1、Designation: D 5272 92 (Reapproved 1999)Standard Practice forOutdoor Exposure Testing of Photodegradable Plastics1This standard is issued under the fixed designation D 5272; 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice defines test conditions applicable whenPractices D 1435 and G 7 are employed for the outdoorexposure
3、 testing of photodegradable plastics.1.2 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 determine the applica-bility of regulatory lim
4、itations prior to use.NOTE 1There is no ISO standard that is equivalent to this standard.2. Referenced Documents2.1 ASTM Standards:D 882 Test Methods for Tensile Properties of Thin PlasticSheeting2D 883 Terminology Relating to Plastics2D 1435 Practice for Outdoor Weathering of Plastics2D 1898 Practi
5、ce for Sampling of Plastics2D 3593 Test Method for Molecular Weight Averages andMolecular Weight Distribution of Certain Polymers byLiquid Size-Exclusion Chromatography (Gel PermeationChromatograph GPC) Using Universal Calibration3D 3826 Practice for Determining Degradation End Point inDegradable Po
6、lyolefins Using a Tensile Test3E 772 Terminology Relating to Solar Energy Conversion4G 7 Practice for Atmospheric Environmental ExposureTesting of Nonmetallic Materials53. Terminology3.1 The terminology given in Terminology E 772 and Ter-minology D 883 is applicable to this practice.4. Significance
7、and Use4.1 When discarded as litter, articles made using photode-gradable plastics are subject to attack by daylight (particularlysolar-ultraviolet radiation), oxygen, heat, and water. The 5exposure angle used in this practice represents typical condi-tions for degradation experienced by litter.4.2
8、This practice requires characterization of the duration ofexposure in terms of solar-ultraviolet radiation. Solar-ultraviolet radiation varies considerably as a function oflocation and time of year. This can cause dramatic differencesin the time required to produce a specified level of degradationin
9、 a polymer. Daro6has shown that when the same lot ofpolyethylene containing an iron-salt prodegradant is exposed atvarious times of the year in a single location, the time requiredto produce an average of two chain scissions per moleculevaried by over 130 %. Daro, and Zerlaut and Anderson7haveshown
10、that this variability can be significantly reduced whentotal solar or solar-ultraviolet radiation, or both, is used tocharacterize the exposure increments.4.3 In addition to variations in level of daylight and solar-ultraviolet radiation, there are significant differences in tem-perature, and moistu
11、re stresses between different locations, andbetween different years, or periods within a single year, at asingle location. Because of this variability, results from this testcannot be used to predict the absolute rate at which photode-gradable plastics degrade. Results from this test can be used toc
12、ompare relative rates of degradation for materials exposed atthe same time in the same location. Results from multipleexposures of a common lot of material (during differentseasons over several years) at different sites can be used tocompare the relative rates at which a particular photodegrad-able
13、plastic will degrade in each location.NOTE 2An inherent limitation in solar-radiation measurements is thatthey do not reflect the effects of variations in temperature and moistureexposure, which often can be as important as solar radiation. The samesolar-ultraviolet radiation increment will not nece
14、ssarily give the samechanges in properties of the test specimen in different exposure sites.Results from this practice must be regarded as giving only a generalindication of the degree of degradability and should always be consideredin terms of characteristics of the exposure site as well.4.4 Where
15、measurement of total solar-ultraviolet radiationis not possible, exposure duration can be determined by the1This practice is under the jurisdiction of ASTM Committee D-20 on Plasticsand is the direct responsibility of Subcommittee D20.96 on EnvironmentallyDegradable Plastics.Current edition approved
16、 July 15, 1992. Published September 1992.2Annual Book of ASTM Standards, Vol 08.01.3Annual Book of ASTM Standards, Vol 08.02.4Annual Book of ASTM Standards, Vol 12.02.5Annual Book of ASTM Standards, Vol 14.02.6Daro, A., et al, “Degradation of Polymer Blends IV, Natural Weathering of LowDensity and L
17、inear Low Density Polyethylene,” European Polymer Journal, Vol 26,No. 1, 1990, pp. 4752.7Zerlaut, G. L., and Anderson, T. A., “Ultraviolet Radiation as a TimingTechnique for Outdoor Weathering of Materials,” Society of Automotive Engineers,SAE Technical Paper Number 850348, 1985.1Copyright ASTM Inte
18、rnational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.number of days, weeks, or months exposed. When this practiceis used, a reference material whose degradation properties havebeen well established must be exposed at the same time as theother materials being
