1、Designation: D 5099 93 (Reapproved 2003)Standard Test Methods forRubberMeasurement of Processing Properties UsingCapillary Rheometry1This standard is issued under the fixed designation D 5099; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods describe how capillary rheometrymay be used to measure the rheological chara
3、cteristics ofrubber (raw or compounded). Two methods are addressed:Method Ausing a piston type capillary rheometer, andMethod Busing a screw extrusion type capillary rheometer.The two methods have important differences, as outlined in7-10 and 11-14, respectively.1.2 These test methods cover the use
4、of a capillary rheom-eter for the measurement of the flow properties of thermoplas-tic elastomers, unvulcanized rubber, and rubber compounds.These material properties are related to factory processing.1.3 Since piston type capillary rheometers impart only asmall amount of shearing energy to the samp
5、le, these measure-ments directly relate to the state of the compound at the time ofsampling. Piston capillary rheometer measurements will usu-ally differ from measurements with a screw extrusion typerheometer, which imparts shearing energy just before therheological measurement.1.4 Capillary rheomet
6、er measurements for plastics are de-scribed in Test Method D 3835.1.5 The values stated in SI units are to be regarded asstandard. The values given in parentheses are for informationonly.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is t
7、heresponsibility of the 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 1349 Practice for RubberStandard Temperatures forTestingD 1485 Test Methods for Rub
8、ber from Natural SourcesSampling and Sample PreparationD 3182 Practice for RubberMaterials, Equipment, andProcedures for Mixing Standard Compounds and Prepar-ing Standard Vulcanized SheetsD 3835 Test Method for Determination of Properties ofPolymeric Materials by Means of a Capillary RheometerD 3896
9、 Practice for Rubber from Synthetic SourcesSamplingD 4483 Practice for Determining Precision for Test MethodStandards in the Rubber and Carbon Black Industries3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 apparent (uncorrected) shear rate (g)shear strainrate (or velocity gra
10、dient) of the rubber extrudate as it passesthrough the capillary die.3.1.1.1 DiscussionThis velocity gradient is not uniformthrough the cross-section of the capillary die. The shear rate iscalculated for the region of highest shear, at the wall of thecapillary. By selecting a die diameter and contro
11、lling thevolume flow per unit time through the die, a specific level ofapparent shear rate may be achieved. Alternately, the shearstress (entrance pressure) may be controlled, and the apparentshear rate measured.3.1.1.2 Mathematically, the apparent shear rate for a New-tonian fluid at the wall is gi
12、ven as follows:g532 QpD3(1)where:g = apparent shear rate,Q = quantity of fluid extruded in one second, mm3,p = the constant pi, approximately 3.142, andD = diameter of the measuring capillary, mm.The units of apparent shear rate are reciprocal seconds (s1).3.1.2 apparent shear stress (t)the measured
13、 resistance toflow through a capillary die; it may be determined by measur-ing the die entrance pressure for a specified die, then applyingappropriate geometric factors.1These test methods are under the jurisdiction of ASTM Committee D11 onRubber and are the direct responsibility of Subcommittee D11
14、.12 on ProcessabilityTests.Current edition approved Nov. 1, 2003. Published December 2003. Originallyapproved in 1993. Last previous edition approved in 1998 as D 5099 93 (1998).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org.
15、For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.2.1 Mathematically, apparent shear stress is given asfollows:t5P
16、4L/D!(2)where:t = apparent shear stress,P = pressure at the entrance to the measuring capillary, Pa,L = length of the measuring capillary, mm, andD = diameter of the measuring capillary, mm.3.1.3 apparent viscosityratio of apparent shear stress toapparent shear rate.3.1.3.1 DiscussionFor an extrusio
17、n capillary rheometer,the ratio is usually calculated at a given shear rate. It isnormally expressed in Pascal seconds (Pa.s). At constanttemperature, the apparent viscosity of most polymers is notconstant, but varies with shear rate. The viscosity is generallyannotated with the shear rate at which
18、the measurement wasmade.3.1.4 capillary rheometeran instrument in which rubbercan be forced from a reservoir through a capillary die; thetemperature, pressure entering the die, and flow rate throughthe die can be controlled and accurately measured.3.1.5 corrected shear rate (gw)a shear rate at the w
19、all ofthe capillary die determined by applying the Rabinowitschcorrection for non-Newtonian materials.3.1.5.1 DiscussionThe Rabinowitsch correction math-ematically adjusts the shear rate values for the fact that the fluidis non-Newtonian, using the power law fluid model. To obtainthe corrected shear
20、 rate, at least two measurements of apparentshear stress and apparent shear rate are made, generally byincreasing the rate of extrusion (Q) with the same measuringcapillary. The Bagley correction of 3.1.6.2 is made to the shearstress values; either by algebraic means if only two measure-ments are ma
21、de, or by a regression equation for a greaternumber of points, (Eq 6) is solved for N8, using the correctedshear stress (tw). Although in theory, N (of (Eq 6) and N (of(Eq 3) should be identical, their respective values may vary asthe Bagley correction (E) varies, hence the designation of N8 in(Eq 3
22、).3.1.5.2 The corrected shear rate (gw) is therefore:gw5gF3N8 1 14NG(3)For most rubbers or elastomers the correction factor forshear rate is typically between 1.5 and 2.1, but there areexceptions.3.1.6 corrected shear stress (tw)the apparent shear stressat the wall of the capillary die; it is correc
23、ted by applying theBagley correction (E) (see 3.1.6.2) for energy losses at theentrance and exit of the die.3.1.6.1 Discussion 1Units are Pascals (Pa); however, thiscorrection is often applied as though it were an additionallength of capillary. The correction is often termed 88end effect.”Capillary
24、entrance angle and geometry have great influence onthe magnitude of this correction.3.1.6.2 Discussion 2Since the magnitude of correction isa function of shear rate, data for this correction are obtained byusing two or more dies of different lengths but of the samediameter (and thus same apparent sh
25、ear rate, as calculated in3.1.1.2). If the data from these additional dies are compared,either graphically or mathematically, a linear relationship ofextrusion pressure with die geometry is usually obtained, of thefollowing form:P 5 cFL 1 EDG(4)where:c = slope of the line, andE = Bagley correction,
26、expressed as the equivalent lengthof capillary in millimetres necessary to extrapolate thepressure line value to zero. This term is often called“end effect.”Both of these terms are functions of the rubber compoundand the shear rate.3.1.6.3 Corrected shear stress (tw) is therefore:tw5P4FLD1 EG(5)or:5
27、PL2 Ps4FLLDL2LsDsG(6)where:PL= pressure drop for long die, Pa,PS= pressure drop for short die, Pa,LL= length of the long die, mm, andLS= length of the short die, mm.3.1.7 corrected viscositythe ratio of corrected shear stressto corrected shear rate.3.1.7.1 DiscussionThe units for viscosity are Pasca
28、l sec-onds (Pa.s). Since the corrections used, as well as the materialproperties, are functions of shear rate, it is very important tostate the particular value of shear rate at which the measure-ment was made.3.1.8 critical shear stressthat value of shear stress atwhich there is a discontinuity in
29、the slope of the log shear stressversus log shear rate plot; manifested by a sudden change insurface roughness of the extrudate.3.1.9 die entrance pressure (P)the pressure in the reser-voir at the die entrance.3.1.10 Newtonian fluida material for which the measuredviscosity is not changed by changin
30、g the shear rate. Simpleliquids such as rubber extender oils are Newtonian; mostpolymeric materials are not.3.1.11 power law fluida material for which the viscosityvaries with the shear rate in accordance with the knownrelationship:t5Kg!N(7)D 5099 93 (2003)2where:K = constant, often called consisten
31、cy index, andN = a material parameter generally called the power lawindex. It is equal to 1.0 for Newtonian fluids andgenerally between 0.18 and 0.33 for compoundedrubbers or elastomers, or both, but there are excep-tions.3.1.11.1 Most non-Newtonian fluids follow this relationshipfor at least short
32、ranges of the shear rate variable. The equationis generally used in its logarithmic form, as follows:log t! 5 log K! 1 N log g! (8)4. Significance and Use4.1 These test methods are useful for characterization ofraw, or compounded, unvulcanized rubber in terms of viscos-ity, or resistance to flow.4.2
