What Are Fibers? - WordPress
What are fibers? The basic unit of fabrics Woven together to form fabric Besides hair, one of the most commonitems left at a crime scene
Trace EvidencePet hair on clothes or rugsHair on brushFingerprints on glassSoil tracked inside on shoesDrop of blood on t shirtA used facial tissue Paint chipsBroken glassFiber from clothingEven though TraceEvidence isTiny Many aconviction dependedon Trace!
Fibers and Forensics How are fibers used in Forensic Science?– To create a link between crime and suspect. Fibers are not specific to an individual, but – often fall off and are picked up during activities and gounnoticed– may provide police with evidence even if a suspect wearsgloves Fibers are a form of trace evidence– Where can fibers originate?– They generally come from clothing, drapery, wigs,carpeting, furniture, and blankets
Fibers are generally usedto place evidence that hastransferred from a victimor suspect’s clothing Locard’s Principle - When two peoplecome in contact there is transfer ofmaterial both ways Some clothing transfers better than others Some clothing accepts transfer particles betterthan others Particles can also transfer from rugs, bedding,or furniture
Other factors that mayinfluence particle transfer: Length of time contact occurred Nature of contact, violent contact mayyield more transfer Length of time that passed since thealleged contact occurred
Man-made or synthetic fibers makeup 1/2 of all fibers found in textilemills You can determine a lot from how a fiberappears under the microscope Type of Fiber Manufacturer even Unusual cross-sections of fiber increase theprobative value
Fiber is often found:Caught in screens or on jaggedsurfacesAround broken glassOn cars involved in a hit and runTransferred during a struggle
Fiber Evidence The problem with fiber evidence is that fibersare not unique. Unlike fingerprints or DNA, they cannotpinpoint an offender in any definitivemanner. There must be other factors involved, such asevidence that the fibers can corroborate orsomething unique to the fibers that set themapart.
How Do Forensic Scientists UseFibers?Fiber evaluation can showType of fiber Color Possibility of violence Location of suspects Point of origin
Fiber CollectionIt is collected in the same manner as hairCollection is time consuming and tediousMost analysis is done under themicroscopeFiber has less parts than hair but is still asvaluable
How Do Forensic Scientists ObtainFibers?Special vacuums Sticky tape Lint Rollers Forceps
Methods of Analyzing FibersWithout Damaging Fibers Microscopes reveal characteristic shapes andmarkings (Infrared microscopy)Infrared spectroscopy reveals chemical structures todifferentiate similar fibers Destructive Testing Methods Burning fibersDissolving fibers in various liquidsForensic Science: Fundamentals & Investigations, Chapter 4
Methods of Analyzing Fibers:Stereoscopic MicroscopeThe most commonly used microscope in crime labsOffers a large working surface for bulky itemsStereoMicroscopeForensic Science: Fundamentals & Investigations, Chapter 4CompoundMicroscope
Development of fibers Till the beginning of 20th century all fibers in use were natural Around 1891-92 the first man-made ‘Artificial Silk’ (Viscose rayon) wasdiscovered In 1938, Dupont developed the first synthetic polyamide fiber ‘Nylon’,followed by the development of polyester Thus a distinct class of man-made fibers/ synthetic fibers weredeveloped 1950-60s –acrylic, PP, PVA, Teflon, Lycra were developed In the last fifty years of research a host of new improved man-madecellulosic, protein, aramid and functional fibers have been developed
How do fibers make up fabric? Fibers aligned into a yarn (thread) Yarn is then woven, knitted,crocheted, knotted, braided etc.into a fabricThe three basic weaving patternsPLAINTWILLSATIN
Weave PatternsForensic Science: Fundamentals & Investigations, Chapter 4
Why is the weaving pattern of interest toforensic scientists? Each type of fabric has its own characteristics which can bediscovered by performing different tests Can tell what material may have been used during a crime
I just thought this was coolSPIDER SPINNERETS – Master Weavers!
Weaving Yarn into a blanket
Man-madefibers likeNylon andRayon –made fromPetroleumproducts!
