Corrosion examples in shuttle mat'ls

Corrosion examples in shuttle mat'ls 60x 1x 235x 1180x

Corrosion examples in shuttle mat'ls

Corrosion area effect Area effect: large cathode & small anode - corrosion accelerated electrochemical cell current density high try to keep potential anodic areas large relative to cathode

Polymers - the nightmare begins I am inclined to think that the development of polymerization is, perhaps, the biggest thing that chemistry has done, where it has the biggest effect on everyday life LORD TODD President of the Royal Society of London

What are polymers? Why important ? • Long chain molecules • Extraordinary range of • physical properties • Many (not all) are cheap • Low densities

How big is n ? Check out chain of beads at right. Imagine each bead is an ethylene unit; Ethylene Polyethylene [ - C H - C H - ] C H = C H n 2 2 2 2 A. 30,000 B. 15,000 C. 150,000 Question: if chain has a molecular weight of 420,000, how many ethylene units does it contain ? Because only 200 ethylene units in this chain (200 - mer), molecular weight only 5,600 (= 28 x 200).

= 1 inch [ - C H - C H - ] 2 2 How big is n ? Commercially produced polyethylenes often have MWs of hundreds of thousands. If ethylene unit is 1" instead of a few angstroms Length of fully stretched out MW 420,000 chain is almost 1/4 mile!

H – – – C C H C H CH4 – H H H – – C C – – – H C C H C2H6 – – H H H H – – – C C C C – C2H4 – – H H Some Basic Chemistry: Single and Double Bonds

Some Basic Chemistry: Functional Groups CH2=CH2 Ethylene O O = = + R–OH R–C–OH R–C–O–R Alcohol Carboxylic Acid Ester O O = = R–NH2 + R–C–OH R–C–NH–R Amine Carboxylic Acid Amide Functional groups - small groups of atoms held together in specific arrangement by covalent bonds Responsible for principal chemical properties of molecule

O Ester linkage O Ethyl Acetate Some Basic Chemistry: Condensation Reactions Ethyl Alcohol or Ethanol reversible reaction CH3 - C - OH + CH3 - CH2 - OH CH3 - C - O - CH2 - CH3 + H2O Acetic Acid

Now…to make a Polymer The molecules are monofunctional: + To make linear chains need bifunctional molecules: Except, reaction goes step-wise

Polyester - step 1 O O O O Monomers HO - C - (CH2)n - C - OH + HO - (CH2)m - OH HO - C - (CH2)n - C - O - (CH2)m - OH + H2O Dimer

O O HO - C - (CH2)n - C - O - (CH2)m - OH + HO - C - (CH2)n - C - OH O O O O Trimer - H2O HO - C - (CH2)n - C - O - (CH2)m - O - C - (CH2)n - C - OH O O M3 + M2 M5 M1 + M1 M2 M2 + M1 M3 M2 + M2 M4 M3 + M1 M4 M5 + M1 M6 M4 + M1 M5 Etc. Polyester Reacting diacid & dialcohol give polyester!

H2N - (CH2)6 - NH2 + HO - C - (CH2)4 - C - OH Hexamethylene Diamine Adipic Acid O O O O H2N - (CH2)6 - N - C - (CH2)4 - C - OH + H2O Amide Group H Nylons

Nylon 6,6 O O - N - (CH2)6 - N - C - (CH2)4 - C - n 6 6 H H “I am making the announcement of a brand new chemical textile fiber ---derivable from coal, air and water -- and characterized by extreme toughness and strength --” Charles Stine V.P. for research, Du Pont, 1938

Nylon “I am making the announcement of a brand new chemical textile fiber ---derivable from coal, air and water -- and characterized by extreme toughness and strength --” Charles Stine V.P. for research, Du Pont, 1938

Nylon May 15 1940 - “Nylon Day” Four million pairs go on sale throughout US Supply exhausted in 4 days.

Nylon Parachute WWII

Post WWII stocking sale, San Francisco.

Corrosion examples in shuttle mat'ls