1、Designation: D3194 17Standard Test Method forRubber From Natural SourcesPlasticity Retention Index(PRI)1This standard is issued under the fixed designation D3194; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last rev
2、ision. 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 gives an indication of the oxidationresistance of raw natural rubber at a specified temperature. Thisresistan
3、ce is indicated by the Plasticity Retention Index (PRI),a ratio expressed as a percentage of the aged plasticity to theoriginal plasticity determined by means of a parallel plateplastometer. A low PRI value indicates a poor resistance tooxidation.1.2 The values stated in SI units are to be regarded
4、as thestandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility 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.
5、2. Referenced Documents2.1 ASTM Standards:2D1485 Practice for Rubber from Natural SourcesSampling and Sample PreparationD3040 Practice for Preparing Precision Statements for Stan-dards Related to Rubber and Rubber Testing (Withdrawn1987)3D3182 Practice for RubberMaterials, Equipment, and Pro-cedures
6、 for Mixing Standard Compounds and PreparingStandard Vulcanized SheetsE145 Specification for Gravity-Convection and Forced-Ventilation Ovens3. Summary of Test Method3.1 A homogenized sample of raw rubber is prepared by aspecified procedure to create a sheet from which six cylindricalpellets of speci
7、fied dimensions are cut, three to be tested inoriginal condition and three to be aged under specified condi-tions.3.2 Plasticity on both the original and aged samples ismeasured as the median final thickness of each set of samplesafter a compressive force of 100 N 6 1 N is applied for aspecified tim
8、e. The PRI is the ratio expressed as a percentageof the aged to the original plasticity.4. Significance and Use4.1 This test method may be used to evaluate the heat and/oroxidation stability (aging) of raw rubber under controlledconditions. High original and aged plasticity values usuallycorrespond
9、to good aging properties. The ratio of the aged tooriginal plasticity values expressed as a percentage, the PRI, isused as an indication of aging.5. Apparatus5.1 Parallel Plate Plastometer4, with a 10 mm diameterplaten. The platen temperature shall be 100 6 1C and theplastometer shall have a timer u
10、nit capable of giving a 15 6 1s initial conditioning period during which the sample shall becompressed to 1 6 0.01 mm and a test period of 15 6 1 s undera compression force of 100 N 61 N. The plastometer shall alsohave a measuring device gauge reading to 0.01 mm. Calibra-tion procedures recommended
11、by the manufacturer of theplastometer should be followed.5.2 Punch, that will die out cylindrical specimens approxi-mately 13 mm in diameter from a prepared sheet of rubber.5.3 Circulating Air Oven, specified in Specification E145,Type IIA. The oven must be capable of maintaining 140 60.5C.5.4 Dishe
12、s or Tray, aluminum, for test specimens, light-weight aluminum dishes approximately 38 mm (1.5 in.) indiameter or an aluminum tray approximately 150 by 150 mm(7 by 7 in.) for aging specimens in the oven.1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand Rubber-like Materi
13、als and is the direct responsibility of Subcommittee D11.22on Natural Rubber.Current edition approved Jan. 1, 2017. Published January 2017. Originallyapproved in 1973. Last previous edition approved in 2009 as D3194 04 (2009).DOI: 10.1520/D3194-17.2For referenced ASTM standards, visit the ASTM websi
14、te, 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.3The last approved version of this historical standard is referenced onwww.astm.org.4The sole source of supply of
15、 the Wallace Rapid Plastimeter known to thecommittee at this time is Leverett A. Anderson Co., P.O. Box 5400, Akron, OH44313. If you are aware of alternative suppliers, please provide this information toASTM International Headquarters. Your comments will receive careful consider-ation at a meeting o
16、f the responsible technical committee,1which you may attend.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization establish
17、ed in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.15.5 Tissue paper or cigarette paper, approximately 40 by 40mm (1.5 by 1.5 in.). This paper shall be bleached,