Fibers can be natural, mineral, orsynthetic“Fiber” is spelled “fibre” in England
IntroductionForensic Science: Fundamentals & Investigations, Chapter 4To make thecase, youneed toknow whatkind of fiberit is
Comparison of natural and synthetic fibers Synthetic fibers are much stronger than naturalfibers. Unlike natural fibers, synthetic fibers are notdamaged by microorganisms. Synthetic fibers can deteriorate in bright sun andmelt at a lower temperature than natural fibers. Under magnification, all synthetic fibers have veryregular diameters. Hairs have a cuticle.
Two Types of Fibers“Fiber” is spelled “fibre” in England
Natural fibers from animals aremade of protein
Wool is anothercommonly found fiberused in clothing,blankets, rugs Wool originates fromsheep Wool has a particularlyknotted, twistedappearance up closeunder a microscope
Wool can come frommultiple sources Sheep Cashmere goatsAlpacaCamel
Angora The hair of the Angora rabbit is allowed togrow 3 or more inches long before it isAngorarabbitsclipped, sheared, or plucked. This processcauses no harm to the animals and arecarried out four times each year. The total annual yield for a single Angorarabbit ranges from 7 to 14 ounces, isenough to construct one small garment,such as a short-sleeved sweater. Clothing of Angora rabbit wool are usuallyhave a very nice feel against the skin.Many people who find garments made ofsheep’s wool scratchy and uncomfortablePolarized microscopy imageof angora fiberAngora woolfind Angora wool comfortable.
Cashmere Properties-fiber is cylindrical, soft and silky, lightweightIn order to avoid pilling by localfriction, the lining must be slipperyCashmere/ Pashmina can be dyed indifferent colours-Cashmere / Pashmina goats Care factors-Preferably dry cleaned, should bedried in shade, not direct sunlightCashmere garments should be foldedand kept and should not be hanged toprevent deformation.-Polarized light microscopyimage of cashmere
Alpaca
What you see in the microscope– Wool
Silk3/19/2017Fabric Styling - Neha Singh
Silk under themicroscopeUnder the microscope the silkfiber looks like a smooth glassrod. Occasionally markingsshow that are caused by thecoating of the silk fiber, calledgum or sericin which has not allbeen removed
Natural fibers from plants aremade of CelluloseKenaf fiberKenaf ProductsSisalHempHemp filament bagCoir (coconut) matTowels from bamboofiberCostume from pina fiberCotton fiberJuteExtraction of Banana fiber
Cotton underthe microscopeCotton has adistinct ribbon likeshape with twists atirregular intervals
Linen Linen is known to be theworld’s strongest naturalfiber. It is so durable it’seven used in papermoney to increasestrength Linen is not as soft ascotton Oinen is very cool andcomfortable in hotweather
What you see in the microscope– Flax (Linen) The linen fiber, like cotton,comes from a plant.However, it comes from adifferent part of the plant, thestem itself Under the microscope thelinen fiber looks like a jointedbamboo rod. These jointsare called nodes and theends of the fibers arepointed
Fiber Classification—Natural Fibers Seed fibers– Fruit fibers– Coir is a coarse fiber obtained from the covering surrounding coconuts.When woven together, they are stronger than flax or cotton. Coir fiber isrelatively waterproof which makes it ideal for such things as doormatsand baskets.Stem fibers–43Cotton is found in the seedpod of the cotton plant. Because of the easewith which cotton can be woven and dyed, it has been used extensivelyfor clothing and household textiles.Hemp, jute, and flax are all produced from the thick region of plantstems. They do not grow as single, unconnected fibers like cotton, but inbundles. These bundles may be six feet in length and extend the entirelength of a plant.
