1、Designation:D785621Standard Specification forColor and Appearance Retention of Solid and VariegatedColor Plastic Siding Products using CIELab Color Space1This standard is issued under the fixed designation D7856;the number immediately following the designation indicates the year oforiginal adoption
2、or,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 appea
3、rance retention of solid andvariegated colored plastic siding products.1.2 Color retention testing provides a method for estimatingthe acceptability of color change in a plastic siding productover an extended period of service.NOTE1The exposure locations and durations specified in thisstandard have
4、been shown to provide a good estimation of the colorchange in vinyl and polypropylene siding products over an extendedperiod of service(see 2.2).It is expected that materials designed for theexposure conditions typical of exterior siding will respond similarly,butthe applicability of this standard t
5、o other types of plastic siding has notbeen empirically established.1.3 This specification is a successor to Specifications D6864and D7251,which cover solid colors and variegated colors,respectively.This specification combines coverage for both,and has the same scope as those standards.1.4 Specifica
6、tions D6864 and D7251 use Hunter Lab colorspace for measurement of colors and evaluation of colorchange.These standards require classification of colors intoregions based on the L,a,and b coordinates of the color,andevaluation of color changes is done using an ellipsoid valueequation having unique c
7、oefficients for each color region.Thisspecification uses CIE 1976 L*a*b*color space for measure-ment and evaluation of color change.Using this method,theneed for separate color regions and evaluation equations hasbeen eliminated.1.5 Provisions for sample selection and preparation,andweathering are t
8、he same in this specification as in Specifica-tions D6864 and D7251.1.6 Characterization of color and appearance for variegatedcolors is complicated by the presence of multiple colors in arandom pattern.The procedure for measuring variegated colorsin this specification is based on using a template t
9、o referencesix spots for color measurement.1.7 This standard specifies outdoor weathering in threespecific climate zones for a single 24-month exposure,and thecolor retention performance requirements under these condi-tions are established to be indicative of acceptable performanceover an extended p
10、eriod of service.However,nothing in thisstandard precludes the use of different or additional climatezones,or different exposure durations,so long as thoseconditions are clearly specified in any reports.1.8 UnitsThe values stated in inch-pound units are to beregarded as standard.The values given in
11、parentheses aremathematical conversions to SI units that are provided forinformation only and are not considered standard.1.9 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-pri
12、ate safety,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.NOTE2There is no known ISO equivalent to this standard.1.10 This international standard was developed in accor-dance with internationally recognized principles on standard-ization es
13、tablished in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D660 Test Method for Evaluating Degree of Checking ofExterior Pa
14、intsD661 Test Method for Evaluating Degree of Cracking ofExterior PaintsD662 Test Method for Evaluating Degree of Erosion ofExterior PaintsD714 Test Method for Evaluating Degree of Blistering ofPaints1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct respo
15、nsibility of Subcommittee D20.24 on Plastic BuildingProducts.Current edition approved July 1,2021.Published July 2021.Originally approvedin 2014.Last previous edition approved in 2015 as D7856 15a.DOI:10.1520/D7856-21.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM
16、Customer Service 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 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopm
