The effect of heat treatment and primary impregnation of Fir wood with borax on the fire resistance and thermal behavior

Document Type : Complete scientific research article

Authors

1 Gorgan University of Agricultural Sciences and Natural Resources

2 faculty member

Abstract

Background and objectives: The wood is used for its aesthetic appearance and at the same time its high mechanical strength, but it also has some disadvantages that limit its application. Wood modification is a science to improve undesirable properties of wood. Thermal modification is a useful method to develop dimensional stability and biological resistance. Heat treatment degrades the fire resistance of wood. The main disadvantage of wood is its flammability. Lignocellulosics burn because the cell wall polymers undergo pyrolysis reactions with increasing temperature to give off flammable gasses. Primary impregnation of wood with borates has been found to reduce flammability of thermally modified wood. Boron compounds work efficiently as fire retardant for cellulosic materials. Boron compounds are recognized as inexpensive, easily applicable and environmentally safe preservatives. The aim of this study was to investigate the effect of heat treatment and primary impregnation of Fir wood with borax on the fire resistance, thermal behavior and dimensional stability.
Materials and methods: Specimens were prepared to dimensions of 150 (L) ×100 (T) ×20 (R) mm and were impregnated with %7 aqueous solution of borax for 40 minutes at the pressure of 4 bar. Heat treatment was carried out at the temperatures of 170 ◦C and 190 ◦C in oven for 3 hours. Specimens were prepared according to ISO 11925 standard specifications to measure fire retarding properties including ignition time, glowing time, carbonized area and mass loss within the burning process. Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) were carried out under air at a heating rate of 10 °C/min. The temperature was heated from the room temperature up to 600 °C. Long-term dimensional stability were measured.
Results: Heat treatment of specimens caused mass loss. The impregnation of wood with borax reduced the mass loss during heat treatment. Heat treatment decreased ignition time. Borax postponed the ignition time of thermally modified wood.TGA thermograms showed that residual char amount was increased in borax preimpregnated-heat treated specimens compared with thermally modified specimens. Char provided insulation and also inhibited propagation of heat. DSC thermograms determined that for borax preimpregnated-heat treated specimens rate of formation of the volatile products reached its maximum at a lower temperature in comparison to thermally modified specimens. During the heat exposure borax formed glassy films on the wood that may inhibit mass transfer of combustible gases. Long-term immersion results confirmed that volumetric swelling and water absorption of thermally modified specimens decreased due to enhancement of hydrophobicity. Volumetric swelling and water absorption of borax preimpregnated specimens increased due to enhancement of hydrophylicity.
Conclusion: Thermally modified wood was susceptible to burning and its fire resistance was decreased. Primary impregnation of Fir wood with borax postponed ignition time and glowing time and eventually increased fire resistance. The lowest carbonized area and mass loss was obtained in borax preimpregnated-heat treated specimens. Thermal analysis showed sharp mass loss for thermally modified wood in comparison to borax preimpregnated-heat treated specimens. Borax increased the resistance of thermally modified wood to thermal degradation and altered pyrolysis route of wood and leaded to the inhibiton of the flame spread. In other words borax decreased the Tmax (maximum degradation temperature). Borax preimpregnated-heat treated specimens of Fir wood decreased dimensional stability in comparison to thermally modified wood.
Key words: Fire resistance, Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Dimensional stability.

