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Fibers

Fibers. Catalyst 1 /7/ 13. Take the next 5-7 minutes to put your presentation together. Save each KeyNote file as LastName.FiberType ” (For example, if your last name is Rodriguez, your file should be saved as Rodriguez.FiberType )

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Fibers

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  1. Fibers

  2. Catalyst 1/7/13 Take the next 5-7 minutes to put your presentation together. • Save each KeyNote file as LastName.FiberType” (For example, if your last name is Rodriguez, your file should be saved as Rodriguez.FiberType) 2. Email ALL KeyNote files as POWERPOINT FILES to gutierrezbr@elizabeth.k12.nj.us. (No dongle so you must email it to me.) 3. When time is called, you must be ready to go or points will be deducted.

  3. Agenda 1/7/13 • Catalyst • Announcements • Extra Credit Opportunity: Create review poster of Hair chapter (more details to be posted on Edmodo) • HW: Answer the first 10 questions of Chapter 6 checkpoint questions. DO NOT COPY FROM EACH OTHER. Answers must be unique or no credit will be given, DUE WEDNESDAY, 1/9/13/. • Fiber Types Presentations

  4. Fiber Types Presentations Evaluation Criteria • Organization of presentation • Clarity of information • Ability to discuss questions • Met all criteria described in original instructions (physical properties, chemical structure, special properties, etc.) • Proper Citation of References

  5. Written Response Expectations • Be specific. • Avoid using the word “things” – what things are you referring to? Hair? Fibers? Fingerprints? • Never start off with the phrase “in my opinion” • Write in complete sentences (with a subject and predicate) • When asked how a piece of evidence can be useful, describe in detail what exactly the investigator is going to do and what he/she is going to look for.

  6. Class Points P8: 7 (on task) Your class can earn class points if: everyonein class: • Comes to class quietly and on time • Stays focused and on task during class • Leaves classroom neat and organized • Students are teaching other students • Majority of class participates • Follows all classroom expectations and procedures • And more…

  7. Fibers Case Study • Fibers -- Atlanta Murders (1979-1981)Over a two-year period, 29 young African Americans were found strangled and smothered in Atlanta, Ga. Eventually, a police stakeout identified a suspect, Wayne Williams, who had a suspicious explanation for why he was on a bridge not far from where a body was found two days later. Lacking witnesses, forensic investigators built a case against Williams that was based almost entirely upon fiber and statistical evidence. Working with chemists from textile maker DuPont, they linked a fiber found in one victim’s hair to an unusual make of carpet in Williams' home, and calculated that the odds of the victim coming in contact with it in the Atlanta area were 1 in 7,792. A fragment of rayon found on another victim’s shorts was consistent with the carpeting in Williams’ station wagon, a match that had a 1-in-3,828 chance of occurring in Atlanta. Either piece of evidence left room for reasonable doubt, but the probability of both happening by coincidence was 1 in 29,827,776. Fiber evidence from other victims drove the odds up into the trillions. It took a jury less than 12 hours of deliberation to find Williams guilty, and he is now serving two life terms.

  8. Overview of Fiber Analysis Unit • Chemical and physical structure and properties of fibers✔ • Polymers✔ • Classifying Fibers • Weave Patterns✔ • Chemical structures of various fibers✔ • Identifying Fibers • Analysis of physical characteristics • Chemical tests

  9. Objective(s) 12/18/12 • Explain why fibers are class evidence. • Distinguish and identify different types of fibers.

  10. Fibers • Considered as class evidence (WHY?) • Have probative value (WHY?) • Are common trace evidence at a crime scene • Can be characterized based on comparison of both physical and chemical properties Kendall/Hunt Publishing Company

  11. Fabric Fabric is made of fibers. Fibersare made of twisted filaments. Types of fibers and fabric: Kendall/Hunt Publishing Company

  12. Synthetic Rayon Nylon Acetate Acrylic Spandex Polyester Natural Silk Cotton Wool Mohair Cashmere Types of Fibers Kendall/Hunt Publishing Company

  13. Polymers • Synthetic fibers are made of polymers, which are long chains of repeating chemical units. • The word polymer means many (poly) units (mer). • The repeating units of a polymer are called monomers. Kendall/Hunt Publishing Company

