Basic properties of step-growth polymerization processes

2 Basic properties of step-growth polymerization processes [Pg.276]

Many polycondensation reactor designs provide large surface areas for mass transfer of condensation byproducts out of the polymer phase. In some processes, high vacuum is applied to encourage byproduct removal. [Pg.277]

Polycondensation can be carried out by various polymerization techniques including melt polymerization, solution polymerization, interfacial polymerization, emulsion polymerization and solid-state polymerization. These polymerization processes will be summarized briefly in the following paragraphs. [Pg.277]

Solution polycondensation is used in industry to produce polyurethanes, polycarbonates and certain types of polyamides and polyesters. Polycondensation in solution is most frequently used when it is difficult or impossible to keep the reactants in the same phase using bulk polymerization, or when the melting point of the resulting polymer is too high. Solution polycondensation takes place at lower temperatures than melt polymerization and enables efficient heat transfer to be maintained due to lower viscosity. However, solution polycondensation requires polymer separation from solution, recovery of solvent, and polymer washing and drying. [Pg.277]

In emulsion polycondensation, the polymer formation reaction occurs in the bulk of one of the liquid phases. This method is employed for irreversible, exothermic polycondensations, accompanied by the liberation of a side product. Highly reactive monomers (e.g., dichlorides or dicarboxylic acids, diamines, etc.) are most suitable for emulsion polycondensation. To date, the number of step-growth polymers that are prepared using emulsion or mini-emulsion polymerization methods is small, and the technological aspects of this technique [Pg.277]