Maharashtra BoardEnglish MediumSTD 12 ScienceChemistryIntroduction to Polymer Chemistry4 Marks
Question
How is polythene manufactured? Give their properties and uses.
✓
Answer
LDP means low density polyethylene. LDP is obtained by polymerization of ethylene under high pressure $(1000 – 2000\ atm)$ and temperature $(350 – 570\ K)$ in presence of traces of $O_2$ or peroxide as initiator.The mechanism of this reaction involves free radical addition and H-atom abstraction. The latter results in branching. As a result the chains are loosely held and the polymer has low density.
Properties of LDP :
LDP films are extremely flexible, but tough chemically inert and moisture resistant.
It is poor conductor of electricity with melting point $110 ^\circ\ C$.
Uses of LDP :
LDP is mainly used in preparation of pipes for agriculture, irrigation, domestic water line connections as well as insulation to electric cables.
It is also used in submarine cable insulation.
It is used in producing extruded films, sheets, mainly for packaging and household uses like in preparation of squeeze bottles, attractive containers, etc.
HDP means high density polyethylene. It is a linear polymer with high density due to close packing.
HDP is obtained by polymerization of ethene in presence of Zieglar-Natta catalyst which is a combination of triethyl aluminium with titanium tetrachloride at a temperature of $333K$ to $343K$ and a pressure of $6-7$ atm.
Properties of HDP :
HDP is crystalline, melting point in the range of $144 – 150 ^\circ\ C$.
It is much stiffer than LDP and has high tensile strength and hardness.
It is more resistant to chemicals than LDP.
Uses of HDP :
HDP is used in manufacture of toys and other household articles like buckets, dustbins, bottles, pipes, etc.
It is used to prepare laboratory wares and other objects where high tensile strength and stiffness is required.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.