Designation:D573–04
Standard Test Method for
Rubber—Deterioration in an Air Oven1
This standard is issued under thefixed designation D573;the number immediately following the designation indicates the year of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript 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.Scope
1.1This test method covers a procedure to determine the influence of elevated temperature on the physical properties of vulcanized rubber.The results of this test method may not give an exact correlation with service performance since perfor-mance conditions vary widely.This test method may,however, be used to evaluate rubber compounds on a laboratory com-parison basis.
1.2The values stated in SI units are to be regarded as the standard.The values given in parentheses are for information only.
1.3This standard does not purport to address all of the safety concerns,if any,associated with its use.It is the responsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.(For specific precautionary statement,see Note1.)
2.Referenced Documents
2.1ASTM Standards:2
D15Methods of Compound and Sample Preparation for Physical Testing of Rubber Products3
D412Test Methods for Vulcanized Rubber and Thermo-plastic Elastomers—Tension
D1349Practice for Rubber—Standard Temperatures for Testing
D3182Practice for Rubber—Materials,Equipment,and Procedures for Mixing Standard Compounds and Prepar-ing Standard Vulcanized Sheets
D3183Practice for Rubber—Preparation of Pieces for Test Purposes from Products
D3184Test Methods for Rubber—Evaluation of NR (Natural Rubber)
D3185Test Methods for Rubber—Evaluation of SBR (Styrene-Butadiene Rubber)Including Mixtures With Oil D4483Practice for Evaluating Precision for Test Method Standards in the Rubber and Carbon Black Manufacturing Industries
E145Specification for Gravity-Convection and Forced-Ventilation Ovens
3.Summary of Test Method
3.1Specimens of vulcanized rubber are exposed to the deteriorating influence of air at specified elevat
ed temperatures for known periods of time,after which their physical properties are determined.These are compared with the properties deter-mined on the original specimens and the changes noted.
3.2Unless otherwise specified,the determination of the physical properties shall be carried out in accordance with Test Methods D412.
3.3Except as may be otherwise specified in this test method,the requirements of Practices D3182and D3183shall be complied with and are made part of this test method.
3.4In case of conflict between the provisions of this test method and those of detailed specifications or test methods for
a particular material,the latter shall take precedence.
4.Significance and Use
4.1Rubber and rubber products must resist the deterioration of physical properties with time caused by oxidative and thermal aging.This test method provides a way to assess these performance characteristics of rubber,under certain acceler-ated conditions as specified.
4.2Please refer to Annex A1for important information on standard compounds used for precision testing for accelerated test aging evaluation.
5.Apparatus
5.1Type IIB ovens specified in Test Method E145are satisfactory for use through70°C.For higher temperatures, Type IIA ovens are necessary.
5.1.1The interior size shall be as follows or of an equivalent volume:
1This test method is under the jurisdiction of ASTM Committee D11on Rubber
and is the direct responsibility of Subcommittee D11.15on Degradation Tests.
Current edition approved July1,2004.Published July2004.Originally approved
in1940.Last previous edition approved in1999as D573–99.
2For referenced ASTM standards,visit the ASTM website,,or
contact ASTM Customer Service at For Annual Book of ASTM
Standards volume information,refer to the standard’s Document Summary page on
the ASTM website.
3Withdrawn.
1
Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States.
Interior size of air oven:
min300by300by300mm(12by12by12in.)
max900by900by1200mm(36by36by48in.) 5.1.2Provision shall be made for suspending specimens vertically without touching each other or the sides of the aging chamber.
5.1.3The heating medium for the aging chamber shall be air circulated within it at atmospheric pressure.
5.1.4The source of heat is optional but shall be located in the air supply outside of the aging chamber proper.
5.1.5The temperature should be automatically recorded over the entire test period using a temperature-measuring device capable of measuring at the specified temperature to within61°C.Located in the upper central portion of the chamber near the center of the aging specimens.For apparatus not equipped with automatic recording capabilities,tempera-ture shall be measured with sufficient frequency to ascertain that the temperature limits specified in10.2are adhered to.
5.1.6Automatic temperature control by means of thermo-static regulation shall be used.
5.1.7The following special precautions shall be taken in order that accurate,uniform heating is obtained in all parts of the aging chamber:
5.1.7.1The heated air shall be thoroughly circulated in the oven by means of mechanical agitation.When a motor-driven fan is used,the air must not come in contact with the fan motor brush discharge because of danger of ozone formation.
5.1.7.2Baffles shall be used as required to prevent local overheating and dead spots.
5.1.7.3The thermostatic control device shall be so located as to give accurate temperature control of the heating medium. The preferred location is adjacent to the recording thermom-eter.
