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Fibers and Textiles

Fibers and Textiles. Chapter 4 . Objectives. Identify and describe common patterns of textile samples Compare and contrast various types of fibers through physical and chemical analysis Describe principal characteristics of common fibers used in their identification

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Fibers and Textiles

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  1. Fibers and Textiles Chapter 4

  2. Objectives • Identify and describe common patterns of textile samples • Compare and contrast various types of fibers through physical and chemical analysis • Describe principal characteristics of common fibers used in their identification • Apply forensic science techniques to analyze fibers

  3. Introduction • Fibers are used in Forensic Science to create a link between crime and suspect. • Fibers are a form of Trace Evidence. • Direct transfer is when a fiber is transferred from victim to suspect or vice versa. • Secondary transfer is a fiber that was picked up and then transferred to a suspect, or from original source to the suspect then to the victim.

  4. How FS use Fibers • Evidence of any kind should be evaluated, especially fibers because there are so many of them in each environment. • Their value depends on their uniqueness • White cotton fiber vs. angora fiber

  5. Uses of Fibers • Type of Fibers • Fiber Color • Number of Fibers Found • Where Fiber was Found • Textile the fiber originated from

  6. Uses of Fibers • Multiple Fiber Transfers • Type of crime committed • Time between crime and discovery of fiber

  7. Sampling and Testing • Fibers are gathered with special vacuums, sticky tape, and forceps. • First task is to identify the fibers type and its characteristics • Shape and color • Polarized light microscopy • Infrared Spectroscopy • Large amounts of Fibers allow testing

  8. Textiles • The most common form of fiber transfer found at a crime scene: shredding of a textile • Clothing, carpets, upholstery • Constructed by weaving, or intertwining together • Yarns – fibers that have been “spun” together

  9. Fiber Classification • Natural Fibers • From animals, plants, and minerals that are minded from the ground • Synthetic Fibers (man-made) • Regenerated fibers and polymers. • Produced by joining many monomers together to form polymers

  10. Natural Fibers • Animal Fibers • Hair, fur, and webbing • All are made of proteins • Fur fibers • Good donor of fibers, but not a textile • Used primarily for coats and gloves

  11. Natural Fibers • Animal Fibers Cont’d • Hair fibers • Most popular animal fibers • Brushed out, shed, collected and clipped naturally from animals • Most common animal hair used in textile is Wool from sheep • Webbed Fibers • Silk, collected from cocoons of the caterpillar Bombyxmori • Because silk fiber are very long, they tend not to shed as easily as hair fibers

  12. Natural Fibers • Plant Fibers • Specialized plant cells • Grouped by which part of the plant they come from • Seeds, fruits, stems, and leaves • Fibers differ greatly in physical characteristics • Amorphous – loose arrangement of fibers that are soft, elastic, and absorbent. • All plant fibers contain Cellulose • Polymer the that is made up of simple glucose units • Cotton is the most common plant fiber

  13. Natural Fibers (plants) • Seed fibers • Cotton is found in the seedpod of the cotton plant. • Fruit fibers • Coir is a course fiber obtained fro the covering surrounding coconuts. • Individual cells of coir fibers are narrow, with thick walls made of cellulose; woven together are stronger than flax or cotton. • Relatively waterproof (doormats and baskets)

  14. Natural Fibers (plants) • Stem fibers • Hemp, jute, and flax are all produced from the thick region of plant stems. • Grow in bundles, can extend the entire length of a plant • Flax is most common stem fiber and is most commonly found in the textile linen. • Leaf fibers • The fiber bundles are taken from the surface of the leaves, and when bound together can reach long lengths. • Manila from abaca (relative of banana tree) • Sisal desert plant used to make ropes, nettings and twines

  15. Natural Fibers (plants) • Mineral fibers • Neither protein or cellulose. • Fiberglass fiber- form of glass where its fibers are very short, very weak, and brittle. • Asbestos – mineral naturally occurring in rocks with a crystalline structure composed of long, thin fibers. Very durable.

  16. Synthetic Fibers • Regenerated fibers • Derived from cellulose and are made mostly plant in origin. • Rayon is most common. • Cellulose chemically combined with acetate or 3 acetate units, form Celanese and polyamide nylon (Capron)

  17. Synthetic Fibers • Synthetic Polymer Fibers • Originate with petroleum products and are non-cellulose based. • 100% man-made • No definite shape or size and can be easily dyed.

  18. Synthetic Polymer Fibers • Polyester • Represents large group of fibers with a common chemical makeup • Polar fleece, wrinkle-resistant pants, and added to many natural fibers to provide additional strength. • Nylon • Similar to polyester, except is easily broken down by light and concentrated acid. • Acrylic • Often found in artificial wool or imitation fur; light fluffy feel • Olefins • High-performance clothing (thermals, socks, carpets) • Quick drying and resistant to wear

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