1、Designation: D7251 11 An American National StandardStandard Specification forColor and Appearance Retention of Variegated Color PlasticSiding Products1This standard is issued under the fixed designation D7251; 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 () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This specification establishes requirements and testmethods for the color and
3、appearance retention of variegatedcolor plastic siding products.1.2 Color retention testing provides a method for estimatingthe acceptability of color change in a siding product over aperiod of years of service.1.3 Characterization of color and appearance for variegatedcolors is complicated by the p
4、resence of multiple colors in arandom pattern. The procedure is based on using a template toreference six spots for color measurement.1.4 Methods of indicating compliance with this specifica-tion are provided.1.5 This standard does not purport to address all of thesafety concerns, if any, associated
5、 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 limitations prior to use.NOTE 1There is no known ISO equivalent to this standard.2. Referenced Documents2.1 ASTM Standards:2D883 Te
6、rminology Relating to PlasticsD1435 Practice for Outdoor Weathering of PlasticsD1600 Terminology forAbbreviated Terms Relating to Plas-ticsD2244 Practice for Calculation of Color Tolerances andColor Differences from Instrumentally Measured ColorCoordinatesE805 Practice for Identification of Instrume
7、ntal Methods ofColor or Color-Difference Measurement of MaterialsG147 Practice for Conditioning and Handling of Nonmetal-lic Materials for Natural and Artificial Weathering Tests3. Terminology3.1 DefinitionsDefinitions are in accordance with termi-nologies in Terminologies D883 and D1600 unless othe
8、rwisenoted.3.2 Definitions of Terms Specific to This Standard:3.2.1 color regionparameters that define the color spacefor a siding sample, measured with Hunter Units, spheregeometry (di:8), Illuminant C, 2 Observer, specular compo-nent included.3.2.1.1 DiscussionThe color values used to classify col
9、orsby region were established by measuring the Hunter L, a, bcolor values from the sample population, calculating theaverage for Hunter L, a, b, and then choosing the integer fromthe corresponding L, a, b average values (that is, by truncatingany fractional result) to be used to classify colors by r
10、egion.Thus, average values greater than zero are truncated down tothe next lowest integer, and average values less than zero aretruncated up to the next highest integer. All values greater than-1 and less than +1 truncate to 0.3.2.2 color retention standardspredictive color regionsdescribed by a thr
11、ee dimensional model which constituteacceptable color retention levels resulting from weathering ofa specific product type and color.3.2.2.1 DiscussionColor retention standards are definedby equations that describe the three dimensional ellipsoidvalue.3.2.3 ellipsoid valuea mathematical calculation
12、derivedby inserting the measured L, a, and b values of aweathered specimen into an ellipsoid equation.3.2.4 temperate northern climatein weathering testing,aNorth American metropolitan area testing site located within73 to 100W longitude and 37 to 45N latitude.3.2.5 variegated plastic sidingsiding h
13、aving discretemarkings of different colors.4. Classification4.1 DefinitionsDefinitions are in accordance with termi-nology in Terminologies D883 and D1600 unless otherwisenoted.1This specification is under the jurisdiction of ASTM Committee D20 onPlastics and is the direct responsibility of Subcommi
14、ttee D20.24 on Plastic BuildingProducts.Current edition approved April 1, 2011. Published April 2011. Originallyapproved in 2006. Last previous edition approved in 2010 as D7251 - 10. DOI:10.1520/D7251-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer S
15、ervice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 194
16、28-2959. United States14.2 Color RegionsThe color region for a color is deter-mined by measuring the Hunter L, a, b color values at sixlocations on each specimen in a sample population andcalculating the average Hunter L, a, b color value. Use theinteger value (by truncating any fractional result) o
17、f theaverage to determine the color region for the color using thefollowing region boundaries.4.2.1 Region 1BrownL = 20 to 49 L = 25 to 49a=1to5 a=8to5b=2to11 b=12to254.2.2 Region 2Medium BlueL = 45 to 64a = 26 to 1b = 25 to 24.2.3 Region 3Light BlueL = 65 to 93a = 12 to 1b = 25 to 24.2.4 Region 4Gr
18、eenL = 50 to 84 L = 50 to 64 L = 50 to 64a = 12 to 1 a = 25 to 3 a = 25 to 13b=1to10 b=11to30 b=1to10L = 65 to 93 L = 85 to 93a = 25 to 13 a = 12 to 3b=25to30 b=1to34.2.5 Region 5Medium BeigeL = 50 to 74 L = 50 to 64 L = 65 to 74a=0to1 a=2to1 a=12to1b=4to12 b=11to15 b=11to124.2.6 Region 6Light Beige
