ASTM E2228-2018 Standard Guide for Microscopical Examination of Textile Fibers.pdf

1、Designation: E2228 18Standard Guide forMicroscopical Examination of Textile Fibers1This standard is issued under the fixed designation E2228; 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 pa

2、rentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This standard describes guidelines for microscopicalexaminations employed in forensic fiber characterization,identification, and comparison.Amicros

3、copical fiber examina-tion can include a variety of light microscopes, such asstereomicroscope, polarized light, comparison, fluorescence,and interference. In certain instances, the scanning electronmicroscope may yield additional information. The particulartest(s) or techniques employed by each exa

4、miner or laboratorywill depend upon available equipment, examiner training, andthe nature and extent of the fiber evidence.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard cannot replace knowledge, skills, o

5、rabilities acquired through education, training, and experienceand is to be used in conjunction with professional judgment byindividuals with such discipline-specific knowledge, skills, andabilities.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its

6、use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized princip

7、les on standard-ization established 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:2D123 Terminology Relating to Texti

8、lesD276 Test Methods for Identification of Fibers in TextilesE1459 Guide for Physical Evidence Labeling and RelatedDocumentationE1492 Practice for Receiving, Documenting, Storing, andRetrieving Evidence in a Forensic Science Laboratory2.2 AATCC Standards:3AATCC Test Methods 20 Fiber Identification:

9、Qualitative3. Terminology3.1 DefinitionsFor definitions of terms used in this guide,refer to Terminology D123.3.2 Definitions of Terms Specific to This Standard:3.2.1 anisotropic, adja characteristic of an object in whichthe refractive index differs depending on the direction ofpropagation or vibrat

10、ion of light through the object.(1)43.2.2 barrier filter, na filter used in fluorescence micros-copy that suppresses unnecessary excitation energy that has notbeen absorbed by the fiber and selectively transmits onlyenergy of greater wavelengths than the cut-off wavelength orwithin a specific wavele

11、ngth range.3.2.3 Becke line, nthe bright halo near the boundary of afiber that moves with respect to that boundary as the micro-scope is focused through best focus when the fiber is mountedin a medium that differs from its refractive index.(1)3.2.4 Becke line method, na method for determining theref

12、ractive index of a fiber relative to its mountant by noting thedirection in which the Becke line moves when the focus ischanged.(1)3.2.4.1 DiscussionThe Becke line always moves towardthe higher refractive index medium (fiber or mountant) whenfocus is raised (stage is lowered) and towards the lowerre

13、fractive index medium when focus is lowered (stage israised). At the point where the index of the fiber matches theindex of the mounting medium, the Becke line is no longer1This guide is under the jurisdiction of ASTM Committee E30 on ForensicSciences and is the direct responsibility of Subcommittee

14、 E30.01 on Criminalistics.Current edition approved Sept. 1, 2018. Published September 2018. Originallyapproved in 2002. Last previous edition approved in 2010 as E2228 10. DOI:10.1520/E2228-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at se

15、rviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American Association of Textile Chemists and Colorists(AATCC), P.O. Box 12215, Research Triangle Park, NC 27709-2215, http:/www.aatcc.org.4The boldface

16、numbers in parentheses refer to a list of references at the end ofthis standard.Copyright 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 stand

17、ardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1visible. The Becke line is generally viewed at a wavelength of589 nm (the D line of Sodiu

18、m nD).(1)3.2.5 birefringence, nthe numerical difference in refrac-tive indices (n) for a fiber, given by the equation:?ni2n?Birefringence (B) can be calculated by determining theretardation (r) and thickness (T) at a particular point in afiber and by using the equation:B 5 r nm!1000T m!(1)3.2.6 comp

19、arison microscope, na system of two micro-scopes positioned side-by-side and connected via an opticalbridge so that two specimens are examined simultaneously ineither transmitted or reflected light.3.2.7 compensator, nany variety of optical devices thatcan be placed in the light path of a polarized

20、light microscopeto introduce known, fixed or variable retardation in a specificvibration direction; the retardation and sign of elongation of thefiber may then be determined.(2)3.2.7.1 DiscussionCompensators may employ a fixedmineral plate of constant or varying thickness or a mineralplate that is r

