fibers
usually made up of many filaments twisted or bonded together to form a thread or yarn
textiles
fabrics woven in a distinctive pattern
class evidence
can only be associated with a group of items that share properties or characteristics
probative value
are able to create connections. the ability of evidence to prove something is relevant to the crime
generic
related to an entire group or class of products; not having a brand name
ligature
something used to knot or bind - can be important to forensic scientists
fabric
a cloth material made up of fibers woven or bonded together in a distinctive manner
filament
single strands of material, usually twisted with other filaments to make a thread or fiber
inorganic
refers to substances not composed primarily of hydrocarbons, that is carbon and hydrogen (ex. asbestos + fiberglass)
olefin
term used for hydrogen containing a carbon - carbon double bond (ex. ethylene, H2C = CH2)
yarn
a continuous strand of fibers or filaments, either twisted or not
warp
the lengthwise yarn or thread in a weave
weft or woof
the crosswise yarn or thread in a weave
blend
a fabric made up of two or more different types of fibers, usually as warp and weft
polymer
giant molecules created when simple molecules called monomers are chemically joined together (ex. mineral silicates, DNA + RNA, cellulose, starch, and keratin)
monomer
simple molecules
polypeptide
a biochemical polymer formed by linking amino acids; the longer chains are called proteins
helix
a spiral arrangement, like a corkscrew, of a long-chain molecule
keratin
the main protein in all animal hair, including human hair
amino acid
contain nitrogen - general compounds containing nitrogen can break down to form ammonia (NH3) - basic
sericulture
raising of silkworms - began in china in 2640 BC
cellulose
starch, makes up cotton, and polysaccharide consisting of chains of glucose monomers.
rayon
natural fibers that have been chemically altered - very pure cellulose fiber and burns like cotton, can be found in beds, blankets, curtains, etc.
acetate
natural fibers that have been chemically altered made from cellulose through reaction with acetic acid - used in making blouses, dresses, draperies, upholstery, cigarette filters, and more
plastics
substances that flow under heat and pressure and can, therefore, be molded into various shapes. All are polymers, but not all polymers are plastics
polyester
can be classified by generic names that describe their chemical type. Produced from a dialcohol and a diaacid (ex. wool and silk)
homopolymer
acrylic fibers often used in sweatshirts polymers made up of are type of repeating unit each is made from one monomer only
polyether
series of carbon atoms connected by oxygen atoms, such as: CO-CH2-CH2n, subscript n refers to number of ether units in polymer
density
physical property of matter - D=M/V, expressed in g/cc and can change with temperature and pressure in the case of gases
refractive index
measure of the bending of a ray of light as it passes from air into a solid or liquid
Becke Line
a halolike shadow appearing around an object immersed in a liquid of a different refractive index
fluorescence
exposed to UV radiation can be caused by the chemical and crystalline properties of fiber itself, by dyes, or optical brightness and other agents added to fabric
optical brightness
colorless dyes that cause blue light to be reflected, thereby making an object look whiter
chromatography
method of separating components of mixtures based on preferential adsorption or portioning of components in a gas, liquid, or solution - there is paper chromatography and TLC chromatography
chromatogram
record of chromatographic separation
elute
extract one material from another, usually by means of a solvent
retention factor (Rf)
a ratio used to characterize and compare components of samples in liquid chromatography
Fourier Transform Infrared analysis (FTIR)
very powerful way to identify fiber type of test is non destructive, and can be performed on single fibers - based on selective absorption of wave lengths of light by particular group in a polymer
optical microscopy
most important method of fiber identification and matching, using polarizing light and comparison microscopes
pyrolysis gas chromatography-mass spectrometry (PGC-MS)
burns a sample under controlled conditions and separates and analyzes each combustion product, can match the resulting chromatogram and product analysis to known standards can be used for short length fibers, but is destructive