Unit 3- Class12- High Polymers (Some commercial polymers)

POLYETHYLENE: is obtained by the polymerization of ethylene at high temperature.

              n (CH2=CH2)------------------>(-CH2-CH2-)n
There are two commercial rate of polyethylene 1. LDPE (low density polyethylene) 2. HDPE (high density polyethylene)

LDPE: is obtained when ethylene is polymerized under very high pressure at 150-2500c in presence of oxygen or azocompounds.
                                     150-2500c 
            n (CH2=CH2)------------------->(-CH2-CH2-)n


Properties: It has a linear structure with extensive branch. It has low density i.e (0.91-0.92g/cc), low crystallinity, low softening point (110-1150c) and molecular weight is between 20,000-50,000.

APPLICATIONS: 1.It is used for packing food and textile materials.
2.It is used for moulding articles such as toys, tubes, pipes etc.
3. It has excellent electrical insulation properties. It is used for cables and wire coverings.