Unit 3- Class 7- High Polymers (Methods of polymerization - Suspension (pearl) polymerization)

Suspension (pearl) polymerization: This polymerization occurs in heterogeneous system. The water insoluble monomer is suspended in water as tiny droplets by continuous agitation. The droplets are prevented from coalescing by using small quantities of water- soluble polymers such as polyvinyl alcohol or colloids. The polymerization is made to occur in each droplet of the monomer using a catalyst. The reaction mass is heated ti initiate the polymerization. After the completion of polymerization pearl like polydispersed polymer mixture is obtained.

Advantages:

1.    The viscosity build up of polymer is negligible.
2.    Isolation of product is easy as it needs only filtration and washing.
3.    High purity products.
4.    The process is more economical since water is used.
5.    Isolated products need no further purification.
6.    Efficient thermal control.

Disadvantages:
1.    This method is applicable only for water insoluble monomers.
2.    It is difficult to control particle size.

Application: This technique is used for the production of polyvinyl acetate, poly styrene, styrene-divinyl benzene etc.