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Forensic Chemistry CHS 5542
Fibers, Hairs and Related Evidence
Background Information and Terminology
Module 5- Part 1Tatiana Trejos, PhD.
Professional Science Fonsic ScienceDepartment of Chemistry and BiochemistryInternational Forensic Research Institute
Florida International University
Forensic Fiber Examinations
Fiber examinations typically involves
both identification of the fiber type
and comparison of K/Q to determine if
there is an association or not
Introduction to Textile Fibers
What is a fiber?
• Natural or man made material that is the basic element of textiles
Natural Fibers
Animal•Silk
• Fibroin
•Wool• Keratin
•Hair Fibers• Keratin
Vegetable• Seed Fibers
Cotton, kapok, coir
• Bast (Stem) Fibers Flax, hemp
• Leaf Fibers Manila, sisal
Mineral• Asbestos
Animal (Protein) Fibers
• Protein• Greek word “proteios” meaning “first”
• Chain-like molecules • Union of α-amino acids joined with peptide
linkage
H
• H2N-C-COOH
R• Acidic and basic group attached to α-carbon atom
Silk
• Composed of fibroin• Very different to keratin
• Continuous filament• Transfer during contact is unlikely
Image source: http://micro.magnet.fsu.edu/primer/techniques/dic/dicgallery/images/wildsilkfiberssmall.jp
Wool
• Keratin• Staple fiber
• Scaled surface• Readily transferred
Wool
Epicuticle
Cortex
Endocuticle
Exocuticle
Cuticular scales
Hair Fibers (animal)
• Goat Family• Mohair (Angora goat – Capra hircus
aegagrus)• Cashmere (Asiatic goat – Capra hircus
laniger)
• Camel Family• Dromedary Camel – (Camelus bactrianus) • Alpaca – (Lama Pacos)• Vicuna – Undercoat hair (similar in all
ways to cashmere)
• Fur Bearing Animals• Angora Rabbit
Vegetable Fibers
• Categorized by the section of the plant from which they are harvested• Seed• Bast (Stem)• Leaf
• Chemical composition dependent on source
Vegetable Fiber Principal Constituents
• Cellulose• Hemi-Cellulose• Lignin• Pectins
Seed Fibers
• Cotton – genus Gossypium• Produces flower, which falls off leaving
boll (pod)• Boll contains seeds with immature
fibers attached• As the fibers mature, the boll expands
and breaks open
• Kapok – Ceiba petrandra • Unsuitable for yarns, formally used as
filling
• Coir• Outer husk of coconut• Mostly used in twine
Stem (Bast) Fibers
• Flax (linen) – Linun usitatissimum• Over 6,000 years old
• Ramie – Boehermeria nivea• Tablecloths
• Hemp – Cannabis sativa• The term “hemp” is used to describe other
fibers• Jute – Corchorus capsularis
• Ropes and cordage
Leaf Fibers
• Sisal – Agave sisalana• Ropes, cordage
• Abaca (Manila Hemp) – Musa textilus• Better quality ropes and cordage
Mineral Fibers
• Asbestos (Greek for incombustible)• Chrysotile - very fine fibers (25 nm diameter)
Man-Made Fibers
• Refers to fibers that were manufactured
• Synthetic fibers are those made from synthesized polymers• Bi-products of the petroleum industry
• Regenerated fibers are those made from regenerating naturally occurring polymers and forming the fiber with that material• Cellulose
Common Man-Made fibers
• Nylon• Polyester• Acrylic• Polypropylene• Cellulosic
• Rayon• Acetate
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