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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page Applications and process overview

Two textbook cases

Bibliography

(1) - BOUAYAD (R.), BIKARD (J.), AGASSANT (J.A.) - Compressible flow in a plate/plate rheometer : application to the experimental determination of reactive expansion's models parameters for polyurethane foam - Int. J. of Forming Processes, in revision (2008).
(2)...

Software tools

Here is a non-exhaustive list of software for numerical simulation of foam injection into a mold:

VirtuFoam: 2D planar and axisymmetric finite element foam calculation modules using Matlab© software – coupling equation of motion, heat, conservation of chemical species, evolution of the material front in a mold.

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