1、Designation: D3847 01 (Reapproved 2018)Standard Practice forRubberDirections for Achieving Subnormal TestTemperatures1This standard is issued under the fixed designation D3847; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar of last revision. 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 practice covers the general requirements forachieving and maintaining temperatures below 21C for ther-mal c
3、onditioning and physical testing of rubber.1.2 This practice describes the acceptable types and con-struction of low-temperature cabinets for conditioning andtesting of rubber, the composition and circulation of heat-transfer media, and the required uniformity and precision oftemperature control.1.3
4、 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 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-p
5、riate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevel
6、opment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D746 Test Method for Brittleness Temperature of Plasticsand Elastomers by ImpactD832 Practice for Rubber Conditi
7、oning For Low Tempera-ture TestingD945 Test Methods for Rubber Properties in Compression orShear (Mechanical Oscillograph)D1053 Test Methods for Rubber PropertyStiffening atLow Temperatures: Flexible Polymers and Coated FabricsD1229 Test Method for Rubber PropertyCompression Setat Low TemperaturesD1
8、329 Test Method for Evaluating Rubber PropertyRetraction at Lower Temperatures (TR Test)D1415 Test Method for Rubber PropertyInternationalHardnessD2136 Test Method for Coated FabricsLow-TemperatureBend TestD2137 Test Methods for Rubber PropertyBrittleness Pointof Flexible Polymers and Coated Fabrics
9、D2240 Test Method for Rubber PropertyDurometer Hard-nessD2632 Test Method for Rubber PropertyResilience byVertical ReboundE197 Specification for Enclosures and Servicing Units forTests Above and Below Room Temperature (Withdrawn1981)33. Significance and Use3.1 Low temperatures are often needed for c
10、onditioning ofrubber prior to testing, as well as during the test. Conditioningis required to attain a specific temperature that is uniformthroughout the specimen or for producing time-dependenteffects. Specimens may be conditioned and tested in the sameor different chambers.3.2 This practice is int
11、ended to apply particularly, but notexclusively, to the following ASTM Standards: Test MethodsD746, D945, D1053, D1229, D1329, D1415, D2136, D2137,D2240, D2632, Practice D832, and Specification E197.4. General Equipment Requirements44.1 The low-temperature cabinet may be refrigeratedmechanically, or
12、 by dry ice or liquid nitrogen, either directly orindirectly.4.1.1 The heat-transfer medium in the test chamber shouldbe air or air mixed with carbon dioxide or nitrogen, unless a1This practice is under the jurisdiction ofASTM Committee D11 on Rubber andRubber-like Materials and is the direct respon
13、sibility of Subcommittee D11.10 onPhysical Testing.Current edition approved June 1, 2018. Published August 2018. Originallyapproved in 1979. Last previous edition approved in 2012 as D3847 01 (2012).DOI: 10.1520/D3847-01R18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcont
14、act 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.4For more detailed information, see Specification E19
15、7.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 established in the Decision on Principles for theDevelopment of Int
16、ernational Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1liquid medium is specified. Although liquids cool the speci-mens faster than gases, they are more likely to cause propertychanges in addition to those caused by temper
17、ature change.Water, ethyl alcohol, and ethylene glycol are usually acceptablefor immersion times that are kept to the minimum for therequired tests.4.1.2 The temperature variation within 250 mm of the testspecimen shall be within 61C of the specified testing tem-perature.4.1.3 The heat-transfer medi
18、um should be circulated thor-oughly in the test chamber by means of mechanical agitation.Afan or stirrer suitably located in the test chamber can be usedfor this purpose.4.1.4 Automatic temperature control should be used.4.2 The size of the test chamber is optional.4.3 The door can be located either
19、 in the top of the testcabinet or in the side. A side-opening door is convenient, andis necessary where the equipment involved must be operatedfrom the side. However, it has the disadvantage of allowing thecold air to pour out when the door is opened. In general, awindow in the door is desired for o
20、bservation and the readingof test equipment indicators. This window should have at leastfive sealed layers of glass, suitably spaced, with dehydrated airbetween the layers to prevent condensation or frosting.4.3.1 Return to the test temperature after the introduction ofspecimens or test apparatus sh
21、ould be as rapid as possibleconsistent with minimal overshoot, but should not exceed 15min. Particular care is required for gaseous media.4.3.2 When the measuring device cannot be located logi-cally within the low-temperature chamber, it should have anextension rod of low thermal conductivity that e
22、xtends throughthe insulated wall and contacts the specimen. An example isgiven in Test Methods D1053.4.4 Chambers used for conditioning of specimens prior tothe test should provide adequate circulation on all sides of thespecimens. Suitable supports include racks, metal clips, andwide-mesh wirescree
23、n frames with at least 25 mm between thescreen and the cabinet floor. For chambers that are in continu-ous use, chamber walls having a maximum heat transmissionfactor of 35 mW/mK (0.24 Btuin./hft2F) are desirable. Forthe operation of the equipment involved in Test MethodsD2240 and D2632, handholes e
