1、Designation: D 1329 02Standard Test Method forEvaluating Rubber PropertyRetraction at LowerTemperatures (TR Test)1This standard is issued under the fixed designation D 1329; 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method describes a temp
3、erature-retractionprocedure for rapid evaluation of crystallization effects and forcomparing viscoelastic properties of rubber and rubber-likematerials at low temperatures. This test method is useful whenemployed in conjunction with other low-temperature tests forselection of materials suitable for
4、low-temperature service.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.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 s
5、tandard 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:D 832 Practice for Rubber Conditioning for Low-Temperature Testing2D 4483 Practice for Determining Precision for Test Method
6、Standards in the Rubber and Carbon Black Industries23. Summary of Test Method3.1 This test method is carried out by (1) elongating thespecimen, (2) locking it in the elongated condition, (3) freezingit to a state of reduced elasticity, (4) releasing the frozenspecimen and allowing it to retract free
7、ly while raising thetemperature at a uniform rate, (5) measuring the length of thespecimen at regular temperature intervals while it is retracting,and (6) computing the percentage retraction at these tempera-tures from the data obtained. In practice, the temperaturescorresponding to 10 % and 70 % re
8、traction are of particularimportance, and are designated as TR10 and TR70, respec-tively.4. Significance and Use4.1 The difference between the temperature at which avulcanizate retracts 10 % (TR10) and the temperature at whicha vulcanizate retracts 70 % (TR70) increases as the tendency tocrystallize
9、 increases.4.2 TR70 correlates with low-temperature compression set.4.3 TR10 has been found to correlate with brittle points invulcanizates based on polymers of similar type.4.4 In general, the retraction rate is believed to correlatewith low-temperature flexibility of both crystallizable andnoncrys
10、tallizable rubbers.5. Apparatus5.1 Specimen Rack, designed to maintain a slight tension onthe specimen of 7 to 21 kPa (1 to 3 psi), and to permit it to bestretched and anchored at any elongation desired up to amaximum to 350 %. Means of measuring the length of thespecimen at any time during the test
11、 within an accuracy of 61mm (60.04 in.) shall be provided. The rack may be designedto hold a number of specimens at the same time.5.2 Insulated Cooling Bath, equipped with stirrer, thermom-eter, and an immersion heater. A rheostat shall be included inthe heater circuit. A suitable thermocouple-poten
12、tiometer mea-suring system may be substituted for the thermometer.5.3 Temperature Measurement, may be conducted in one oftwo ways: (a) a typical glass thermometer with appropriaterange and sensitivity (61C (62F); or (b) a more modernthermocouple or resistive element, electronic temperature mea-surin
13、g system, accurate to 61C.5.4 Liquid Coolant, which does not attack the test specimenunder the conditions of the test. Methanol cooled with dry iceis satisfactory for most samples. Gaseous media may beemployed as the coolant when the design of the apparatus issuch that tests using it will duplicate
14、those obtained with thestandard liquid media.1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand is the direct responsibility of Subcommittee D11.14 on Time and Temperature-Dependent Physical Properties.Current edition approved Dec. 10, 2002. Published January 2003. Origin
15、allyapproved in 1954. Last previous edition approved in 1998 as D 1329 88 (1998).2Annual Book of ASTM Standards, Vol 09.01.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.5 An apparatus specially designed for the TR test3,4isschema
16、tically illustrated in Fig. 1. The sample rack is shown onthe left, and the overall assembly on the right. The bath consistsof an unsilvered Dewar flask that is contained in an insulatingwooden frame, 0. The frame contains a wide slot in front,through which the test can be observed and the temperatu
17、resread. Other details of the apparatus are given in Section 8.6. Test Specimens6.1 The test specimens may be prepared by dieing out witha die of the design shown in Fig. 2. The choice of die length isgoverned by the elongation required and the limitations of thespecimen racks. For most work a 38 mm
18、 (1.50 in.) die issuitable. Thickness of the specimens shall be 2.0 6 0.2 mm(0.08 6 0.01 in.). Any other method of obtaining test speci-mens of uniform cross section is satisfactory, provided that asuitable clamp is used on the rack.6.2 Three specimens per material shall be tested.7. Initial Specime
