Bending creep of Maritime pine wood (Pinus pinaster Ait.) chemically modified

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Abstract

The long-term performance of a structural member is determined by its durability and deformation with time. The bending creep behaviour of modified wood was assessed experimentally over a period of 35 days (840 hours).

Four chemical modification processes were used: 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU), mmethylated melamine formaldehyde resin (MMF), tetraethoxysilane (TEOS) and amid wax (WA). Wood stakes with 20.10.200 mm RTL dimensions of Portuguese Maritime pine (Pinus pinaster Ait.) from sapwood part of the stem were used for evaluated the primary creep. Experiments were conducted at bending stresses amounting to 0.1, 0.2, 0.4 of the mean immediate wood bending strength obtained at equilibrium moisture content (EMC). Applying the same stress level (SL, 0.2), wood creep was also determined at the constant low and high moisture content. As results: Between low and medium SL (8 and 16 N/mm2), unmodified wood at indoors conditions did not show any effect in the creep factors (kc). However, at high SL (35 N/mm2) a slight increase (not significant) in the kc was found. It seems that the kc was nearly independent of the SL.

In the lumen fill modification (TEOS and wax), the deposited material has not affected the creep behaviour under various SL. The cell wall modification (with DMDHEU and MMF resins) did not show any differences in the kc for low and medium SL (8 and 16 N/mm2). However, resin modification under high SL (35 N/mm2) has shown a significant reduction related to unmodified wood. Between both types of resin (DMDHEU and MMF) and levels of modification (WPG), significant effect was not found. At saturated conditions, lumen fill modification (TEOS and wax) did not show any effect on creep. In the cell wall modification (DMDHEU and MMF resin), significant reduction was recorded due to the embrittlement effect imparted by the modification (deposit of resin in the cell wall).

Armstrong L.D. 1972. Deformation of wood in compression during moisture movement. Wood Science, 5 (2), 81-86.

Bach L. 1973. Reiner-Weisenberg’s theory applied to time-dependent fracture of wood subjected to various modes of mechanical loading. Wood Science, 5 (3), 161-171.

Bodig J., Jayne B.A. 1982. Mechanics of wood and wood composites. Van Nostrand Reinhold Compony, New York.

Bollmus S. 2011. Biologische und technologische Eigenschaften von Buchenholz nach einer modifizierung mit 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU). Ph.D. Thesis, Georg-August-Universität, Göttingen, Gemany (in German).

Boyd J.D. 1982. An anatomical explanation for visco- elastic and mechano sorptive creep in wood, and effects of loading rate on strength. In: New Perspectives in Wood Anatomy (ed.: P. Baas), Martinus Nijhoff, W. Junk Publishers, Hague, 171-222.

Buffon G.L.L. 1740. Experiences sur la force du bois. Paris L›Academie Royale des Sciences. Histoire et Memoires, Vol. 292.

Clouser W.S. 1959. Creep of small wood beams under constant bending load. Report 2150, USDA Forest Service, Forest Products Laboratory, Madison, WI.

DIN 52 186. 1978. Testing of wood; bending test. Deutsches Institut Für Normung e.V. Normen über Holz, Biegeversuch, Beuth, Berlin, (in German).

Dinwoodie J.M., Higgins J.-A., Paxton B.H., Robson D.J. 1990. Creep research on particleboard, 15 year’s work at the UK Building Research Establishment. Holz als Roh und Werkstoff, 48, 5-10.

Dinwoodie J.M., Paxton B.H., Higgins J.-A., Robson D.J. 1991. Creep in chipboard, Part 10: The effect of variable climate on the creep behaviour of a range of chipboards and one wafer board. Wood Science Technology, 26 (1), 39-51.

Donath S., Militz H., Mai C. 2004. Wood modification with alkoxys. Wood Science and Technology, 38, 555-566.

ENV 1995-1. 2003. EC 5, Eurocode 5 - Design of timber structures - Part 1-1: General - Common rules and rules for buildings. CEN European Committee for Standardization, Bruxelles.