21、otated, or have its thickness varied by tilting, toalter the thickness presented to the optical path (and retardationintroduced) by a set amount.3.2.8 compensator, full-wave (or red plate), na compen-sator (usually a plate of gypsum, selenite or quartz) thatintroduces a fixed retardation between 530

22、 to 550 nm (approxi-mately the retardation of the first order red color on theMichel-Lvy chart).(1, 2)3.2.9 compensator, quarter-wave, na compensator (usu-ally a mica plate) that introduces a fixed retardation between137147 nm (approximately the retardation of first-order grayon the Michel-Lvy chart

23、).(1, 2)3.2.10 compensator, quartz wedge, na wedge, usually cutfrom quartz, having continuously variable retardation extend-ing over several orders (usually 3 to 7) of interference colors.(1)3.2.11 compensator, Snarmont, na quarter-wave plateinserted above the specimen in the parallel “0” position w

24、ith acalibrated rotating analyzer; measures low retardation andrequires the use of monochromatic light.3.2.12 compensator, tilting (Berek), na compensator typi-cally containing a plate of calcite or quartz, which can be tiltedby means of a calibrated drum to introduce variable retarda-tion.3.2.13 co

25、rtex, nthe main structural component of hairconsisting of elongated and fusiform (spindle-shaped) cells; thecortex may contain pigment grains, air spaces called corticalfusi, and structures called ovoid bodies.3.2.14 crimp, nthe curl, wave, or compression that isnaturally occurring or otherwise impa

26、rted to a fiber.3.2.15 cuticle, nin mammalian hair fibers, the layers offlattened cells enclosing the cortex, which form an envelope ofoverlapping scales surrounding the fiber.3.2.16 delustrant, na pigment, usually titanium dioxide,used to dull the luster of a manufactured fiber.(3)3.2.17 dichroism,

27、 nthe property of exhibiting differentcolors, especially two different colors, when viewed alongdifferent axes by plane polarized light.3.2.18 dislocations, ndistinct features that occur in naturalfibers (for example, flax, ramie, jute, hemp) in the shape of Xs,Is, and Vs that are present along the

28、fiber cell wall; thesefeatures are often useful for identification.3.2.19 dispersion of birefringence, nthe variation of bire-fringence with wavelength of light.3.2.19.1 DiscussionWhen dispersion of birefringence issignificant in a particular fiber, anomalous interference colorsnot appearing in the

29、regular color sequence of the Michel-Lvychart may result. Strong dispersion of birefringence may alsointerfere with the accurate determination of retardation inhighly birefringent fibers.3.2.20 dispersion staining, nan optical staining techniquein which colors are produced by the differential refrac

30、tion ofdifferent wavelengths of light due to mounting the sample in aliquid having a different dispersion of refractive index.(1)3.2.20.1 DiscussionThe procedure employs central or an-nular stops placed in the objective back focal plane of amicroscope. Using an annular stop with the substage irisclo

31、sed, a fiber mounted in a high dispersion medium shows acolored boundary of a wavelength where the fiber and themedium match in refractive index. Using a central stop, thefiber shows colors complementary to those seen with anannular stop.3.2.21 dye, nsoluble substances that add color to textiles.(3)

32、3.2.21.1 DiscussionDyes are classified into groups thathave similar chemical characteristics (for example, aniline,acid, and azo). They are incorporated into the fiber by chemicalreaction, absorption, or dispersion.(3)3.2.22 excitation filter, na filter used in fluorescencemicroscopy that transmits

33、specific bands or wavelengths ofenergy capable of inducing visible fluorescence in varioussubstrates.3.2.23 extinction, nthe condition in which a birefringentparticle appears dark when viewed between crossed polarizers.(2)3.2.23.1 DiscussionMost fibers exhibit extinction whentheir long axis is orien

34、ted parallel to the privileged direction ofone of the polarizing filters.3.2.24 fluorescence, nthe emission of light by a fiber thathas absorbed light or other electromagnetic radiation of shorterwavelength (higher energy).(2)E2228 1823.2.25 fluorescence microscope, na microscope equippedwith a high

35、 energy light source (usually a xenon or mercuryvapor lamp) and a set of excitation and barrier filters, used toinduce and observe fluorescence in fibers and other particles ormaterials.3.2.26 inorganic fibers, na class of fibers of naturalmineral origin (for example, chrysotile asbestos) and manmad

36、emineral origin (for example, fiberglass).3.2.27 interference colors, ncolors produced by the inter-ference of two out-of-phase rays of white light when abirefringent material is observed at a non-extinction positionbetween crossed polars.3.2.27.1 DiscussionThe retardation at a particular point ina

37、birefringent fiber can be determined by comparing theobserved interference color to the Michel-Lvy chart.3.2.28 isotropic, adja characteristic of an object in whichthe refractive index remains constant irrespective of the direc-tion of propagation or vibration of the light through the object.(1)3.2.

