1、Designation: D 832 07Standard Practice forRubber Conditioning For Low Temperature Testing1This standard is issued under the fixed designation D 832; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A numbe
2、r 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 practice covers the characteristic mechanical be-havi
3、or of rubbers at low temperatures, and outlines the condi-tioning procedure necessary for testing at these temperatures.1.2 One of the first stages in establishing a satisfactorytechnique for low temperature testing is the specification of thetime and temperature of exposure of the test specimen. It
4、 hasbeen demonstrated that any one or more of the followingdistinct changes, which are detailed in Table 1, may take placeon lowering the test temperature:1.2.1 Simple temperature effects,1.2.2 Glass transitions, and1.2.3 First order transitions (crystallization), and solubilityand other effects ass
5、ociated with plasticizers.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 pr
6、ior to use.2. Referenced Documents2.1 ASTM Standards:2D 471 Test Method for Rubber PropertyEffect of LiquidsD 1053 Test Methods for Rubber PropertyStiffening atLow Temperatures: Flexible Polymers and Coated FabricsD 1329 Test Method for Evaluating Rubber PropertyRetraction at Lower Temperatures (TR
7、Test)D 1566 Terminology Relating to RubberD 2136 Test Method for Coated FabricsLow-Temperature Bend TestD 5964 Practice for Rubber IRM 902 and IRM 903 Re-placement Oils for ASTM No. 2 and ASTM No. 3 Oils3. Significance and Use3.1 Low temperature testing of rubber can yield repeatableresults only if
8、the preconditioning of the samples is consistent.Properties such as brittleness and modulus are greatly affectedby variations in time/temperature exposures. This practice isintended to provide uniform conditioning for the various lowtemperature tests conducted on rubbers.4. General Conditioning4.1 A
9、t least 16 h should elapse between vulcanization andtesting of a sample.4.1.1 If the time between vulcanization and testing is lessthan 16 h, it shall be agreed upon between customer andsupplier and noted in the report section of the test methodemployed.5. Simple Temperature Effects (Viscoelasticity
10、)5.1 Most elastic properties of rubber change as the tempera-ture is changed.As the temperature is reduced toward the glasstransition temperature, Tg, the specimen becomes increasinglystiff, loses resilience, and increases in modulus and hardness.At some point, still above Tg, the resilience reaches
11、 a mini-mum. As the temperature is lowered beyond this point, theresilience then increases until a temperature just above Tgisreached.5.2 Viscoelastic changes are usually complete as soon as thespecimen has reached thermal equilibrium. Longer exposuretime should be avoided to minimize crystallizatio
12、n orplasticizer-time effects that might influence the test results. Themagnitude of these changes depends on the composition of thematerial and the test temperature.6. Glass Transition6.1 Glass transition is a reversible physical change in amaterial from a viscous or rubbery state to a brittle glass
13、y state(refer to Terminology D 1566: transition, glass; transitionsecond order). It does not involve a change in phase and is nota thermodynamic change. It generally occurs over a smalltemperature range. It is designated as Tg. The Tgof polymers,obtained from measurements of change of modulus withch
14、ange in temperature, depend upon both the rate of specimendeformation and the rate of temperature change. Primary1This practice is under the jurisdiction ofASTM Committee D11 on Rubber andis the direct responsibility of Subcommittee D11.14 on Time and Temperature-Dependent Physical Properties.Curren
15、t edition approved May 1, 2007. Published June 2007. Originallyapproved in 1945. Last previous edition approved in 2001 as D 832 92 (2001)e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volu
16、me 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.properties, such as hardness and ultimate elongation, andtemperature coefficients of properties such as v
17、olume andenthalpy, change rapidly near Tg. Thus, thermal expansivityand specific heat appear discontinuous at Tg.6.2 Some rubbers such as copolymers or polymer blendsmay show more than a single Tgbecause of separate contribu-tions by their polymeric components. There may also bedamping peaks not dir