Epmeier H., Westin M., Rapp A. 2004. Differently modified wood: Comparison of some selected properties. Scandinavian Journal of Forest Research, 19 (5), 31-37.

Epmeier H., Kliger R. 2005. Experimental study of material properties of modified Scots pine. Holz als Roh- und Werkstoff, 63, 430-436.

Epmeier H., Johansson M., Kliger R., Westin M. 2007a. Material properties and their interrelation in chemically modified clear wood of Scots pine. Holzforschung, 61, 34-42.

Epmeier H., Johansson M., Kliger R., Westin M. 2007b. Bending creep performance of modified timber. Holz als Roh-und Werkstoff, 65, 343-351.

Grossmann P.U.A. 1976. Requirements for a model that exhibits mechano-sorptive behaviour. Wood Science and Technology, 10, 163-168.

Hearmon R.F.S. 1966. Vibration testing of wood. Forest Product Journal, 16, 29-39.

Krause A. 2006. Holzmodifizierung mit N-Methylolvernetzern. Ph.D. Thesis, Georg-August-Universitat Goettingen (in German).

Liu T. 1994. Creep of wood under a large span of loads in constant and varying environments. Part 2: Theoretical investigations. Holz als Roh und Werkstoff, 52 (1), 63-70.

Lopes D.B., Mai C., Militz H. 2013a. Physical properties of chemical modified Portuguese pinewood.= Manuscript in print.

Lopes D.B., Mai C., Militz H. 2013b. Mechanical properties of chemical modified Portuguese pinewood. Manuscript in print.

Lopes D.B., Mai C., Militz H. 2013c. Mechano-sorptive creep of Portuguese modified wood. Manuscript in print.

Lopes D.B., Mai C., Militz H. 2014. Resistance of Portuguese modified wood to marine borers. Ciencia y Tecnologia, 16 (1), in print.

Machek L., Edlund M.L., Sierra-Alvarez R., Militz H. 2003. A non-destructive approach approach for assessing decay in preservative treated wood. Wood Science and Technology, 37, 411-417.

Mai C., Xie Y., Xiao Z., Bollmus S., Vetter G., Krause A., Militz H. 2007. Influence of the modification with different aldehyde-based agents on the tensile strength. 3 European Conference on Wood Modification, Cardiff, UK, 49-56.

Militz H. 1993. Treatment of timber with water soluble dimethylol resins to improve their dimensional stability and durability. Wood Science and Technology, 27, 347-355.

Norimoto M., Gril J., Rowell R.M. 1992. Rheological properties of chemically modified wood: relationship between dimensional and creep stability. Wood and Fiber Science, 24 (1), 25-35.

Pfeffer A.G. 2011. Effect of water glass, silane and DMDHEU treatment on the colonisation of wood by sap-staining fungi. PhD dissertation, Georg-August- Universität, Göttingen, Germany.

Ranta-Maunus A., Kortesmaa M. 2000. Creep of timber during eight years in natural environments. World Conference on Timber Engineering Whistler, CA, 31 July-3 August. http://www.vtt.fi/inf/pdf/jurelinkit/RTE_Ranta-Maunus3.pdf

Rowell R.M. 1996. Physical and mechanical properties of chemically modified wood. In: Chemical modification of lingo-cellulosic materials (ed.: R.M. Rowell). Marcel Dekker, New York, 295-310.

Schniewind A.P. 1968. Recent progress in the study of the theology of wood. Wood Science and Technology, 2, 188-206.

Scholz G., Krause A., Militz H. 2009. Capillary water uptake and mechanical properties of wax soaked Scots pine. 4 European Conference on Wood Modification, 27-29 April Stockholm, Sweden, 209-212.

Xie Y., Krause A., Militz H., Turkulin H., Richter K., Mai C. 2007. Effect of treatments with 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU). on the tensile properties of wood. Holzforschung, 61, 43-50.

Folia Forestalia Polonica

Seria A - Forestry; The Journal of Forest Research Institute

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