Truth comes out of error more easily than out of confusion

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Truth comes out of error more easily than out of
confusion ? Francis Bacon
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3 types isotactic syndiotactic atactic
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isotactic
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Polypropylene - largely isotactic isotactic
character of PP allows "crystallization" as a
result, material can be stiffer
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Polystyrene - atactic Polypropylene -
largely isotactic PVC -
largely atactic
(some syndiotactic sequences) PMMA
-atactic
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miscible immiscible
single phase phase separated
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increasing
molecular weight
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Chains have different molecular weights There is
a distribution
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Is it important?
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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
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Step 1 make preform by extrusion or injection
molding
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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
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• 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

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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