Fiber Classification—Natural FibersMineral Fibers: Fiberglass—a fibrous form of glass Asbestos—a crystalline structureForensic Science: Fundamentals & Investigations, Chapter 4
What you see in the microscope– Mineral fiber (Asbestos)
Synthetic Fibers Petroleum is the basis for these fibers, and they havevery different characteristics from other fibers. Monomers in large vats are joined together to formpolymers. The fibers produced are spun together intoyarns. They have no internal structures, and undermagnification they show regular diametersMore than half of all fibers used in the production of textilematerials are man-made.Polyester and nylon fibers are the most commonlyencountered man-made fibers, followed by acrylics,rayons, and acetates.The shape of a man-made fiber can determine the valueplaced on that fiber.The cross section of a man-made fiber can bemanufacturer-specific
Synthetic FibersCellulose esters-- These are derived from cellulose and produced by chemicallymodifying the natural polymers to create an entirely new compound not foundin nature. Examples:-Rayon- most common. first man-made fiber; soft, versatile.-Acetate- less expensive, less polluting than rayon.Synthetic polymer fibersPetroleum Plastics- these originate from derivatives of petroleum, coal andnatural gas. They are totally man-made. Example:– Nylon- most durable man-made fabric; extremely light weight. Firstintroduced as artificial silk for pantyhose.– Acrylic- most widely used man-made fiber. Inexpensive and tends toball easily.– Polyester- -provides warmth from a lightweight, soft and resilient fabric.Common in polar fleece and many wrinkle resistant pants.– Spandex- extreme elastic properties.
RayonFirstmanufacturedin 1911
Rayon inthemicroscope
AcetateBreathable fabricLuxurious feel, appearanceWide range of colorsShrink, moth & mildew resistant
What yousee in themicroscope– Acetate
Fiber Classification—Synthetic Polymer FibersSynthetic Polymer Fibers Petroleum base Very different from otherfibers Monomers join to formpolymers Fibers are spun togetherinto yarns No internal structures Uniform diameters
Fiber Classification—Synthetic Cellulose FibersRegenerated Fibers (derived from cellulose):Rayon ooMost common in this groupImitates natural fibers, but strongerCelenese ooCellulose chemically combined with acetateFound in many carpetsPolyamide nylon oooCellulose combined with three acetate unitsBreathable and lightweightUsed in performance clothing
Fiber Classification—Synthetic Polymer FibersPolyester oooo“Polar fleece”spandex nylonWrinkle-resistantNot easily broken down by light or concentrated acidAdded to natural fibers for strengthNylon ooEasily broken down by light and concentrated acidOtherwise similar to polyesterForensic Science: Fundamentals & Investigations, Chapter 4
AcrylicSoft, warmWool-likeFiber retains shapeResilientQuick-dryingShrink, moth, fade resistant
AcrylicGeneral cross-section and surface view of acrylic fiber -Comfort factors-The slight waviness of theacrylic fibers provides slightbulkiness to the yarns andwarmth Care factors-Easily laundered, machinewashable, dries fastAcrylics have a soft handleBlanketsModacrylic winterwearInflight productsPolice vests
AramidGreat strengthStretch resistantDoes not meltHighly flame-resistantFibers maintain shape andstructure even at very hightemperatures
High strength, high modulusorganicApplicationsfibers Para-aramidse.g. Kevlar (Dupont)Twaron ( Acordis) Ultra high molecular weightpolyethylene (UHMWPE)e.g. DyneemaSpectra ( Allied signal)Bullet proof helmetBullet proofvestCut resistant glovesusing yarn made ofkevlar sheath andspandex coreDyneema cut resistantgloves3/19/2017Fabric Styling - Neha SinghKevlar andPTFE rope
LyocellSoft, strong absorbentEasily dyedFiber can be made into manytextures
MelamineWhite fiber, easily dyedFlame resistantDoes not conduct heatPlastic used to make “unbreakable”DishesUsed to make airplane seatsFirefighter’s protective wear
Fiber Classification—Synthetic Polymer FibersAcrylic oooInexpensiveTends to “ball” easilySubstitute for artificial wool or furOlefins oooHigh performanceQuick dryingResistant to wearForensic Science: Fundamentals & Investigations, Chapter 4
MicrofilamentsSea islandtypemicrofibermanufacturedby TorayJapanSplittablemicrofiber( KaneboJapan,Elaston) Linear density of approximately1.0 dtex or less Usually made from polyester/nylon Brand names: Mitrelle, Setila,Micrell, Tactel Used for production of fashionableclothing and also bacteria barrierfabric for medical applications Split technique of productionproduces microfilaments that canbe used for wiping cloth for opticaland microelectronic industries
Microfilament productsMicrofilament fabric can be constructed tobeimpermeable to water droplets while allowing air andmoisture vapour circulation, with good wickingproperties.Microfilament spunlace nonwoven : Soft,drapableandmuch lighterthantraditional textiles. Highly dense andcompact fiber structure, very goodbarrier properties, thermal insulation,wind resistance and UV protection andhighly breathable with very goodmoisturemanagement.
