1、Designation: E2228 10Standard 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 section describes guidelines for microscopicalexaminations employed in forensic fiber characterization, iden-tification, and comparison. Sever
3、al types of light microscopesare used, including, stereobinocular, polarized light, compari-son, fluorescence, and interference. In certain instances, thescanning electron microscope may yield additional informa-tion. Select which test(s) or techniques to use based upon thenature and extent of the f
4、iber evidence.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.2. Referenced Documents2.1 ASTM Standards:2D123 Terminology Relating to TextilesD276 Test Methods for Identification of Fibers in Textiles2.2 AATCC Standards:3AAT
5、CC Test Method 20:Qualitative Test Method 202007Fiber Analysis: 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 anisotropica characteristic of an object, which hasoptical properties
6、 that differ according to the direction in whichlight travels through the object when viewed in polarized light.3.2.2 barrier filtera filter used in fluorescence microscopythat suppresses unnecessary excitation light that has not beenabsorbed by the fiber and selectively transmits only light ofgreat
7、er wavelengths than the cut-off wavelength.3.2.3 Becke linethe bright halo near the boundary of afiber that moves with respect to that boundary as the fiber ismoved through best focus when the fiber is mounted in amedium that differs from its refractive index.3.2.4 Becke line methoda method for dete
8、rmining therefractive index of a fiber relative to its mountant by noting thedirection in which the Becke line moves when the focus ischanged.3.2.4.1 DiscussionThe Becke line will always move to-ward the higher refractive index medium (fiber or mountant)when the focal distance is increased and when
9、the focaldistance is decreased away from the objective and will movetoward the lower refractive index medium when the sample ismoved toward the objective.3.2.5 birefringencethe numerical difference in refractiveindices for a fiber, given by the equation: n n. Birefrin-gence can be calculated by dete
10、rmining the retardation (r) andthickness (T) at a particular point in a fiber and by using theequation:B 5 r nm!/1000T m!1This guide is under the jurisdiction of ASTM Committee E30 on ForensicSciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.Current edition approved
11、Sept. 15, 2010. Published October 2010. Originallyapproved in 2002. Last previous edition approved in 2002 as E2228 02. DOI:10.1520/E2228-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volu
12、me 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, http:/www.aatcc.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West
13、 Conshohocken, PA 19428-2959, United States.3.2.6 comparison microscopea system of two micro-scopes positioned side-by-side and connected via an opticalbridge in which two specimens may be examined simulta-neously in either transmitted or reflected light.3.2.7 compensatorany variety of optical devic
14、es that canbe placed in the light path of a polarizing microscope tointroduce fixed or variable retardation comparable with thatexhibited by the fiber; the retardation and sign of elongation ofthe fiber may then be determined.3.2.7.1 DiscussionCompensators may employ a fixedmineral plate of constant
15、 or varying thickness or a mineralplate that may be rotated, or have its thickness varied by tiltingto alter the thickness presented to the optical path (andretardation introduced) by a set amount.3.2.8 compensator, full wave (or red plate)a compensatorusually a plate of gypsum, selenite or quartz,
16、which introducesa fixed retardation between 530 to 550 nm (approximately theretardation of the first order red color on the Michel-Levychart).3.2.9 compensator, quarter wavea compensator, usuallywith a mica plate, which introduces a fixed retardation between125 to 150 nm.3.2.10 compensator, quartz w
17、edgea wedge, cut fromquartz, having continuously variable retardation extendingover several orders of interference colors (usually 3 to 7).3.2.11 compensator, Snarmonta quarter-wave plate in-serted above the specimen in the parallel “0” position with acalibrated rotating analyzer; measures low retar
18、dation andrequires the use of monochromatic light.3.2.12 compensator, tilting (Berek)a compensator typi-cally containing a plate of calcite or quartz, which can be tiltedby means of a calibrated drum to introduce variable retardationup to about ten orders.3.2.13 cortexthe main structural component o
19、f hair con-sisting of elongated and fusiform (spindle-shaped) cells; thecortex may contain pigment grains, air spaces called corticalfusi, and structures called ovoid bodies.3.2.14 crimpthe waviness of a fiber.3.2.15 crossover marksoblique flattened areas along silkfibers caused by the overlapping o
