The material. Polyethylene, (—CH2—)n, first synthesized in 1933, looks like the simplest of molecules, but the number of ways in which the—CH2 units can be linked is large. It is the first of the polyolefins, the bulk thermoplastic polymers that account for a dominant fraction of all polymer consumption. Polyethylene is inert, and extremely resistant to fresh and saltwater, food, and most water-based solutions. For this reason it is widely used in household products, food containers, and chopping boards. Polyethylene is cheap and particularly easy to mold and fabricate. It accepts a wide range of colors, can be transparent, translucent or opaque, has a pleasant, slightly waxy feel, can be textured or metal coated, but is difficult to print on.
Composition
(—CH2—CH2—)n
PE is widely used for containers and packaging. Ecoproperties: material
|
Annual world production |
68 X 106 – |
69 X 106 |
tonne/yr |
|
Reserves |
*1.7 X 109 |
tonne |
|
|
Embodied energy, primary production |
77 – |
85 |
MJ/kg |
|
CO2 footprint, primary production |
2 – |
2.2 |
kg/kg |
|
Water usage |
*38 – |
1 .1 e2 |
l/kg |
|
Eco-indicator |
310 – |
350 |
millipoints/kg |
|
Ecoproperties: processing |
|||
|
Polymer molding energy |
*6.1 – |
6.8 |
MJ/kg |
|
Polymer molding CO2 footprint |
*0.49 – |
0.54 |
kg/kg |
|
Polymer extrusion energy |
*2.4 – |
2.7 |
MJ/kg |
|
Polymer extrusion CO2 footprint |
*0.19 – |
0.21 |
kg/kg |
|
Recycling |
|||
|
Embodied energy, recycling |
32 – |
36 |
MJ/kg |
|
CO2 footprint, recycling |
0.82 – |
0.91 |
kg/kg |
|
Recycle fraction in current supply Recycle mark HDPE |
7.5 – 4 LDPE |
9.5 |
% |
Typical uses. Oil container, street bollards, milk bottles, toys, beer crate, food packaging, shrink wrap, squeeze tubes, disposable clothing, plastic bags, paper coatings, cable insulation, artificial joints, and as fibers—low-cost ropes and packing tape reinforcement.
