Abstract
Rising demands for fire resistance properties of wood construction and elements matching new standards have been an important part of building codes during the last decade. On the other side, lack of more detailed research on interaction between wood species and selected fire retardant chemicals even with basically one is evident. This is particularly truth with domestic wood species. In this research, beech and poplar veneers were immersed in 25% solutions of monoammonium phosphate (MP) and sodium acetate (SA) and impregnated for different periods of time. To determine the preliminary level of fire retardancy achieved in veneers before manufacturing of finished plywood, thermo gravimetric (TG) and derivative thermo gravimetric (DTG) methods were used. TG and DTG analyses of treated and untreated wood, as well as of fire retardants alone, were performed. The next properties of impregnated and no impregnated veneers and plywood were determined: absorption of imp regnant solution (A), weight percent gain (WPG) of imp regnant, equilibrium moisture content (EMC), pH values, and in the case of plywood, strength and fire resistance. Fire resistance of plywood was tested in accordance with standard test for resistance to the effects of fire and the most efficient fire retardant, monoammonium phosphate, had the same result as TG/DTG analyses, which pointed out the validity of TG methods in predicting fire resistance of future products.
Highlights
Wood construction for many years has been classified in building codes under three standard types - heavy timber, ordinary and light frame
Fire resistance of plywood was tested in accordance with standard test for resistance to the effects of fire and the most efficient fire retardant, monoammonium phosphate, had the same result as TG/derivative thermogravimetric (DTG) analyses, which pointed out the validity of TG methods in predicting fire resistance of future products
A bsorption and weight percent gain of impregnant in veneers Absorption (A) and weight percent gain (WPG) of impregnant in veneers are shown in Fig. 3 for poplar veneers (a) and for beech veneers (b)
Summary
Wood construction for many years has been classified in building codes under three standard types - heavy timber, ordinary and light frame. Forms of wood found in construction, have expanded from timber and decking to a wide variety of wood-based materials Products such as plywood, laminated veneer lumber and more recently composites of plywood and particleboard (such as wafer board and strand board) are commonly used. One method involves surface coating to protect the underlying wood members Such treatments increase time to ignition and reduce flame spread following ignition. The second and more important application is by soak treatment This application assumed absorption of fire-retardant compounds, such as different inorganic salts. Such impregnating treatments both reduce flame spread and produce wood-based products which are accepted in the building codes, since they have improved fire endurance. In this study some factors affecting absorption step and thermal degradation of impregnated beech and poplar veneers as common domestic wood species, with monoammonium phosphate (MP) and with sodium acetate (SA) have been investigated
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