General Types of fabric
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This document discusses different types of fibers, including natural fibers like cotton, silk, and wool, and synthetic fibers like nylon, polyester, and acrylic. It describes how fibers are classified based on their origin as vegetable, animal, or mineral. The document also discusses how fabrics are produced through weaving or knitting, and the different weave patterns like plain, twill, and satin weaves. It provides details on how synthetic fibers are made from polymers and how their properties can be distinguished forensically.
General Types of fabric
- 1. Prof.Dr/ Hala Fawzy By : Mahmoud Galal Zidan
- 2. Fibers Are considered class evidence Have probative value Are common trace evidence at a crime scene Can be characterized based on comparison of both physical and chemical properties 2 By:MahmoudGalalZidan
- 3. Vegetable Inorganic Animal Plants Nature created from altered natural sources synthesize Artificial Types of fibers and fabric: 3 By:MahmoudGalalZidan
- 5. Classification Natural fibers are classified according to their origin: Vegetable or cellulose Animal or protein Mineral 5 By:MahmoudGalalZidan
- 6. 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 . Fiber Comparison Can you describe the difference(s) between the cotton on the left and the rayon on the right? 6 By:MahmoudGalalZidan
- 7. 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 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 7 By:MahmoudGalalZidan
- 8. Synthetic Fibers Made from derivativesof petroleum,coal, and naturalgas 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 8 8 By:MahmoudGalalZidan
- 9. 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. 9 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 9 By:MahmoudGalalZidan
- 10. Weave Patterns Plain Weave The simplest and most common weave pattern The warp and weft yarns pass under each other alternately Design resembles a checkerboard 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. 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 10 By:MahmoudGalalZidan
- 11. 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 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. 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. 11 By:MahmoudGalalZidan
- 12. Round 4-lobed Octalobal Irregular Multi-lobed or Serrate Trilobal Dogbone or Dumbbell Filament Cross Sections 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 . 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. 12 By:MahmoudGalalZidan
- 13. Dyes 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. 13 13 By:MahmoudGalalZidan