Polyethene
By DarthVader
Date: 2022-08-21
Topic: 158 see comments
Post views: 1078
Polyethene
Polyethene is made by reacting together molecules ethane.
LDPE was discovered in 1936 by heating ethane (hydrocarbon alkene) under high pressure (1000 atmospheres)
HDPE was discovered in the 1950s when a new method using catalysts (substances which speed up the reaction), was developed eliminating the need for high pressures.
Density (kg m-3) | Thermal Conductivity (W m-1 K-1) | Tensile Strength (MN m-2) | Tensile Modulus | Melting Temperature (K) | |
HDPE | 960 | 0.2 | 30 | 1 | 404 |
LDPE | 920 | 0.2 | 13 | 0.2 | 390 |
Polymer Chains (Straight/branches)
The original LDPE was less dense because the polymer chains contained lots of branches which split off from the long chains. These branches cause more disorder in the structure and means that less molecules can pack together.
HDPE contains more ‘straight’ chains that do not have branches, these straight chains can fold together more neatly and form a more crystaline structure where more molecules can pack togther closer.
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