  14. Fiber Polymers • Amino acids – composed of a carboxyl group and amino group • Amino acids chemically combine to form polypeptides

  15. Polyester Synthesis – Polymerization Reaction

  16. Polymer

  17. Forensics Fiber Analysis • 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 forensically.

  18. Objective We will be able to: • Analyze weave patterns • Compare and contrast the chemical structures of different types of fibers • Explain how the chemical structure of a fiber affects its properties

  19. Basic Chemistry (Chemistry is EVERYWHERE. Stop the groaning and get over it.) • Organic chemistry deals with carbon-containing compounds • Carbon can form ______ bonds • Most atoms want ______ valence electrons • Chemical reactions occur because _________. • Electronegativity is how attractive an atom is to electrons in a chemical bond. COPY THIS.

  20. Classification Natural fibers are classified according to their origin: Vegetable or cellulose Animal or protein Mineral Kendall/Hunt Publishing Company

  21. 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 Kendall/Hunt Publishing Company

  22. Fiber Comparison Can you describe the difference(s) between the cotton on the left and the rayon on the right? Kendall/Hunt Publishing Company

  23. Protein Fibers Wool—animal fiber coming most often from sheep, but may be goat (mohair), rabbit (angora), camel, alpaca, llama, or vicuña Silk—insect fiber that is spun by a silkworm to make its cocoon; the fiber reflects light and has insulating properties Kendall/Hunt Publishing Company

  24. Mineral Fibers Asbestos—a natural fiber that has been used in fire-resistant substances Rock wool—a manufactured mineral fiber Fiberglass—a manufactured inorganic fiber Kendall/Hunt Publishing Company

  25. Synthetic FibersMade from derivatives of petroleum, coal, and natural gas Nylon—most durable of man-made fibers; extremely lightweight Polyester—most widely used man-made fiber Acrylic—provides warmth from a lightweight, soft, and resilient fiber Spandex—extreme elastic properties Kendall/Hunt Publishing Company

  26. Fabric Production Fabrics are composed of individual threads or yarns that are made of fibers and are knitted, woven, bonded, crocheted, felted, knotted, or laminated. Most are either woven or knitted. The degree of stretch, absorbency, water repellence, softness, and durability are all individual qualities of the different fabrics. Kendall/Hunt Publishing Company

  27. Weave Terminology

  28. Weave Pattern Notes • Create a table in your notebook that looks like the one below.

  29. Weave Patterns Kendall/Hunt Publishing Company

  30. Plain Weave • Simplest and most common • The warp and weft yarns pass under each other alternately • Looks like a checkerboard Kendall/Hunt Publishing Company

  31. Twill Weave • The warp yarn is passed over one to three weft yarns before going under one. • Makes a diagonal weave pattern. • Design resembles stair steps. • Denim is one of the most common examples. Kendall/Hunt Publishing Company

  32. Satin Weave • The yarn interlacing is not uniform • Creates long floats • Interlacing weave passes over four or more yarns • Satin is the most obvious example Kendall/Hunt Publishing Company

  33. Knitted Fabric • made by interlocking loops into a specific arrangement. • formed into successive rows of loops and then drawn through another series of loops to make the fabric. Kendall/Hunt Publishing Company

  34. Round ] 4-lobed Octalobal Trilobal Irregular Dogbone or Multi-lobed Dumbbell or Serrate 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.

  35. Fiber, fiber, fiber • You will be assigned a type of fiber. Research the following: • The chemical structure of that fiber • The physical properties of that fiber • Other special properties of that fiber • How to differentiate that fiber from others • You will take the information you have researched and create a KeyNote slide(s) • Include images/diagrams where appropriate • Use concise language and avoid using excessive text (DO NOT JUST COPY AND PASTE) • Cite your reference(s) using MLA format

  36. Fiber Types Presentations Evaluation Criteria • Organization of presentation • Clarity of information • Ability to discuss questions • Met all criteria described in original instructions (physical properties, chemical structure, special properties, etc.) • Proper Citation of References

  37. Group assignments

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