1、Designation: D3835 16Standard Test Method forDetermination of Properties of Polymeric Materials byMeans of a Capillary Rheometer1This standard is issued under the fixed designation D3835; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, 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. Scope1.1 This test method covers measurement of the rheologicalproperties of polymeric materials at various te
3、mperatures 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 rate
4、 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 unreinforcedthermoplastics, cure cycles of thermosetting materials, a
5、ndother polymeric materials having a wide range of melt viscosi-ties.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 Plastics
6、 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 the user
7、 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:2D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD1238 Test Method for Mel
8、t Flow Rates of Thermoplasticsby Extrusion PlastometerE691 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 Terminology D883.3.2 Definitions of Terms Specific to
9、This Standard:3.2.1 apparent valuesviscosity, shear rate, and shear stressvalues calculated assuming Newtonian behavior and that allpressure drops occur within the capillary.3.2.2 critical shear ratethe shear rate corresponding to thecritical shear stress (1/s).3.2.3 critical shear stressthe value o
10、f 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 acquired from
11、 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 relative to the
12、die diameter.3.2.8 shear raterate of shear strain or velocity gradient inthe melt, usually expressed as reciprocal time such as second1(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 the capi
13、llary (die).1This test method is under the jurisdiction ofASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.30 on Thermal Properties.Current edition approved May 1, 2016. Published May 2016. Originallyapproved in 1979. Last previous edition approved in 2008 as D3835
14、- 08. DOI:10.1520/D3835-16.2For 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 American National
15、Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.11 viscosityratio of she
16、ar 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.3.2.11.2 Viscosity determined on materials exhibiting non-Newtonian flow behavior is referred to a
17、s apparent viscosityunless corrections are made as specified in Section 11.3.2.12 zero shear viscosity, 0the 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
18、thermal 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 change
19、s in processing conditions. Unlike TestMethod D1238, 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 is 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 must be deter-mined 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 5dQQ3100
22、 5E*RT2dT 3100 (1)(B) For a constant-rate rheometer:% error in P 5dPP3100 5E*RT2dT 3100 (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 shall
23、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. It is possible that b is not constant over a range ofoutput rates. The effect of pressure variation on output rate, theother variab
24、les remaining constant, is given by:% error in Q 5dQQ3100 5 bdPP3100 (3)Thus a 0.5 % error in pressure measurement implies an errorof b/2 % in output rate.As the value of b normally ranges from1 to 3, a corresponding error in Q of 0.5 to 1.5 % could resultfrom this 0.5 % error in P. It is therefore
25、necessary that theprecision of the force and output rate measurements be within1.0 % of the absolute values.5.1.3 Capillary DimensionsThe output rate and force varywith 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 vari
26、ations only in r and L is given by:% error in Q 5dQQ3100 5 bdPP3100 5 31b!drr3100 2 bdLL3100 (4)As the value of b normally ranges from 1 to 3, the resultanterror in Q due to a variation in r of 60.5 % can be 2 to 3 %,and the resultant error in Q due to variation in L of 60.5 % canbe 0.5 to 1.5 %. If
27、 Q is being held constant, similar variationsin r and L 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 it is possible to force molten thermoplastic from areservoir through a capillary die and in which tempe
28、rature,applied force, output rate, and barrel and die dimensions arecontrolled and measured accurately as described as follows.Equipment that operates under constant stress or constant ratehas been shown to be equally useful.6.2 BarrelThe barrel (Note 2) shall have a smooth,straight bore. The barrel
29、 bore shall be finished by techniquesknown to produce approximately 12 rms or better in accor-dance with ANSI B46.1. Care must be taken to ensure that thepreheat time is adequate for the barrel diameter to reachtemperature homogeneity and that such time is not adverselyaffecting material degradation
30、.NOTE 2Cylinders with Rockwell hardness, C scale, greater than 50have shown good service life when used at temperatures below 300C.6.3 The capillary (Note 3) shall have a smooth straight borethat is held to within 60.00762 mm (60.0003 in.) in diameterand shall be held to within 60.025 mm (60.001 in.
