1、Designation: G114 14Standard Practices forEvaluating the Age Resistance of Polymeric Materials Usedin Oxygen Service1This standard is issued under the fixed designation G114; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 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 These practices describe procedures that are used todetermine the age resistance of plastic, thermosetting,elastom
3、eric, and polymer matrix composite materials exposedto oxygen-containing media.1.2 While these practices focus on evaluating the ageresistance of polymeric materials in oxygen-containing mediaprior to ignition and combustion testing, they also haverelevance for evaluating the age resistance of metal
4、s, andnonmetallic oils and greases.1.3 These practices address both established procedures thathave a foundation of experience and new procedures that haveyet to be validated. The latter are included to promote researchand later elaboration in this practice as methods of the formertype.1.4 The resul
5、ts of these practices may not give exactcorrelation with service performance since service conditionsvary widely and may involve multiple factors such as thoselisted in subsection 5.8.1.5 Three procedures are described for evaluating the ageresistance of polymeric materials depending on application
6、andinformation sought.1.5.1 Procedure A: Natural AgingThis procedure is usedto simulate the effect(s) of one or more service stressors on amaterials oxygen resistance, and is suitable for evaluatingmaterials that experience continuous or intermittent exposureto elevated temperature during service.1.
7、5.2 Procedure B: Accelerated Aging Comparative OxygenResistanceThis procedure is suitable for evaluating materialsthat are used in ambient temperature service, or at a tempera-ture that is otherwise lower than the aging temperature, and isuseful for developing oxygen compatibility rankings on alabor
8、atory comparison basis.1.5.3 Procedure C: Accelerated Aging Lifetime PredictionThis procedure is used to determine the relationship betweenaging temperature and a fixed level of property change, therebyallowing predictions to be made about the effect of prolongedservice on oxidative degradation.1.6
9、The values stated in SI units are to be regarded as thestandard, however, all numerical values shall also be cited inthe systems in which they were actually measured.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of t
10、he user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific precau-tionary statements are given in Section 10.2. Referenced Documents2.1 ASTM Standards:2D395 Test Methods for Rubber PropertyCompressi
11、on SetD412 Test Methods for Vulcanized Rubber and Thermoplas-tic ElastomersTensionD638 Test Method for Tensile Properties of PlasticsD1349 Practice for RubberStandard Conditions for Test-ingD1708 Test Method for Tensile Properties of Plastics by Useof Microtensile SpecimensD2240 Test Method for Rubb
12、er PropertyDurometer Hard-nessD2512 Test Method for Compatibility of Materials withLiquid Oxygen (Impact Sensitivity Threshold and Pass-Fail Techniques)D2863 Test Method for Measuring the Minimum OxygenConcentration to Support Candle-Like Combustion ofPlastics (Oxygen Index)D3039 Test Method for Ten
13、sile Properties of Polymer Ma-trix Composite MaterialsD3045 Practice for Heat Aging of Plastics Without LoadD4809 Test Method for Heat of Combustion of LiquidHydrocarbon Fuels by Bomb Calorimeter (PrecisionMethod)1These practices are under the jurisdiction of ASTM Committee G04 onCompatibility and S
14、ensitivity of Materials in Oxygen Enriched Atmospheres and isthe direct responsibility of Subcommittee G04.02 on Recommended Practices.Current edition approved Oct. 1, 2014. Published November 2014. Originallyapproved in 1993. Last previous edition approved in 2007 as G114 07. DOI:10.1520/G0114-14.2
15、For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C7
16、00, West Conshohocken, PA 19428-2959. United States1G63 Guide for Evaluating Nonmetallic Materials for Oxy-gen ServiceG72 Test Method for Autogenous Ignition Temperature ofLiquids and Solids in a High-Pressure Oxygen-EnrichedEnvironmentG74 Test Method for Ignition Sensitivity of NonmetallicMaterials
17、 and Components by Gaseous Fluid ImpactG86 Test Method for Determining Ignition Sensitivity ofMaterials to Mechanical Impact in Ambient Liquid Oxy-gen and Pressurized Liquid and Gaseous Oxygen Envi-ronmentsG125 Test Method for Measuring Liquid and Solid MaterialFire Limits in Gaseous OxidantsG126 Te
