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Classification of fibers

Classification of fibers can be done by:  Type (Natural and manufactured)  Length (Short staple, long staple, continuous filament)  Size (Ultra fine, fine, regular, course)

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Forensic Science: Fundamentals & Investigations, Chapter 4

Fiber Classification —Natural Fibers 3

Animal fibers  (made of proteins): Wool from sheep, cashmere and mohair from goats, angora from rabbits, and hair from alpacas, llamas, and camels are commonly used in textiles.  Shimmering (shine) silk from caterpillar (worm) cocoons is longer and not as easily shed. – Triangular structure scatters light like a prism

Fiber Classification —Natural Fibers 4

Plant fibers (made of the polymer cellulose): – Seeds, fruits, stems & leaves    can absorb water are insoluble in water are very resistant to damage from harsh chemicals   can only be dissolved by strong acids can be common at crime scenes because they become brittle over time

5 Fiber Classification —Natural Fibers

Plant fibers :  Cotton from seedpods is the plant fiber most commonly used in textiles (shown above). – Can be woven & dyed easily  Coir from coconuts is durable.

 – Hemp, jute, and flax from stems grow in bundles. Flax is the most common, found in linen  – Manila and sisal from leaves deteriorate more quickly.

Manila is from abaca leaves, related to the banana tree

Cotton

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Many cottons are also blended with other natural fibers, such as linen , for particular properties       Cellulosic fiber From “bolls” (seed pods) growing on bushes Comfortable Soft and durable Porous or leaky, cool to wear “Environmentally friendly” cotton can be grown in a range of colors

Flax (Linen) (Tisi)

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Flax is the fiber name; linen is the fabric name.      World’s oldest textile fiber Cellulosic fiber from stem of flax plant Stiff, wrinkles (folds) easily Absorbent (leaky), cool to wear in heat Other uses – – Dish towels Tablecloths

8 Fiber Classification —Natural Fibers

Mineral Fibers:  Fiberglass is a fibrous form of glass.  – – – Asbestos is a naturally occurring mineral with a crystalline structure.

Very durable Pipe coverings, brake linings, ceiling tiles, floor tiles, fire resistant work clothes, shingles, siding, insulation When it’s broken, fibers shatter into tiny fragments that become airborne. If inhaled, they cut the lungs and scar tissue may become cancerous.

9 Fiber Classification —Synthetic (artificially produced) Fibers

 Until the nineteenth century only plant and animal fibers were used to make clothes and textiles.  Half the products produced today are artificially produced. – Regenerated fibers or Polymers  Polymers are monomers joined together – Artificially produced fibers include rayon, acetate, nylon, acrylics, and polyesters.

Fiber Classification —Synthetic (artificially produced) Fibers 10

Regenerated Fibers (derived from cellulose):    Rayon is the most common of this type of fiber. It can imitate (duplicate) natural fibers, but it is stronger. Celenese ® is cellulose chemically combined with acetate and is often found in carpets. Polyamide nylon is cellulose combined with three acetate units, is breathable, lightweight, and used in performance clothing.

11 Fiber Classification —Synthetic (artificially produced) Fibers

   Synthetic Polymer Fibers : – Petroleum is the basis for these fibers, and they have very different characteristics from other fibers.

Non-cellulose Monomers in large vats are joined together to form polymers. The fibers produced are spun together into yarns. They have no internal structures, and under magnification they show regular diameters.

Fiber Classification—Synthetic

(artificially produced) Fibers

12 nylon Examples of synthetic polymer fibers:

   Polyester —found in “polar fleece,” wrinkle-resistant, and not easily broken down by light or concentrated acid; added to natural fibers for strength. Nylon —easily broken down by light and concentrated acid; otherwise similar to polyester. Acrylic —inexpensive, tends to “ball” easily, and used as an artificial wool or fur.  Olefins —high performance, quick drying, and resistant to wear.

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Natural & Synthetic Comparison

 Man-made fibers are not damaged by microorganisms like natural fibers  Man-made fibers can deteriorate in bright sunlight and melt at a lower temperature than natural fibers.

14 Comparison of Natural and Synthetic Fibers Visual Diagnostics of Some Common Textile Fibers under Magnification

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