New strategies for fire retardancy of pine and beech wood

Abstract

Different treatments have been applied to pine and beech samples in order to evaluate their fire behavior. Boron and phosphorous flame retardants have been tested, as well as the synergic effect between boron salts and alkaline silicates. Boron acid and salts act releasing water and forming a protective an insulating glaze on the wood surface. However, boron compounds are easily leached by water and their use is limited to indoor applications. Therefore in this work two non-water soluble phosphates: bisphenol diphenyl phosphate and triphenyl phosphate have been also considered. After this first evaluation, the optimal flame retardant formulation has been mixed with an alkaline silicate in order to investigate possible synergisms to improve fire properties of wood. In both cases fire behavior has been tested by the dripping test, using a radiator device, and by the limiting oxygen index (LOI). Morphology of the samples after impregnation and presence of the treatment agents have been evaluated in an electron scanning microscope.