20、f extruded silk fibers beforethey have dried completely.3.2.16 cuticlein mammalian hair fibers, the layers offlattened cells enclosing the cortex, which form an envelope ofoverlapping scales surrounding the fiber.3.2.17 delustranta pigment, usually titanium dioxide,used to dull the luster of a manuf
21、actured fiber.3.2.18 dichroismthe property of exhibiting different col-ors, especially two different colors, when viewed along differ-ent axes by plane polarized light.3.2.19 dislocationsdistinct features that occur in naturalfibers (for example, flax, ramie, jute, hemp) in the shape of Xs,Is, and V
22、s that are present along the fiber cell wall; thesefeatures are often useful for identification.3.2.20 dispersion of birefringencethe variation of bire-fringence with wavelength of light.3.2.20.1 DiscussionWhen dispersion of birefringence issignificant in a particular fiber, anomalous interference c
23、olorsnot appearing in the regular color sequence of the Michel-Levychart may result. Strong dispersion of birefringence may alsointerfere with the accurate determination of retardation inhighly birefringent fibers.3.2.21 dispersion staininga technique for refractive indexdetermination that employs c
24、entral or annular stops placed inthe objective back focal plane of a microscope.3.2.21.1 DiscussionUsing an annular stop with the sub-stage iris closed, a fiber mounted in a high dispersion mediumwill show a colored boundary of a wavelength where the fiberand the medium match in refractive index. Us
25、ing a central stop,the fiber will show colors complimentary to those seen with anannular stop.3.2.22 dyesoluble substances that add color to textiles.3.2.22.1 DiscussionDyes are classified into groups thathave similar chemical characteristics (for example, aniline,acid, and azo). They are incorporat
26、ed into the fiber by chemicalreaction, absorption, or dispersion.3.2.23 excitation filtera filter used in fluorescence micros-copy that transmits specific bands or wavelengths of energycapable of inducing visible fluorescence in various substrates.3.2.24 inorganic fibersa class of fibers of natural
27、mineralorigin (for example, chrysotile asbestos) and manmade mineralorigin (for example, fiberglass).3.2.25 interference colorscolors produced by the interfer-ence of two out-of-phase rays of white light when a birefrin-gent material is observed at a non-extinction position betweencrossed polars; th
28、e retardation at a particular point in abirefringent fiber may be determined by comparing the ob-served interference color to the Michel-Lvy chart.3.2.26 isotropica characteristic of an object in which theoptical properties remain constant irrespective of the directionof propagation or vibration of
29、the light through the object.3.2.27 ligninthe majority non-carbohydrate portion ofwood; it is an amorphous polymeric substance that cementscellulosic fibers together and is the principal constituents ofwoody cell walls.3.2.28 lumenthe cavity or central canal present in manynatural fibers (for exampl
30、e, cotton, flax, ramie, jute, hemp); itspresence and structure are often useful aids in identification.3.2.29 lusterthe gloss or shine possessed by a fiber,resulting from its reflection of light; the luster of manufacturedfibers is often modified by use of a delustering pigment.3.2.30 manufactured f
31、ibera class name for various generaof filament, tow, or staple produced from fiber formingsubstance which may be (1) polymers synthesized from chemi-cal compound, (2) modified or transformed natural polymers,or (3) glass.3.2.31 medullathe central portion of a hair composed of aseries of discrete cel
32、ls or an amorphous spongy mass.3.2.31.1 DiscussionThe medulla may be air-filled, and ifso, will appear opaque or black using transmitted light or whiteusing reflected light. In animal hair, several types have beendefined: uniserial or multiserial ladder, cellular or vacuolated,and lattice.3.2.32 Mic
33、hel-Lvy charta chart relating thickness, bire-fringence, and retardation so that any one of these variables canbe determined for an anisotropic fiber when the other two areknown.E2228 1023.2.33 microscopicalconcerning a microscope or the useof a microscope.3.2.34 modification ratioa geometrical para
34、meter used inthe characterization of noncircular fiber cross-sections; themodification ratio is the ratio in size between the outsidediameter of the fiber and the diameter of the core; it may alsobe called “aspect ratio.”3.2.35 natural fibersa class name of fibers of plant origin(for example, cotton
