Corrosion examples in shuttle mat'ls

1x 60x

235x 1180x

Corrosion examples in shuttle mat'ls

Corrosion examples in shuttle mat'ls

Corrosion examples in shuttle mat'ls

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 TODDPresident of the RoyalSociety of London

What are polymers?Why important ?

• Long chain molecules

• Extraordinary range of physical properties

• Many (not all) are cheap

• Low densities

Question: if chain has a molecularweight of 420,000, how many ethylene units does it contain ?

A. 30,000B. 15,000C. 150,000

Because only 200 ethylene units in this chain (200 - mer), molecular weight only 5,600 (= 28 x 200).

Ethylene PolyethyleneCH2= CH2 [-CH2- CH2-]n

Check out chain of beads at right. Imagine each bead is an ethylene unit;

How big is n ?

How big is n ?

Commercially produced polyethylenesoften have MWs of hundreds of thousands. If ethylene unit is 1" instead of a few angstroms

Length of fully stretched outMW 420,000 chain is almost 1/4 mile!

[-CH2- CH2-] = 1 inch

Some Basic Chemistry:Single and Double Bonds

CC C –– ––

H

HH H CH4

CC C –– ––

H

HH C ––

–

H

HH C2H6

C C C –––

H

HC–

–

H

H– C2H4

Functional groups - small groups of atoms held together in specific arrangement by covalent bonds

Responsible for principal chemical properties of molecule

Some Basic Chemistry:Functional Groups

CH2=CH2

Ethylene

R–OH R–C–OH

=O

R–C–O–R+Alcohol Carboxylic Acid Ester

=O

R–NH2 R–C–OH R–C–NH–R+Carboxylic AcidAmine Amide

=O =O

Some Basic Chemistry:Condensation Reactions

Acetic Acid

Ethyl Alcohol or Ethanol reversible

reaction

Ester linkage

O

Ethyl Acetate

OCH3 - C - OH + CH3 - CH2 - OH

CH3 - C - O - CH2 - CH3 + H2O

Except, reaction goes step-wise

Now…to make a Polymer

The molecules are monofunctional:

+

To make linear chains need bifunctional molecules:

O O

HO - C - (CH2)n - C - O - (CH2)m - OH + H2O

O O

Polyester - step 1

HO - C - (CH2)n - C - OH + HO - (CH2)m - OH

Dimer

Monomers

Polyester

HO - C - (CH2)n - C - OH

O O

HO - C - (CH2)n - C - O - (CH2)m - OH +

O O

HO - C - (CH2)n - C - O - (CH2)m - O - C - (CH2)n - C - OH

O OO O- H2O

Trimer

M1 + M1 M2

M2 + M1 M3

M2 + M2 M4

M3 + M1 M4

M4 + M1 M5

M3 + M2 M5

M5 + M1 M6

Etc.

Reacting diacid & dialcohol give polyester!

Nylons

H2N - (CH2)6 - NH2 + HO - C - (CH2)4 - C - OH

O

H2N - (CH2)6 - N - C - (CH2)4 - C - OH + H2O

OO

O

Adipic AcidHexamethylene Diamine

Amide Group

H

Nylon 6,6 - N - (CH2)6 - N - C - (CH2)4 - C -

O O

n6 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.