18、rminology Relating to the Compatibility and Sensi-tivity of Materials in Oxygen Enriched Atmospheres2.2 CGA Standard:CGA G-4.3 Type I QVL E Commodity Specification forOxygen32.3 Military Standard:MIL-PRF-27210 Amendment 1Oxygen, AviatorsBreathing, Liquid and Gas43. Terminology3.1 Definitions of Term
19、s Specific to This Standard:3.1.1 agingsee Terminology G126.3.1.2 accelerated aginga type of artificial aging wherebythe effect of prolonged exposure during service is simulated byaging at elevated temperature.3.1.3 artificial agingsee Terminology G126.3.1.4 oxidative degradationphysical or mechanic
20、al prop-erty changes occurring as a result of exposure to oxygen-containing media.3.1.5 oxygen-containing mediaair media containinggreater than 21 mole % oxygen, or oxygen-enriched mediacontaining greater than 25 mole % oxygen.3.1.6 oxygen resistanceresistance of a material to ignitespontaneously, p
21、ropagate by sustained combustion, or undergooxidative degradation.3.1.7 oxygen serviceapplications involving theproduction, storage, transportation, distribution, or use ofoxygen-containing media.3.1.8 natural agingsee Terminology G126.3.1.9 physical agingaging that occurs during normal stor-age and
22、 which is a function of time after molding or curing.4. Summary of Practice4.1 These practices can be used to evaluate systematicallythe effect of natural aging (Procedure A) or accelerated aging(Procedures B and C) on oxygen resistance. To apply itsprinciple, the user first characterizes the materi
23、al, then subjectsthe material to an aging stressor or stressors, followed byre-characterizing the material. Caution must be taken in inter-preting results because interactions occurring in service may bedifferent from those simulated during aging.4.2 It is always more accurate, although not alwayspr
24、actical, to determine the effect of natural aging (ProcedureA)without resorting to accelerated aging (Procedures B and C).Accelerated aging procedures are more useful for determiningmaterial rankings (Procedure B) or for making lifetime predic-tions (Procedure C).4.3 Summary of Practice for Evaluati
25、ng the Effect of Agingin Incident Studies:4.3.1 In incident studies, in which initial characterizationdata are not available, historical or average property data maybe used to draw coarser conclusions about the effect of agingon oxygen resistance.4.4 Practices for Natural Aging (Procedure A) and Acc
26、el-erated Aging for Comparative Oxygen Resistance (ProcedureB):4.4.1 The effect of aging is reported as positive or negativedepending upon whether the property used to evaluate oxygenresistance increases or decreases, and the magnitude of theeffect is reported as the degree to which the measured pro
27、pertychanges relative to that of the unaged material.4.5 Practice for Accelerated Aging for Lifetime Prediction(Procedure C):4.5.1 The time necessary to produce a fixed level ofproperty change is determined at a series of elevated agingtemperatures, and the time necessary to produce the same levelof
28、 property change at some lower temperature is then deter-mined by linear extrapolation.4.5.2 A practice for evaluating the effect of acceleratedaging on physical and mechanical properties under conditionsof variable time and temperature has been validated forsignificance and is described in detail.
29、This practice is similarto that given in Practice D3045 but is specific to aging inoxygen-containing media.4.5.3 A practice for evaluating the effect of acceleratedaging on ignition and combustion properties under conditionsof variable time and temperature has not been validated forsignificance, but
30、 may yield meaningful results. The practicedescribed is included to promote research and possible devel-opment into an established method.4.5.4 There can be very large errors when accelerated agingArrhenius approaches are used to estimate the time necessaryto produce a fixed level of property change
31、 at some lowertemperature. This estimated time to produce a fixed level ofproperty change or “failure” at the lower temperature is oftencalled the “service life.” Because of the errors associated withthese calculations, this time should be considered to be the“maximum expected” rather than “typical.