24、quipped with gloves andinsulated sleeves should be installed in the walls of the testcabinet. The interior walls surrounding the chamber should bemade of a good thermal conductor to promote uniform tem-perature and minimum radiant effects. Any heating elementswithin a gaseous medium chamber should b
25、e shielded from thespecimen since they could have radiant effects.4.5 A millivolt-type indicating potentiometer with an elec-tronic control mechanism has been found suitable for measur-ing the temperature and controlling the relay that opens andcloses the coolant valve. Copper-constantan thermocoupl
26、e wireof 30 gauge (0.255 mm) has been found to be most satisfactory.Such instrumentation is desirable when extremely accuratetemperature measurement and control are required.5. Mechanically Refrigerated Units5.1 In general, the mechanically refrigerated low-temperature cabinets consist of multiple-s
27、tage compressor andsuitable cooling coils that surround the test chamber. Suitableinsulation is provided between the test chamber and the outsidewalls of the cabinet.Automatic temperature control is obtainedby either a thermostatic control located in the test chamber,which turns the compressor on or
28、 off, or by a suitable pressurecontrol, which regulates the refrigerant temperature.Air is usedas the heat-transfer medium in the test specimen compartment.5.2 Mechanically refrigerated equipment is well-adapted tocontinuous operation at a fixed temperature. Except for ratherhigh maintenance and ini
29、tial costs, this type of equipment isless expensive to operate continuously from a power standpointthan are the dry ice units. Another advantage of mechanicalrefrigeration is the lower temperatures available. By theinstallation of electric strip heaters and suitable automaticcontrols, temperatures u
30、p to room temperature and above canbe obtained. Heaters should be shielded from test specimens toavoid radiant effects.6. Dry Ice Units (Direct-Type)6.1 In the direct type of dry ice low-temperature cabinets, asuitable fan or blower located in the dry ice compartmentcirculates the carbon dioxide vap
31、or from the dry ice chamberinto the test specimen chamber and back. By means of a presetdamper between the dry ice compartment and the test chamber,the inlet and outlet openings can be adjusted for maximumefficiency. A bimetallic thermoregulator, located in the testcompartment, controls the “on” and
32、 “off” operation of the fanin the dry ice compartment, thus providing automatic tempera-ture control. To ensure uniformity of temperature in the testcompartment, a fan is provided. More accurate temperaturecontrol can be obtained by the addition of thermostaticallycontrolled heaters inside the test
33、chamber, making sure thatthey are shielded from the test specimens.6.2 Commercial direct dry ice units are available in either0.028 or 0.227-m3(1 or 8-ft3) capacities and provide atemperature range from 73 to +104C (99 to +219F). Theseunits are particularly adapted for intermittent use where a wider
34、ange of testing temperatures is desired. Only a short time isrequired to cool the test chamber to a low temperature.7. Dry Ice Units (Indirect-Type)7.1 In the indirect type of dry ice low-temperature cabinets,air is used as the heat-transfer medium and no carbon dioxidefrom the dry ice comes in cont
35、act with the test specimens. Thetest chamber is cooled by circulating the carbon dioxide vaporcompletely around the outside of the test chamber which, inturn, is insulated from the outside of the cold box. In general,this type is a more costly construction than the direct type andis not quite as eff
36、icient. The time required to cool the testchamber to a low temperature is somewhat greater and is morecomparable in this respect to the mechanically refrigeratedunits.7.2 Commercial indirect dry ice units are available in eithera 1 or 8-ft3test chamber capacity. These units operate over aD3847 01 (2
37、018)2temperature range from 68 to +104C (90 to +219F). Twofans are provided, one for circulating the carbon dioxidearound the outside of the test chamber and the other forcirculating the air heat-transfer medium inside the test cham-ber. An automatic switch on the door shuts down the latter fanwhen
38、the door is opened, thus tending to prevent frosting.8. Packaged Air Units8.1 Temperature-regulated air or carbon dioxide may becirculated through insulated pipes or ducts from a separate unitto the test chamber. This unit may be portable so that it isusable with various test chambers.8.2 The temper
39、ature may be controlled by a thermoswitchthat operates either the fan motor or a damper that recirculatespart or all of the cold gas so that it bypasses the test chamber.Motor- or solenoid-driven dampers that operate in the dry icecompartment for temperature control may cause trouble due tofrosting
40、the mechanism. No entirely satisfactory method hasyet been devised for removing sufficient moisture from theheat-transfer medium to eliminate frosting completely.Desiccants, such as calcium chloride and calcium sulfate, havebeen used.9. Non-Recirculating Gas9.1 Liquid nitrogen or liquid carbon dioxi
41、de may be intro-duced into the test chamber in amounts sufficient to maintainthe desired low temperature.Any concentrated flow of cold gasdirectly onto the specimen should be avoided. This method isparticularly desirable when very low humidity is required.10. Keywords10.1 brittleness point; low temp
42、erature; subnormal test tem-perature ; temperature dependent test; thermal conditioningASTM 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
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45、ts 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. Individual reprints (single or mu
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