19、L = 75 to 84 L = 85 to 93 L = 75 to 84a=0to1 a=12to1 a=12to1b=4to12 b=4to12 b=11to124.2.7 Region 7GoldL = 65 to 93 L = 65 to 93a=0to4 a=5to25b=13to30 b=16to304.2.8 Region 8YellowL = 65 to 93a = 12 to 1b=13to304.2.9 Region 9WhiteL = 85 to 100 All L = 94 to 100a=2to1b=1to34.2.10 Region 10Light GrayL =
20、 65 to 84a=0to1b=1to34.2.11 Region 11MauveL = 65 to 93 L = 65 to 93 L = 50 to 64 L = 50 to 64a=2to25 a=5to25 a=2to25 a=2to1b=2to12 b=13to15 b=2to30 b=16to304.2.12 Region 12Medium GrayL = 50 to 64a=0to1b=1to34.2.13 Region 13Dark GrayL = 25 to 49a=1to5b=1to14.2.14 Region 14Dark BlueL = 25 to 44a = 25
21、to 3b = 25 to 24.2.15 Region 15Dark GreenL = 25 to 49a = 20 to 2b=1to114.2.16 Region 16Dark RedL = 25 to 49a=6to30b=1to254.2.17 Region 17PurpleL = 25 to 44 L = 45 to 49 L = 50 to 93a=4to30 a=2to30 a=2to25b = 25 to 2 b = 25 to 2 b = 25 to 14.3 Ellipsoid Value EquationsUse the following equationsto de
22、termine the ellipsoid value representing the change incolor due to weathering. Use the equation that corresponds tothe color region determined for the specimens initial color(prior to weathering) in 4.2.4.3.1 Region 1BrownL 2 1.6!25.2!21a11.0!23.0!21b 2 0.5!22.5!25 Ellipsoid Value4.3.2 Region 2Mediu
23、m BlueL11.0!26.0!21a10.6!22.9!21b 2 0.8!25.4!25 Ellipsoid Value4.3.3 Region 3Light BlueL10.3!26.4!21a10.1!22.7!21b 2 0.8!24.3!25 Ellipsoid Value4.3.4 Region 4GreenL 2 0.2!25.9!21a 2 0.8!24.8!21b 2 0.2!25.6!25 Ellipsoid Value4.3.5 Region 5Medium BeigeL10.1!26.1!21a 2 0.0!22.8!21b 2 0.4!23.9!25 Ellips
24、oid Value4.3.6 Region 6Light BeigeL 2 0.0!25.0!21a 2 0.2!22.6!21b 2 0.3!25.4!25 Ellipsoid Value4.3.7 Region 7GoldL10.6!26.6!21a10.3!23.4!21b10.4!24.7!25 Ellipsoid Value4.3.8 Region 8YellowL10.3!25.5!21a 2 1.0!23.3!21b10.1!25.5!25 Ellipsoid ValueD7251 1124.3.9 Region 9WhiteL 2 0.6!28.2!21a10.0!23.3!2
25、1b 2 1.9!25.3!25 Ellipsoid Value4.3.10 Region 10Light GrayL11.8!27.0!21a 2 0.2!22.1!21b 2 1.3!24.0!25 Ellipsoid Value4.3.11 Region 11MauveL 2 0.4!26.5!21a 2 0.8!24.0!21b 2 1.1!24.5!25 Ellipsoid Value4.3.12 Region 12Medium GrayL11.0!26.6!21a10.3!22.5!21b 2 1.2!23.7!25 Ellipsoid Value4.3.13 Region 13D
26、ark GrayL 2 0.1!25.1!21a10.8!23.4!21b10.1!23.0!25 Ellipsoid Value4.3.14 Region 14Dark BlueL 2 0.3!25.2!21a 2 1.0!23.6!21b11.3!24.5!25 Ellipsoid Value4.3.15 Region 15Dark GreenL 2 0.0!25.0!21a10.4!23.0!21b10.2!23.8!25 Ellipsoid Value4.3.16 Region 16Dark RedL 2 0.4!25.4!21a 2 0.8!24.0!21b 2 0.2!23.0!2
27、5 Ellipsoid Value4.3.17 Region 16PurpleL 2 0.0!26.0!21a 2 0.0!25.0!21b 2 0.0!25.2!25 Ellipsoid Value5. Procedure for Measuring Color Retention5.1 Test Site Setup and Exposure Duration Test Times:5.1.1 Samples shall be exposed at three test sites: TemperateNorthern represented by a site located in Lo
28、uisville, KY orCleveland, OH; hot, humid represented by a site located inMiami, FL, and hot, dry represented by a site located inPhoenix, Arizona. Additional test sites are permitted as agreedupon by the buyer and the seller.5.1.2 All exposures shall be conducted at an angle of 45facing South and ba
29、cked using unpainted plywood in accor-dance with Practices D1435 and G147.5.1.3 Remove test specimens for color measurement at24-month exposure. In some cases, 24 months are not sufficientto distinguish material durability differences and longer expo-sure periods are necessary. Additional exposure t
30、imes arepermitted as agreed upon by the buyer and the seller.5.2 Sampling and Specimen Preparation:5.2.1 Samples shall be representative of the product to beevaluated.NOTE 2Samples prepared in the laboratory in the same manner ascommercial samples are an acceptable alternate to a commercial part. If
31、the commercial product is extruded, the laboratory specimen must beextruded; if the commercial product is injection molded, the laboratoryspecimen must be injection molded, and so forth.5.2.2 Select a minimum of four specimens per sample pertest site to allow for three test specimens and one file sp
32、ecimenfor each sample evaluated.5.2.3 The file specimen will be used for a visual assessmentof variegation/contrast change. The test specimens will bemeasured for color and weathered.5.2.4 Specimens shall be a flat section and a minimum of 3by 10 in. (76 by 254 mm). The variegated pattern shall bepa
33、rallel to the long edge of the specimen.5.2.5 Use the Variegated Color Measurement Template toidentify the 6 spots on each test specimen for color retentiontesting. The center points of these six spots are specified in Fig.1. The diameter of the six spots is specified as 0.50 in. (12.2mm) minimum. T
