Polymer Technology

The emulsion polymerization process involves the polymerization of monomer in an aqueous medium containing surfactant and a watersoluble initiator, producing PVC latices. PVC latices are colloidal dispersions of spherical particles, ranging in size between 0 1 and 3.0 ~lm most PVC latices are spray dried and then milled to obtain fine powders. When mixed with plasticizers they disperse readily to form

stable suspensions. During mixing most of the agglomerates are broken down into original latex particles. Such dispersions are known as plastisols or pastes, and the powder is called dispersion or paste polymer. The surfactant layer around the particle surface prevents their adsorbing the plasticizers at room temperature so they can be used as liquids and may then be spread on to fabric or other substrate, poured on molds or deposited to produce flooring, wall covering, artificial leather, balls, toys or gloves.

The emulsion polymerization of PVC consists of the following stages:

1 )Polymerization,
2)VCM removal,
3)Latex storage,
4 )Drying,
5)Milling,
6)Packing and storage

A recipe for a simple batch emulsion polymerization is as follows:

Demineralized water 110 – 140 parts
Vinyl Chloride 100
Emulsifier 0.1-1.0
Initiator 0.1-0.2
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The techniques used in polymerization depend upon following factors:

1. Physical form of reactants; gas, liquid or solid.
2. Solvents used
3. Type of polymerization mechanism
4. Required physical form of polymer; solid, emulsion, solution

These factors lead to different polymerization techniques.

1. Bulk Polymerization
2. Solution polymerization
3. Suspension polymerization
4. Emulsion polymerization
5. Melt polycondensation
6. Solution polycondensation
7. Interfacial Condensation
8. Solid and Gas Phase polymerization