1、Designation: D 6954 04Standard Guide forExposing and Testing Plastics that Degrade in theEnvironment by a Combination of Oxidation andBiodegradation1This standard is issued under the fixed designation D 6954; the number immediately following the designation indicates the year oforiginal adoption or,
2、 in the case of revision, the 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 guide provides a framework or road map tocompare and rank the controlled l
3、aboratory rates of degrada-tion and degree of physical property losses of polymers bythermal and photooxidation processes as well as the biodegra-dation and ecological impacts in defined applications anddisposal environments after degradation. Disposal environ-ments range from exposure in soil, land
4、fill, and compost inwhich thermal oxidation may occur and land cover andagricultural use in which photooxidation may also occur.1.2 In this guide, established ASTM International standardsare used in three tiers for accelerating and measuring the lossin properties and molecular weight by both thermal
5、 andphotooxidation processes and other abiotic processes (Tier 1),measuring biodegradation (Tier 2), and assessing ecologicalimpact of the products from these processes (Tier 3).1.3 The Tier 1 conditions selected for thermal oxidation andphotooxidation accelerate the degradation likely to occur in a
6、chosen application and disposal environment. The conditionsshould include a range of humidity or water concentrationsbased on the application and disposal environment in mind.The measured rate of degradation at typical oxidation tempera-tures is required to compare and rank the polymers beingevaluat
7、ed in that chosen application to reach a molecularweight that constitutes a demonstrable biodegradable residue(using ASTM International biometer tests for CO2evolutionappropriate to the chosen environment). By way of example,accelerated oxidation data must be obtained at temperaturesand humidity ran
8、ges typical in that chosen application anddisposal environment, for example, in soil (20 to 30C), landfill(20 to 35C), and composting facilities (30 to 65C). Forapplications in soils, local temperatures and humidity rangesmust be considered as they vary widely with geography. Atleast one temperature
9、 must be reasonably close to the end useor disposal temperature, but under no circumstances shouldthis be more than 20C away from the removed that tempera-ture. It must also be established that the polymer does notundergo a phase change, such as glass transition temperature(Tg) within the temperatur
10、e range of testing.1.4 The residues resulting from the oxidations are thenexposed to appropriate disposal or use environments in stan-dard biometric test methods to measure the rate and degree ofbiodegradation (Tier 2).1.5 The data generated under Tier 1 evaluation and thedetermined time for the bio
11、degradation in the chosen environ-ment (Tier 2) allow ranking relative to other polymers evalu-ated under similar environmental conditions with this guide.The degree and time for biodegradation should be consistentwith ASTM International methods, and any residues from theintermediate oxidation stage
12、 and from biodegradation must beshown to be environmentally benign and not persistent (Tier 3).NOTE 1The intended use of this guide is for comparison and rankingof data to aid in the design and development and the reduction ofenvironmental impacts of polymers that require no more than 24 monthsto ox
13、idize and biodegrade in the intended use and disposal options andcreate no harmful or persistent residues under the appropriate disposalconditions (for example, two seasons of crop-growing conditions in soil).1.6 It is cautioned that the results of any laboratory exposurein this guide cannot be dire
14、ctly extrapolated to actual disposalenvironments; confirmation to real world exposure is ulti-mately required as with all ASTM International standards.1.7 The values stated in SI units are to be regarded asstandard.NOTE 2There is no ISO standard that is the equivalent of this standardguide. Note thi
15、s changed all subsequent Note numbers.1This guide is under the jurisdiction of ASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.96 on Biodegradable Plastics andBiobased Products.Current edition approved May 1, 2004. Published May 2004.1Copyright ASTM International,
16、100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1.8 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-priate safety and health practices and
17、 determine the applica-bility of regulatory requirements prior to use.2. Referenced Documents2.1 ASTM Standards:2D 883 Terminology Relating to PlasticsD 3826 Practice for Determining Degradation End Point inDegradable Polyethylene and Polypropylene Using a Ten-sile TestD 3987 Test Method for Shake E
