Polymers
1.0 Introduction
2.0 Polymers and polymerization
3.0 Free-radical vinyl polymerization
4.0 Ionic Polymerization
5.0 Natural Rubber
6.0 Synthetic Rubber
7.0 Polyvinyl Chloride (PVC)
8.0 Teflon or PTFE (Polytetrafluoro ethylene)
9.0 Nylon-66
6.1 Buna Rubbers
Butadiene polymerises in the presence of sodium to give a rubber substitute viz. $BuNa$. It is of two types:
$1.$ Buna - N or GRA: It is synthetic rubber obtained by copolymerisation of one part of acryl nitrile and two parts of butadiene.
It is more rigid responds less to heat and very resistant to swelling action of petrol, oils and other organic solvents.
$2.$ Buna -S or GRS (General purpose Styrene rubber): It is a copolymer of three moles of butadiene and one mole of styrene and is an elastomer. It is obtained as a result of free radical copolymerisation of its monomers.
It is generally compounded with carbon black and vulcanised with sulphur. It is extremely resistant to wear and tear and finds use in manufacture of tyres and other mechanical rubber goods.
