General Polymerization Process

Polymerization of the monomer in bulk may be carried in the liquid or vapour state. The monomer and activator are mixed in the reactor are heated and cooled as needed. As most polymerization reaction are exothermic, provision must be made to remove the excess heat. In some cases, the polymer are soluble in the liquid monomers, causing the viscosity of the solution to increase greatly. In other cases, the polymer is not soluble in the monomer and it precipitates out after small amount of polymerization occurs.

Classification of Fillers and Reinforcements

Organic Origin	Inorganic Origin
Cellulosic: Wood Flour Shell flour Cotton or cellulose Paper pulp	Mineral Fillers: Calcium carbonate Mica Kaolin Silica Talc Carbide Mettalic oxide Sulfates Silicates Titanates
Shredded Textiles Sisal	Powdered metals: Iron Lead and zinc Copper Aluminum
Carboneous: Graphite filaments Carbon blacks	Filaments: Fiberglass Basalt fibers Boron and other metals Aluminium oxide
Synthetic: Aramid yarns and fibers

Solution Polymerization:
This method is often used when the exothermic heat is too great to be controlled in bulk polymerization. The monomer and initiator are dissolved in a non-reactive solvent which serve to slow the reaction and thus moderate the heat given off. The heat evolved may be controlled by refusing the solvent. The polymer concentration usually has to be low to avoid too high a viscosity. This method produces polymers of low to medium molecular weight.

Suspension Polymerization
In this process the monomer is suspended in water by agitation, and stabilizers such as talc, fuller’s earth, and bentonite are added to stabilize the suspension and prevent polymer globules from adhering to each other. Normally, the initiator is soluble in the monomer. Each monomer globule polymerizes as a spherical pearl of high molecular weight. The heat of polymerization is removed by the water, permitting accurate temperature control. The stabilizer must be separated from the polymer, and sometimes, because of partial miscibility of the monomer and water, subsidiary polymerization may occur in the aqueous phase, producing of low molecular weight polymer.

Emulsion Polymerization
This is similar to suspension polymerization but the monomer is broken up into droplets that form aggregates called micelles. The monomer is on the interior of the micelles, and the initiator is in the water. Soap, or another emulsifying agent, is used to stabilize to micelles. The initiator diffuses into the micelle to start polymer growth. Emulsion polymerization are rapid and can be carried out at relatively low temperature weight can be prepared by this process.