Keywords

Main Subjects

References

1- Militz, H. 1991.The improvement of dimensional stability and durability of wood through treatment with non-catalysed acetic acid anhydride. Holz als Roh-und Werkstoff, 49: 147-152.
2- Sailer, M., Rapp, A.O., Leithoff, H., Peek, R.D. 2000. Upgrading of wood by application of an oil heat treatment. Holz als RohWerkstoff. 58(1/2): 15-22.
3- Kamdem, D.P., Pizzi, A., and Jermannaud, A. 2002. Duribility of heat-treated wood. Holz Roh Werkst. 60(1): 1-6.
4- Delichatsios, M., Paroz, B., and Bhargava, A. 2003. Flammability properties for charring materials, Fire Safety J. 38(3): 219- 228. DOI: 10.1016/S0379- 7112 (02) 00080-2.
5- Parsapajouh, D., Faezipour, M., and Taghiyari, H. 2011. Industrial timber preservation, 5th Ed., Tehran University Publications, Tehran, 657p. (In Persian)
6- Stark, N.M., White, R.H., Mueller, S.A., and Osswald, T.A. 2010. Evaluation of various fire retardants for use in wood flour-polyethylene composites, Polymer Degradation and Stability. 95: 1903-1910.
7- Kartal, S.N., Hwang, W.J., and Imamura, Y. 2007. Water absorption of boron-treated and heat-modified wood. J Wood Sci. 53: 454-457.
8- Salman, S., Petrissans, A., Thevenon, M.F., Dumarcay, S., Perrin, D., Pollier, B., and Gerardin, P. 2014. Development of new wood treatments combining boron impregnation and thermo modification: effect of additives on boron lecheability. Eur. J Wood Prod. 72: 355-365.
9- Obanda, D.N., Shpe, F.T., and Barnes, H.M. 2008. Reducing leaching of boron based wood preservatives- a review of research. Bioresource Technol. 99: 7312-7322.
10- Lioyd, J.D., Fogel, J.L., and Vizel, A. 2001. The use of Zirconium as an inert fixative for borates in preservation. International Research Group on Wood Preservation. IRG Secretariat, Stockholm, Sweden.
11- Wang, W., Cao, J., Cui, F., and Wang, X. 2012. Effect of PH on chemical components and mechanical properties of thermally modified wood, “Wood and Fiber Science, 44(1): 46-53.
12- Uner, I.H., Deveci, I., Baysal, E., Turkoglu, T., Toker, H., and Peker, H. 2016. Thermal analysis of oriental beech wood treated with some borates as fire retardants. Maderas. Ciencia y tecnologia, 18(2): 293-304.
13- Uysal, B., and Ozciftci, A. 2004. The effects of impregnation chemicals on combustion properties of laminated wood material. Combustion Science and Technology, 176(1): 117-133.
14- Baysal, E. 2002. Determination of oxygen index levels and thermal analysis of Scots pine (Pinus sylvestris L.) impregnated with melamine formaldehyde-boron combination. Jornal of fire science, 20(5): 373-389.
15- Karastergiou, P.S., and Philippou, J.L. 2000. Thermogravimetric analysis of fire retardant treated particleboards.Wood and fire safety. Pp: 385-394.
16- Percin, O., Sofuoglu, S.D., and Uzun, O. 2015. Effects of Boron Impregnation and Heat Treatment on some mechanical
7931 )
properties of Oak (Quercus petraea Libel.) wood. Bioresources 10(3): 3963-3978.
17- Rusche, H. 1973. Thermal degradation of wood at temperatures up to 200°C. Part II. Reaction kinetics of loss of mass during heat treatment of wood. Holz als Roh-und Werkstoff., 31: 8. 307-312.
18- Awoyemi, L., and Westermark, U. 2005. Effects of borate impregnation on the response of wood strength to heat treatment. Wood Sci Technol, 39: 484-491.
19- Jaskolowski, W., Ogrodnik, P., and Chmielewska, A.L. 2014. The study of time to ignition of woods under external heat flux by piloted ignition and autoignition. Forestry and Wood Technology NO. 86: 133-137.
20- Cekovska, H., Gaff, M., Osvald, A., Kacik, F., Kubs, J., and Kaplan, L. 2017. Fire resistance of thermally modified spruce wood. Bioresource.12(1): 947-959.
21- Jana, M. 2013. Fire Safety Properties of Heat Treated Wood. Research journal of recent sciences. 2(12): 80-82.
22- Manninen, A.M., Pasanen, P., and Holopainen, J.K. 2002. Comparing the VOC emissions between air- dried and heat treated Scots pine wood, Atmos. Environ. 36(11): 1763-1768. DOI: 10.1016/S1352-2310(02) 00152-8.
23- Martinka, J., Tomas, C., Kral, J., and Balog, K. 2013. An Examination of the Behaviour of Thermally Treated Spruce Wood under Fire Conditions. Wood research. 58(4): 599-606.
24- Mohebby, B., Talaii, A., and Kazemi Najafi, S. 2007. Influence of acetylating on fire resistance of beech plywood. Materials Letters, 61: 359-362. (In Persian)
25- Rowell, R.M. 1991. Chemical modification of wood. Cited in wood and cellulose chemistry, New York marcel dekker Inc.chap. 15: 709-756.
26- Hakkou, M., Petrissans, M., El Bakali, I., Gerardin, P., and Zoulalian, A. 2005 .Wettability changes and mass loss during heat treatments of wood. Holzforschung., 59: 35-3.
27- Hill, C. 2006. Wood Modification - Chemical, Thermal and other processe, John Wiley and Sons press, England.
28- Podgorski, L., Chevet, B., Onic, L., and Merlin, A. 2000. Modification of wood wettability by plasma and corona treatments. International journal of Adhesion and Adhesivees. 20(2): 103-111.
29- Rowell, R., Lange, S., and Davis, M. 2000. In: Evans, P.D. (ed) Proceedings of 5th Pacific Rim bio-based composites symposium, Canberra, Australia,December 10 13, 2000. ACIAR Proceedings, Pp: 425-438.

Files

Share

How to cite

Statistics