Fibers
Catalyst 1/7/13
Take the next 5-7 minutes to put your presentation
together.
1. Save each KeyNote file as LastName.FiberType”
(For example, if your last name is Rodriguez, your file
should be saved as Rodriguez.FiberType)
2. Email ALL KeyNote files as POWERPOINT FILES to
gutierrezbr@elizabeth.k12.nj.us. (No dongle so you must
email it to me.)
3. When time is called, you must be ready to go or points
will be deducted.
Agenda 1/7/13
• Catalyst
• Announcements
– Extra Credit Opportunity: Create review poster
of Hair chapter (more details to be posted on
Edmodo)
– HW: Answer the first 10 questions of Chapter 6
checkpoint questions. DO NOT COPY FROM
EACH OTHER. Answers must be unique or no
credit will be given, DUE WEDNESDAY, 1/9/13/.
• Fiber Types Presentations
Fiber Types Presentations Evaluation
Criteria
•
•
•
•
Organization of presentation
Clarity of information
Ability to discuss questions
Met all criteria described in original instructions
(physical properties, chemical structure, special
properties, etc.)
• Proper Citation of References
Written Response Expectations
• Be specific.
– Avoid using the word “things” – what things are
you referring to? Hair? Fibers? Fingerprints?
• Never start off with the phrase “in my opinion”
• Write in complete sentences (with a subject and
predicate)
• When asked how a piece of evidence can be
useful, describe in detail what exactly the
investigator is going to do and what he/she is going
to look for.
Class Points
Your class can earn class points if:
everyone in class:
 Comes to class quietly and on
time
 Stays focused and on task during
class
 Leaves classroom neat and
organized
 Students are teaching other
students
 Majority of class participates
 Follows all classroom
expectations and procedures
 And more…
P8: 7
(on task)
Fibers Case Study
• Fibers -- Atlanta Murders (1979-1981)
Over a two-year period, 29 young African Americans were found strangled
and smothered in Atlanta, Ga. Eventually, a police stakeout identified a
suspect, Wayne Williams, who had a suspicious explanation for why he
was on a bridge not far from where a body was found two days later.
Lacking witnesses, forensic investigators built a case against Williams that
was based almost entirely upon fiber and statistical evidence. Working
with chemists from textile maker DuPont, they linked a fiber found in one
victim’s hair to an unusual make of carpet in Williams' home, and
calculated that the odds of the victim coming in contact with it in the
Atlanta area were 1 in 7,792. A fragment of rayon found on another
victim’s shorts was consistent with the carpeting in Williams’ station
wagon, a match that had a 1-in-3,828 chance of occurring in Atlanta.
Either piece of evidence left room for reasonable doubt, but the
probability of both happening by coincidence was 1 in 29,827,776. Fiber
evidence from other victims drove the odds up into the trillions. It took a
jury less than 12 hours of deliberation to find Williams guilty, and he is
now serving two life terms.
Overview of Fiber Analysis Unit
• Chemical and physical structure and properties of
fibers✔
– Polymers✔
• Classifying Fibers
– Weave Patterns✔
– Chemical structures of various fibers✔
• Identifying Fibers
– Analysis of physical characteristics
– Chemical tests
Objective(s) 12/18/12
• Explain why fibers are class evidence.
• Distinguish and identify different types of
fibers.
Fibers
• Considered as class evidence
(WHY?)
• Have probative value (WHY?)
• Are common trace evidence at
a crime scene
• Can be characterized based on
comparison of both physical
and chemical properties
Kendall/Hunt Publishing Company
10
Fabric
Fabric is made of fibers.
Fibers are made of twisted
filaments.
Types of fibers and fabric:
Natural
• animal
• vegetable
• inorganic
Artificial
• Synthesized
• created from altered
natural sources
(rayon)
Kendall/Hunt Publishing Company
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Types of Fibers
Synthetic
Natural
Rayon
Silk
Nylon
Cotton
Acetate
Wool
Acrylic
Mohair
Spandex
Cashmere
Polyester
Kendall/Hunt Publishing Company
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Polymers
• Synthetic fibers are made of polymers, which
are long chains of repeating chemical units.
• The word polymer means many (poly) units
(mer).
• The repeating units of a polymer are called
monomers.
Kendall/Hunt Publishing Company
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Fiber Polymers
• Amino acids – composed of a carboxyl group and
amino group
• Amino acids chemically combine to form
polypeptides
Polyester Synthesis – Polymerization
Reaction
Polymer
Forensics Fiber Analysis
• By varying the chemical structure of the
monomers or by varying the way they are
joined together, polymers are created that
have different properties.
• As a result of these differences, they can be
distinguished from one another forensically.
