Slide 1

Slide 2

Slide 3

3 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. 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, forensically they can be distinguished from one another.

Slide 4

1. Wool Polymer= Polypeptide chains (forming the protein keratin) Monomer= amino acids (one of which is cysteine...cysteine contains Sulfur) http://www.leydenglenlamb.com/photos.htm

Slide 5

1. Wool Polymer= Polypeptide chains (forming the protein keratin) Monomer= amino acids (one of which is cysteine...cysteine contains Sulfur) 2. Silk Polymer= protein Monomer= amino acids (but less of a variety than wool) http://entomology.unl.edu/images/silkworm/silkworm1.jpg

Slide 6

1. Wool Polymer= Polypeptide chains (forming the protein keratin) Monomer= amino acids (one of which is cysteine...cysteine contains Sulfur) 2. Silk Polymer= protein Monomer= amino acids (but less of a variety than wool) 3. Cotton Polymer= cellulose (plant) Monomer= glucose http://www.texaspolicecentral.com/Texas-Patriotism.php

Slide 7

1. Wool Polymer= Polypeptide chains (forming the protein keratin) Monomer= amino acids (one of which is cysteine...cysteine contains Sulfur) 2. Silk Polymer= protein Monomer= amino acids (but less of a variety than wool) 3. Cotton Polymer= cellulose (plant) Monomer= glucose 4. Linen Polymer= cellulose (flax plant) Longer chains than cotton which makes it brittle Monomer= glucose http://www.flowers-cs.com/flax.html

Slide 8

1. Rayon Cellulose fiber, then chemically altered, burns like cotton 2. Acetate Made from a reaction between cellulose and acetic acid

Slide 9

1. Polyamides linked by amino group Example: Nylon Stronger and more chemically inert than natural fibers Image from: http://www.imageenvision.com/collection/fitness.html

Slide 10

1. Polyamideslinked by amino group Example: Nylon Stronger and more chemically inert than natural fibers 2. Polyesters linked by ester group Stronger linkage than polyamides Linkage can be linear (flexible) or cross- linked (rigid) Image from: http://www.imageenvision.com/collection/fitness.html

Slide 11

1. Polyamideslinked by amino group Example: Nylon Stronger and more chemically inert than natural fibers 2. Polyesterslined by ester group Stronger linkage than polyamides Linkage can be linear (flexible) or cross-linked (rigid ) 3. Spandexstructurally similar to polyamide Made of segments of polyurethane connected to long segments of polyesters Resulting spandex can stretch up to 600 times and recover original strength http://www.fingerpainrelief.com/rubber-band-therapy-for-finger-pain /

Slide 12

12 Testing for Identification Microscopic observation Burningobservation of how a fiber burns, the odor, color of flame, smoke and the appearance of the residue Thermal decompositiongently heating to break down the fiber to the basic monomers Chemical testssolubility and decomposition

Slide 13

13 Dyes Components that make up dyes can be separated and matched to an unknown. There are more than 7000 different dye formulations. Chromatography is used to separate dyes for comparative analysis. The way a fabric accepts a particular dye may also be used to identify and compare samples.

Slide 14

14 Collection of Fiber Evidence Bag clothing items individually in paper bags. Make sure that different items are not placed on the same surface before being bagged. Make tape lifts of exposed skin areas of bodies and any inanimate objects Removed fibers should be folded into a small sheet of paper and stored in a paper bag.

Slide 15

15 Fiber Evidence Fiber evidence in court cases can be used to connect the suspect to the victim or to the crime scene. In the case of Wayne Williams, fibers weighed heavily on the outcome of the case. Williams was convicted in 1982 based on carpet fibers that were found in his home, car and on several murder victims.

Slide 16

Clip 1 http://www.youtube.com/watch?v=cmlunCbBV_o&f eature=related If link is broken, go to YouTube and search Oil Absorbing Polymer Clip 2 http://www.youtube.com/watch?v=YWoQ3D6RMXs &feature=related If link is broken, go to YouTube and search Spangler's Polymer Experiment on The Ellen Show