19、 tested. The reference material used mustbe agreed upon by all interested parties. The time to produce aspecified level of degradation for each material in this simul-taneous exposure is then compared. It is also a good practice touse reference materials when exposure length is determined bytotal so
20、lar or solar UV radiant exposure.NOTE 3A reference material can be a single lot of material which hasshown consistent results after a number of exposures. It is not necessarythat the composition or properties of the reference material be character-ized and certified by a recognized standards agency
21、or group.5. Apparatus5.1 Use exposure racks constructed in accordance with therequirements of Practice G 7. Unless otherwise specified,position the exposure racks so that specimens face the equatorand so that the exposed surfaces are 5 from the horizontal. Ifother exposure rack orientations are used
22、, they must bereported.5.2 Use one of the following rack constructions for expos-ing photodegradable plastic specimens:5.2.1 Exposure Rack APositionable mounting bars usedfor attaching specimens shall be arrayed over a regular meshexpanded-metal (aluminum or stainless steel) sheet backing.Use 1618 g
23、age metal with approximately 0.5-in. openings. Itis recommended that the surface area of the expanded metal be60 to 70 % open. Use a noncorroding material for the mountingbars. 6061T6 aluminum or untreated wood are typical materi-als used for the mounting bars. Fig. 1 is a top view showingtypical ra
24、ck construction.5.2.2 Exposure Rack BUnpainted exterior-grade plywoodforms the rack surface to which specimens are directly at-tached. Replace the plywood when there is any evidence ofdelamination or fiber separation which could produce sharpedges and damage exposed specimens. Medium-density over-la
25、y (MDO) or high-density overlay (HDO) plywood aresatisfactory substrates and will require less frequent replace-ment than plywood with no overlay.NOTE 4There is less air circulation around the specimens when RackB exposures are used. Degradation rates from exposures using Rack B willbe somewhat fast
26、er than those using Rack A because specimen tempera-tures will be higher. Comparisons between materials should only be madewith exposures conducted at the same time and using the same rack type.5.3 Solar Radiometers:5.3.1 Ultraviolet RadiometerA total ultraviolet (UV) ra-diometer that measures ultra
27、violet radiation in the wavelengthregion from 295 to 385 nm should be used.8Calibrate theradiometer in suitable radiometric units, preferably in watts persquare metre per volt (Wm2V1), and shall be maintained inat least semiannual calibration against a standard source ofspecial irradiance.9Narrow ba
28、nd radiometers (for example,with 20 nm bandpass) can also be used if agreed upon by allinterested parties. Narrow band radiometers must also becalibrated at least semiannually against a standard source ofspectral irradiance. A certificate of calibration shall be providedwith all total solar-ultravio
29、let or narrow band irradiance mea-surements. It is recommended that calibrations be traceable toa recognized national standards agency such as the NationalInstitute for Science and Technology in the United States.NOTE 5The use of narrow band filter UV radiometers having selec-tive spectral sensitivi
30、ty may not be sensitive to all variations of solar-ultraviolet radiation. Monitoring at a narrow band (for example, 20 nm)may not relate to the total photodegradation of the plastic material, whichis a result of a complex interaction of many factors, including sensitivityacross a broad wavelength re
31、gion.8Model TUVR Total Ultraviolet Radiometer manufactured by the EppleyLaboratory, 12 Sheffield Ave., Newport, RI 02804, has been found to be suitable forthis purpose when maintained in frequent calibration.9Suitable calibrations may be obtained from some manufacturers, and from theEppley Laborator
32、y, 12 Sheffield Ave., Newport, RI 02804.FIG. 1 Typical Rack Construction for Exterior Exposures of Photodegradable PlasticsD 527226. Sampling6.1 Sample in accordance with Practice D 1898.7. Procedure7.1 Attach the ends of specimens of photodegradable plasticto be exposed to the positionable mounting
33、 bars or plywoodrack. Films or specimens that are nearly flat can be attachedusing a pressure sensitive tape with a durable adhesive andbacking.10Staples may be used with plywood racks or withwood mounting bars. Specimens with odd shapes can beattached directly to the expanded metal or plywood using
34、nonferrous bolts and large washers or by any other suitablemethod. Make sure that the test specimens are inscribed orotherwise labeled with an identifying number, letter, or symbol.Expose at least three replicate specimens for each material andexposure increment used.7.2 Ensure that the UV radiomete