34、hose shown in the diagram are for illustrationonly.5.2.6 The exact locations of these test spots must bedetermined and recorded for each test specimen to allowmeasurement of color change following exposure testing.5.2.7 The locations and spot sizes identified in 5.2.5 for eachtest specimen shall not
35、 change once the exposure test is started.5.2.8 Mark each specimen permanently to ensure retentionof identity during and after exposure testing.NOTE 3Use of a vibratool leaves a permanent mark that satisfies thiscriteria.5.3 Data Record:5.3.1 Measured specimen color values shall be reported toone de
36、cimal place.5.3.2 Calculation of color units shall be reported to onedecimal place.5.4 Practice:5.4.1 Obtain test and file specimens in accordance with 5.2.5.4.2 Measure the original tristimulus X, Y, and Z values forthe six spots identified in 5.2.5 for each test specimen. Color ismeasured using sp
37、here geometry (di:8), illuminant C, 2observer, specular component included in accordance withPractice E805. The minimum aperture size for color measure-ment 0.50 in. (12.2 mm).5.4.3 Calculate the Hunter L, a, and b units in accordancewith the equations in the section on “Hunter L, a, and b ColorSpac
38、e and Color-Difference Equation” in Test Method D2244using the average of the six measurements and record in apermanent record.5.4.4 The measured average color of each test specimen isthe specimens initial color and is used to determine colorchange after specified periods of exposure testing.5.4.5 R
39、epeat steps 5.4.2 through 5.4.4 for each test speci-men.5.4.6 Calculate the average color in Hunter L, a, b for thethree test specimens to determine their color region as definedin 4.2.5.4.6.1 Calculate the overall average color of the three testspecimens for each test site from step 5.4.5.5.4.6.2 A
40、 single color region must be determined and usedat all test sites. If the color regions determined for each test siteare not the same, re-measure the test specimens for thenon-conforming test site. If the three test sites still do not agree,D7251 113calculate the overall average color for test speci
41、mens from allsites to determine the samples color region.5.4.7 Expose the test specimens at the test sites in accor-dance with 5.1.1 and 5.1.2. Record in a permanent record thetest start date.5.4.8 Remove the test specimens at the exposure interval(s)in accordance with 5.1.3. Record in a permanent r
42、ecord thedate the specimens are removed from the exposure test rack forcolor measurement.5.4.9 The exposed test specimens shall be measured forcolor and evaluated for appearance. It is recommended thatcolor measurement and appearance evaluation be conducted atthe test site. Color measurement shall t
43、ake place within sevendays of specimen removal from the exposure test rack. It isrecommended that color measurement take place within 48 h ofthe specimens removal from the exposure test rack.NOTE 4Additional color development is known to occur for PVCproducts after removal from exposure to ultraviol
44、et (UV) light. Thisartificial color change is referred to as Dark Time Yellowing. Colormeasurement within 48 h of removal is strongly recommended for PVCproducts.5.4.10 Wash the exposed test specimens in accordance withthe procedure in Annex A1.5.4.11 Inspect each exposed test specimen for appearanc
45、eand surface condition. Record observations and inspection datein a permanent record.5.4.12 Referencing the file specimen, evaluate each testspecimen for loss of variegation in accordance with 6.3.FIG. 1 Variegated Color Measurement TemplateD7251 1145.4.13 Measure and record the color of each test s
46、pecimenin accordance with 5.4.2 through 5.4.3 for each exposure time.Record in a permanent record the date the color of thespecimen(s) is measured.5.4.14 Referencing each test specimens initial color deter-mined in 5.4.5, calculate and record the color change in HunterL, a, and b units for each test
47、 specimen.5.4.15 In cases where specimens are evaluated at exposuretimes other than 24 months, the specimens shall be returned tothe exposure test rack within seven days for continuation of thetest; it is recommended the samples be returned to the test rackswithin 48 h. Record in a permanent record
48、the date thespecimens are returned to the exposure test rack.NOTE 5In case of dispute, the referee procedure shall be the use ofseparate specimens for each exposure time that can then be disposed aftercolor measurements are made.6. Performance Requirements6.1 Using the ellipsoid value equations in 4
49、.3, calculate theellipsoid value for each test specimen using the measured colorchange determined in 5.4.14 and the appropriate color regiondetermined in 5.4.6.6.2 Acceptable color retention is determined by the averageellipsoid value of the three test specimens at each test locationbeing less than or equal to 1.0. This v
