Transcript Fiber Analysis

Drill
• How are natural fibers different from
synthetic fibers?
• What is the most common types of natural
fibers?
Fiber Analysis
Chapter 4 A Study of
Fibers and Textiles
• identify and describe common weave
patterns of textile samples
• compare and contrast various types of
fibers through physical and chemical
analysis
• describe principle characteristics used to
identify common fibers
• apply forensic science techniques to
analyze fibers
Natural Fibers
• ______________ are the plant fibers most
______________ used in textile materials.
• Type of cotton, _________ and degree of
_________ contributes to the diversity of
these fibers.
• Processing techniques and color
applications also influence the value of
cotton fiber identification.
Natural Fibers
• Other plant fibers used in the production of
textile materials include ______, _____
and _____.
• The animal fiber most frequently used is
________, typically from sheep.
• ____________ of fiber determined by
usage in final fabric application.
Fiber Classification
—Natural Fibers
_________ fibers (made of proteins):
• Wool from ______, cashmere and mohair
from ______, angora from ______, and
hair from alpacas, llamas, and camels are
commonly used in textiles.
• Shimmering silk from caterpillar
_________ is longer and not as easily
shed.
Classification
—Natural
Fibers
Plant fibers
(made of the polymer cellulose):
• can ________ water.
• are __________ in water.
• are very ___________ to damage from
harsh chemicals.
• can only be _________ by strong ______.
• can be ___________ at crime scenes
because they become ________ over
time.
Fiber Classification
—Natural Fibers
Plant fibers:
• Cotton from _________ is the plant fiber most
commonly used in textiles (shown above).
• _______ from ________ is durable.
• Hemp, jute, and flax from stems grow in
bundles.
• __________ and sisal from leaves deteriorate
more quickly.
Mineral Fibers:
• __________ is a fibrous form of glass.
• __________ is a naturally occurring mineral
with a crystalline structure.
Fiber Classification
—Synthetic (artificially
produced) Fibers
Until the nineteenth century only plant and
animal fibers were used to make clothes
and textiles.
__________ the products produced today
are artificially produced.
Artificially produced fibers include ______,
________, _________, _________, and
____________.
Blue Cotton (denim)
Orange Cotton
Flax and Wool
Fiber Classification
—Synthetic (artificially
produced) Fibers
Regenerated Fibers (derived from cellulose):
•
__________ is the most common of this
type of fiber. It can imitate natural fibers,
but it is __________.
• __________is cellulose chemically
combined with __________ and is often
found in carpets.
• ____________ nylon is cellulose
combined with three acetate units, is
breathable, lightweight, and used in
performance clothing.
Fiber Classification
—Synthetic (artificially
produced)
Fibers
Synthetic Polymer Fibers:
___________ is the basis for these fibers, and they
have very different characteristics from other fibers.
____________ in large vats are joined together to form
polymers. The fibers produced are spun together into
yarns.
They have no ____________ structures, and under
magnification they show regular diameters.
Fiber Classification—Synthetic
(artificially produced) Fibers
Examples of synthetic polymer fibers: spandex
nylon
• _________—found in “polar fleece,” wrinkle-
resistant, and not easily broken down by light or
concentrated acid; added to natural fibers for
strength.
• __________—easily broken down by light and
concentrated acid; otherwise similar to polyester.
• ___________—inexpensive, tends to “ball”
easily, and used as an artificial wool or fur.
• ___________—high performance, quick drying,
and resistant to wear.
Green Polyester
Red Polyester
Man-made Fibers
• The shape of a ___________ fiber can
determine the value placed on that fiber.
• Cross section of a man-made fiber can be
manufacturer-__________.
• Some ___________ are more common
than others, and some shapes may only
be produced for a ________ of time.
Man-made Fibers
Comparison of Natural and
Synthetic Fibers
Visual Diagnostics of Some Common Textile Fibers
under Magnification
Yarns, fabrics, and textiles
• Fibers can be twisted (spun) into ______ of any
length, thick or thin, loose, or tight. A blend can be
made to meet different needs such as resistance
to __________.
• Fibers can be woven into ________ or ________.
– Threads are arranged side by side (the _______).
– More threads (the _____) then are woven back
and forth crosswise in one of a number of
different patterns through the warp.
Yarns, fabrics, and textiles
Weave Patterns
Man-made Fibers
• More than ______ of all fibers used in
textile manufacturing are man-made.
• ___________ and ________ fibers are the
most _________encountered man-made
fibers, followed by __________,
_________ and __________.
Sampling and Testing
•
Weaving spun fibers (yarns) together
produces clothing and many textiles.
• ___________ from an article of clothing
or a textile is the most _________ form of
fiber transfer.
• Natural fibers require only an _______
microscope to find characteristic _______
and _________.
• ___________________ can reveal
something of the chemical structure of
other fibers that, otherwise, may look very
much alike.
Sampling
and Testing
• If a large quantity of fibers is found, some
can be subjected to ________ tests such
as burning them in a flame (see analysis
key above) or ___________ them in
various liquids.
• Crimes can be solved in this way by
___________ fibers found on different
suspects with those found at the crime
scene.
. . . . . . . . . . . . . . . . . Summary
• Fibers are spun into yarns having specific
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characteristics.
Yarns are woven, with different patterns, into
clothing or textiles.
Fibers, trace evidence, are a form of class
evidence used by crime scene investigators.
Fiber evidence may be gathered using different
techniques.
Fibers may be analyzed using burn tests, tests
for solubility in different solutions, polarized light
microscopy, or infrared spectroscopy.