Effect of melamine on the foam kinetics of polyurethane model system. II. Effect of melamine particles on film formation

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.

Thermal decomposition, combustion and fire‐retardancy of polyurethanes—a review of the recent literature

“…In order to increase the shelf life in the polyol dispersion, melamine can be microencapsulated. Sandor et al 135, 136 studied the effect of melamine on foaming and on the mechanical properties of the final foam. Different melamine grades were used both in high‐resilience and in conventional systems.…”