5.1.7.4An actual check shall be made by means of maxi-mum reading thermometers placed in various parts of the oven to verify the uniformity of the heating.
6.Sampling
6.1The sample size shall be sufficient to allow for the determination of the original properties on three specimens and also on three or more specimens for each exposure period of the test.At least24h must elapse between completion of the vulcanization of the samples and the start of the aging test.
6.2When minimum requirements are specified,one test on three dumbbells shall be considered sufficient.But if the results are below the specified requirements,two additional specimens shall be prepared from the original sample and tested.Should the results of either of these tests be below the specified requirements,the sample shall be considered to have failed to meet the specifications.
7.Test Specimens
7.1Dumbbell-shaped specimens prepared as described in Test Methods D412shall be considered stan
dard.Their form shall be such that no mechanical,chemical,or heat treatment will be required after exposure.If any adjustments(for example,to thickness)are necessary,they should be performed prior to exposure.
7.2The cross-sectional dimensions of test specimens for calculating the physical properties shall be measured prior to exposure in the aging chamber.Gage lines used for measuring elongation shall be applied after the specimens have been aged. Only specimens of similar dimensions having approximately the same exposed areas may be compared with each other. 8.Number of Test Specimens
8.1At least three test specimens shall be used to determine the original physical properties of each sample and also three or more specimens of the same material for each exposure period of the test.
8.2When minimum requirements are specified,one test shall be made for tensile strength and elongation.If the results are below the specified requirements,two additional specimens shall be prepared from the original sample and tested.Should the results of either of these tests be below the specified requirements,the samples shall be considered to have failed to meet the specifications.
9.Tests of Unaged Specimens
9.1The stress-strain properties or tensile strength and ulti-mate elongation and any other required properties of the original unaged specimens shall be determined within96h of the start of the aging period.Results on specimens that are found to be imperfect shall be discarded and retests shall be made.
9.2When rubber compounds are to be tested for the purpose of determining compliance with specifications,it shall be permissible to determine the original properties required in9.1 simultaneously with the determination of the values after the first aging period even though the elapsed time exceeds96h.
10.Procedure for Accelerated Aging
10.1Place the specimens for aging in the oven after it has been preheated to the operating temperature.If possible,avoid simultaneous aging of a mixed group of different compounds. For instance,high-sulfur compounds should not be aged with low-sulfur compounds and those containing antioxidants shall not be aged with those having no antioxidants.Some migration is known to occur.
10.2The operating temperature may be any elevated stan-dard temperature as shown in Practice D1349,as agreed upon. N OTE1—Caution:It should be noted that,for each10°C increase in temperatur
e,the rate of oxidation may be approximately double.With rapid aging types of rubber or those containing or contaminated by certain oxidizing chemicals,the rate of oxidation may be catalyzed to such an extent as to become violent with increasing temperatures.
10.3Start the aging interval at the time the specimens are placed in the oven and continue for a measured time interval. The selection of suitable intervals of aging will depend on the rate of deterioration of the particular material being tested. Intervals frequently used are3,7,and14days.
10.4Use aging intervals such that the deterioration will not be so great as to prevent determination of thefinal physical properties.In experimental work,it is desirable to use a range of periods,while for routine tests of known materials,fewer intervals may be
employed.
10.5At the termination of the aging interval,remove the specimens from the oven,cool to room tempera
ture on aflat surface,and allow them to rest not less than16h nor more than 96h before determination of the physical properties.Apply the gage lines to the specimens for use in measuring elongations.
11.Physical Tests of Aged Specimens
11.1The tensile strength and ultimate elongation or the stress-strain properties of the specimens aged for different intervals shall be determined as the intervals terminate in the progress of aging,disregarding the fact that more specimens may still be aging.In determining the physical properties after aging,thefinal values shall be the median of results from three specimens except that under the following conditions two additional specimens shall be exposed and tested and the median of the values for thefive specimens shall be used: 11.1.1If one or more values do not meet the specified requirements when testing for compliance with specifications.
11.1.2If referee tests are being made.After completion of the tests,the broken specimens shall be examined visually and manually and their condition noted.
12.Calculation
12.1Express the results of the aging test as a percentage of the change in each physical property(tensile strength,ultimate elongation,or tensile stress),calculated as follows:
P5[~A2O!/O]3100(1) where:
P=percentage change in property,
O=original value,and
A=value after aging.
13.Report
13.1Report the following information:
13.1.1The results calculated in accordance with Section12, 13.1.2All observed and recorded data on which the calcu-lations are based,
13.1.3Type of aging test,
13.1.4Aging interval,
13.1.5Aging temperature,
13.1.6Duration,temperature,and data of vulcanization of the rubber,if known,
13.1.7Dates of original andfinal determinations of physical properties,and
13.1.8Dimensions of test specimens.