19、n Extension7.1 The initial extension (elongation) of specimens to betested should be chosen with the following considerations:7.1.1 To study the effect of crystallization at low tempera-tures use a value of either: (1) 250 %, (2) half the ultimateelongation if 250 % is unobtainable, or (3) 350 % if
20、theultimate elongation is greater than 600 %.7.1.2 To avoid the effect of crystallization, use an elongationof 50 %.7.2 For long exposures, the 50 % elongation may be used incombination with a conditioning procedure, in accordance withPractice D 832. In such studies, crystallization of the long-time
21、 conditioned specimen is indicated by the displacement ofthe TR curve toward the higher temperature. Tests conducted at50 % elongation without previous long-time conditioning havebeen found to correlate fairly well with stiffness tests.8. Procedure8.1 Fill the bath, N (Fig. 1) to within about 50 mm
22、(2 in.) ofthe top with methanol. Start the stirrer, P. Cool the methanol bydipping into it, for short intervals, a wire cage filled withchopped dry ice. Care must be employed at the beginning ofthis operation to prevent excessive frothing. When the tem-perature drops to 70C (94F) chopped dry ice can
23、 be addeddirectly to the methanol.8.2 Insert one end of the test specimen, B, in the stationaryclamp, C1, at the bottom of the sample rack, A, and the otherend in the movable clamp, C. Stretch to the length desired,reading the length by means of the indicator, E, attached to theconnecting wire, F, a
24、nd moving over the graduated scale, G.Anchor the specimen in the elongated position by tighteningthe thumb nut, D. Adjust the flexible cord, H, that is attachedto the wire, F, at one end and to a counterweight at the otherend, so that it moves freely over the pulley, I. (The counter-weight should be
25、 3 to 5 g heavier than the clamp and wire thatit counterbalances.) Repeat this operation for the other speci-mens in the rack. Insert the thermometer, K, in the holder, L.8.3 Place the rack, A, in the bath. This must be done slowlyto avoid frothing. Tighten the thumb nuts, that anchor the racksuppor
26、t, M, to the bath.8.4 If the temperature of the batch rises above 70C(94F) when the rack is inserted, add a little dry ice to reducethe temperature to between 70 and 73C.8.5 Let stand 10 min, then release the thumb nuts, D, andallow the specimens to retract freely.8.6 Turn on the heater, R, and main
27、tain a temperature rise of1C/min (2F/min) by adjusting the rheostat.3A modified Scott T-50 tester has been used by some investigators. See Svetlik,J. F., and Sperberg, L. R., “The T-R (Temperature Retraction) Test Characterizingthe Low-Temperature Behavior of Elastomeric Compositions,” India Rubber
28、World,May, 1951, p. 182.4See Smith, O. H., Hermonat, W. A., Haxo, H. E., and Meyer, A. W., “RetractionTest for Serviceability of Elastomers at Low Temperatures,” Analytical Chemistry,Vol 23, 1951, p. 322.FIG. 1 Retraction ApparatusFIG. 2 Die for Preparing Test SpecimensD13290228.7 Take the first rea
29、ding at 70C (94F), and continue toread the length at 2 min intervals until retraction is 75 %completed.NOTE 1When one standard specimen length and initial elongation aremaintained, temperatures at which specific degrees of retraction occurmay be read directly.8.8 If a methanol-dry ice system does no
30、t produce tempera-tures low enough to freeze the specimens to practically anonelastic state, then other cooling media may be employed.9. Calculations9.1 Calculate retraction values at any specific temperatureas follows:retraction, % 5 Le2 Lt!/Le2 Lo!# 3 100 (1)where:Lo= length of specimen in the uns
31、tretched condition,Le= length of specimen in the stretched condition, andLt= length of specimen at the observed temperature.9.2 Calculate the temperature at any specific retraction asfollows:9.2.1 Determine the length of the test specimen at thedesired retraction Lr, by means of the following formul
32、a:Lr5 Le2 % retraction/100!Le2 Lo! (2)9.2.2 Note the nearest temperature corresponding to thelength, Lr, and determine the exact temperature by interpola-tion.10. Report10.1 Report the following information:10.1.1 The median values of the following:10.1.1.1 Testing elongation, in percent.10.1.1.2 Te
33、mperatures at which the specimen retracts 10,30, 50, and 70 %. These temperatures shall be designated,respectively, as TR10, TR30, TR50, and TR70.10.1.1.3 Difference between TR10 and TR70 in degreesCelsius.10.1.2 The method or equipment used to measure tempera-ture (glass thermometer, thermocouple,
34、etc.).10.1.3 Length of the test specimens before elongation.10.1.4 Time and temperature of initial conditioning.10.1.5 Rate of temperature rise, and10.1.6 Coolant used.11. Precision and Bias511.1 This precision and bias section has been prepared inaccordance with Practice D 4483. Refer to this pract
