1) Low density
polythylene        -
polymerization
It is made by a method called free radical polymerization under
high pressure. It was the first and typcal grade of polythene ever
made.
2. High density
polythylene        - post
- polymerization
It is made by catalytic polymerization if petroleum using
catalysts
3. Phenol
Formaldehyde            Â
- Polymerization
They are formed by a step-growth polymerization reaction that
can be either acid- or base-catalysed.
4. heavily cross-linked
polyisoprene       - post -
polymerization
Sulphur treatment to improve cross-linking
5. lightly cross-linked
polyisoprene        Â
- polymerization
They have light cross links that they posses while being formed
naturally.