18、xtraction of Solid Wastewith WaterD 5071 Practice for Exposure of Photodegradable Plasticsin a Xenon Arc ApparatusD 5208 Practice for Fluorescent Ultraviolet (UV) Exposureof Photodegradable PlasticsD 5272 Practice for Outdoor Exposure Testing of Photode-gradable PlasticsD 5338 Test Method for Determ
19、ining Aerobic Biodegrada-tion of Plastic Materials Under Controlled CompostingConditionsD 5510 Practice for Heat Aging of Oxidatively DegradablePlasticsD 5526 Test Method for Determining Anaerobic Degrada-tion of Plastic Materials Under Accelerated Landfill Con-ditionsD 5951 Practice for Preparing R
20、esidual Solids Obtainedafter Biodegradability Standard Methods for Plastics inSolid Waste for Toxicity and Compost Quality TestingD 5988 Test Method for Determining Aerobic Biodegrada-tion in Soil of Plastic Materials or Residual PlasticMaterials after CompostingD 6002 Guide for Assessing the Compos
21、tability of Environ-mentally Degradable PlasticsD 6400 Specification for Compostable PlasticsE 1440 Guide for an Acute Toxicity Test with the RotiferBrachionus2.2 Other Standards:EPA TITLE 40 CFA 40CFR62, 40CFR50-189, 40CFR260-299, 40CFR300-399, 700-799, and 49CFR100-1803OECD Guideline 207 Earthworm
22、, Acute Toxicity Tests4OECD Guideline 208 Terrestrial Plants, Growth Test4ORCA Guidelines for the Evaluation of Feedstock forSource Separated Biowaste Composting and Biogasifica-tion53. Terminology3.1 Definitions:3.1.1 Definitions of most terms applicable to this guideappear in Terminology D 883 and
23、 Guide D 6002.3.2 Definitions of Terms Specific to This Standard:3.2.1 environmental degradation of a plastic, nabiotic orbiotic degradation process or both that occurs in a givenenvironment and includes photodegradation, oxidation, hy-drolysis, and biodegradation. Living organisms effect bioticdegr
24、adation processes and abiotic degradation processes arenonbiological in nature.3.2.1.1 DiscussionTerm not defined in TerminologyD 883.3.2.2 gels, ncross-linked polymer structures insoluble insolvents that do not break the primary or cross-linking bonds inthe polymer. Cross-links created during oxobi
25、odegradadationof polymers are chemical bonds created by the degradationprocess, mostly carbon-carbon bonds, and thus extremelyresistant to solvent degradation.63.2.3 oxidation, nprocess promoted thermally or by irra-diation in the presence of oxygen.4. Summary of Guide4.1 This guide may be used to c
26、ompare and rank the rateand degree of thermal oxidative degradation of a plasticmaterial relatively to a molecular weight range that can beestablished as biodegradable in a chosen environment. Subse-quently, the biodegradation of these degraded polymers indiverse environments such as soil, compost,
27、landfill, and watermay be compared and ranked using standard biometric testmethods and measuring carbon dioxide evolution.NOTE 3If composting is the designated disposal route, SpecificationD 6400 is the only ultimate and definitive applicable specification formeasuring biodegradation or compostabili
28、ty. Oxidation followed bybiodegradation under the conditions found in this guide does not conferthe designation “compostable” or any connotation that the applications areacceptable for composting in a commercial or municipal compostingfacility.4.2 This guide uses a tiered criteria-based approach toa
29、ssess the consecutive oxidation and biodegradability of plasticproducts and ecological impacts in defined applications. This isshown schematically in Section 6. Each tier in this guideincludes objectives and a summary that presents test methods,method principles, test duration, and interpretation of
30、 results.4.3 The tiered approach is chosen in the laboratory forconvenient separation of oxidative degradation, biodegrada-tion, and ecological impact stages even though in the realworld all three are likely to be concurrent rather than consecu-tive.4.4 Tiered Methodology:4.4.1 Tier 1 measures the r
31、ate and extent of molecularweight loss resulting from oxidation that is indicative of lossesin physical properties from oxidation. Tier 1 requires eitheraccelerated testing or long-term testing over a range of relativehumidity or amount of moisture. Accelerated testing must beperformed under conditi
32、ons and temperatures that are accept-ably typical of the specific application and disposal environ-ments under consideration. Practices D 5208, D 5510, and2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM
33、Standards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from United States Environmental Protection Association (EPA),Ariel Rios Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20460.4Available from OECD, 2 rue Andre Pascal, F-75775 Paris Cedex 16,
34、France.5Available from ORCA, Avenue E. Mounier 83, Box 1, Brussels, BelgiumB-1200.6Vollmert, B., Polymer Chemistry, Springer-Verlag, New York, 1973, p. 27, alsopp. 543- 561.D6954042D 5071 may be used to specify the oxidative conditions andPractice D 3826 may be used to define the point of embrittle-
