Unit 3- Class5- High Polymers (Methods of polymerization)

 In this class, let us learn about the methods of polymerization.

Methods of polymerization: Industrial polymerization can be carried out by different techniques. The principal polymerization methods are

1. Bulk polymerization 2. Solution polymerization 3. Suspension polymerization 4. Emulsion polymerization. 


Bulk polymerization: It is a homogeneous polymerization. The method is used for the liquid monomer. The monomer is taken in the liquid state and the initiator, chain transfer agents are dissolved in it. The reaction mass is heated or exposed to a radiation source for initiating the polymerization and is kept under agitation for proper mass and heat transfer.

Advantages:
1. Bulk polymerization is quite simple.
2. High purity products are obtained.      
3. Products need neither isolation nor purification.

Disadvantages:
1. As the polymerization proceeds the viscosity of the medium increases leading to polymer products with broad molecular weight distribution.
2. Mixing becomes difficult.
3. Reaction is highly exothermic.
3. As the medium gets viscous, the diffusibility of the growing polymer chain becomes restricted, the probability of the chain collision becomes less, termination becomes difficult, active radical sites accumulate and the rate of polymerization increase enormously. This phenomenon is called auto acceleration.

 Applications:
 This technique is used in the free radical polymerization of methyl methacrylate to poly- methyl methacrylate, styrene to polystyrene, vinyl chloride to PVC etc.


This is it for today's class, in the next class we will learn more about other various methods of polymerization. Untill then revise the Polymers that has been done.Take Care.