NylonEarly man-made fiber(1930’s)Very strong fiberSupple fabricResilient, holds its shapeAbrasion-resistantLustrous fabricWater-resistantOil and chemical resistantUsed to make seatbelts,clothing, carpets, bedding,drapes, parachutes, tents
What you see inthe microscope –Nylon
Polypropylene ( Olefin fibers) Polarized microscopeimage of PP filament CarpetsPP productsDifferent types of yarn, tapes,sheets and nonwoven productscan be madeUsed widely in the production ofdisposable medical protectiveapparels, carpets and industrialtextilesMedical productsGrass matsCrop coversBagsAntiweed fabric
PolyesterPolyester fabrics and fibers are extremely strong.Polyester is very durable: resistant to mostchemicals, stretching and shrinking, wrinkleresistant, mildew and abrasion resistant.Polyester is hydrophobic in nature and quickdrying. It can be used for insulation bymanufacturing hollow fibers.Polyester retains its shape and hence is good formaking outdoor clothing for harsh climates.It is easily washed and dried
Polyester
Spandex
Sampling and Testing: An ExampleForensic Science: Fundamentals & Investigations, Chapter 4
HOW CAN WE TELL THE DIFFERENCE BETWEENSYTHETIC AND NATURAL FIBERS?Step 1: Natural vs synthetic, use a comparisonmicroscope Examine the color, diameter, cross-section shape,pitting or striations, etc. Synthetic fibers have smooth surfaces, uniform size& shape
HOW CAN WE TELL THE DIFFERENCE BETWEENSYTHETIC AND NATURAL FIBERS?Step 2: chemical composition of synthetics Use Infrared spectroscopy, refractive index orpolarized light to identify types of synthetic fiber Dye can be extracted and the colors separated by thinlayer chromatography (TLC) Forensic Science: Fundamentals & Investigations, Chapter 4
Some man-made fibers are circularlike hairs, but the is no medulla orcuticle
. . . . . . . . . . . . . . . . . SummaryFibers are analyzed using burn tests, tests forsolubility in different solutions, polarized lightmicroscopy, or infrared spectroscopy. Fibers are classified as natural or synthetic. Natural fiber sources include: oooAnimal hairPlant seeds, fruit, stems, or leavesMinerals.Forensic Science: Fundamentals & Investigations, Chapter 4
READ the slides. Then answer the questions (on paper)1) Synthetic fibers are made of large moleculescalled polymers which are made of smallerrepeating units called monomers. These fibersare mass produced. Why is that a problem forforensic scientists?2) Fibers collected as trace evidence are oftenconsidered to be class evidence and notindividual evidence. For example, the presence ofa white cotton fiber found on a suspect and foundon a victim at a crime scene is not enoughevidence to convict the suspect. Justify thisstatement.3) Give 4 examples of natural fibers.4) What is the most common one?79
READ the slides. Then answer the questions (on paper)5) List 2 natural animal fibers. What are they madeof? What would they look like under themicroscope?6) List 2 natural plant fibers. What are they made of?What would they look like under the microscope?7) What is an example of a mineral fiber and whatdoes it look like under the microscope?8) List 2 Petrochemical fibers. What does each onelook like under the microscope?9) The 2 non-destructive tools used to identify fibersare 10) The 2 destructive tests (one we did in lab) are 11) Prior to the 19th century, all fibers were:12) Give a short description of the timeline for manmade fibers.80
READ the slides. Then answer the questions (on paper)13) Why are more than half the fibers in the worldtoday man-made?14) What is the strongest fiber?15) What are 2 ways that synthetic fibers aresuperior to natural fibers?16) What are 2 ways that natural fibers are superiorto synthetic fibers?17) Name 3 different fibers that are produced byanimals.18) Name 3 different fibers that are produced frompetroleum, such as coal, oil, or natural gas81
