Download Fibers and Textiles

Objectives
0 Identify and describe common patterns of textile
samples
0 Compare and contrast various types of fibers through
physical and chemical analysis
0 Describe principal characteristics of common fibers
used in their identification
0 Apply forensic science techniques to analyze fibers
Introduction
0 Fibers are used in Forensic Science to create a link
between crime and suspect.
0 Fibers are a form of Trace Evidence.
0 Direct transfer is when a fiber is transferred from
victim to suspect or vice versa.
0 Secondary transfer is a fiber that was picked up and
then transferred to a suspect, or from original source
to the suspect then to the victim.
How FS use Fibers
0 Evidence of any kind should be evaluated, especially
fibers because there are so many of them in each
environment.
0 Their value depends on their uniqueness
0 White cotton fiber vs. angora fiber
Uses of Fibers
0 Type of Fibers
0 Fiber Color
0 Number of Fibers Found
0 Where Fiber was Found
0 Textile the fiber originated from
Uses of Fibers
0 Multiple Fiber Transfers
0 Type of crime committed
0 Time between crime and discovery of fiber
Sampling and Testing
0 Fibers are gathered with special vacuums, sticky tape,
and forceps.
0 First task is to identify the fibers type and its
characteristics
0 Shape and color
0 Polarized light
microscopy
0 Infrared
Spectroscopy
0 Large amounts of
Fibers allow testing
Textiles
0 The most common form
of fiber transfer found at
a crime scene: shredding
of a textile
0 Clothing, carpets,
upholstery
0 Constructed by weaving,
or intertwining together
0 Yarns – fibers that have
been “spun” together
Fiber Classification
0 Natural Fibers
0 From animals, plants, and
minerals that are minded
from the ground
0 Synthetic Fibers (man-
made)
0 Regenerated fibers and
polymers.
0 Produced by joining many
monomers together to form
polymers
Natural Fibers
0 Animal Fibers
0 Hair, fur, and webbing
0 All are made of proteins
0 Fur fibers
0 Good donor of fibers, but not a textile
0 Used primarily for coats and gloves
Natural Fibers
0 Animal Fibers Cont’d
0 Hair fibers
0 Most popular animal fibers
0 Brushed out, shed, collected and clipped
naturally from animals
0 Most common animal hair used in textile
is Wool from sheep
0 Webbed Fibers
0 Silk, collected from cocoons of the
caterpillar Bombyx mori
0 Because silk fiber are very long, they
tend not to shed as easily as hair fibers
Natural Fibers
0 Plant Fibers
0 Specialized plant cells
0 Grouped by which part of the plant
they come from
0 Seeds, fruits, stems, and leaves
0 Fibers differ greatly in physical
characteristics
0 Amorphous – loose arrangement of
fibers that are soft, elastic, and
absorbent.
0 All plant fibers contain Cellulose
0 Polymer the that is made up of simple
glucose units
0 Cotton is the most common plant fiber
Natural Fibers (plants)
0 Seed fibers
0 Cotton is found in the seedpod
of the cotton plant.
0 Fruit fibers
0 Coir is a course fiber obtained
fro the covering surrounding
coconuts.
0 Individual cells of coir fibers are
narrow, with thick walls made of
cellulose; woven together are
stronger than flax or cotton.
0 Relatively waterproof (doormats
and baskets)
Natural Fibers (plants)
0 Stem fibers
0 Hemp, jute, and flax are all produced
from the thick region of plant stems.
0 Grow in bundles, can extend the entire
length of a plant
0 Flax is most common stem fiber and is
most commonly found in the textile
linen.
0 Leaf fibers
0 The fiber bundles are taken from the
surface of the leaves, and when bound
together can reach long lengths.
0 Manila from abaca (relative of banana
tree)
0 Sisal desert plant used to make ropes,
nettings and twines
Natural Fibers (plants)
0 Mineral fibers
0 Neither protein or cellulose.
0 Fiberglass fiber- form of glass
where its fibers are very short, very
weak, and brittle.
0 Asbestos – mineral naturally
occurring in rocks with a
crystalline structure composed of
long, thin fibers. Very durable.
Synthetic Fibers
0 Regenerated fibers
0 Derived from cellulose and are made mostly plant in
origin.
0 Rayon is most common.
0 Cellulose chemically combined with acetate or 3 acetate
units, form Celanese and polyamide nylon (Capron)
Synthetic Fibers
0 Synthetic Polymer Fibers
0 Originate with petroleum
products and are non-cellulose
based.
0 100% man-made
0 No definite shape or size and
can be easily dyed.
Synthetic Polymer Fibers
0 Polyester
0 Represents large group of fibers
with a common chemical
makeup
0 Polar fleece, wrinkle-resistant
pants, and added to many
natural fibers to provide
additional strength.
0 Nylon
0 Similar to polyester, except is
easily broken down by light and
concentrated acid.
0 Acrylic
0 Often found in artificial wool or
imitation fur; light fluffy feel
0 Olefins
0 High-performance clothing
(thermals, socks, carpets)
0 Quick drying and resistant to
wear