1、Designation: D3847 01 (Reapproved 2012)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 and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D746 Test Method for Brittleness Temperature of Plasticsand Elastomers by ImpactD832 Practice for Rubber Conditioning For Low Tempera-ture TestingD945
6、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 TemperaturesD1329 Test Method for Evaluating Rubber P
7、ropertyRetraction 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 FabricsD2240 Test Method for Rubber PropertyDu
8、rometer 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 conditioning ofrubber prior to testing,
9、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 intended to apply particularly, but notexc
10、lusively, 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 by dry ice or liquid nitrogen, either
11、directly orindirectly.4.1.1 The heat-transfer medium in the test chamber shouldbe air or air mixed with carbon dioxide or nitrogen, unless aliquid 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
12、 temperature change.Water, ethyl alcohol, and ethylene glycol are usually acceptablefor immersion times that are kept to the minimum for therequired tests.1This practice is under the jurisdiction ofASTM Committee D11 on Rubber andis the direct responsibility of Subcommittee D11.14 on Time and Temper
13、ature-Dependent Physical Properties.Current edition approved Dec. 1, 2012. Published February 2013. Originallyapproved in 1979. Last previous edition approved in 2007 as D3847 01 (2007).DOI: 10.1520/D3847-01R12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Cust
14、omer 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 E197.Copyright A
15、STM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.1.2 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 medium should be circulated thor-oughly in the te
16、st 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 in the top of the testcabinet or in the side
17、. 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 observation and the readingof test equipment i
18、ndicators. 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 should be as rapid as possibleconsistent with m
19、inimal 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 extends throughthe insulated wall and contacts
20、 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 wirescreen frames with at least 25 mm between thescree
21、n 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 equipped with gloves andinsulated sleeves shou
22、ld 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 be shielded from thespecimen since they could
23、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 thermocouple wireof 30 gauge (0.255 mm) has been found t
24、o 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-stage compressor andsuitable cooling coils tha
25、t 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 off, or by a suitable pressurecontrol, which
26、 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 initial costs, this type of equipment isless exp
27、ensive 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 up to room temperature and above canbe obtaine
28、d. 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 vapor from the dry ice chamberinto the test spec
29、imen 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 “off” operation of the fanin the dry ice com
30、partment, 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 chamber, making sure thatthey are shielded fr
31、om 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 widerange of testing temperatures is desired. Only
32、 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 contact with the test specimens. Thetest chamber
33、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 efficient. The time required to cool the testcha
34、mber 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 atemperature range from 68 to +104C (90 to +219F). Twofan
35、s 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 the door is opened, thus tending to prevent frosting.D3847 01
36、 (2012)28. 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 temperature may be controlled by a thermoswitchthat
37、 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 the mechanism. No entirely satisfactory metho
38、d 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 dioxide may be intro-duced into the test chamber i
39、n 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 temperature; subnormal test tem-perature ; temper
40、ature 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 the validity of any such patent rights, and t
41、he 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 either for revision
42、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 shoul
43、dmake 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 multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (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 ASTM website (www.astm.org/COPYRIGHT/).D3847 01 (2012)3
