29 terms

Bertino Forensics: Chapter 4 Fibers Notes

Fibers Notes
are the smallest indivisible unit of a textile, it must be at least 100 times longer than wide. Fibers are twisted together to make up yarn.
a flexible, flat material made by interlacing (weaving) yarns (or threads)
fibers composed of polymers packed side by side in a repeated pattern, usually stiff and strong
term means, many parts. There are natural and synthetic polymers
term means single part. These single parts repeat in a polymer.
Fibers that have been spun together
direct transfer
is the transferring of particles or fibers when the suspect and victim come into direct contact
Secondary Transfer
when fibers are picked up by a victim at an earlier time and then transferred to a suspect
natural fibers
Are any and all fibers that originate from animals, plants and minerals taken directly from the ground. They are often twisted and have variable diameters under the microscope.
animal fibers
These contain fur, hair, and webbing. They all contain proteins in their composition and have many uses including but not limited to clothing, carpets, drapes, and bedding. Although usually associated with hair or fur, some fabrics such as silk is woven from webbing from a silk worm. Animal fibers have cuticles and a medulla visible under the microscope
plant fibers
Fibers made up of plants cells. They are grouped by the part of the plant they come from, like seed, stem, fruit, and leaves. Examples are cotton (seed), jute, hemp and flax
stem fibers
include hemp, jute, and flax
mineral fibers
Produced from industrial processing of mined materials. They include fiberglass and asbestos
synthetic fibers
fibers made from petroleum based polymers or regenerated natural fibers. These have very uniform (the same throughout) diameters because they are extruded out of a machine.
regenerated fibers
are those that are changed through chemical processing of natural cellulose fibers to form rayon and other light weight fabrics
synthetic polymers
polymers that are made from petroleum products and are long polymers
a common synthetic fiber used in many clothing types. Can be made with recycled plastics.
is lighter yet similar to polyester except that it breaks down easily in light and acids
warp and weft
longitude part of weave and crosswise threads
refractive index
This index is the measurement of how much light is bent when traveling through an object and into air.
thread count
In a woven fabric, the number of warp threads plus the number of weft threads per square inch. Example 100 warp threads plus 150 weft threads gives a thread count of 250.
burn test
reaction to heat, manner of burning, smoke color and odor, type of residue. Often synthetic fibers melt.
gathering fibers
forensic scientists may use fiber vacuum, sticky tape or tweezers.
disadvantages of synthetic fibers
they can deteriorate in bright sunlight and melt at a lower temperature than natural fibers.
the mineral fiber from this rock is used in break pads, fire retardant coatings, ceiling tiles, pipe insulation and more.
weave patterns
plain, basket, satin, twill are common ones
oldest loom
4400 BC
early collection
necessary because 95% of fibers are lost in the first 24 hours.
disadvantages of natural fibers
more expensive, may shrink when washed, absorb moisture, can be less durable

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