Penetration depth of phenol-formaldehyde (PF) resin into beech wood studied by light microscopy
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Using light microscopy (LM), the distribution and penetration depth of phenol–formaldehyde (PF) resin into wood specimens were examined after the seventh dry–wet cycle following the anti-swelling efficiency method. PF resins with the average molecular weights (Mw) of 297, 421, 655 and 854 g/mol at concentrations of 9, 18 and 27 wt% in water were vacuum-impregnated into beech wood (Fagus sylvatica) blocks (25 × 25 × 10 mm3). The measurements of the increase in cell wall thickness (bulking) showed that the 297 and 421 g/mol oligomers resulted in greater cell wall bulking (14.9 and 15.4%, respectively) than the 655 and 854 g/mol oligomers (11 and 9.9% bulking, respectively). The presence of chemical agents in the wood was detected based on the safranin staining intensity of the specimen’s transverse sections. The amount of safranin adsorbed on the beech wood sections decreased as the amount of resin incorporated into the cell walls increased, apparently due to a decrease in the number of free microvoids available for safranin adsorption. Less intense dye staining was observed in treated sample sections compared with untreated transverse sections. The lowest amount of safranin was found in wood that was treated with phenol oligomers of 297 and 421 g/mol; wood treated with oligomers of 655 and 854 g/mol adsorbed greater amounts of safranin. Thus, high-molecular-weight PF resins were more uniformly distributed in the specimen and mainly located in the fiber lumens. The results show that safranin staining and visual evaluation by LM is a simple and reliable method to determine the location of PF resin in treated wood.
The authors express their appreciation to Pollmeier Massivholz GmbH and Co. for financial support. The authors also express personal thanks to Dr. Elke Fliedner at Prefere Resins Germany GmbH for providing data related to the characteristics of PF resins.
- Bicke S, Militz H (2014) Modification of beech veneers with low molecular weight phenol–formaldehyde for the production of plywood: comparison of the submersion and vacuum impregnation. In: Abstract book of 7th European conference of wood modification, Lisbon, Portugal, March 2014Google Scholar
- Deka M, Saikia CN, Baruah KK (2000) Treatment of wood with thermosetting resins: effect on dimensional stability, strength and termite resistance. Ind J Chem Technol 7:312–317Google Scholar
- Imamura Y, Kajita H, Higuchi N (1998) Modification of wood by treatment with low molecular phenol–formaldehyde resin (1). Influence of neutral and alkaline resins (in Japanese). In: Abstracts of the 48th Annual Meeting of Japan Wood Research society, Shizuoka, Japan, April 1998Google Scholar
- Krause A, Jones D, Van der Zee M, Militz H (2003) Interlace treatment—Wood modification with N-methylol compounds. In: First European conference on wood modification, Gent Belgium, pp 317–327Google Scholar
- Rowell RM (2005) Chemical modification of wood. In: Rowell RM (ed) Handbook of wood chemistry, wood composites, Chapter 14. CRC Press, Boco Raton, pp 381–420Google Scholar
- Ryu JY, Imamura Y, Takahashi M, Kajita H (1993) Effect of molecular weight and some other properties of resins on the biological resistance of phenolic resin treated wood. Mokuzai Gakkaishi 39(4):486–492Google Scholar
- Ryu JY, Takahashi M, Imamura Y, Sato T (1991) Biological resistance of phenol-resin treated wood. J Jpn Wood Res Soc 37(9):852–858Google Scholar
- Smith WB, Côtê WA, Siau JF, Vasishth RC (1985) Interactions between water-borne polymer systems and the wood cell wall. J Coat Technol 57:27–35Google Scholar
- Takahashi M, Imamura Y (1990) Biological resistance of phenol-resin treated wood. IRG/WP/3602, 21st annual meeting, Rotorua, New ZelandGoogle Scholar
- Wepner F, Krause A, Militz H (2006) Weathering resistance of N-methylol-treated plywood panels. In: 2nd International symposium on veneer processing and products. Vancouver, Canada, pp 305–314, May 2006Google Scholar
- Xie Y, Krause A, Militz H (2014) 17th Chapter: wood protection with dimethyloldihydroxy-ethyleneurea and its derivatives, in book “Deterioration and Protection of Sustainable Biomaterials”, pp 287–301Google Scholar