18、 unglazedacid-free tissue paper, of approximately 1.7 g/m2.6. Precautions6.1 The initial thickness of the prepared sheet can affect thefinal thickness after testing.Ascertain the required mill openingby preliminary trial; it will vary with the rubber and the mill.6.2 The temperature and speed of the
19、 testing operations canaffect the results. An increase in temperature or the time topreheat or time to read the dial micrometer can result in low,final plasticity readings.7. Sampling7.1 The natural rubber sample shall be obtained in accor-dance with Practice D1485.8. Test Specimen Preparation8.1 Te
20、st Specimen Preparation Method A (original proto-col):8.1.1 Homogenize the piece to be tested (mass approxi-mately 360 g) 10 times through a mill as described in PracticeD3182. The mill rolls should be at 70 6 5C (158 6 9F) withan opening of approximately 1.65 mm (0.065 in.).After each ofthe first s
21、ix passes, roll the rubber into a cylinder and passendwise through the mill rolls. After the sixth pass, the sampleshall not be rolled, but is folded.8.1.2 Take a test portion of about 30 g from the homog-enized sample and pass it three times (doubling the sheetbetween passes) between mill rolls at
22、room temperature withthe opening adjusted so that the final sheet thickness isapproximately 1.7 mm (0.07 in.). After the third pass, doublethe sheet, which should be uniform in texture and free of holes,and press the two halves lightly together.8.1.3 Die out six or more test specimens from the doubl
23、edsheet with the punch and measure their thickness until six testpellets are obtained with a thickness of 3.4 6 0.2 mm (0.134 60.008 in.) having a volume of 0.40 6 0.04 cm3(0.2441 60.002441 in.3). Randomly divide these into two sets of three,one for test before aging and the other for test after agi
24、ng.8.2 Test Specimen Preparation Method B (alternative pro-tocol):8.2.1 Homogenize the piece to be tested (mass approxi-mately 360 g) 10 times through a mill as described in PracticeD3182.8.2.2 The mill rolls should be at room temperature with anopening of approximately 1.65 mm (0.065 in.). After ea
25、ch ofthe first six passes, roll the rubber into a cylinder and passendwise through the mill rolls. After the sixth pass, the sampleshall not be rolled, but is folded.8.2.3 Take a test portion of about 30 g from the homog-enized sample and pass it three times (doubling the sheetbetween passes) betwee
26、n mill rolls at room temperature withthe opening adjusted so that the final sheet thickness isapproximately 1.7 mm (0.07 in.). After the third pass, doublethe sheet, which should be uniform in texture and free of holes,and press the two halves lightly together.8.2.4 Die out six or more test specimen
27、s from the doubledsheet with the punch and measure their thickness until six testpellets are obtained with a thickness of 3.4 6 0.2 mm (0.134 60.008 in.) having a volume of 0.40 6 0.04 cm3(0.2441 60.002441 in.3). Randomly divide these into two sets of three,one for test before aging and the other fo
28、r test after aging.9. Procedure9.1 Aging:9.1.1 Before aging is started, the oven must be stabilized at140 6 0.5C for at least12 h.9.1.2 The dishes or tray containing the three pellets (8.3) tobe aged must be arranged within the calibrated region of theoven. Insert the tray and close the oven door qu
29、ickly to preventexcessive oven heat loss. Start timing as soon as the oven dooris closed.9.1.3 After 30 6 0.25 min remove the tray from the ovenand remove the dishes from the tray. Allow them to cool toroom temperature for a minimum of 30 min and a maximum of2 h before testing.9.2 Measurement of Pla
30、sticity:9.2.1 The platen of the plastometer shall have come toequilibrium at 100 6 1C for 15 min before making measure-ments.9.2.2 Place two pieces of tissue paper (5.5) between theheated platens and set the thickness measuring device to zerowhen the platens are closed.9.2.3 Insert a pellet at room
31、temperature between two piecesof tissue paper and place the whole assembly centrally betweenthe heated platens. Put the machine lever into operation. Aftera 15-s conditioning period, the timing device automaticallyreleases the force of 100 N 61 N to compress the specimen.This load period is automati
