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Truth comes out of error more easily than out of confusion
– Francis Bacon
Truth comes out of error more easily than out of confusion
– Francis Bacon
3 typesisotacticsyndiotacticatactic
3 typesisotacticsyndiotacticatactic
TacticityTacticity
TacticityTacticity
CH3CH3
propylene monomer: CH2=CHpropylene monomer: CH2=CH
Ex: polypropyleneEx: polypropylene
CH3CH3
upon polymerization: –CH2–C–upon polymerization: –CH2–C–
HH
isotacticisotactic
TacticityTacticity
CH3
propylene: CH2=CH
TacticityTacticity
atacticatactic
syndiotacticsyndiotactic
TacticityTacticity
Polypropylene - largely isotactic
isotactic character of PP allows "crystallization"
as a result, material can be stiffer
Polypropylene - largely isotactic
isotactic character of PP allows "crystallization"
as a result, material can be stiffer
TacticityTacticity
Polystyrene - atactic
Polypropylene - largely isotactic
PVC - largely atactic (some syndiotactic sequences)
PMMA -atactic
Polystyrene - atactic
Polypropylene - largely isotactic
PVC - largely atactic (some syndiotactic sequences)
PMMA -atactic
Copolymers Copolymers
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-
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-
Blends Blends
miscible immisciblemiscible immiscible
single phase phase separatedsingle phase phase separated
blendblend
Molecular weight Molecular weight
Gases
Liquids
IncreasingMolecular 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
--------------------------------
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"Semi-solid"
Solids
increasingmolecular weight
Molecular weight Molecular weight
Chains have different molecular weights
There is a distribution
Molecular weight Molecular weight
Is it important?
Mol. Wt.Mol. Wt.
Melt ViscosityMelt ViscosityTensile StrengthTensile Strength
Mol. Wt.Mol. Wt.
Molecular weight Molecular weight
Is it important?Is it important?
Very important in processing
If viscosity too high, polymer difficult to process
Very important in processing
If viscosity too high, polymer difficult to processIf too low, an extruded material won't hold together until it solidifies
If too low, an extruded material won't hold together until it solidifies
Blow molding Blow molding
Step 1: make preform by extrusion or injection molding
Step 1: make preform by extrusion or injection molding
Blow molding Blow molding
Step 1: make preform by extrusion or injection 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
Step 2: use air pressure to inflate preform inside closed, hollow mold. Polymer expands to take shape of cooled mold & solidifies under pressure
Polymers are different Polymers are different
Polymers are different Polymers are different
• Normal crystalline materials– Either crystalline (~100 %, neglecting defects ) or amorphous at a particular temperature
– Melt at a sharp, well-defined temperature
• 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
• Crystallizable polymers– Never 100% Crystalline– Melt over a Range of Temperatures
Assignment:
Review today's classnotesa. tacticity - typesb. copolymers - typesc. blendsd. molecular weighte. blow moldingf. changes of state in polymersg. crystallization
Assignment:
Review today's classnotesa. tacticity - typesb. copolymers - typesc. blendsd. molecular weighte. blow moldingf. changes of state in polymersg. crystallization
