In the production of polyurethane foam, catalysts play an important role. With a good selection of the catalyst, the desired profile in reaction, foaming, flowability, and foam properties can be obtained. In this article a deeper insight into the molecular catalyst structure-polymer properties relationship will be given. The selection of catalyst is based on its activity as well as performance on physical foam properties. Depending on the molecular structure of the catalyst, the activity will be different. This activity relates to the catalysis of the gel and blow reaction but also the allophonate, biuret, and trimerisation reactions. Via a model system, each of these reactions is studied to understand the reaction mechanism in a better way.

To study the influence of the flame-retardant melamine on foam properties of a polyurethane model system, single, vertical liquid foam films were studied. The presence of particles gives the possibility to observe the complete circulation in the film. The films of the model system have been found to be mobile films showing marginal regeneration. Film formation was combined with surface-tension measurements on the pool surface. The changes in the surface tension of the pool were measured and the amount of surfactant diffused from the surface of the pool to the surface of the film were calculated. This quantity was found to be a few percent of the moles necessary for equilibrium coverage. The fresh film surface is nearly independent of the pool surface and the meniscus behaves as a slit, producing a film with a nearly surfactant-free surface. Two characteristic phenomena were observed during film formation from a suspension containing 25 pphp melamine ultrafine: (1) The convective currents are slower in the melamine-filled film than in the corresponding melamine-free lamellae.(2) No surface tension difference was seen on the surface of the pool after film formation. It seems that the melamine hinders the surface diffusion.

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ABSTRACT:To study the influence of the flame-retardant melamine on foam properties of a polyurethane model system, single, vertical liquid foam films were studied. The presence of particles gives the possibility to observe the complete circulation in the film. The films of the model system have been found to be mobile films showing marginal regeneration. Film formation was combined with surface-tension measurements on the pool surface. The changes in the surface tension of the pool were measured and the amount of surfactant diffused from the surface of the pool to the surface of the film were calculated. This quantity was found to be a few percent of the moles necessary for equilibrium coverage. The fresh film surface is nearly independent of the pool surface and the meniscus behaves as a slit, producing a film with a nearly surfactant-free surface. Two characteristic phenomena were observed during film formation from a suspension containing 25 pphp melamine ultrafine: (1) The convective currents are slower in the melamine-filled film than in the corresponding melamine-free lamellae.(2) No surface tension difference was seen on the surface of the pool after film formation. It seems that the melamine hinders the surface diffusion.