READ the slides. Then answer the questions (on paper)19)Name 3 different fibers that are produced byplants.20) A crime-scene investigator views two small, redfibers. One fiber was obtained from the crimescene off the victim’s body, and the other redfiber was removed from the cuff of the suspect’spants. Although the two fibers appear to be fromthe same fabric, the crime-scene investigatordetermines that the two fibers are indeed verydifferent. List five other characteristics of thefibers that can be detected under a compoundmicroscope that could be used to distinguish thetwo red fibers.82
READ the slides. Then answer the questions (on paper)21. A fiber is collected at a crime scene. When viewed under acompound microscope, what two traits would indicate thatthe fiber was a human hair and not a piece of fiberobtained from an article of clothing?22. Why are fibers are an excellent source of trace evidence?23. Natural fibers can be harvested from .24. Why was asbestos, a mineral fiber, used so extensively inthe 20th century?25. What are some common shapes for man-made fibers?26. What if a woman’s roommate borrowed her coat and wasthen involved in a crime that left textile evidence behind?How could investigators distinguish between the womaninvolved in the crime and the owner of the coat?27. Would you ever be 100% sure of the conclusion youmade? Explain83
material both ways Some clothing transfers better than others Some clothing accepts transfer particles better . In the last fifty years of research a host of new improved man-made cellulosic, protein, aramid and functional fibers have been developed . Clothing of Angora rabbit wool are usually have a very nice feel against the skin.
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group consisting of thermoplastic meltblown man-made fibers, thermoplastic spunbonded man-made fibers, thermo plastic man-made staple fibers and combinations thereof, this first layer being light weight, and a second layer of cellulosic-based fibers, preferably cotton fibers, the first and second layers being thermally bonded together over about 5
World Conference on Earthquake Engineering October 12-17, 2008, Beijing, China Optical fibers are classified into two types, single-mode fibers and multi-mode fibers. Single-mode fibers feature small cores (around 3.5 x 10-4 inches or 9 microns in diameter) and broadcast infrared laser light of wavelength 1,300 to 1,550nm.
skeletal muscle fibers. For instance, bundles of very fine fibers—myofibrils—extend lengthwise along skeletal muscle fibers and almost fill their sarcoplasm. Myofibrils, in turn, are made up of still finer fibers,called thick and thin myofilaments (Figure 11-1,D). Find the label sarcomere in
thick and opaque. From the resulting fascia, connective tissue fibers form the perimysium -as an organization of dense connective tissue that envelops a group of muscle fibers- and the endomysium -which is mainly reticular connective tissue surrounding each muscle fibers involved in their relationship with the basal lamina of each of the fibers.
A. The motor unit 1. A motor unit consists of one motor neuron and all of the muscle fibers it contracts. 2. Size of motor unit varies with muscle and fineness of movement. 3. All muscles consist of a number of motor units and the fibers belonging to a motor unit are dispersed and intermingle amongst fibers of other units. 4. The muscle fibers .File Size: 2MBPage Count: 9
materials has the potential to close the performance gap between these two classes of fibers. 2.1. The CNT composite fibers by solution spinning As the dispersion of nanotube in polymer matrix is an important factor in preparation of polymer/CNT composite fibers, solution processing has been extensively used to prepare these fibers.
of photonic crystal fibers with particular emphasis on recent advances in the field. I. INTRODUCTION Photonic crystal fibers (PCFs) have in recent years attracted much scientific and technological interest. Broadly speaking, PCFs may be defined as optical fibers in which the core and/or cladding regions consist of microstructured rather than .
