Estudo tecnológico do tetraborato de sódio como retardante de chamas para madeira

Abstract

In Brazil, combustion capacity and insecurity in the face of fire-related risks are con sidered restrictions for the construction of buildings with their wooden structure due to the lack of knowledge of the behavior of wood in relation to fire. However, from the 70s, studies on the performance of materials against combustion, made it possible to affirm that “wood presents a good performance against fire when compared to other materials”. Still, through the use of flame retardant products applied in this, it beco mes possible to reduce or inhibit the spread of fire in a marked way in this material, providing benefits regarding its use, since the application of retardants in wood al lows a considerable increase in time of escape from environments in the event of fire, decreasing the production of local smoke, allowing people the time to evacuate th e burning place safely. According to the Brazilian Association of the Flame Retardants Industry (ABICHAMA), "flame retardants are chemical substances that have the ac tion of retarding the ignition, reducing the burning speed and minimizing the smoke emission of the materials to which they are incorporated". Therefore, this study had as main objectives: to evaluate whether the sodium tetraborate salt (borax) diluted in three different concentrations (7.5%, 9.5% and 11.5%) has flame retardant capacity when applied in four species hardwoods (Corymbia maculata, Eucalyptus dunnii, Eu calyptus grandis and Eucalyptus saligna) and a coniferous species of wood (Pinus elliottii) and also to verify if the said salt has the capacity to reduce the loss of mass of the samples when submitted to combustion. Still, it was sought to verify the capa city of this one to maintain the relative mechanical resistance of the wood after bur ning. For such, long and short term combustion analyzes were carried out, following the precepts of Tondi et al. (2012). The samples were also impregnated with com mercial flame retardant based on nitrogenous compounds and borates (CNB), in or der to compare the salt retardant capacity to a product used in the market for the same purposes. Thermogravimetric analyzes (TGA) of the treated species were car ried out, aiming to compare with their behavior when burning in the long term. Che mical analyzes of the bands of the main components of the wood in the study were also carried out through non-destructive spectroscopy (FTIR), in order to verify the influence of treatments on their combustion degradation. The mechanical characteri zation was performed by janka hardness tests, before and after the flammability of the samples, with the intention of verifying the ability of the salt to preserve the relati ve mechanical resistance of this polymer after combustion. It was concluded that bo rax concentrations are capable of retarding the flame and reducing the mass loss of the studied wood, with better efficiency in Pinus elliottii, presenting itself as a cheap alternative for use in this polymer for such purpose. Furthermore, borax also showed the ability to preserve the relative mechanical strength of wood after combustion in relation to samples without treatment. Key words: combustion; flame retardant; loss of wood mass.