18、ectly attributable to glass transitions. Aglass transition occurs at a temperature below which thethermal energies of molecular segments are insufficient to freethem from the force field of their immediate neighbors withinthe experimental time scale.6.3 Values determined for Tgare higher for test me
19、thods thatrequire high frequency distortions of the specimen than forthose that require low frequency distortions. The latter seem tohave the greater resolving power for multiple peaks. For thosemethods in which the test temperature is changed at a con-trolled rate, Tgdepends upon the rate that is c
20、hosen. Therefore,Tgis not a true material property since it depends upon the testmethod used to obtain it. The method used should always bestated.7. First Order Transitions (Crystallization)7.1 Afirst order transition is a reversible change in phase ofa material; in the case of polymers, it is usual
21、ly crystallizationor melting of crystals (refer to Terminology D 1566: transition,first order). When a specimen is equilibrated at a temperatureat which crystallization is possible, changes in propertiesresulting from the crystallization may begin immediately orafter an induction period of up to sev
22、eral weeks. The time toreach an equilibrium state of crystallization is likewise widelyvariable. Both times are dependent on the material being testedand the temperature. Crystallization increases the hardness andmodulus.Aspecimen that has crystallized once may crystallizemuch more rapidly on subseq
23、uent tests, unless, in the mean-time, it has been heated sufficiently to destroy the crystalnuclei.7.2 Examples of materials that crystallize relatively rapidlyin certain temperature ranges include Thiokol A3polysulfiderubber, chloroprenes (excepting the RT types), natural rubber,and some butadiene
24、copolymers cured without sulfur or withlow sulfur. Materials that may require much longer times forcrystallization effects to become evident include butyl rubber,high sulfur cures of natural rubber, most silicone rubbers, somepolyurethane rubbers, RT types of chloroprene, and rubberscontaining fluor
25、ine.7.3 The temperature at which crystallization proceeds mostrapidly is specific to the polymer involved. For natural rubber,this is near 25C; for chloroprenes, 10C; for butadienecopolymers, 45C; for dimethyl silicones, 55C; forpolyester-type polyurethanes, 10C; and for butyl rubber,35C. Both above
26、 and below these temperatures, crystalliza-tion is slower. Accordingly, any attempt to compare materials(particularly those subject to change in properties resultingfrom crystallization or plasticizer time effects) on a basis ofexposure at a given temperature for a specified time is almostcertain to
27、 be misleading. Such specific temperature may be3The sole source of supply of this material known to the committee at this timeis Thiokol Chemical Corp, Newtown-Yardly Rd., Newtown, PA 18940. If you areaware of alternative suppliers, please provide this information to ASTM Interna-tional Headquarter
28、s. Your comments will receive careful consideration at a meetingof the responsible technical committee,1which you may attend.TABLE 1 Differentiation Between Crystallization and Glass TransitionProperty Crystallization Glass TransitionPhysical effects(1,2,4,6,7)ABecomes stiff (hard) but not necessari
29、ly brittle Becomes stiff and brittleTemperature-volume relation(1,2,3,4,5,8)Significant decrease in volume No change in volume, butdefinite change in coefficient ofthermal expansionLatent heat effect (4,5,8) Heat evolved on crystallization Usually no heat effect, butdefinite change in specific heatR
30、ate (2,4,6,7,8) Minutes, hours, days, or even months may be required. In general, astemperature is lowered, rate increases to a maximum and thendecreases with increase in deformation. Rate also varies withcomposition, state of cure, and nuclei remaining from previouscrystallizations, or from compoun
31、ding materials such as carbon black.Usually rapid; takes place withina definite narrow temperaturerange regardless of thermalhistory of specimen. May belimited rate effect (2)Temperature of occurrence(4,5,7,8Optimum temperature is specific to the polymer involved. Very wide limits, depending oncompo
32、sitionEffect on molecular structure(1,2,5,6,8)Orientation of molecular segments; random if unstrained, approachingparrallelism under strainChange in type of motion ofsegments of moleculeMaterials exhibitingproperties (5,7,8)Unstretched polymers including natural rubber (low sulfur vulcanizates),chlo