Objective
We will be able to:
• Analyze weave patterns
• Compare and contrast the chemical structures of
different types of fibers
• Explain how the chemical structure of a fiber affects
its properties
Basic Chemistry (Chemistry is
EVERYWHERE. Stop the groaning and get
over it.)
• Organic chemistry deals with carbon-containing
compounds
• Carbon can form ______ bonds
• Most atoms want ______ valence electrons
• Chemical reactions occur because _________.
• Electronegativity is how attractive an atom is to
electrons in a chemical bond.
COPY THIS.
Classification
Natural fibers are
classified according to
their origin:
1.
Vegetable or cellulose
2.
Animal or protein
3.
Mineral
Kendall/Hunt Publishing Company
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Cellulose Fibers
Cotton—vegetable fiber;
strong, tough, flexible,
moisture-absorbent, not
shape-retentive
Rayon—chemically altered
cellulose; soft, lustrous,
versatile
Cellulose acetate—cellulose
that is chemically altered to
create an entirely new
compound not found in
Kendall/Hunt Publishing Company
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Fiber Comparison
Can you describe the difference(s) between the cotton on
the left and the rayon on the right?
Kendall/Hunt Publishing Company
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Protein Fibers
Wool—animal fiber
coming most often from
sheep, but may be goat
(mohair), rabbit (angora),
camel, alpaca, llama, or
vicuña
Silk—insect fiber that is
spun by a silkworm to
make its cocoon; the
fiber reflects light and
has insulating properties
Kendall/Hunt Publishing Company
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Mineral Fibers
Asbestos—a natural fiber that has been used
in fire-resistant substances
Rock wool—a manufactured mineral fiber
Fiberglass—a manufactured inorganic fiber
Kendall/Hunt Publishing Company
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Synthetic Fibers
Made from derivatives of petroleum, coal,
and natural gas
Nylon—most durable of man-made fibers;
extremely lightweight
Polyester—most widely used man-made
fiber
Acrylic—provides warmth from a lightweight,
soft, and resilient fiber
Spandex—extreme elastic properties
Kendall/Hunt Publishing Company
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Fabric Production
Fabrics are composed of individual threads or
yarns that are made of fibers and are knitted,
woven, bonded, crocheted, felted, knotted, or
laminated. Most are either woven or knitted. The
degree of stretch, absorbency, water repellence,
softness, and durability are all individual
qualities of the different fabrics.
Kendall/Hunt Publishing Company
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Weave Terminology
Weave Pattern Notes
• Create a table in your notebook that looks like
the one below.
Plain
Twill
Satin
Weave Patterns
Kendall/Hunt Publishing Company
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Plain Weave
• Simplest and most
common
• The warp and weft yarns
pass under each other
alternately
• Looks like a
checkerboard
Kendall/Hunt Publishing Company
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Twill Weave
• The warp yarn is passed
over one to three weft
yarns before going
under one.
• Makes a diagonal
weave pattern.
• Design resembles stair
steps.
• Denim is one of the
most common
examples.
Kendall/Hunt Publishing Company
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Satin Weave
• The yarn interlacing is not
uniform
• Creates long floats
• Interlacing weave passes
over four or more yarns
• Satin is the most obvious
example
Kendall/Hunt Publishing Company
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Knitted Fabric
• made by interlocking
loops into a specific
arrangement.
• formed into successive
rows of loops and then
drawn through another
series of loops to make
the fabric.
Kendall/Hunt Publishing Company
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Filament Cross Sections
Round
]
4-lobed
Octalobal
Trilobal
Irregular
Dogbone or
Multi-lobed
Dumbbell
or Serrate
Synthetic fibers are forced out of a nozzle when they
are hot, and then they are woven. The holes of the
nozzle are not necessarily round; therefore, the fiber
filament may have a unique shape in cross section. 37
Fiber, fiber, fiber
• You will be assigned a type of fiber. Research the
following:
– The chemical structure of that fiber
– The physical properties of that fiber
– Other special properties of that fiber
– How to differentiate that fiber from others
• You will take the information you have researched and
create a KeyNote slide(s)
– Include images/diagrams where appropriate
– Use concise language and avoid using excessive text
(DO NOT JUST COPY AND PASTE)
– Cite your reference(s) using MLA format
Fiber Types Presentations Evaluation
Criteria
•
•
•
•
Organization of presentation
Clarity of information
Ability to discuss questions
Met all criteria described in original instructions
(physical properties, chemical structure, special
properties, etc.)
• Proper Citation of References
Group assignments
Type of Fiber
Person 1
Person 2
Wool
Amanda
Allan
Nylon
Sara
Brian
Cotton
Tania
Lissette
Rayon
Omar
Rood
Acetate
Jessica
Stephanie
Silk
Natalie
Steven
Polyester
Abigail
Brandon
Acrylic
Christopher