Forces free-radical-growth

The inherent driving force of the partition of reactants between phases has a strong impact on both the kinetics and the product properties, especially if the polymerization mechanism has strict stoichiometric requirements. This is the main reason why heterophase polymerizations via step-growth mechanisms frequently face serious problems. Similar issues may be valid for some radical polymerization techniques where active reactants (e.g., control agents) must partition equally between aU particles. The most common type of polymerization mechanism applied in the production of emulsion polymers is free-radical addition, and this will form the focus of the present chapter. 

Growth of the polyethylene chain proceeds when the free radical on the end of a growing chain reacts with an ethylene molecule brought into close proximity by the force of the high pressure. The incoming ethylene attaches to the end of the chain via a carbon-carbon covalent bond, and an unpaired electron is transferred to the new chain end. 

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