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).

Properties of Polymer::

Types of Polymers

Addition polymerisation

Step-growth polymers, also called condensation polymers ,are made by

combining two molecules by removing a small molecule.

Example: Condensation Reactions

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