35、r is mounted at an angle of5 from the horizontal, facing the equator. If a differentexposure angle is used, mount the UV radiometer at the sameangle.7.3 Mount the specimens on the exposure rack for the timedesired to produce the prescribed level of total solar-ultravioletradiation. It is recommended
36、 that a series of exposure incre-ments be used for each material being tested to determine therate of degradation as a function of total solar or solar-ultraviolet radiant energy dose. Table 1 shows monthly andannual average total solar-ultraviolet radiation incident on 5surfaces in representative h
37、umid subtropical and desert cli-mates.7.4 If total ultraviolet radiant energy is used to determineexposure increments, measure the increments using the instru-mentation in accordance with 5.3.1. Express total solar-ultraviolet exposures in joules per square metre, with datareported to four significa
38、nt figures. If agreed on by allinterested parties, the ultraviolet radiant energy in specifiednarrow wavelength intervals (or bands) that closely conform tospectral regions where the plastic material is most sensitivemay also be employed to follow exposure increments.7.5 After specimens are exposed
39、for the desired amount oftotal solar-ultraviolet radiation, measure the specified propertyor properties to determine the level of degradation. Typicalproperties measured are molecular weight (in accordance withTest Method D 3593) and tensile strength and elongation (inaccordance with Test Methods D
40、882). For polyolefins, degreeof oxidation can be monitored using a carbonyl index which isthe ratio of carbonyl infrared absorbance at approximately1715 cm1to an invariant absorbance characteristic of thepolymer (for example, C-H stretch at approximately30002840 cm1). The degradation end point of po
41、lyolefinscan be determined by a tensile test in accordance with PracticeD 3826. Measure the same properties of an unexposed speci-men of each material being tested. If a reference material isused, determine its properties and express the time to degra-dation for all other materials as a function of
42、the time toproduce a specific degree of degradation in the referencematerial.8. Report8.1 Report the following information for each materialexposed:8.1.1 Complete identification and description (for example,dimensions) of material tested.8.1.2 Location of exposure and type of exposure rack used.8.1.
43、2.1 Any exposure angle other than 5.8.1.3 Dates exposure started and completed.8.1.3.1 Total time exposed (expressed in days, weeks, ormonths).8.1.4 Solar-ultraviolet radiant exposure:8.1.4.1 If total ultraviolet radiation is used, it shall beexpressed in joules per square metre. Record manufacturer
44、 andmodel of UV radiometer employed, date of last calibration, andcalibrating laboratory.8.1.5 General appearance and results of tests used to char-acterize the properties on unexposed samples of each materialbeing exposed.8.1.6 General appearance and results of tests used to char-acterize the prope
45、rties of specimens from each exposureincrement. Report the average and standard deviation fromeach test used to measure properties of replicate specimens.8.1.7 Complete description or reference to characterizationtests used to evaluate material properties.9. Precision and Bias9.1 It is not practicab
46、le to specify the precision of theprocedure in this practice because it is dependent upon theASTM test methods used to determine the specific propertiesbeing measured. The precision and bias for the individual testmethods can be used in the analysis of data from exposuresused to assess the differenc
47、es in materials.9.2 Because of the variability in solar radiation, tempera-ture, and moisture levels between sites and between differenttimes at the same site, results from this practice should only beused to compare relative rates of degradation for materialsexposed at the same time in the same loc
48、ation using the sameexposure rack construction.10Number 425 aluminum foil tape from 3M, Building 220-8E, 3M Center, St.Paul, MN 55144 (612-736-1413) is satisfactory.TABLE 1 Average Monthly Solar-Ultraviolet Radiation (295 to 385nm) on a 5 SurfaceMonthAverage Solar-Ultraviolet Radiation (MJ/m2, 29538
49、5 nm)Subtropical ClimateMiami, FL (26N latitude)Desert ClimatePhoenix, AZ (34N latitude)January 16.9 16.4February 19.6 19.4March 23.6 28.5April 31.7 36.3May 33.8 41.3June 32.0 40.4July 31.0 39.1August 28.3 37.2September 26.2 30.9October 23.2 24.5November 16.0 17.8December 16.1 14.5Annual 301.4 346.3D 5272310. Keywords10.1 aging; degradable plastic; exterior exposure; outdoorexposure; photodegradation; ultraviolet radiation; weatheringASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin thi
