fibres ref: kendall hunt publishing company. fibres 2 2 fibres
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FIBRESRef: Kendall Hunt Publishing company
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Fibres
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Fabric is made of fibres
Fibres are made of twisted filaments
Types of fibres and fabric: Natural—animal, vegetable, or
inorganic
Artificial—synthesized or created from altered natural sources
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Fabric
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Types of fibres
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Synthetic Natural
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Classification
•Natural fibres are classified according to their origin:
• Vegetable or cellulose
• Animal or protein
• Mineral
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Cotton—
Rayon—
Cellulose acetate—
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Cellulose Fibres
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Fibre Comparison
• Can you describe the difference(s) between the cotton on the left and the rayon on the right?
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Protein Fibres
Wool—
Silk—
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vicuña llama
alpaca silkworm
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Asbestos—
Rock wool—
Fiberglass—
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Mineral Fibres
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Nylon—
Polyester—
Acrylic—
Spandex—Kendall/Hunt Publishing Company 10
Synthetic FibresMade from derivatives of petroleum, coal, and natural gas
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fabrics are composed of individual threads or yarns made of fibres and are knitted, woven, bonded, crocheted, felted, knotted, or laminated most are either woven or knitted degree of stretch, absorbency, water repellence, softness, and durability are individual qualities
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Fabric Production
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Yarn—a continuous strand of fibres or filaments that may be twisted together
Warp—lengthwise yarn
Weft—crosswise yarn
Blend—a fabric made up of two or more different types of fibres
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Weave Terminology
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Plain Weave
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The warp yarn is passed over one to three weft yarns before going under one.
Makes a diagonal weave pattern.
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Twill Weave
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The yarn interlacing is not uniform
Creates long floats
Interlacing weave passes over four or more yarns
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Satin Weave
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Knitted Fabric
Knitted fabrics are made by interlocking loops into a specific arrangement. It may be one continuous thread or a combination. Either way, the yarn is formed into successive rows of loops and then drawn through another series of loops to make the fabric.
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Synthetic fibres are made of
The word polymer means
The repeating units of a polymer are called
By varying the chemical structure of the monomers or by varying the way they are joined together, polymers are created that have different properties
As a result of these differences, they can be distinguished from one another forensicallyKendall/Hunt Publishing Company 17
Polymers
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Filament Cross Sections
Synthetic fibres 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 fibre filament may have a unique shape in cross section.
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R ound 4-lobed
Octalobal
Irregular
Multi-lobed
or Serrate
T rilobal
Dogbone or
Dumbbell
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Microscopic observation
Burning—
Thermal decomposition—
Chemical tests—
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Testing for Identification
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Density—
Refractive index—
Fluorescence—
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Testing for Identification
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Components that make up dyes can be separated and matched to an unknown
There are more than 7,000 different dye formulations
Chromatography is used to separate dyes for comparative analysis
The way a fabric accepts a particular dye may also be used to identify and compare samples
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Dyes
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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 and any inanimate objects.
Removed fibres should be folded into a small sheet of paper and stored in a paper bag.
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Collection of Fibre Evidence
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For additional information about fibres and other trace evidence, check out truTV’s Crime Library at:
www.crimelibrary.com/criminal_mind/forensics/trace/1.html
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