35、, flax, and ramie), animal origin (forexample, silk, wool, and specialty furs) or of mineral origin(for example, asbestos).3.2.36 pigmenta finely divided insoluble material used todeluster or color fibers (for example, titanium dioxide and ironoxide).3.2.37 plane polarized lightlight that is vibrati
36、ng in oneplane.3.2.38 pleochroismthe property of exhibiting differentcolors, especially three different colors, when viewed alongdifferent axes by plane polarized light.3.2.39 polarized lighta bundle of light rays with a singlepropagation direction and a single vibration direction.3.2.39.1 Discussio
37、nThe vibration direction is always per-pendicular to the propagation direction. It is produced by use ofa polarizing filter, from ordinary light by reflection, or doublerefraction in a suitable pleochroic substance.3.2.40 polarized light microscopea microscope equippedwith two polarizing filters, on
38、e below the stage (the polarizer)and one above the stage (the analyzer).3.2.41 privileged direction (of a polarizer)the direction ofvibration to which light emerging from a polarizer has beenrestricted.3.2.42 refractive indexfor a transparent medium, a dimen-sionless number that is the ratio of the
39、velocity of light in avacuum to the velocity of light in that medium.3.2.43 relative refractive indexthe estimate of the refrac-tive index of a fiber in relation to the index of its surroundingmedium.3.2.44 retardation (r)the actual distance of one of thedoubly refracted rays behind the other as the
40、y emerge from ananisotropic fiber; dependent upon the difference in the tworefractive indices, n n, and the thickness of the fiber.3.2.45 sign of elongationa property of fibers referring tothe elongation of a fiber in relation to refractive indices.3.2.45.1 DiscussionIf elongated in the direction of
41、 thehigh refractive index, the fiber is said to be positive; ifelongated in the direction of the low refractive index, it is saidto be negative.3.2.46 spherulitesspheres composed of needles or rods alloriented perpendicular to the outer surface, or a plane sectionthrough such a sphere; a common form
42、 of polymer crystalli-zation from melts or concentrated solutions.3.2.47 stereomicroscopea microscope containing twoseparate optical systems, one for each eye, giving a stereo-scopic view of a specimen.3.2.48 surface dyea colorant bound to the surface of afiber.3.2.49 synthetic fibersa class of manu
43、factured polymericfibers, which are synthesized from chemical compounds (forexample, nylon and polyester).3.2.50 technical fibera bundle of natural fibers composedof individual elongated cells that can be physically or chemi-cally separated and examined microscopically for identifyingcharacteristics
44、 (for example, hemp, jute, and sisal).3.2.51 thermoplastic fibera synthetic fiber that will softenor melt at high temperatures and harden again when cooled.3.2.52 ultimatesindividual fibers from a technical fiber(see 3.2.50).4. Significance and Use4.1 Microscopical examination is one of the least de
45、struc-tive means of determining rapid and accurate microscopiccharacteristics and generic polymer type of textile fibers.Additionally, a point-by-point, side-by-side microscopic com-parison provides the most discriminating method of determin-ing if two or more fibers are consistent with originating
46、fromthe same source. This guideline requires specific pieces ofinstrumentation outlined herein.5. Summary of Guide5.1 Textile fibers are examined microscopically. They maybe mounted on glass microscope slides in a mounting mediumunder a cover slip. The fibers are then examined microscopi-cally with
47、a combination of various illumination sources,filters, and instrumentation attached to a microscope to deter-mine their polymer type and record any microscopic charac-teristics. Known and questioned fibers are then compared todetermine if they exhibit the same microscopic characteristicsand optical
48、properties.6. Sample Handling6.1 Items of evidence may be visually inspected and twee-zers used to remove fibers of interest. Simple magnifiers andstereomicroscopes, with a variety of illumination techniques,may also be employed. Other methods such as tape lifting orgentle scraping are usually condu
49、cted after a visual examina-tion. Tape lifts should be placed on clear plastic sheets, glassmicroscope slides, or another uncontaminated substrate thateases the search and removal of selected fibers. Tapes shouldnot be over loaded. The tape lifts or any material recoveredfrom scraping should be examined with a stereomicroscopeand fibers of interest isolated for further analysis. Fibers ontape lifts may be removed using tweezers, other microscopictools and solvents (1-6).4Tape should not be attached to paperor
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