38、29 light microscope, na microscope that employs lightin the visible or near-visible portion of the electromagneticspectrum.3.2.30 lignin, nthe majority non-carbohydrate portion ofwood; it is an amorphous polymeric substance that cementscellulosic fibers together and is the principal constituent ofwo

39、ody cell walls.3.2.31 lumen, nthe cavity or central canal present in manynatural fibers (for example, cotton, flax, ramie, jute, hemp); itspresence and structure are often useful aids in identification.3.2.32 luster, nthe gloss or shine possessed by a fiber,resulting from its reflection of light; th

40、e luster of manufacturedfibers is often modified by use of a delustering pigment.3.2.33 manufactured fiber, na class name for variousgenera of fibers (including filaments) produced from fiber-forming substances which can be (1) polymers synthesizedfrom chemical compounds synthetic fibers, (2) modifi

41、ed ortransformed natural polymers regenerated fibers, and (3)minerals, for example, glasses.(3)3.2.34 medulla, nthe central portion of a hair composed ofa series of discrete cells or an amorphous spongy mass.3.2.34.1 DiscussionThe medulla may be air-filled, and ifso, appears opaque or black using tr

42、ansmitted light or whiteusing reflected light. In animal hair, several types have beendefined: uniserial or multiserial ladder, cellular or vacuolated,and lattice.3.2.35 Michel-Lvy chart, na chart relating thickness,birefringence, and retardation so that any one of these variablescan be determined w

43、hen the other two are known.(1)3.2.36 microscopical, adjconcerning a microscope or theuse of a microscope.3.2.37 modification ratio, na geometrical parameter usedin the characterization of noncircular fiber cross-sections.3.2.37.1 DiscussionThe modification ratio is the ratio insize between the outs

44、ide diameter of the fiber and the diameterof the core; it may also be called “aspect ratio.”3.2.38 natural fibers, na class name for various genera offibers (including filaments) of: (1) animal (that is, silk andwool); (2) mineral (that is, asbestos); or (3) vegetable origin(that is, cotton, flax, j

45、ute, and ramie).(3)3.2.39 pigment, na finely-divided insoluble material usedto deluster or color fibers (for example, titanium dioxide andiron oxide).(3)3.2.40 plane polarized light, nemitted or observed light inwhich the electric field vibrates in one direction in a singleplane.3.2.41 pleochroism,

46、nthe property of exhibiting differentcolors, especially three different colors, when viewed alongdifferent axes by plane polarized light. The phenomenon ofsubstances showing different absorption colors in differentvibration directions. The observed colors change with theorientation of the crystal an

47、d can be seen only with planepolarized light.(1)3.2.42 polarized light, na bundle of light rays with asingle propagation direction and a single perpendicular vibra-tion direction.(1)3.2.43 polarized light microscope, na microscopeequipped with two polarizing filters, one below the stage (thepolarize

48、r) and one above the stage (the analyzer).3.2.44 privileged direction (of a polarizer), nthe directionof vibration to which light emerging from a polarizer has beenrestricted.3.2.44.1 DiscussionIn modern microscopes, the polariz-ers privileged direction is oriented in the east-west directionand the

49、analyzers privileged direction is oriented in thenorth-south direction.3.2.45 refractive index (n), nthe ratio of the velocity oflight in a vacuum to the velocity of light in some medium.(1)3.2.46 relative refractive index, nthe estimate of therefractive index of a fiber in relation to the index of itssurrounding medium.3.2.47 retardation (r), nthe actual distance of one of thedoubly refracted rays behind the other as they emerge from ananisotropic fiber; dependent upon the difference in the tworefrac