2. Reactive foaming stages
Whether for flexible casting or injection molding, the reagents are mixed in the injection head and then injected. Reactions start immediately – or with a delay (induction) – and the mixture deposited by the head begins to expand and polymerize from a macroscopic point of view.
From a physical point of view, a number of concomitant phenomena, whose kinetics are associated with those of chemical reactions, oppose or combine to create foam:
nucleation of thermodynamically stable gas pockets;
the growth of these gas pockets, linked to their internal pressure (a function of temperature and the outgassing reaction, and therefore a function of the diffusion mechanisms of gases dissolved in the mixture and the permeability of the polymer/CO 2 ...
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Reactive foaming stages
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