31、) in length.The bore and its finish are critical. It shall have no visible drillor other tool marks and no detectable eccentricity. The capil-lary bore shall be finished by techniques known to produceabout 12 rms or better when measured in accordance withANSI B46.1. Dies having a flat (180) inlet an
32、gle and dielength to diameter ratios greater than or equal to 20 arerecommended. It is possible to use other inlet angles, butcomparisons must be made using only dies with identical inletcones. The inlet cone shall expand from the capillary at fixedangle to a diameter no less than 50 % of the barrel
33、 diameter.NOTE 3Hardened steel, tungsten carbide, Stellite, and Hastelloy arethe most 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 capillarys
34、hall normally be between 15 and 40. Smaller ratios of L/D may be usedin selected situations, but are more likely to result in the necessity ofD3835 162applying large corrections to the data (1, 2).46.3.1 The precision with which capillary dimensions aremeasured is dependent upon both the capillary r
35、adius andlength. With capillaries of diameter smaller than 1.25 mm(0.050 in.) the specified 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 k
36、nownand reported.6.4 PistonThe piston shall be made of metal of a hardnessof Rockwell 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
37、 piston-barrel-sealingmethods (O-rings, split seals, multi-lands, etc.) outside thesetolerances 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
38、 1 % over the range of forcemeasurement, or correct for this effect. Demonstration 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
39、in.) less than the barreldiameter. The finish of the piston foot shall be 12 rms whenmeasured 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 settem
40、perature (see Note 4). Due to shear heating and chemical orphysical changes in the material, holding this degree of controlduring an actual test might not be possible. In such a case, thetemperature shall be reported with each data point collected.The temperature specified shall be the temperature o
41、f thematerial 6 min after a full charging of the barrel measured inthe center of the 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 becali
42、brated by the following method. A traceable temperaturesensor shall be inserted into 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. T
43、hesensor shall be positioned such that it acquires the averagetemperature centered 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 ele
44、ment with thedie or barrel wall. Proper insulation or immersion levels, orboth, shall be adhered to, as required, for sufficient accuracy. Itis acceptable to omit charging the barrel with typical materialif it has been demonstrated that for the sensor in question thesteady-state temperature in air r
45、esults are statistically equiva-lent (95 % confidence limits) to the standard charge tempera-ture results. The controlling point temperature device must becalibrated to within 60.1C of the reference temperaturesensor after steady-state temperature has been achieved. Sub-sequent temperature checks of
46、 the controlling temperatureprobe must not exceed 60.2C of the reference probe tempera-ture. Calibration of the temperature-indicating device shall beverified at a temperature that is within 625C of each runtemperature.NOTE 5Any type of temperature sensor (thermometer, RTD, opticprobe, etc.) is allo
47、wed under 6.1.6 provided it is traceable and falls withinthe element size restriction and positioning requirements.7. Test Specimen7.1 The test specimen shall be of any form such as powder,beads, pellets, strips of film, or molded slugs, which whenintroduced into the bore of the cylinder will do so
48、withoutundue force. In some cases preforming or pelletizing a powderis desirable. In the case of preformed plugs, any application ofheat to the sample must be kept to a minimum and shall be heldconstant for all specimens thus formed.8. Conditioning8.1 Many thermoplastic materials do not require cond
49、ition-ing prior to testing. Materials that contain volatile components,are chemically reactive, or have other unique characteristicsare most likely to require special conditioning procedures. Inmany cases, moisture accelerates degradation or possiblyotherwise affect reproducibility of flow-rate measurements. Ifconditioning is necessary, see the applicable material specifi-cation and Practice D618.9. Procedural Conditions9.1 Typical test temperature conditions of several materialsare given as follows. These are listed for information only. The