32、”NOTE 1Errors in accelerated aging Arrhenius approaches arise fromchanges in this oxidative degradation mechanism at elevated temperature.5. Significance and Use5.1 This practice allows the user to evaluate the effect ofservice or accelerating aging on the oxygen resistance ofpolymeric materials use
33、d in oxygen service.3Available from Compressed Gas Association (CGA), 4221 Walney Rd., 5thFloor, Chantilly, VA 20151-2923, http:/.4Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 RobbinsAve., Philadelphia, PA19111-5098, http:/www.dsp.dla.mil.G114 1425.2 The use of
34、 this practice presupposes that the propertiesused to evaluate the effect of aging can be shown to relate tothe intended use of the material, and are also sensitive to theeffect of aging.5.3 Polymeric materials will, in general, be more suscep-tible than metals to aging effects as evidenced by irrev
35、ersibleproperty loss. Such property loss may lead to catastrophiccomponent failure, including a secondary fire, before primaryignition or combustion of the polymeric material occurs.5.4 Polymers aged in the presence of oxygen-containingmedia may undergo many types of reversible and irreversiblephysi
36、cal and chemical property change. The severity of theaging conditions determines the extent and type of changes thattake place. Polymers are not necessarily degraded by aging, butmay be unchanged or improved. For example, aging may driveoff volatile materials, thus raising the ignition temperaturewi
37、thout compromising mechanical properties. However, agingunder prolonged or severe conditions (for example, elevatedoxygen concentration) will usually cause a decrease in me-chanical performance, while improving resistance to ignitionand combustion.5.5 Aging may result in reversible mass increase(phy
38、sisorption), irreversible mass increase (chemisorption),plasticization, discoloration, loss of volatiles, embrittlement,softening due to sorption of volatiles, cracking, relief ofmolding stresses, increased crystallinity, dimensional change,advance of cure in thermosets and elastomers, chainscission
39、ing, and crosslinking.5.6 After a period of service, a materials properties may besignificantly different from those when new.All materials ratedfor oxygen service should remain resistant to ignition andcombustion (primary fire risk). Furthermore, all materials ratedfor oxygen service should be resi
40、stant to oxidative degradationand retain relevant physical and mechanical properties duringservice, because part failure can indirectly lead to an unaccept-able ignition or combustion risk (secondary fire risk).5.7 In cases where aging makes a material more susceptibleto fire or causes significant o
41、xidative degradation, aging testsmay be used to evaluate whether the material will becomeunacceptable during service. In cases where aging makes amaterial less susceptible to fire, aging tests may be used toevaluate whether a material can be conditioned (artificiallyaged) to prolong its service life
42、time.5.8 Oxygen resistance as determined by this practice doesnot constitute grounds for material acceptability in oxygenservice. Determination of material acceptability must be per-formed within the broader context of review of system orcomponent design, plausible ignition mechanisms, ignitionproba
43、bility, post-ignition material properties, and reactioneffects such as are covered by Guide G63.5.9 The potential for personnel injury, facility damage,product loss, or downtime occurring as a result of ignition,combustion, or catastrophic equipment failure will be least forsystems or components usi
44、ng air and greatest for systems orcomponents using pure oxygen.5.10 In terms of physical and mechanical properties, agingis expected to have a greater influence on a polymers ultimateproperties such as strength and elongation, than bulk propertiessuch as modulus.5.11 In terms of fire properties, agi
45、ng is expected to have agreater influence on a polymers ignition properties (forexample, autogenous ignition temperature (AIT), mechanicaland pneumatic impact) than its propagation properties (forexample, upward and downward flame propagation). To date,the only background on aging influences is that
46、 of theBundesanstalt fr Materialforschung und -prfung (BAM)which has assessed the effect of aging at elevated pressure andtemperature on a materials AIT. BAM has used the AIT testresults to establish maximum constraints on the use of mate-rials at elevated pressure and temperature.56. Rationale for
47、Aging Tests6.1 The body of information on the effect of natural agingon oxygen resistance under conditions of multiple stressors issmall, and so, this practice is intended to promote testingtowards the goal of developing better practices to evaluate thecompeting effects of multiple stressors.6.2 The
48、 body of information on the effect of acceleratedaging on ignition and combustion is small, and so, this practiceis intended to promote testing towards the goal of developingpotential practices to evaluate the effect of accelerated aging onignition and combustion.7. Apparatus7.1 General Consideratio
49、ns:7.1.1 The apparatus used for aging can vary widely. Agingin ambient pressure air, gravity-convection ovens or forced-ventilation ovens may be used. When aging in pressurizedoxygen-enriched media, pressure-rated cell-type ovens or oxy-gen pressure chambers that provide a greater margin of safetymust be used because of the increased risk of ignition orcombustion.7.1.2 This practice focuses on small-scale aging methodsinvolving a requisite number and type of specimens in accor-dance with the ASTM test method for the specific propertybeing de
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