1. Truth comes out of error more easily than out of confusion

 – Francis Bacon

2. Tacticity
3 types
isotactic
syndiotactic
atactic

3. Tacticity Ex: polypropylene CH3 propylene monomer: CH2=CH CH3
upon polymerization: –CH2–C– H

4. Tacticity
isotactic
CH3
propylene: CH2=CH

5. Tacticity
syndiotactic
atactic

6. Tacticity Polypropylene - largely isotactic
isotactic character of PP allows "crystallization"
as a result, material can be stiffer

7. Tacticity Polystyrene - atactic Polypropylene - largely isotactic
PVC largely atactic
(some syndiotactic sequences)
PMMA atactic

8. Copolymers -A-B-B-B-A-A-B-A-B-A-A-A-B-A-B-B-A-B-B-A-A-A-B-
Random Copolymers
-A-B-B-B-A-A-B-A-B-A-A-A-B-A-B-B-A-B-B-A-A-A-B-
Alternating Copolymers
-A-B-A-B-A-B-A-B-A-B-A-B-A-B-A-B-A-B-A-B-A-B-
Graft Copolymers
-B-B-B-B-B-B-B-B-B-B-B-B-B-B-B-B-B-B-B-B-B-B-
A-A-A-A-A-A-A-A-
A-A-A-A-A-A-A-A-A-A-
A-A-A-A-A-A-
Block Copolymers
-A-A-A-A-A-A-B-B-B-B-B-B-B-B-B-B-A-A-A-A-A-A-

9. Blends
miscible immiscible
blend
single phase phase separated

10. Molecular weight molecular weight CH4 CH3 - CH2 _ CH3 CH3 - CH3
Gases
Liquids
Increasing
Molecular Weight 16 30 44 58
114
450
420030
CH4
CH3 - CH2 _ CH3
CH3 - CH3
CH3 - CH2 - CH2 - CH3
CH3 - (CH2)6 _ CH3
CH3 - (CH2)30 _ CH3
CH3 - (CH2)30000 _ CH3
"Semi-solid"
Solids
increasing
molecular weight

11. Molecular weight Chains have different molecular weights
There is a distribution

12. Molecular weight Is it important? Tensile Strength Melt Viscosity
Mol. Wt.
Melt Viscosity
Tensile Strength

13. Molecular weight Is it important? Very important in processing
If viscosity too high, polymer difficult to process
If too low, an extruded material won't hold together until it solidifies

14. Blow molding
Step 1: make preform by extrusion or injection molding

15. Blow molding Step 1: make preform by extrusion or injection molding
Step 2: use air pressure to inflate preform inside closed, hollow mold. Polymer expands to take shape of cooled mold & solidifies under pressure

16. Polymers are different

17. Normal crystalline materials
Polymers are different
Normal crystalline materials
Either crystalline (~100 %, neglecting defects ) or amorphous at a particular temperature
Melt at a sharp, well-defined temperature
Crystallizable polymers
Never 100% Crystalline
Melt over a Range of Temperatures

20. Assignment:
Review today's classnotes
a. tacticity - types
b. copolymers - types
c. blends
d. molecular weight
e. blow molding
f. changes of state in polymers
g. crystallization