2. 1. Overview
1.1 Chemical structure
2. properties
2.1 physical properties
2.2 chemical properties
3. Processes
3.1 Monomer
3.2 Polymerization
3.3 Manufacture
4. Uses
5. Groups of polyethylene
6. Advantages
7. Disadvantages
3. The most common plastic
global production is ca. 80 million tones
chemical formula: (C2H4)nH2
4. » Very simple structure, the simplest of all
commercial polymers.
» carbon atoms + two hydrogen atoms.
5. » thermoplastic polymer
» consists of long hydrocarbon chains
» white waxy
» the melting point is typically in the range 120 to 180 °C
» May or may not be observable
Depending on:
- crystallinity
- molecular weight
- melting point
6. » excellent chemical resistance
not attacked by strong acids or strong bases
» resistant to gentle oxidants and reducing agents
» burns slowly with a blue flame having a yellow tip
giving off an odour of paraffin
» can be dissolved in hydrocarbons
» insoluble in water and most organic solvents
» does not conduct electricity
» can be dissolved at elevated temperatures
7. » ingredient of monomer is ethylene.
gaseous hydrocarbon with the formula C2H4
» ethylene must be of high purity
» Ethylene is generated by dehydration of
ethanol.
8. » highly exothermic.
» metal chlorides or metal oxides are used.
» common catalysts consist of titanium(III)
chloride.
9.
10. » cracking/decomposing petroleum
small, reactive ethane molecules
can be rearranged
» Ethene molecules polymerize to long chains of
polyethylene
chains close to each other by weak bonds
forming a material, comparable with the fibers of a
felt
11. » children's toys
» bullet proof vests
» Packaging
- Plastic bag, e.g. grocery bags
- Plastic films
- Containers
- Bottles, e.g. shampoo bottles
- Geomembranes: (HDPE) and (LDPE)
12. » two types of polyethylene:
1. HDPE: high density poly ethene ---> low
pressure
2. LDPE: low density poly ethene --> high
pressure
» LDPE : soft thus suitable for manufacture of
packaging, films soft tubes and hoses
» HDPE: for piping
13. 1. Polyethylene film most lightweight and durable packaging
mediums available
2. Plastic packaging contributes to reducing food spoilage rates.
3. Polyethylene ducting is compatible with most fans, heaters,
air conditioners, air handling units, etc
4. Polyethylene Bags use less energy and resources to create
than glass or paper.
5. Clear polyethylene allows recipients to view the contents
(such as a magazine cover)
14. 1. Polyethylene is not biodegradable, it accumulates if
dumped in the soil
2. Polyethylene threatens the life in the water bodies.
3. Polyethylene is likely to clog the drains problems in
the water flow of the pipes
4. Polyethylene is harmful for animals if swallowed.
5. If polyethylene is burnt in open air Hydrogen cyanide
is released
