What is polythene? Write down its properties and types. Explain the preparation,properties,and uses of different types of polythene.

(N/A) Polythene is a polymer formed by the polymerization of ethene. It consists of linear or slightly branched long-chain molecules.
These are thermoplastic polymers,meaning they soften on heating and harden on cooling.
There are two main types of polythene:
$(a)$ Low Density Polythene $(LDP)$:
Preparation: It is obtained by the polymerization of ethene under high pressure of $1000$ to $2000 \ atm$ at a temperature of $350 \ K$ to $570 \ K$ in the presence of traces of dioxygen or a peroxide initiator.
Properties: $LDP$ has a branched-chain structure. It is chemically inert,tough,flexible,and a poor conductor of electricity.
Uses: Used in the insulation of electricity-carrying wires,squeeze bottles,toys,and flexible pipes.
$(b)$ High Density Polythene $(HDP)$:
Preparation: It is formed by the addition polymerization of ethene in a hydrocarbon solvent in the presence of a Ziegler-Natta catalyst (triethylaluminium and titanium tetrachloride) at $333 \ K$ to $343 \ K$ and a pressure of $6-7 \ atm$.
Properties: $HDP$ consists of linear molecules,leading to close packing and high density. It is chemically inert,tougher,and harder than $LDP$.
Uses: Used for manufacturing buckets,dustbins,bottles,and pipes.