Unit 3: Hair and Fibers

1
Warm-Up Find the 6 differences between the two
pictures.
Source http//www.slylockfox.com/arcade/6diff/ind
ex.html
2
The answers are
Source http//www.slylockfox.com/arcade/6diff/ind
ex.html
3
Objective

• SWBAT distinguish and identify different types of
  fibers.

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Agenda

1. Types of Fiber
2. Patterns of Fiber
3. Fiber Analysis Lab
4. Testing Collection of Evidence
5. Atlanta Child Murders Documentary
6. Exit Slip

5
Fibers

• Class evidence
• Have probative value
• Common trace evidence
• Can be characterized based on comparison of both
  physical and chemical properties

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Fabric

• Fabric is made of fibers.
• Fibers are made of twisted filaments.
• Types of fibers and fabric
• Naturalanimal, vegetable or inorganic
• Artificialsynthesized or created from altered
  natural sources

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Types of Fibers

• Synthetic
• Rayon
• Nylon
• Acetate
• Acrylic
• Spandex
• Polyester

• Natural
• Silk
• Cotton
• Wool
• Mohair
• Cashmere

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Classification

• Natural fibers are classified according to their
  origin
• Vegetable or cellulose
• Animal or protein
• Mineral

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Cellulose Fibers

• Cottonvegetable fiber strong, tough, flexible,
  moisture absorbent, not shape retentive
• Rayonchemically-altered cellulose soft,
  lustrous, versatile
• Cellulose acetate cellulose chemically-altered
  to create an entirely new compound not found in
  nature.

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Fiber Comparison

• Can you tell the difference(s) between the cotton
  on
• the left and the rayon on the right?

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Protein Fibers

• Woolanimal fiber coming most often from sheep,
  but may be goat (mohair), rabbit (angora), camel,
  alpaca, llama, vicuna
• Silkinsect fiber that is spun by a silk worm to
  make its cocoon fiber reflects light and has
  insulating properties

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Mineral Fibers

• Asbestosa natural fiber that has been used in
  fire-resistant substances
• Rock woola manufactured mineral fiber
• Fiberglassa manufactured inorganic fiber

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Synthetic Fibers(Made from derivatives of
petroleum, coal and natural gas)

• Nylonmost durable of man-made fibers extremely
  light weight
• Polyestermost widely used man-made fiber
• Acrylicprovides warmth from a lightweight, soft
  and resilient fiber
• Spandexextreme elastic properties

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Weave Terminology

• Yarna continuous strand of fibers or filaments,
  either twisted or not
• Warplengthwise yarn
• Weftcrosswise yarn
• Blenda fabric made up of two or more different
  types of fiber.

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Weave Patterns
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Knitted Fabric

• Made by interlocking loops into a specific
  arrangement
• One continuous thread or a combination

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Polymers

• Synthetic fibers are made of polymers
• Long chains of repeating chemical units
• Repeating units are called monomers.
• Polymers are created that have different
  properties by varying
• the chemical structure of the monomers
• the way they are joined together

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Filament Cross-Sections

• Synthetic fibers are forced out of a nozzle when
  they are hot, and then they are woven. The holes
  of the nozzle are not necessarily round
  therefore, the fiber filament may have a unique
  shape in cross-section.

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Fiber Analysis Lab
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Testing for Identification

• Microscopic observation
• Burningobservation of how a fiber burns, the
  odor, color of flame, smoke and the appearance of
  the residue
• Thermal decompositiongently heating to break
  down the fiber to the basic monomers
• Chemical testssolubility and decomposition

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Testing for Identification

• Densitymass of object divided by the volume of
  the object
• Refractive Indexmeasuring the bending of light
  as it passes from air into a solid or liquid
• Fluorescenceused for comparing fibers as well as
  spotting fibers for collection

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Dyes

• Components can be separated and matched to an
  unknown.
• More than 7000 different dye formulations
• Chromatography
• The way a fabric accepts a particular dye may
  also be used to identify and compare samples.

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Identification and Comparison of Fibers

• Fourier Transform Infrared analysis (FTIR)based
  on selective absorption of wavelengths of light
• Optical microscopyuses polarizing light and
  comparison microscopes
• Pyrolysis gas chromatography-mass spectrometry
  (PGC-MS)burns a sample under controlled
  conditions, separates and analyzes each
  combustion product

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Collection ofFiber Evidence

• Bag clothing items individually in paper bags.
  Make sure that different items are not placed on
  the same surface before being bagged.
• Make tape lifts of exposed skin areas of bodies
  and any inanimate objects
• Removed fibers should be folded into a small
  sheet of paper and stored in a paper bag.

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Fiber Evidence

• Used to connect the suspect to the victim or to
  the crime scene
• In the case of Wayne Williams, fibers weighed
  heavily on the outcome of the case. Williams was
  convicted in 1982 based on carpet fibers that
  were found in his home, car and on several murder
  victims.

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Atlanta Child Murders Documentary

• 18. How many male victims were there?
• 19. How did Wayne Williams do on the polygraph
  test?
• 20. What is measured in a polygraph test?
• 21. What was the case against Wayne Williams
  built on?
• 22. How many murders was Wayne Williams tried on?
  
• 23. What was the shape of the fibers on the
  carpet/green fibers?
• 24. What fibers were caught to the victims
  shorts and how was this relevant to Wayne
  Williams?
• 25. What other fibers were found with Wayne
  Williams and his victims?

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Homework

• Hair Fiber Analysis Pre-Lab due Wednesday

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Exit SlipSeptember 23, 2014

• 1. Get out a mobile device or use one of the
  computers and go to m.socrative.com. You can also
  use one of the iPads that has the Socrative app.
• 2. When prompted, enter 417101 for the room
  number.
• QUESTION What are different types of fiber?