Forensic Science Study Guide Chapter 6 Fibers Name:_________________ 1. Why are fibers considered class evidence? They can’t be traced back to an individual. 2. Fabric is made of __fibers___________. Fibers are made of twisted ___filaments________. 3. What are the 2 type of fibers and fabric? Natural, artificial 4. Name 6 types of synthetic fibers: Rayon,Nylon, Acetate, Acrylic, Spandex, Polyester 5. Name 5 types of natural fibers: Silk, cotton, wool, Mohair, Cashmere 6. Natural fibers are classified according to their __origin__________: a. Vegetable or cellulose b. Animal or protein c. Mineral 7. Cellulose fibers: Cotton—vegetable fiber; strong, tough, flexible, moisture-absorbent, not shape-retentive Rayon—chemically altered cellulose; soft, lustrous, versatile Cellulose acetate—cellulose that is chemically altered to create an entirely new compound not found in nature 8. Protein fibers: Wool—animal fiber coming most often from sheep, but may be goat (mohair), rabbit (angora), camel, alpaca, llama, or vicuña Forensic Science Study Guide Chapter 6 Fibers Name:_________________ Silk____________—insect fiber that is spun by a silkworm to make its cocoon; the fiber reflects light and has insulating properties 9. Mineral Fibers: a. Asbestos—a natural fiber that has been used in fire-resistant substances b. Rock wool—a manufactured mineral fiber c. Fiberglass—a manufactured inorganic fiber 10. Synthetic Fibers : Made from derivatives of petroleum, coal, and natural gas. 11. a. Nylon—most durable of man-made fibers; extremely lightweight b. Polyester—most widely used man-made fiber c. Acrylic—provides warmth from a lightweight, soft, and resilient fiber d. Spandex—extreme elastic properties 12. Weave terminology: Yarn—a continuous strand of fibers 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 fibers 13. Weave Patterns: a. Plain Forensic Science Study Guide Chapter 6 Fibers Name:_________________ b. Satin c. Twill 14. Which weave is the most common pattern? Plain weave 15. Which design resembles a stair steps? Twill 16. Denim is an example of what weave pattern? Twill 17. In which weave pattern does the warp yarn is pass over one to three weft yarns before going under One? Twill 18. ____Knitting____________ are made by interlocking loops into a specific arrangement. It may be continuous thread or a combination. Forensic Science Study Guide Chapter 6 Fibers Name:_________________ 19. Synthetic fibers are made of polymers, which are long chains of repeating chemical units. 20. The word __polymer_______ means many units. 21. Filament Cross Sections: R ound 4- Octalobal T rilobal Irregular Dogbone or Multi- Dumbbell or 21. 22. Testing for identification: a. Density____________________—the mass of an object divided by the volume of the object b. Refractive index—measurement of the bending of light as it passes from air into a solid or liquid c. Fluorescence—absorption and reemission of light; used for comparing fibers as well as spotting fibers for collection Forensic Science Study Guide Chapter 6 Fibers Name:_________________ 23. There are more than 7,000_________________ different dye formulations. 24. Chromatography is used to separate dyes for comparative analysis. 25. Collection of fiber evidence: Bag clothing items individually in paper bags. Make sure that different items are, are not placed on the same surface before being bagged. Make tape lifts of exposed skin areas and any inanimate objects. Removed fibers should be folded into a small sheet of paper and stored in a paper bag. 26. Wayne Williams was convicted in 1982 based on ___carpet Fibers______________ that were found in his home, in his car, and on several murder victims. .