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Flammability studies of sodium thiosulphate or metabisulphite impregnated wood using cone calorimeter
Author(s) -
Šimkovic Ivan,
Martvoňová Helena,
Maniková Desana,
Grexa Ondrej
Publication year - 2007
Publication title -
fire and materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.482
H-Index - 58
eISSN - 1099-1018
pISSN - 0308-0501
DOI - 10.1002/fam.930
Subject(s) - cone calorimeter , chemistry , sodium , nuclear chemistry , flammability , fire retardant , ignition system , calorimetry , pyrolysis , organic chemistry , char , physics , thermodynamics
Spruce wood boards impregnated with Na 2 S 2 O 3 or Na 2 S 2 O 5 were studied with the cone calorimeter. The presence of Na 2 S 2 O 3 lowered the average heat release rate in comparison to untreated material. The total amounts of CO and CO 2 production were reduced by the treatment and also the specific extinction area and mass loss rate decreased. Washing of the salt from the material with water caused partial loss of the properties. Addition of the second impregnation step using acids (HCOOH, H 3 BO 3 or H 3 PO 4 ) resulted in the fixation of the sulphur in wood, but gave not the results of single‐step modification for thiosulphate. With Na 2 S 2 O 5 and without acid, the CO and time‐to‐ignition values were higher and average heat release rate smaller in comparison to unmodified material. Combined one step Na 2 S 2 O 5 /H 3 BO 3 treatment lowered the CO, CO 2 and specific extinction area values in comparison to the modification with Na 2 S 2 O 5 , similarly like it was observed for Na 2 S 2 O 3 /H 3 BO 3 two‐step‐treatment. According to time‐to‐ignition values, Na 2 S 2 O 5 alone at 5% addition is a better flame retardant than Na 2 S 2 O 3 at 7%, but the effect is diminished at 10% amount or presence of acids. The total smoke release curves showed decrease due to modification in both phases of the process. Introduction of water washing as well as the acid treatment further lowered the values. The best results were achieved with 15% Na 2 S 2 O 3 –2% H 3 PO 4 –H 2 O system. According to the total smoke release curve the specimen produced more than five times smaller amount of smoke than untreated material in the first phase of the process. It seams that the concentration of Na 2 S 2 O 5 is less affecting the properties than the synergistic effect of the Na 2 S 2 O 3 or Na 2 S 2 O 5 /H 3 BO 3 system. Although the level of smoke is low, the presence of elemental sulphur causes smaller times‐to‐ignition than on starting material. Copyright © 2006 John Wiley & Sons, Ltd.