32、cally adjusted, exactly 15-s dura-tion. The final thickness expressed in units equivalent to 0.01mm remains locked after the 15s load period on the dialmicrometer until the operating handle is moved to open theinstrument. Record the measured thickness from the dialmicrometer. Repeat the above for ea
33、ch of the pellets, both agedand in original condition.9.2.4 The measured thickness for each pellet within either ofthe groups should not vary by more than 6 0.01 mm from themedian value of that group. Run additional pellets, if needed,to get three of each group within this tolerance.10. Calculation1
34、0.1 The plasticity is 100 times the final thickness asexpressed in units equivalent to 0.01 mm.10.2 Using the median values of these plasticity results ofboth original (Po) and aged test specimens, calculate the PRI asfollows:PRI 5 plasticity aged/plasticity original! 3100 (1)11. Report11.1 The repo
35、rt shall include the following:11.1.1 Three values of the plasticity for the original and theaged test pieces,11.1.2 Type of oven used, andD3194 17211.1.3 Plasticity Retention Index (PRI) using Method A orMethod B.12. Precision and Bias512.1 This precision and bias section has been prepared inaccord
36、ance with Practice D4483. Refer to this practice forterminology and other statistical details.12.2 The precision results in this precision and bias sectiongive an estimate of the precision of the test method with thematerials used in the particular interlaboratory program asdescribed below. The prec
37、ision parameters should not be usedfor acceptance/rejection testing of any group of materialswithout documentation that they are applicable to those par-ticular materials and the specific testing protocols that includethis test method.12.3 A Type 1, Class II interlaboratory precision programwas cond
38、ucted (except for sample No. 6, which was Type 1,Class I). Both repeatability and reproducibility are short term.A period of a few days separate test results, which wererepeated on three separate days. Participation included 13laboratories, and six materials were used. Therefore, p = 13, q= 6, and n
39、 = 3. A test result is the median value obtained fromthree determinations as specified in Section 10.12.4 Other than sample No. 1, which was IIR, the materialsused were natural rubber. They were prepared through step 8.2of this test method. Participants were required to die out andtest the cut pelle
40、ts. Sample identification: No. 1 = Butyl rubber,No. 2 = PA80 coagulated latex, No. 3 = SIR20, No. 4 = No.1RSS, No. 5 = CV50, and No. 6 = SIR20 cut pellets.12.5 The results of the precision calculations are given inTable 1, with the materials arranged in increasing mean PRIvalue.12.6 The precision fo
41、r these tests on a relative basis may beexpressed as follows (sample No. 1 IIR excluded):12.6.1 RepeatabilityThe repeatability (r) of this test hasbeen established as 9.8 %. Two single measurements (determi-nations) that differ by more than the tabulated (r) (expressed aspercentage of their mean val
42、ue) must be considered suspect,that is, having arisen from different sample populations. Sucha decision dictates that appropriate action be taken.12.6.2 ReproducibilityThe reproducibility (R) of this testhas been established as 34.5 %. Two single measurements(determinations) that differ by more than
43、 the tabulated (R)(expressed as percentage of their mean value) must be consid-ered suspect, that is, having arisen from different samplepopulations. Such a decision dictates that appropriate action betaken.12.7 BiasIn test method terminology, bias is the differencebetween an average test value and
44、the reference (true) testproperty value. Reference values do not exist for this testmethod since the value or level of the test property isexclusively defined by the test method. Bias, therefore, cannotbe determined.13. Keywords13.1 natural rubber; plasticity; P.R.I.; retention indexASTM Internation
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48、 at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-95
49、85 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D11-1066.TABLE 1 ASTM Test Method D3194 Type 1 PrecisionWallacePlasticity (PRI)ABSampleMeanValueWithin Laboratories Between Laboratoriessrr (r) SRR (R)6
