Iupac

IUPAC name is polyethene or poly(methylene) which is widely used as plastic eg. plastic shopping bag. Polyethylene is a thermoplastic polymer. A thermoplastic is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently. Polyethylene consists of carbon and hydrogen elements. Most important commercial use of ethene is making polymers and polyethylene is created through polymerisation of ethene. Polymerisation is where many identical small monomers combine to make one large polymer.
CH2=CH     +     CH2=CH2     +     CH2=CH2     +     CH2=CH2 ---------> -CH2-CH2-CH2-CH2-CH2-CH2-
Ethene(s) Polyethene
Polyethene is an addition polymer, as the double bond opens and no compound other than polymer is created. Polyethylene is classified into several different categories based mostly on its density and branching. The most important polyethylene grades are HDPE, LLDPE and LDPE.
HDPE has a density of greater or equal to 0.941 g/cm3 which also has low degree of branching and strong intermolecular forces. It can be produced by chromium/slica catalysts, Ziegler-Natta catalysts or metallocene catalysts. LLDPE has a density between 0.915-0.925 g/cm3 which has short branches that are usually made up of copolymerization of ethylene with short chain alpha-olefins. LDPE has a density between 0.910-0.940 g/cm3 and have a high degree of short and long chain branching which can mean that the chains do not pack into the crystal structure. Therefore the intermolecular forces are weaker because dipole-dipole force attraction is less.
Gas-phase process | Ziegler-Natta process |
    * High pressure (1000-3000 atmos.) |     * Pressure (2-3atmos.) |
    * Initiator (peroxide or oxygen) |     * Catalyst mixture of TiCl3 |
    * Significant chain branching |     * No chain branching |
    * Low density |     * High density |
    * Eg. shopping bags |     * Eg. Toys |
    * Amorphous chained structure |     * Crystalline linear chains |...