forensics chapter 4- a study of fibers and textiles

amorphous

without a defined shape; fibers composed of a loose arrangement of polymers that are soft, elastic, and absorbing (for example, cotton)

crystalline

regularly shaped; fibers composed of polymers packed side by side, which make it stiff and strong (for example, flax)

direct transfer

the passing of evidence, such as a fiber, from victim to suspect or vice versa

fiber

the smallest indivisible unit of a textile, it must be at least 100 times longer than wide.

mineral fiber

a collection of mineral crystals formed into a recognizable pattern

monomer

a small molecule that may bond to other monomers to become a polymer

natural fiber

a fiber produced naturally and harvested from animal, plant, or mineral sources

polymer

a substance composed of long chains of repeating units

synthetic fiber

a fiber made from a man-made substance such as plastic

secondary transfer

the transfer of evidence such as a fiber from a source (for example, a carpet) to a person (suspect), and then to another person (victim)

a flexible, flat material made by interlacing yarns (or "threads")

textile

yarn

fibers that have been spun together

direct transfer says that

fibers may be transferred directly from victim to suspect or suspect to victim

secondary transfer says that

if a victim has fibers on his person that he picked up and then transferred to a suspect when fibers are transferred from the original source to a suspect and then to a victim

a forensic scientist will ask questions about the following

-type of fiber

-fiber color

-number of fibers found

-where the fiber was found

-textile the fiber originated from

-mult. fiber transfers

-type of crime committed

-time between crime and discovery of fiber

fiber evidence is gathered with

special vacuums, sticky tape, and forceps

two methods that can analyze fibers without damaging them are

polarizing light microscopy and infrared spectroscopy

______ are made up of fibers that have been ____ together.

yarns; spun

fibers are classified as either

natural fibers or synthetic fibers

the most common animal hair used in textiles is ____ from _____

wool; sheep

all produce natural plant fibers

seeds, fruits, stems, and leaves

all plant fibers share the common polymer which is...?

cellulose

a common seed fiber

cotton

the most common stem fiber

flax

flax is most commonly found in the textile ______

linen

a fiber form of glass

fiberglass

until the 19th century only ______ or _______ fibers were used to make clothing and textiles. Half of the fabrics produced today are _____________ __________ (______-_________)

plant; animal

synthetic fibers; man-made

the fibers are produced by

first joining many monomers together to form polymers

regenerated fibers (modified natural fibers) are derived from

cellulose and are mostly plant in origin

the most common type of regenerated fibers is

rayon

synthetic polymer fibers originate with ________ products and are _____________ fibers.

petroleum; cellulose based

has properties similar to polyester, except its easily broken down by light and concentrated acid

nylon

comparison of natural and synthetic fibers:

________ fibers can deteriorate in bright sunlight and melt at a lower temp than the ________ fibers.

man-made; natural

fibers are woven into ______ or _______.

textiles; fabrics

weave patterns have common names like:

tabby, twill, satin

the simplest weave pattern is the _______, or _________.

plain; tabby

thread count

number of threads that are packed together for any given amount of fabric

know what the weave patterns look like