ASTM E2228-2002 Standard Guide for Microscopic Examination of Textile Fibers《纺织纤维的显微镜检验用标准指南》.pdf

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1、Designation: E 2228 02Standard Guide forMicroscopic Examination of Textile Fibers1This standard is issued under the fixed designation E 2228; 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 (e) 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. Seve

3、ral 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 fib

4、er evidence.2. Referenced Documents2.1 ASTM Standards:D 276 Test Methods for Identification of Fibers in Textiles23. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 anisotropica characteristic of an object, which hasoptical properties that differ according to the direction in whi

5、chlight travels through the object when viewed in polarized light.3.1.2 barrier filtera filter used in fluorescence microscopythat suppresses unnecessary excitation light that has not beenabsorbed by the fiber and selectively transmits only light ofgreater wavelengths than the cut-off wavelength.3.1

6、.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.3.1.4 Becke line methoda method for determining therefractive index of a fiber relativ

7、e to its mountant by noting thedirection in which the Becke line moves when the focus ischanged. The Becke line will always move toward the higherrefractive index medium (fiber or mountant when the focaldistance is increased and when the focal distance is decreasedaway from the objective and will mo

8、ve toward the lowerrefractive index medium when the sample is moved toward theobjective.3.1.5 birefringencethe numerical difference in refractiveindices for a fiber, given by the formula: n n. Birefrin-gence can be calculated by determining the retardation (r) andthickness (T) at a particular point

9、in a fiber and by using theformula: B = r (nm)/1000T (m).3.1.6 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.3.1.7 compensatorany variety of

10、optical devices 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. Compensators may employa fixed mineral plate of constant or

11、varying thickness or amineral plate that may be rotated, or have its thickness variedby tilting to alter the thickness presented to the optical path(and retardation introduced) by a set amount.3.1.8 compensator, full wave (or red plate)a compensatorusually a plate of gypsum, selenite or quartz, whic

12、h introducesa fixed retardation between 530 to 550 nm (approximately theretardation of the first order red color on the Michel-Levychart).3.1.9 compensator, quarter wavea compensator, usuallywith a mica plate, which introduces a fixed retardation between125 to 150 nm.3.1.10 compensator, quartz wedge

13、a wedge, cut fromquartz, having continuously variable retardation extendingover several orders of interference colors (usually 3 to 7).3.1.11 compensator, Snarmonta quarter-wave plate in-serted above the specimen in the parallel “0” position with acalibrated rotating analyzer. Measures low retardati

14、on andrequires the use of monochromatic light.3.1.12 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.3.1.13 cortexthe main structural component of ha

15、ir con-sisting of elongated and fusiform (spindle-shaped) cells. Thecortex may contain pigment grains, air spaces called corticalfusi, and structures called ovoid bodies.3.1.14 crimpthe waviness of a fiber.3.1.15 crossover marksoblique flattened areas along silkfibers caused by the overlapping of ex

16、truded silk fibers before1This 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 August 10, 2002. Published October 2002.2Annual Book of ASTM Standards, Vol 07.01.1Copyright AST

17、M International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.they have dried completely.3.1.16 cuticlethe layer of scales composing the outersurface of a hair shaft. Cuticular scales are normally classifiedinto three basic types: coronal (crown-like), spinous

18、(petal-like), and imbricate (flattened).3.1.17 delustranta pigment, usually titanium dioxide,used to dull the luster of a manufactured fiber.3.1.18 dichroismthe property of exhibiting different col-ors, especially two different colors, when viewed along differ-ent axes by plane polarized light.3.1.1

19、9 dislocationsdistinct features that occur in naturalfibers (for example, flax, ramie, jute, hemp) in the shape of Xs,Is, and Vs that are present along the fiber cell wall. Thesefeatures are often useful for identification.3.1.20 dispersion of birefringencethe variation of bire-fringence with wavele

20、ngth of light. When dispersion of bire-fringence is significant in a particular fiber, anomalous inter-ference colors not appearing in the regular color sequence ofthe Michel-Levy chart may result. Strong dispersion of bire-fringence may also interfere with the accurate determination ofretardation i

21、n highly birefringent fibers.3.1.21 dispersion staininga technique for refractive indexdetermination that employs central or annular stops placed inthe objective back focal plane of a microscope. Using anannular stop with the substage iris closed, a fiber mounted in ahigh dispersion medium will show

22、 a colored boundary of awavelength where the fiber and the medium match in refractiveindex. Using a central stop, the fiber will show colors compli-mentary to those seen with an annular stop.3.1.22 dyesoluble substances that add color to textiles.Dyes are classified into groups that have similar che

23、micalcharacteristics (for example, aniline, acid, and azo). They areincorporated into the fiber by chemical reaction, absorption, ordispersion.3.1.23 excitation filtera filter used in fluorescence micros-copy that transmits specific bands or wavelengths of energycapable of inducing visible fluoresce

24、nce in various substrates.3.1.24 inorganic fibersa class of fibers of natural mineralorigin (for example, chrysotile asbestos) and manmade mineralorigin (for example, fiberglass).3.1.25 interference colorscolors produced by the interfer-ence of two out-of-phase rays of white light when a birefrin-ge

25、nt material is observed at a non-extinction position betweencrossed polars. The retardation at a particular point in abirefringent fiber may be determined by comparing the ob-served interference color to the Michel-Lvy chart.3.1.26 isotropica characteristic of an object in which theoptical propertie