35、ment.NOTE 4For measuring the extent of disintegration/fragmentation, asieve test is required. In this tier, the fragments are subjected to molecularweight analysis and a total mass balance is obtained in the process.Exposure temperatures may range from 20 to 70C in the presence of airand specified m
36、oisture or water levels for selected periods of time. At leastone temperature must be reasonably close to the end use or disposaltemperature, but under no circumstances should this be more than 20Caway from that temperature. It must also be established that the polymerdoes not undergo a phase change
37、, such as glass transition temperature (Tg)within the temperature range of testing. As an alternate degradationprocess, the test samples may be exposed to photooxidation in air as perPractices D 5208 or D 5071 and the mass change of the plastic recordedafter exposure.4.4.2 Tier 1 accelerated oxidati
38、on tests are not indicators ofbiodegradability and should not be used for the purpose ofmeeting the specifications as described in Specification D 6400and claiming compostability or biodegradation during com-posting. (If oxidation is thought to be sufficiently rapid in Tier1, suggesting that compost
39、ing may be a disposal environment,then Specification D 6400 must be done and all the specifica-tions in Section 6 (Detailed Requirements) must be met.4.5 Gel Formation and Consequences During OxidationPhaseDiscussion:4.5.1 Gel formation is a frequent side reaction of theoxidative degradation of poly
40、mers, especially polyolefins. Gelsare cross-linked structures arising from the free radical natureof oxidative degradation. They are insoluble in nonreactivesolvents, that is, solvents that do not break additional bonds.Normally, gels are not available to biodegradation. Some gelsdissolve on further
41、 oxidative degradation and become availablefor ultimate biodegradation. However, the prooxidant (catalyst)may be excluded from the gel structure because of solubilitychanges in gel phase. In this case, the gel would become anondegradable or very slowly degradable new fraction withinthe polymer. It i
42、s important to establish the extent of gel and itsnature or permanence in the polymer residue and report thesefindings.4.5.2 The purpose of Tier 2 is to estimate the biodegrad-ability of all the fragmented products from Tier 1 underlaboratory scale conditions appropriate to the application usingcurr
43、ent Test Methods D 5988 and D 5338. The entire materialfrom the Tier 1 exposure is subjected to biodegradation testing.The percent biodegradation shall be calculated and reported asstated in the above referenced standards. The results from Tier1 and Tier 2 shall be combined and used for comparison a
44、ndranking purposes between polymers of interest.4.5.3 Tier 3 involves considerations of the ecological im-pacts in the final disposal medium such as soil, as in allbiodegradation testing methods, which is basically a compari-son of the test medium before and following oxidation andbiodegradation.5.
45、Significance and Use5.1 This guide is a sequential assembly of extant butunconnected standard tests and practices for the oxidation andbiodegradation of plastics, which will permit the comparisonand ranking of the overall rate of environmental degradation ofplastics that require thermal or photooxid
46、ation to initiatedegradation. Each degradation stage is independently evalu-ated to allow a combined evaluation of a polymers environ-mental performance under a controlled laboratory setting. Thisenables a laboratory assessment of its disposal performance in,soil, compost, landfill, and water and fo
47、r use in agriculturalproducts such as mulch film without detriment to that particularenvironment.NOTE 5For determining biodegradation rates under composting con-ditions, Specification D 6400 is to be used, including test methods andconditions as specified.5.2 The correlation of results from this gui
48、de to actualdisposal environments (for example, agricultural mulch films,composting, or landfill applications) has not been determined,and as such, the results should be used only for comparativeand ranking purposes.5.3 The results of laboratory exposure cannot be directlyextrapolated to estimate ab
49、solute rate of deterioration by theenvironment because the acceleration factor is material depen-dent and can be significantly different for each material and fordifferent formulations of the same material. However, exposureof a similar material of known outdoor performance, a control,at the same time as the test specimens allows comparison of thedurability relative to that of the control under the test condi-tions.6. Procedures6.1 Test sample selected to be in the thickness of theapplication form.6.2 The tier testing procedure is outlined schematically inFig. 1.6.3 In
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