ASTM_D_542_-_14.pdf

Designation:D54214Standard Test Method forIndex of Refraction of Transparent Organic Plastics1This standard is issued under the fixed designation D542;the number immediately following the designation indicates the year oforiginal adoption 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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope*1.1 This test method covers a procedure for measuring theindex of refraction of transparent organic plastic materials.1.2 A refractometer method is presented.This procedurewill satisfactorily cover the range of refractive indices foundfor such materials.Refractive index measurements requireoptically homogeneous specimens of uniform refractive index.NOTE1This test method and ISO 489 are technically equivalent.1.3 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 limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2C162 Terminology of Glass and Glass ProductsD618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsE284 Terminology of AppearanceE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:ISO 489 Determination of the Refractive Index of Transpar-ent PlasticsPart A33.Terminology3.1 Definitions:3.1.1 For definitions of terms used in this test method,seeTerminologies D883 and E284.3.1.2 dispersionvariation of refractive index with wavelength of light.C162,C143.1.3 index of refraction,nthe numerical expression of theratio of the velocity of light in a vacuum to the velocity of lightin a substance at a specified wavelength.E284,E124.Significance and Use4.1 This test method measures a fundamental property ofmatter which is useful for the control of purity and compositionfor simple identification purposes,and for optical parts design.This test method is capable of readability to four figures to theright of the decimal point.5.Apparatus5.1 The apparatus for this test method shall consist of anAbbe refractometer(Note 2),a suitable source of white light,and a small quantity of a suitable contacting liquid(Note 2 andNote 3).NOTE2Other suitable refractometers can be used with appropriatemodification to this procedure as described in Section 7.NOTE3Asatisfactory contacting liquid is one which will not soften orotherwise attack the surface of the plastic within a period of 2 h of contact.The index of refraction of the liquid must be higher,but not less than oneunit in the second decimal place,than the index of the plastic beingmeasured;for example,ndof the sample=1.500,ndof the contactingliquid 1.510.6.Sampling6.1 Sampling shall be statistically adequate to ensure thatthe specimens were produced and obtained by a process instatistical control.6.2 Samples can be drawn from any materials presentation(for example,pellets,film,sheet,fabricated articles,etc.)which permits preparation of a satisfactory specimen as de-scribed herein.7.Test Specimens7.1 The test specimen shall be of a size that will conve-niently fit on the face of the fixed half of the refractometerprisms(Note 4).Aspecimen measuring 6.3 by 12.7 mm on oneface is usually satisfactory.NOTE4For maximum accuracy in the refractometer method,the1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.40 on Optical Properties.Current edition approved March 1,2014.Published March 2014.Originallyapproved in 1939.Last previous edition approved in 2013 as D542-13.DOI:10.1520/D0542-14.2For 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.3Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.*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 States1 surface contacting the prism must be flat.This surface is judged forflatness,provided the specimen has been satisfactorily polished,byobserving the sharpness of the dividing line between the light and darkfield as viewed in the ocular.A sharply defined straight dividing lineindicates satisfactory contact between the specimen and prism surfaces.7.2 The surface to be used in contact with the prism shall beflat and shall have a good polish.A second edge surfaceperpendicular to the first and on one end of the specimen shallbe prepared with a fair polish(Note 5).The polishe