1、Designation: D 5099 08Standard 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 revision, the year
2、 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 characteristics ofrubbe
3、r (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 of a capillary rhe
4、om-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 sample, these measure-
5、ments directly relate to the state of the compound at the time ofsampling. Piston type capillary rheometer measurements willusually differ from measurements with a screw extrusion typerheometer, which imparts shearing energy just before therheological measurement.1.4 Capillary rheometer measurements
6、 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 theresponsibilit
7、y 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 1418 Practice for Rubber and Rubber Lati
8、cesNomenclatureD 1485 Practice for Rubber 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 b
9、y Means of a Capillary RheometerD 3896 Practice for Rubber From Synthetic SourcesSamplingD 4483 Practice for Evaluating Precision for Test MethodStandards in the Rubber and Carbon Black ManufacturingIndustries3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 The following terms
10、appear in logical order for thesake of clarity:3.1.2 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.3.1.3 die entrance pressure (
11、P)the pressure in the reser-voir at the die entrance, in Pa.3.1.4 volumetric flow rate (Q)the flow rate through thecapillary die, in mm3/s.3.1.5 apparent (uncorrected) shear rate (ga)shear strainrate (or velocity gradient) of the rubber extrudate as it passesthrough the capillary die (Eq 1), in s1.3
12、.1.5.1 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 controlling thevolumetric flow rate (Q) through the die, a specific level of
13、apparent shear rate may be achieved. Alternately, the shearstress (die entrance pressure, P) may be controlled, and theapparent shear rate measured.Mathematically, the apparent shear rate for a Newtonianfluid at the wall is given as follows:ga532 Qp D3(1)1These test methods are under the jurisdictio
14、n of ASTM Committee D11 onRubber and are the direct responsibility of Subcommittee D11.12 on ProcessabilityTests.Current edition approved May 1, 2008. Published May 2008. Originallyapproved in 1993. Last previous edition approved in 2003 as D 5099 93 (2003).2For referenced ASTM standards, visit the
15、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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Un
16、ited States.where:ga= apparent shear rate, s1,Q = volumetric flow rate, mm3/s,p = the constant pi, approximately 3.142, andD = diameter of the capillary die, mm.3.1.6 apparent shear stress (ta)the measured resistance toflow through a capillary die (Eq 2).ta5P4L/D!(2)where:ta= apparent shear stress,
17、Pa,P = pressure at the entrance to the capillary die, Pa,L = length of the capillary die, mm, andD = diameter of the capillary die, mm.3.1.7 apparent viscosity (ha)ratio of apparent shear stressto apparent shear rate, in Pa-s.3.1.7.1 DiscussionFor a capillary rheometer, the apparentviscosity is usua
18、lly calculated at a given shear rate.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 the measurement wasmade.3.1.8 Newtonian fluida fluid for which viscosity does notvary with
19、 changing shear rate. Simple liquids such as rubberextender oils are Newtonian; most polymeric materials are not.3.1.9 power law fluida fluid material for which theviscosity varies with the shear rate in accordance with therelationship:t5Kg!N(3)where:K = constant, often called consistency index, and
20、N = 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, with some exceptions.Most non-Newtonian fluids follow the relationship in Eq 3for at least short ranges of the shear
21、rate variable. Eq 3 isgenerally used in its logarithmic form, as:logt! 5 log K! 1 N log g! (4)3.1.10 corrected shear stress (tw)the shear stress at thewall of the capillary die; it is calculated from the apparent shearstress by applying the Bagley correction E in Eq. 5 for energylosses at the entran
22、ce and exit of the die.3.1.10.1 DiscussionThe Bagley correction, often termed“end effect,” is normally applied as though it were an addi-tional length of capillary, in terms of an added L/D ratio. TheCapillary entrance angle and geometry have great influence onthe magnitude of this correction.3.1.10
23、.2 DiscussionSince the magnitude of the Bagleycorrection is a function of shear rate, data for this correction areobtained by using two or more dies of different lengths butpreferably of the same diameter and volumetric flow rate (andthus the same apparent shear rate). If the data from theseaddition
24、al dies are compared, either graphically or mathemati-cally, a linear relationship of extrusion pressure with diegeometry is usually obtained, of the following form:P 5 cFLD1 EG(5)where:c = slope of the line, andE = Bagley correction, expressed as the negative capillarylength to diameter (L/D) ratio
25、 resulting from extrapo-lating the pressure value to zero when plotted againstL/D.Both c and E values are functions of the rubber compound,the shear rate and the capillary entrance angle.Corrected shear stress (tw) is therefore:tw5P4FLD1 EG(6)or:5PL2 Ps4FLLDL2LsDsG(7)where:PL= pressure drop for long
26、 die, Pa,PS= pressure drop for short die, Pa,LL= length of the long die, mm,LS= length of the short die, mm,DL= diameter of the long die, mm, andDS= diameter of the short die, mm.3.1.11 corrected shear rate (gw)shear rate at the wall ofthe capillary die determined by applying the Rabinowitschcorrect
27、ion for non-Newtonian materials.3.1.11.1 DiscussionThe Rabinowitsch correction math-ematically adjusts shear rate values for the fact that the fluid isnon-Newtonian, using the power law fluid model (Eq 3). Toobtain the corrected shear rate, at least two measurements ofapparent shear stress and appar
