Chapter 4

Fiber Examination

Fibers can be classified as:

1. Natural fibers – derived from

animal or plant sources

2. Man-made fibers –

chemically produced

Fibers may be classified as to

structure:

• One type of fiber – polymeric –

cotton

• Blends – heteropolymeric – two or

more polymers blended

• Co-polymeric – differing, natural

polymers - wool & silk

Natural Animal Fibers

• Hair from sheep (wool), goats (mohair, cashmere), camels, llamas, alpacas and vicunas

• Fur from mink, rabbit, beaver or muskrat

• Can be examined and

identified microscopically

Natural Plant Fibers

Cotton is the most common

appearing having a ribbon-like

shape with twisted fibers

Man-made Fibers• Rayon introduced in 1911

• Nylon made in 1939

• Generic families of fibers

include:

Dacron

Fortrel

Kodel

Regenerated Fibers

• The first man-made products

were produced from cellulose

wood fibers and cotton

• These include rayon,

acetate and triacetate

Synthetic Fibers

• Are produced solely from

chemicals

• Include nylons, polyesters

and acrylics

• Are often polymers

(macromolecules) in long

chains

Fiber Analysis

Pass light through synthetic fibers emerges polarized and produces a specific refractive index which can be compared to known standards

Some collected fibers• Notice the similarities &

differences

Silk Fibers

Fibers- beautiful & easy to photograph

Study weave patterns

Fiber Count

Linen Lycra

Viewer

Microscope

Weave

Patterns

Blue shirt comparison

Jeans comparison

Burn

Testing

of

Fibers

Fiber Testing - Ignite fibers 1 a. fiber melts b. fiber does not melt shrinks away, melts, very hot ignites readily, burns like paper 2 3

a. no smoke b. black smoke c. white smoke a. ignites quickly b. ignites slowly acrid smell sweet smell burned plastic smell steady flame fibers closest to hard ash, residue round ash very brittle irregular, hard, shiny bead difficult to identify crumbles melts & burns at same time hard to extinguish nylon a. burning hair smell b. no smell (polyamide no cellulose, animal fibers cellulose, plant fibers

from petroleum) 5 6 linen acrylic polyester (natural gas and (coal & petroleum) petroleum)

a. blue flame b. no flame a. yellow flame b. non-yellow brittle black steady flame

residue hard to keep burning hard or gummy bead

silk wool

(worm (hair

cocoon) with oils)

cotton b. non-drips

fabric can be blown out slight ash fine, light gray ash

plant a. drips flickering flame hard to extinguish

acetate rayon (wood fibers) (wood fibers

& cotton)

4

Other Tests on Fibers

• Seizing – scrape off starch

• Mercerization & tensile strength

• Microscopic examination & comparison

• Acetate – dissolve in acetone

• Fiber Etch® - dissolves cellulose

• Nitric acid – cotton, wool or blend?

• Boil & dissolve in KOH

• Protein – heat fiber in water, check for base