33、roprene, Thiokol A polysulfide rubber, butadiene copolymers withhigh butadiene content, most silicones, some polyurethanes. Butylrubbers crystallize when strained. Straining increases rate ofcrystallization of all of the above materials.AllAThe numbers in parentheses refer to the following reference
34、s:(1) Juve, A. E., Whitby, G. S., Davis, C. C., and Dunbrook, R. F., Synthetic Rubber, John Wiley refer to Test Method D 471and Practice D 5964) for 70 h at 100C. Part of the liquidplasticizer has been extracted and replaced by the oil, which isa relatively poor plasticizer; hence the change in TR10
35、.CONDITIONING PROCEDURES FORMECHANICAL TESTS9. Tests for Simple Temperature Effects (ViscoelasticEffects) Only9.1 Make tests at 70, 55, 40, 25, 10, 0, and +23C,respectively. Hold the test specimen at each test temperatureuntil it reaches thermal equilibrium. Calculated times requiredfor thermal equi
36、librium are given in Table 2.9.2 In a flat sheet specimen, the time required for thermalequilibrium may be taken as being directly proportional to thesheet thickness. Thus, for a 25-mm thick slab, the times givenin Table 2 for a 2.5 mm thick sheet should be multiplied by 10.9.2.1 If the air temperat
37、ure is changed 100C, the tempera-ture differentials would be 10, 5, 2, and 1C, respectively, forthe respective time periods. For any temperature change, T, thetemperature differential in Table 2 should be multiplied byT/10.9.2.2 For example, if the test specimen described in TestMethods D 1053, at a
38、 room temperature of 20C is placed in airat 70C, the temperature change would be 90C; and at theend of 510 s, the temperature differential between the center ofthe specimen and air would be 0.9C, making the temperatureof the center of the test specimen 69.1C.9.2.3 The above times can be reduced at l
39、east 50 % byproviding air circulation with velocities of 4.5 m/s past thespecimen, and by about 85 % by using a circulating liquid bath.9.2.4 The required measurements of modulus, hardness, orbrittleness should be made as soon as the specimen has reachedequilibrium temperature except for any conditi
40、oning timerequired by the method, while maintaining the specimen at thesame temperature.10. Tests for Effects of First Order Transition(Crystallization) Only10.1 Test each material at the temperature at which itcrystallizes most rapidly, when this is known.10.1.1 For unstressed specimens, this tempe
41、rature is near:10.1.1.1 25C for natural rubber,10.1.1.2 10C for chloroprenes,10.1.1.3 45C for butadiene copolymers,10.1.1.4 55C for silicones,10.1.1.5 56C for cis-1,4 butadiene, and10.1.1.6 10C for polyurethanes.10.2 When the temperature of maximum rate of crystalliza-tion is unknown, make tests at
42、a series of temperaturesincluding, but not necessarily limited to, 70, 55, 40, 25,10, 0, and +10C.10.3 Allow the temperature of the specimen to come toequilibrium as described in Section 9; then make one set of therequired measurements immediately and another after 72 h.Increased stiffness is an ind
43、ication of crystallization or of aplasticizer effect.10.3.1 Test in a gaseous medium unless otherwise specified.11. Tests for Effects Associated with Plasticizers11.1 It is suggested that tests for maximum effects associ-ated with plasticizers be made at 5C above the brittle pointtemperature.11.2 Fo
44、llow the procedure in Section 10 except for studiesof effects on brittle point temperatures, where tests should bemade after 15 min, 60 min, and as many other intervals asdesired up to 7 days.TABLE 2 Calculated Conditioning Time Required for Centerof Rubber Specimen to Reach Approximate Temperature
45、ofSurrounding Still Air for Temperature Change of 10CTemperature Dif-ferential BetweenAir and Center ofSpecimen, CTime Required, sTestMethodsD 1053Specimen2.5-mmThickSheetCylinder 12.7 mmThick, 19 mmin Diameter1.0 255 522 17400.5 332 682 22500.2 433 888 29400.1 510 980 3420D83207311.3 For tests long
46、er than 60 min, a gaseous medium shouldbe used.12. Keywords12.1 brittleness; brittle point; crystallization; enthalpy; firstorder transition; glass transition; low temperature test; modu-lus; plasticizer effects; resilience; second order transition;simple temperature effects; solubility; stiffening;
47、 subnormaltemperature; thermodynamic change; viscoelasticityASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such pa
48、tent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited ei
49、ther for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, 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.