35、ice forterminology and other statistical calculations details.11.2 A Type 1 (interlaboratory) precision was evaluated in1985. Both repeatability and reproducibility are short term, aperiod of a few days separates replicate test results. A test resultis the mean value, as specified in this test metho
36、d, obtained ontwo determination(s) or measurement(s) of the property orparameter in question.11.3 Five different materials or compounds were used in theinterlaboratory program, these were tested in two laboratorieson two different days. One of the laboratories had two differentoperators perform the
37、testing so that a total of three differentoperators were involved. The statements are based on thetesting of five compounds by three operators on two days.11.4 Standard vulcanized sheets were prepared by the sup-plying laboratory. Each participant die cut the test specimens.A test result is defined
38、to be the average of two separatelyprepared specimens. Precision statements were prepared forTR 10, 30, 50, 70, and (70-10) where each operator determinedtest results in accordance with Section 9.11.5 Within laboratories, Srvalues of zero were obtained forSrfor selected parameters for several of the
39、 test compounds.These values are to no variation between the results obtainedon two different test days by any of the three operators.11.6 Due to the occurrence of zero values for Sr, the valuesof Sr(and SR) were pooled for TR levels (10 to 70) and formaterials. This was done to obtain a better esti
40、mate of the trueSr(and SR) for the expression of precision. A tabulation of theSrand SRvalues and the results of the pooling calculations isgiven in Table 1. With the exception of Material 1, the valuesof Srand SRare essentially constant for the other fourmaterials. Based upon this the general preci
41、sion for TR values(10 to 70) is given in Table 2.11.7 The precision for the difference in TR (70-10) is givenin Table 3. The precision of this test method may be expressedin the format of the following statements that use what is calledan appropriate value of r, R,(r), or (R), that is, that value to
42、 beused in decisions about test results (obtained with the testmethod). The appropriate value is that value of r or Rassociated with a mean level in the precision tables closest tothe mean level under consideration at any given time, for anygiven material in routine testing operations.11.8 Repeatabi
43、lityThe repeatability r, of this test methodhas been established as the appropriate value tabulated in theprecision tables. Two single test results, obtained under normaltest method procedures, that differ by more than this tabulated5Supporting data are available from ASTM Headquarters. Request RR:
44、D11-1037.TABLE 1 Pooling of Within Laboratory Srand BetweenLaboratory SRMaterial or Sr:Compound TR 10 TR 30 TR 50 TR 70Pooled,SrMean TR Value, K(C)1 0.0 0.0 0.0 0.20 0.10 264.4 (8.6)2 0.0 0.20 0.82 0.20 0.437 235.3 (37.8)3 0.82 0.0 0.61 0.0 0.511 241.0 (32.0)4 0.20 0.0 0.20 0.82 0.434 235.8 (37.3)4
45、0.0 0.61 0.61 0.84 0.602 240.6 (32.8)Pooled Sr0.378 0.287 0.540 0.540 (0.450)SR:Material TR 10 TR 30 TR 50 TR 70Pooled,SRMean TR Value, K(C)1 1.01 0.76 0.64 0.18 0.714 264 (8.6)2 7.30 5.70 1.04 0.90 4.68 235.3 (37.8)3 0.25 2.38 4.26 6.71 4.15 241.0 (32.0)4 2.06 0.79 0.88 1.54 1.415 235.8 (37.3)5 0.0
46、6 0.83 0.73 1.37 0.881 240.6 (32.8)Pooled SR3.42 2.83 2.05 3.17 (2.914)D1329023r (for any given level) must be considered as derived fromdifferent or non-identical sample populations.11.9 ReproducibilityThe reproducibility R, of this testmethod has been established as the appropriate value tabulated
47、in the precision tables. Two single test results obtained in twodifferent laboratories, under normal test method procedures,that differ by more than the tabulated R (for any given level)must be considered to have come from different or non-identical sample populations.11.10 Repeatability and reprodu
48、cibility expressed as a per-centage of the mean level, (r) and (R), have equivalentapplication statements as above for r and R. For the (r) and (R)statements, the difference in the two single test results isexpressed as a percentage of the arithmetic mean of the two testresults. (See, however, the c
49、aveat statement, a footnote in Table3on(r) and (R) for TR (70-10).)11.11 BiasIn test method terminology, bias is the differ-ence between an average test value and the reference (or true)test property value. Reference values do not exist for this testmethod since the value (of the test property) is exclusivelydefined by the test method. Bias, therefore, cannot be deter-mined.12. Keywords12.1 crystallization; low temperature retraction; rubber;temperature retraction; testing at subnormal temperatures; TRtest; viscoelastic propertiesASTM Intern