33、 The data produced by these test methods have beenfound useful for both quality control tests and compounddevelopment. However, direct correlation with factory condi-tions is not implied.4.3 Flow performance data permits quality control of in-coming raw rubbers because the flow parameters are sensit
34、iveto molecular weight and to molecular weight distribution.Therefore, these test methods may distinguish differencesbetween lots.4.4 The shear viscosity or flow viscosity of compoundedrubber batches in the raw (unvulcanized) state will not only besensitive to the raw polymer molecular properties, b
35、ut will alsobe affected by type and amount of filler, plasticizer or softenerlevels, amount and type of copolymer blend, and other com-pounding materials. These test methods can serve as a qualitycontrol tool for either incoming custom mixed compounds orfor in-house quality assurance checks on produ
36、ction mixing.These test methods are useful for research and development ofnew products by measuring the rheological effect on a rubbercompound of new polymers, resins, softeners, etc.5. Interferences5.1 Since flow properties of these non-Newtonian materialsare not linear, capillary rheometers should
37、 be operated atconditions of flow (temperature, pressure, and rate) similar tothat of selected commercial processes. These processes includemixing, calendering, extrusion, and molding of rubber com-pounds.5.2 Piston type rheometers impart only very small amountsof shear or mixing energy before the m
38、easurement is made.Consequently, the measurement relates to the state of thepolymer or compound at the time the sample was taken. If it isdesirable to relate directly to a down-stream process involvingsignificant amounts of mixing energy, it is sometimes desirableto shear the polymer on a roll mill
39、before the rheometricalmeasurement is made.5.3 Screw extrusion type rheometers impart significantamounts of energy to the rubber compound before the mea-surement is made. Interpretation of the data for factoryoperations such as production of extrusions, calendering, orinjection molding is therefore
40、more straightforward than forcompression molding operations, where factory work input isquite small.6. Sampling and Conditioning of Samples6.1 Condition the sample obtained in accordance withMethods D 1485 or D 3896 until it has reached room tempera-ture (23 6 3C (73 6 5F) throughout.6.2 Massed Spec
41、imenPrepare a massed specimen, as in6.2.1, only if indicated in Table 1. Massing is used to combinethe rubber crumbs, homogenize the specimen, and extracttrapped air.6.2.1 Pass 250 6 5 g of the sample between the rolls of thestandard laboratory mill (described in Practice D 3182) havinga roll temper
42、ature of 50 6 5C (122 6 9F) and having adistance between the rolls of 1.4 6 0.1 mm (0.055 6 0.005 in.)as determined by a lead slug. Immediately fold the specimen inhalf and insert the folded end into the mill for a second pass.Repeat this procedure until a total of nine passes have beencompleted. Op
43、en the mill rolls to 3 6 0.1 mm (0.125 6 0.005in.), fold the specimen in half, and pass it between the rollsonce. Do not allow the specimen to rest between passes or toband on the mill rolls at any time.6.3 Conditioning must also be carefully controlled. Pistontype rheometers impart very little shea
44、r energy; therefore, anystructure that is formed on resting of the sample is still presentwhen that sample reaches the die. Although screw-type rhe-ometers do impart shear work during processing, it is importantto standardize the amount of mill mastication prior to feedingto the extruder. Some compo
45、unds, especially silica filled ones,may reform bonds with the rubber matrix if more than fourhours have passed since their initial mill processing. If so, theyshould be warmed up by giving them five passes through atight mill. Do not let them band on the mill, in order tominimize polymer break down
46、during this operation.TEST METHOD APISTON EXTRUSIONCAPILLARY RHEOMETER7. Summary of Test Method7.1 Raw or compounded unvulcanized rubber is placed in atemperature controlled cylinder fitted at one end with atransition section of conical cross section and a preciselymeasured length of metal capillary
47、 tubing (the die). The otherTABLE 1 Sample PreparationType RubberASample Preparation,Reference SectionTest Temperature, CNBS 388 6.1 only 100 6 0.5 or1256 0.5NR 6.1 only 100 6 0.5BR 6.1 only 100 6 0.5CRIRNBRSBRBIIR 6.1 only 100 6 0.5 orCIIR 125 6 0.5IIREPDM 6.1 only 125 6 0.5EPMSynthetic rubber blac
48、kmasterbatch6.1 and 6.2.1 100 6 0.5Compounded stock 6.1 only reclaimed material 100 6 0.5Miscellaneous If similar to any group above, test accordingly. If not,establish a procedure.ASee Practice D 1418.D 5099 93 (2003)3end of the cylinder contains a close fitting piston withprovisions for driving th
49、is piston through the cylinder either atconstant rate or with constant force. The sample is driventhrough the die while measuring or controlling the rate ofextrusion and the pressure on the sample at the entrance of thedie.7.2 The extrusion is performed at two different rates througha standard die of 1.5 mm diameter and 15 mm (nominal) lengthand at both of these rates through a die of 1.5 mm diameter and22.5 mm length.7.3 The data produced by this test method have been founduseful for both quality control tests and compound develop-ment. Howe
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