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High Polymer
Habib
20121107042
ACCE
Definitions::
• Polymer: a long chain molecule made up of many small identical units.
• Monomer: the smallest repeating unit of a polymer (propene in polypropylene).
Step-growth polymers, also called condensation polymers ,are made by
combining two molecules by removing a small molecule.
Nylon is actually a “copolymer” because is it made from two monomers. Polyester is a another
copolymer.
Polyester is made from the two monomers, terephthalic acid and ethylene glycol. This makes a popular
plastic called PETE, which is short for Polyethylene Terephthalate. The synthesis is also called a
dehydration reaction because of water elimination .
Random Copolymer::
Alternate Copolymer::
Block Copolymer
When small groups of monomers are attached to each other in alternating fashion, the product is called
a block copolymer.
Graft Copolymer::
When ‘sections’ of one type of polymer is attached or ‘grafted’ to the main chain of another
polymer.
Terpolymer::
When three types of ‘mers’ polymerized together, it is known as a terpolymer.
Acrylonitrile Butadiene Styrene (ABS) is a terpolymer of Acrylic, Butadiene rubber, and Styrene.
Branching::
During the polymerization process, reactions can also happen off of the side of the main chain. These
side-chains are known as branching.
Branch Polymer::
Homopolymer::
Molecular Weight
Molecular weight is the sum of the atomic weights of the atoms that make up the molecule.
Carbon has an atomic weight of 12.011 grams/mole. 12 is close enough for what we’re doing
A mole is 6.0221415×1023 atoms or molecules
This is known as Avogadro's number.
Molecular Weight
There are two types of molecular weight average:
The first is the Number Average Molecular Weight ( )
The second is the Weight Average Molecular Weight ( )
Properties
Increasing the molecular weight of the material increases many of the properties of the material by
increasing the entanglement of the molecules.
A higher molecular weight:
Increases the chemical resistance - to a point
-It takes more damage to the main chains of the molecules before it will affect the strength of the
material
-The big loophole to this is if you have a chemical
that is very similar to the chemical makeup of the
main chain, it will dissolve it much more easily
Properties
A higher molecular weight:
Increases how far the material can stretch before rupturing (ductility)
-The higher degree of entanglement allows the material to be pulled further before the chains break