、ll or other tool marks and no detectable eccentricity.The capillary bore shall be finished by techniques known toproduce about 12 rms or better when measured in accordancewith ANSI B46.1. Dies having a flat (180) inlet angle and dielength to diameter ratios greater than or equal to 20 arerecommended
32、. Other inlet angles may be used, but compari-sons should be made using only dies with identical inlet cones.The inlet cone shall expand from the capillary at fixed angle toa diameter no less than 50 % of the barrel diameter.NOTE 3Hardened steel, tungsten carbide, Stellite, and Hastelloy arethe most
33、 generally used capillary materials. The capillary shall have adiameter such that the ratio of barrel diameter, D, to capillary diameter, d,is normally between 3 and 15.The length-to-diameter ratio of the capillaryshall normally be between 15 and 40. Smaller ratios of L/D may be usedD3835082in selec
34、ted situations, but are more likely to result in the necessity ofapplying large corrections to the data (1, 2).46.3.1 The precision with which capillary dimensions can bemeasured is dependent upon both the capillary radius andlength. With capillaries of diameter smaller than 1.25 mm(0.050 in.) the s
35、pecified precision is difficult. Due to theextreme sensitivity of flow data to capillary dimensions, it ismost important that both the capillary dimensions and theprecision with which the dimensions are measured are knownand reported.6.4 PistonThe piston shall be made of metal of a hardnessof Rockwe
36、ll hardness, C scale, of greater than 45. The land ofthe piston shall be 0.0254 6 0.007 mm (0.0010 6 0.0003 in.)smaller in diameter than the barrel and at least 6.35 6 0.13 mm(0.250 6 0.005 in.) in length. Alternative piston-barrel-sealingmethods (O-rings, split seals, multi-lands, etc.) outside the
37、setolerances are acceptable, provided there is less than 0.1 g ofmaterial going past the sealing device (see 12.4). Machines thatmeasure plunger force must demonstrate that piston-tip fric-tional effects are less than 1 % over the range of forcemeasurement, or correct for this effect. Demonstration
38、of lowfrictional force is not required for pressure-measurement de-vices; however, adequate seals are still needed for properflow-rate calculations. Above the land, the piston shall berelieved at least 0.25 mm (0.010 in.) less than the barreldiameter. The finish of the piston foot shall be 12 rms wh
39、enmeasured in accordance with ANSI B46.1.6.5 Make provisions for heating and temperature controlsystems such that the apparatus maintains the temperature of afluid, at rest, in the barrel to within 60.2C of the settemperature (see Note 4). Due to shear heating and chemical orphysical changes in the
40、material, it may not be possible to holdthis degree of control during an actual test. In such a case, thetemperature shall be reported with each data point collected.The temperature specified shall be the temperature of thematerial 6 min after a full charging of the barrel measured inthe center of t
41、he barrel 12.7 mm above the top of the die.NOTE 4Ahigh melt-flow-rate polypropylene 20 (g/10 min) has beenfound useful for calibrations of control probes.6.6 The temperature sensing device in the apparatus shall becalibrated by the following method. A traceable temperaturesensor shall be inserted in
42、to the rheometer barrel containing atypical charge of material (see Note 5). The combined accuracyof the sensor and display unit shall be 0.1C or better. Thereference unit shall display temperature to 0.1C or better. Thesensor shall be positioned such that it acquires the averagetemperature centered
43、 vertically at 12.7 mm above the top of thedie and centered radially within the barrel. For large sensor (forexample, large bulb thermometers) elements provisions shallbe made to avoid direct contact of the sensing element with thedie or barrel wall. Proper insulation or immersion levels, orboth, sh
44、ould be adhered to, as required, for sufficient accuracy.Charging the barrel with typical material can be omitted if ithas been demonstrated that for the sensor in question thesteady-state temperature in air results are statistically equiva-lent (95 % confidence limits) to the standard charge temper
45、a-ture results.The controlling point temperature device should becalibrated to within 60.1C of the reference temperaturesensor after steady-state temperature has been achieved. Sub-sequent temperature checks of the controlling temperatureprobe should not exceed 60.2C of the reference probetemperatur
46、e. Calibration of the temperature-indicating deviceshall be verified at a temperature that is within 625C of eachrun temperature.NOTE 5Any type of temperature sensor (thermometer, RTD, opticprobe, etc.) is allowed under 6.1.6 provided it is traceable and falls withinthe element size restriction and
47、positioning requirements.7. Test Specimen7.1 The test specimen may be in any form that can beintroduced into the bore of the cylinder such as powder, beads,pellets, strips of film, or molded slugs. In some cases it may bedesirable to preform or pelletize a powder. In the case ofpreformed plugs, any
48、application of heat to the sample must bekept to a minimum and shall be held constant for all specimensthus formed.8. Conditioning8.1 Many thermoplastic materials do not require condition-ing prior to testing. Materials that contain volatile components,are chemically reactive, or have other unique c
49、haracteristicsare most likely to require special conditioning procedures. Inmany cases, moisture accelerates degradation or may otherwiseaffect reproducibility of flow-rate measurements. If condition-ing is necessary, see the applicable material specification andPractice D 618.9. Procedural Conditions9.1 Typical test temperature conditions of several materialsare given as follows. These are listed for information only. Themost useful data are generally obtained at temperatures con-sistent with processing experience. The shear stress and sh
