1、Designation: D 3847 01 (Reapproved 2007)Standard Practice forRubberDirections for Achieving Subnormal TestTemperatures1This standard is issued under the fixed designation D 3847; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、year 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.1. Scope1.1 This practice covers the general requirements forachieving and maintaining temperatures below 21C for ther-ma
3、l conditioning 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.
4、1.3 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 appr
5、o-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 746 Test Method for Brittleness Temperature of Plasticsand Elastomers by ImpactD 832 Practice for Rubber Conditioning For Low Tempera-ture Testing
6、D 945 Test Methods for Rubber Properties in Compressionor Shear (Mechanical Oscillograph)D 1053 Test Methods for Rubber PropertyStiffening atLow Temperatures: Flexible Polymers and Coated FabricsD 1229 Test Method for Rubber PropertyCompressionSet at Low TemperaturesD 1329 Test Method for Evaluating
7、 Rubber PropertyRetraction at Lower Temperatures (TR Test)D 1415 Test Method for Rubber PropertyInternationalHardnessD 2136 Test Method for Coated FabricsLow-Temperature Bend TestD 2137 Test Methods for Rubber PropertyBrittlenessPoint of Flexible Polymers and Coated FabricsD 2240 Test Method for Rub
8、ber PropertyDurometerHardnessD 2632 Test Method for Rubber PropertyResilience byVertical ReboundE 197 Specification for Enclosures and Servicing Units forTests Above and Below Room Temperature33. Significance and Use3.1 Low temperatures are often needed for conditioning ofrubber prior to testing, as
9、 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 notexclu
10、sively, to the following ASTM Standards: Test MethodsD 746, D 945, D 1053, D 1229, D 1329, D 1415, D 2136,D 2137, D 2240, D 2632, Practice D 832, and SpecificationE 197.4. General Equipment Requirements44.1 The low-temperature cabinet may be refrigerated me-chanically, or by dry ice or liquid nitrog
11、en, 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 aliquid medium is specified. Although liquids cool the speci-mens faster than gases, they are more likely to cause propertychanges in addition to thos
12、e caused by 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
13、 and Temperature-Dependent Physical Properties.Current edition approved May 1, 2007. Published July 2007. Originally approvedin 1979. Last previous edition approved in 2001 as D 3847 01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceas
14、tm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.4For more detailed information, see Specification E 197.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United
15、States.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 medium should be circulated thor-oughly in the test chamber by means of mechanical agitation.Afan or stirrer suitably located in the test chamber
16、 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. A side-opening door is convenient, andis necessary where the equipment involved must be operat
17、edfrom 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 indicators. This window should have at leastfive sealed layers of glass, suitably spaced, with de
18、hydrated 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 minimal overshoot, but should not exceed 15min. Particular care is required for gaseous media.4.3
19、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 the specimen. An example isgiven in Test Methods D 1053.4.4 Chambers used for conditioning of s
20、pecimens 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 thescreen and the cabinet floor. For chambers that are in continu-ous use, chamber walls having a maxim
21、um heat transmissionfactor of 35 mW/mK (0.24 Btuin./hft2F) are desirable. Forthe operation of the equipment involved in Test MethodsD 2240 and D 2632, handholes equipped with gloves andinsulated sleeves should be installed in the walls of the testcabinet. The interior walls surrounding the chamber s
22、hould 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 have radiant effects.4.5 A millivolt-type indicating potentiometer with an elec-tronic contro
23、l 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 to be most satisfactory.Such instrumentation is desirable when extremely accuratetemperature m
24、easurement 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 that surround the test chamber. Suitableinsulation is provided between the test chamber and the
25、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 regulates the refrigerant temperature.Air is usedas the heat-transfer medium in the test spe
26、cimen 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 expensive to operate continuously from a power standpointthan are the dry ice units. Another adv
27、antage of mechanicalrefrigeration is the lower temperatures available. By theinstallation of electric strip heaters and suitable automaticcontrols, temperatures up to room temperature and above canbe obtained. Heaters should be shielded from test specimens toavoid radiant effects.6. Dry Ice Units (D
28、irect-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 specimen chamber and back. By means of a presetdamper between the dry ice compartment and the tes
29、t 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 compartment, thus providing automatic tempera-ture control. To ensure uniformity of temperature
30、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 from the test specimens.6.2 Commercial direct dry ice units are available in either0.028 or 0.2
31、27-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 a short time isrequired to cool the test chamber to a low temperature.7. Dry Ice Units (Indi
32、rect-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 is cooled by circulating the carbon dioxide vaporcompletely around the outside of the test ch
33、amber 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 testchamber to a low temperature is somewhat greater and is morecomparable in this respect to the me
34、chanically 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). Twofans are provided, one for circulating the carbon dioxidearound the outside of the test chamber
35、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.8. Packaged Air Units8.1 Temperature-regulated air or carbon dioxide may becirculated through insulat
36、ed pipes or ducts from a separate unitD 3847 01 (2007)2to 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 operates either the fan motor or a damper that recirculatespart or all of the cold gas so t
37、hat 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 method hasyet been devised for removing sufficient moisture from theheat-transfer medium to elimi
38、nate frosting completely. Desic-cants, such as calcium chloride and calcium sulfate, have beenused.9. Non-Recirculating Gas9.1 Liquid nitrogen or liquid carbon dioxide may be intro-duced into the test chamber in amounts sufficient to maintainthe desired low temperature.Any concentrated flow of cold
39、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; temperature dependent test; thermal conditioningASTM International takes no position respecting t
40、he 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 the riskof infringement of such rights, are entirely their own responsibility.This standard
41、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 of this standard or for additional standardsand should be addressed to ASTM International H
42、eadquarters. 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
43、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).D 3847 01 (2007)3
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