14.Precision and Bias4
14.1This precision and bias section has been prepared in accordance with Practice D4483.Refer to this practice for terminology and other statistical calculation details.
14.2A Type2(interlaboratory)precision was evaluated in 1974.Both repeatability and reproducibility are short term,a period of a few days separates replicate test results.A test result is expressed on the basis of a median value,as specified by Test Methods D412obtained on three determinations or measure-ments of the property or parameter in question.
14.3Six different materials were used in the interlaboratory program,these were tested in three laboratories on two different days.These precision results were obtained for a variety of compounds prepared in accordance with Methods D15prior to its removal from the Annual Book of ASTM Standards.Please see Annex A1for more details on this work.
14.4The results of the precision calculations for repeatabil-ity and reproducibility for both percent tensil
e strength change and percent elongation change are given in Table1,in ascending order of material average or level,for each of the materials evaluated.
14.4.1The precision of this test method may be expressed in the format of the following statements that use an appropriate value of r,R,(r),or(R),that is,that value to be used in decisions about test results(obtained with the test method). The appropriate value is that value of r or R associated with a mean level in the precision tables closest to the mean level under consideration at any given time,for any given material in routine testing operation.
14.5Repeatability—The repeatability,r,of this test method has been established as the appropriate value tabulated in the precision tables.Two single test results,obtained under normal test method procedures,that differ by more than this tabulated r(for any given level)must be considered as derived from different or non-identical sample populations.
14.6Reproducibility—The reproducibility,R,of this test method has been established as the appropriate value tabulated
4Supporting data have beenfiled at ASTM International Headquarters and may be obtained by requesting Research Report RR:D11-1056.
TABLE1Type2Precision Results—100°C Aging
Part1—Percent Tensile Strength Change,48h
Material or
Compound
Mean Test
Level
Within
Laboratories
Between
Laboratories
Sr r SR R
NR(1G)−56.6  3.289.28  5.9116.7 SBR(9B)−14.2  3.429.68  3.028.55 NBR(1F)−11.5  2.46  6.96  2.497.05 CR(2D)−10.6  3.8310.8  5.1114.5 OESBR(10B3)−7.6  2.34  6.62  5.5615.7
IIR(2E)−1.1  3.479.82  3.7710.7   3.189.00  3.9011.04 Part2—Percent Change in Elongation,Average of48,96h Aging
NR(1G)−55.6  5.0814.47.7922.0 SBR(9B)−48.3  5.3815.2  6.0917.2 OESBR(10B3)−40.5  3.209.06  5.1114.5 NBR(1F)−39.67.1020.17.1120.1
CR(2D)−12.17.8522.29.0025.5
IIR(2E)−6.2  2.567.24  3.9711.2   5.2014.7  6.5118.4
N OTE1—The averaging of results for48and96h of aging gives an increased DF estimate of precision.
N OTE2—
Sr=within laboratory standard deviation
r=repeatability(in measurement units)
(r)=repeatability(in percent)
SR=between laboratory standard deviation
R=reproducibility(in measurement units)
(R)=reproducibility(in
percent)
in the precision tables.Two single test results obtained in two different 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.
14.7The precision results indicate that the repeatability and reproducibility of both percent tensile strength change and percent elongation change are essentially the same.Also the value of r or R,or bo
th,does not vary with the magnitude of percent elongation or percent tensile strength change.No values are given for(r)or(R)because of the near zero average values for some of the materials.
14.8Bias—In 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 test method since the value(of the test property)is exclusively defined by the test method.Bias,therefore,cannot be deter-mined.
15.Keywords
15.1accelerated aging;elevated temperature;oxidative ag-ing;rubber articles;rubber products;thermal aging
ANNEX
(Mandatory Information)
A1.FORMER TEST METHOD(D15)COMPOUNDS USED FOR PRECISION TESTING
A1.1Introduction
A1.1.1Testing to develop precision data was begun by some Subcommittees in D11prior to the removal of Methods D15,Compound and Sample Preparation for Physical Testing of Rubber Products.In this initial precision work,some of the standard compounds that were currently included in Methods D15were used.Since that time,these standard Methods D15 compounds have been either modified or removed from the Annual Book of ASTM Standards.They were replaced by a series of new standards,for example,Test Methods D3184on NR,Test Methods D3185on SBR,and so forth.
A1.1.2To provide a source of reference for the compounds removed from Methods D15,those compounds used in mea-suring precision,especially those used in Subcommittee D11.15,are included in Tables A1.1-A1.6taken directly from Methods D15.These tables are listed below.
