ic2.11.3 explaining polymer properties © oxford university press 2011 explaining polymer properties
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IC2.11.3 Explaining polymer properties
© Oxford University Press 2011
Explaining polymer properties
IC2.11.3 Explaining polymer properties
© Oxford University Press 2011
There are two types of poly(ethene): Low density poly(ethene), LDPE. High density poly(ethene), HDPE.
IC2.11.3 Explaining polymer properties
© Oxford University Press 2011
The two types of poly(ethene) are both made from ethene but each has its own properties.
LDPE is not as strong as HDPE but it is more transparent. LDPE is flexible and HDPE is stiff.
This is because they are made under different conditions.
IC2.11.3 Explaining polymer properties
© Oxford University Press 2011
LDPE is made at a temperature of 100–300°C and pressure of 1500–3000 atm. An oxygen or peroxide initiator is used in the reaction.
IC2.11.3 Explaining polymer properties
© Oxford University Press 2011
LDPE polymer molecules have side branches. The branches prevent the polymer molecules from lining up in a regular pattern, so the density is lower.
IC2.11.3 Explaining polymer properties
© Oxford University Press 2011
HDPE is made at a temperature of 300°C and pressure of 1 atm. An aluminium-based metal oxide catalyst is used in the reaction.
IC2.11.3 Explaining polymer properties
© Oxford University Press 2011
HDPE polymer molecules have few side branches.
Its molecules line up in a pattern, so the density is higher.
The molecules are held together more strongly, so HDPE is stronger and has a higher melting point than LDPE.