28、ent shear rate are made,generally by increasing the volumetric flow rate (Q) with thesame measuring capillary. The Bagley correction is made to theshear stress values; either by algebraic means if only twomeasurements are made, or by a regression equation for agreater number of points. Eq 3 may be s
29、olved for N, where Nis designated as N, using corrected shear stress (tw) values andthe corresponding apparent shear rate gavalues. Although intheory, N calculated from Eq 3 using apparent shear stress (ta)and apparent shear rate gavalues and N calculated from Eq 3using corrected shear stress (tw) a
30、nd apparent shear rate gavalues should be identical, their values may vary as the Bagleycorrection (E) varies, hence the designation of N in (Eq 8).The corrected shear rate gwis:gw5gaF3N 1 14NG(8)For most rubbers or elastomers the correction factor forshear rate is typically between 1.5 and 2.1, wit
31、h some excep-tions.3.1.12 corrected viscosity (hw)the ratio of corrected shearstress to corrected shear rate.3.1.12.1 DiscussionSince the corrections used, as well asthe material properties, are functions of shear rate, it is veryD5099082important to state the particular value of shear rate at which
32、 themeasurement was made.3.1.13 critical shear stressthat value of shear stress atwhich there is a discontinuity in the slope of the log shear stressversus log shear rate plot; manifested by a sudden change insurface roughness of the extrudate (sometimes referred to asmelt fracture).4. Significance
33、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 The data produced by these test methods have beenfound useful for both quality control tests and compounddevelopment. However, direct correlation
34、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 sensitiveto molecular weight and to molecular weight distribution.Therefore, these test methods may distinguish differencesbetween lots.4.4 The shear vis
35、cosity or flow viscosity of compoundedrubber batches in the raw (unvulcanized) state will not only besensitive to the raw polymer molecular properties, but will alsobe affected by type and amount of filler, plasticizer or softenerlevels, amount and type of copolymer blend, and other com-pounding mat
36、erials. These test methods can serve as a qualitycontrol tool for either incoming custom mixed compounds orfor in-house quality assurance checks on production mixing.These test methods are useful for research and development ofnew products by measuring the rheological effect on a rubbercompound of n
37、ew polymers, resins, softeners, etc.5. Interferences5.1 Since flow properties of these non-Newtonian fluids arenot linear, capillary rheometers should be operated at condi-tions of flow (temperature, pressure, and rate) similar to that ofselected commercial processes. These processes include mix-ing
38、, calendering, extrusion, and molding of rubber compounds.5.2 Piston type capillary rheometers impart only very smallamounts of shear or mixing energy before the measurement ismade. Consequently, the measurement relates to the state of thepolymer or compound at the time the sample was taken. If it i
39、sdesirable to relate directly to a down-stream process involvingsignificant amounts of mixing energy, it is sometimes desirableto shear the polymer on a roll mill before the rheologicalmeasurement is made.5.3 Screw extrusion type capillary rheometers impart sig-nificant amounts of energy to the rubb
40、er compound before themeasurement is made. Interpretation of the data for factoryoperations such as extrusion, calendering, or injection moldingis therefore more straightforward than for compression mold-ing operations, where factory work input is quite small.6. Sampling and Conditioning of Samples6
41、.1 Condition the sample obtained in accordance withPractice D 1485 or D 3896 until it has reached room tempera-ture (23 6 3C (73 6 5F) throughout.6.2 Massed SpecimenPrepare a massed specimen, as in6.2.1, only if indicated in Table 1. Massing is used to combinethe rubber crumbs, homogenize the specim
42、en, 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 temperature 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. Immedia
43、tely 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. Open 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
44、 to rest between passes or toband on the mill rolls at any time.6.3 Conditioning must be carefully controlled. Piston typerheometers impart very little shear energy; therefore, anystructure that is formed on resting of the sample is still presentwhen that sample reaches the die. Although screw-type
45、rhe-ometers do impart shear work during processing, it is importantto standardize the amount of mill mastication prior to feedingto the extruder. Some compounds, especially silica filled ones,may reform bonds with the rubber matrix if more than fourhours have passed since their initial mill processi
46、ng. 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 during this operation.TEST METHOD APISTON TYPE CAPILLARYRHEOMETER7. Summary of Test Method7.1 Raw or compounded unvulcanized rubber is placed in
47、 atemperature controlled cylinder fitted at one end with atransition section of conical cross section and a preciselymeasured length of metal capillary tubing (the die). The otherend of the cylinder contains a close fitting piston withprovisions for driving this piston through the cylinder either at
48、constant rate or with constant force. The sample is drivenTABLE 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
49、 6 0.5EPMSynthetic rubber blackmasterbatch6.1 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.D5099083through the die while measuring or controlling the rate ofcapillary extrusion and the pressure on the sample at theentrance of the die.7.2 The capillary extrusion is performed at two differentrates through a standard die of 1.5 mm diameter and 15 mm(nominal) length (10:1 L/D) and at both of