A1.1.3The formulations for the compounds in Tables A1.1-A1.6are placed in this test method temporarily.This test method is selected as a location since it is the most frequently used standard test for evaluating compounds for accelerated aging performance.
A1.2Cure Times for Compounds
A1.2.1The cure times for compounds selected in the D11.15precision testing are as follows:
Time,Temper-Compound min,ature,°C Polychloroprene(neoprene)30150
Natural(1G)30145
SBR(9B)50145
OE–SBR(10B3)50145
Butyl(2E)80150
NBR(1F)40150
A1.3Materials and Mixing
A1.3.1In the precision test programs that generated Type2 Precision data for D11.15standards,that is,that precision which includes compound weighing,mixing,and curing com-ponents of variation,a special testing procedure was employed.
A common supply was set up for all the materials needed to prepare compounds in accordance with the tables of this Annex.All laboratories that participated in any interlaboratory program drew their materials from this common uniform supply;thus the within-materials source of variation was reduced to the lowest possible(practical)level.
A1.3.2Mixes of the selected compounds were made on specified days(2days normally being selected)to determine within-laboratory variability as specified in Practice D4483.
TABLE A1.1Type A—Standard Formulations for Styrene-
Butadiene Rubbers
NBS9B SBR or OE-SBR100.00
Zinc oxide370  3.00
Stearic acid372  1.00
Sulfur371  1.75
Furnace black A37850.00
TBBS384  1.00
156.75 Batch factor  3.0
A Current Industry Reference Black(IRB)may be used in place of NBS378, although slightly different results may be obtained.Weigh ingredients to nearest 0.1g for SBR and carbon black and to the nearest0.01g for other
ingredients.
TABLE A1.2Type A—Standard Formulations for Styrene-Butadiene Rubber Compounds(expressed on100Part Rubber Basis)
Material NBS 10B1Non-OE
Rubbers
10B225-Oil
Rubbers
10B337.5-Oil
Rubbers
10B450-Oil
Rubbers
10B562.5-Oil
Rubbers
10B675-Oil
Rubbers
OE-SBR125.00137.50150.00162.50175.00 Zinc oxide370  3.00  3.75  4.12  4.50  4.88  5.25 Stearic acid372  1.00  1.25  1.38  1.50  1.63  1.75 Sulfur371  1.75  2.19  2.42  2.63  2.85  3.06 Furnace black A37850.0062.5068.7575.0081.2587.50 TBBS384  1.00  1.25  1.38  1.50  1.63  1.75
156.75195.94215.55235.13254.74274.31 A Current Industry Reference Black(IRB)may be used in place of NBS378,although slightly different results may be obtained.
TABLE A1.3Standard Formulas for Neoprene Rubber
Compounds A
Material NBS Standard
Sample No.
ID2D
Neoprene W (100100)
Magnesium oxide37644
Stearic acid3720.51
SRF carbon black382 (29)
Zinc oxide37055
<0.350.5 Phenyl beta naphthylamine37722
Specific gravity(calculated)  1.29  1.39
A For mill mixing,use33recipe weight.
TABLE A1.4Standard Formulas for Butyl Rubber Compounds A
Material NBS Standard
Sample No.
IE2E3E
Butyl rubber388100100100 Zinc oxide370553
Sulfur37122  1.75 Stearic acid372 (31)
Benzothiazyl disulfi
Tetramethyl thiuram-disulfide374111
50...
Oil furnace black(HAF type)378B (50)
Specific gravity(calculated)0.97  1.12  1.13
A For mill mixing,use23recipe weight.
B IRB or Industry Reference Black may be used as a suitable alternative,but the same results may not be obtained.
editor evaluating revisionTABLE A1.5Standard Formula for Testing Carbon Black
Material
NBS Standard
Sample No.
IG
Natural 100.00
Stearic acid372  3.00
Zinc oxide370  5.00
Benzothiazyl disulfide3730.60
Sulfur371  2.50
50.00B
Specific gravity(calculated)  1.13
A Available from the Firestone Tire and Rubber Co.Specially selected Liberian crepe with600%modulus of7006100psi when tested in compound1A.
B For all carbon blacks except FT and MT.For those blacks where75parts are used,the calculated specific gravity is1.19.
TABLE A1.6Standard Formulas for Nitrile Rubber Compound Material
NBS Standard
Sample No.
IF
Nitrile rubber391100
Zinc oxide3705
Sulfur371  1.5
Stearic acid3721
Benzothiazyl disulfide3731
Gas furnace black38240
Specific gravity(calculated)
1.18

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