26、s remain constant irrespective of the directionof propagation or vibration of the light through the object.3.1.27 ligninthe majority non-carbohydrate portion ofwood. It is an amorphous polymeric substance that cementscellulosic fibers together. The principal constituents of woodycell walls.3.1.28 lu

27、menthe cavity or central canal present in manynatural fibers (for example, cotton, flax, ramie, jute, hemp). Itspresence and structure are often useful aids in identification.3.1.29 lusterthe gloss or shine possessed by a fiber,resulting from its reflection of light. The luster of manufacturedfibers

28、 is often modified by use of a delustering pigment.3.1.30 manufactured fibera class name for various fami-lies of fibers produced from fiber-forming substances, whichmay be synthesized polymers, modified or transformed naturalpolymers and glass.3.1.31 medullathe central portion of a hair composed of

29、 aseries of discrete cells or an amorphous spongy mass. It may beair-filled, and if so, will appear opaque or black using trans-mitted light or white using reflected light. In animal hair,several types have been defined: uniserial or multiserial ladder,cellular or vacuolated, and lattice.3.1.32 Mich

30、el-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.3.1.33 microscopicalconcerning a microscope or the useof a microscope.3.1.34 modification ratioa geometrical parameter used

31、 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.”3.1.35 natural fibersa class name of fibers of plant origin(for example, cotton, flax, ra

32、mie), animal origin (for example,silk, wool, and specialty furs) or of mineral origin (forexample, asbestos).3.1.36 pigmenta finely divided insoluble material used todeluster or color fibers (for example, titanium dioxide, ironoxide).3.1.37 plane polarized lightlight that is vibrating in oneplane.3.

33、1.38 pleochroismthe property of exhibiting differentcolors, especially three different colors, when viewed alongdifferent axes by plane polarized light.3.1.39 polarized lighta bundle of light rays with a singlepropagation direction and a single vibration direction. Thevibration direction is always p

34、erpendicular to the propagationdirection. It is produced by use of a polarizing filter, fromordinary light by reflection, or double refraction in a suitablepleochroic substance.3.1.40 polarized light microscopea microscope equippedwith two polarizing filters, one below the stage (the polarizer)and o

35、ne above the stage (the analyzer).3.1.41 privileged direction (of a polarizer)the direction ofvibration to which light emerging from a polarizer has beenrestricted.3.1.42 refractive indexfor a transparent medium, a dimen-sionless number that is the ratio of the velocity of light in avacuum to the ve

36、locity of light in that medium.3.1.43 relative refractive indexthe estimate of the refrac-tive index of a fiber in relation to the index of its surroundingmedium.3.1.44 retardation (r)the actual distance of one of thedoubly refracted rays behind the other as they emerge from ananisotropic fiber. Dep

37、endent upon the difference in the tworefractive indices, n n, and the thickness of the fiber.3.1.45 sign of elongationa property of fibers referring tothe elongation of a fiber in relation to refractive indices. IfE2228022elongated in the direction of the high refractive index, the fiberis said to b

38、e positive; if elongated in the direction of the lowrefractive index, it is said to be negative.3.1.46 spherulitesspheres composed of needles or rods alloriented perpendicular to the outer surface, or a plane sectionthrough such a sphere. A common form of polymer crystalli-zation from melts or conce

39、ntrated solutions.3.1.47 stereomicroscopea microscope containing twoseparate optical systems, one for each eye, giving a stereo-scopic view of a specimen.3.1.48 surface dyea colorant bound to the surface of afiber.3.1.49 synthetic fibersa class of manufactured polymericfibers, which are synthesized

40、from chemical compounds (forexample, nylon, polyester).3.1.50 technical fibera bundle of natural fibers composedof individual elongated cells that can be physically or chemi-cally separated and examined microscopically for identifyingcharacteristics (for example, hemp, jute, and sisal).3.1.51 thermo

41、plastic fibera synthetic fiber that will softenor melt at high temperatures and harden again when cooled.3.1.52 ultimatesindividual fibers from a technical fiber(see 3.1.50).4. Significance and Use4.1 Microscopic examination is one of the least destructivemeans of determining rapid and accurate micr

42、oscopic charac-teristics and generic polymer type of textile fibers. Addition-ally, a point-by-point, side-by-side microscopic comparisonprovides the most discriminating method of determining if twoor more fibers are consistent with originating from the samesource. This guideline requires specific p

43、ieces of instrumenta-tion 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 a combination of various illumination sources,filters

44、, 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 properties.6. Sample Handling6.1 Items of evidence ma

45、y 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 conducted after a visual examina-tion. Tape lifts should b

46、e 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 is

47、olated for further analysis. Fibers ontape lifts may be removed using tweezers, other microscopictools and solvents (1-6).3Tape should not be attached to paperor cardboard.6.2 Care should be taken to ensure contamination does notoccur. This must be accomplished by examining questionedand known items

48、 in separate areas and/or at different times.The work area and tools must be thoroughly cleaned andinspected before examining items that are to be compared.7. Analysis7.1 Fibers should be first examined with a stereomicro-scope. Physical features such as crimp, length, color, relativediameter, luste

49、r, apparent cross section, damage, and adheringdebris should be noted. Fibers may then be tentatively classi-fied into broad groups such as synthetic, natural, or inorganic.If the sample contains yarns, threads, or sections of fabric,construction should be recorded (7-9).7.1.1 If all of the physical characteristics appear the sameunder the stereoscope, an examination of the fibers with acomparison microscope should be conducted. This side-by-side, point-by-point examination is a valuable technique todiscriminate between fibe