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Licensed Unlicensed Requires Authentication Published by De Gruyter March 10, 2022

Effect of PF resin penetration on interphase microstructure and quantitative micromechanical properties of different grained-wood laminates

Zhenrui Li ORCID logo, Keying Long, Yu Zhang ORCID logo, Kaiqiang Chen and Lanying Lin
From the journal Holzforschung


Wood, a natural anisotropic material, behaves differently in the radial (R) and tangential direction (T), which also gives rise to different penetration capacity of adhesive into wood tissues. The present study investigates the penetration behavior of adhesive in the interphase of three different wood laminates, namely R-R, T-R, and T-T combinations, and its effect on microstructure and micromechanical properties of the latewood bonding interphase using confocal laser scanning microscopy (CLSM) and nanoindentation (NI). The results showed that the average penetration depth (AP) of the radial surface (SR) was higher than that of the tangential surface (ST) and a significant improvement in the mechanics of cells compared with the control cell (C). the maximum reduced elastic modulus (E r ) and hardness (H) found at the fourth cell row were 21.7 GPa and 0.62 GPa for R-R laminate, respectively, which increased by 43% and 29% compared with C (15.1 GPa, 0.48 GPa), and the maximum E r and H found at the first cell row were 23.2 GPa and 0.65 GPa for T-T laminate, respectively, which increased by 52% and 44% compared with C (15.3 GPa, 0.45 GPa). The results provide an important platform for better understanding and predicting the properties of wood glue line and bonding interphase.

Corresponding author: Lanying Lin, Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, China, E-mail:

Funding source: National Natural Science Foundation of China

Award Identifier / Grant number: 31890772

  1. Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: This study was supported by the National Natural Science Foundation of China (Grant no. 31890772).

  3. Conflict of interest statement: The authors declare no conflicts of interest regarding this article.


Altgen, M., Awais, M., Altgen, D., Kluppel, A., Makela, M., and Rautkari, L. (2020). Distribution and curing reactions of melamine formaldehyde resin in cells of impregnation-modified wood. Sci. Rep. 10: 3366, in Google Scholar

Bastani, A., Adamopoulos, S., and Militz, H. (2015). Effect of open assembly time and equilibrium moisture content on the penetration of polyurethane adhesive into thermally modified wood. J. Adhes. 93: 575–583, in Google Scholar

Bockel, S., Harling, S., Grönquist, P., Niemz, P., Pichelin, F., Weiland, G., and Konnerth, J. (2020). Characterization of wood-adhesive bonds in wet conditions by means of nanoindentation and tensile shear strength. Eur. J. Wood Wood Prod. 78: 449–459, in Google Scholar

Dill-Langer, G., Lütze, S., and Aicher, S. (2002). Microfracture in wood monitored by confocal laser scanning microscopy. Wood Sci. Technol. 36: 487–499, in Google Scholar

Fengel, D. (1972). Structure and function of the membrane in softwood bordered pits. Holzforschung 26: 1–9, in Google Scholar

Frazier, C.E. and Ni, J.W. (1998). On the occurrence of network interpenetration in the wood-isocyanate adhesive interphase. Int. J. Adhesion Adhes. 18: 81–87, in Google Scholar

Furuno, T., Imamura, Y., and Kajita, H. (2004). The modification of wood by treatment with low molecular weight phenol-formaldehyde resin: a properties enhancement with neutralized phenolic-resin and resin penetration into wood cell walls. Wood Sci. Technol. 37: 349–361.10.1007/s00226-003-0176-6Search in Google Scholar

Gavrilović-Grmuša, I., Dunky, M., Miljković, J., and Djiporović-Momčilović, M. (2010a). Radial penetration of urea-formaldehyde adhesive resins into beech (Fagus moesiaca). J. Adhes. Sci. Technol. 24: 1753–1768.10.1163/016942410X507812Search in Google Scholar

Gavrilović-Grmuša, I., Miljković, J., and Ðiporović-Momčilović, M. (2010b). Influence of the degree of condensation on the radial penetration of urea-formaldehyde adhesives into Silver Fir (Abies alba, Mill.) wood tissue. J. Adhes. Sci. Technol. 24: 1437–1453.10.1163/016942410X501034Search in Google Scholar

Gavrilović-Grmuša, I., Dunky, M., Miljkovic, J., and Djiporovic-Momcilovic, M. (2012). Influence of the viscosity of UF resins on the radial and tangential penetration into poplar wood and on the shear strength of adhesive joints. Holzforschung 66: 849–856, in Google Scholar

Gindl, W. (2001). SEM and UV-microscopic investigation of glue lines in Parallam® PSL. Holz als Roh- Werkst. 59: 211–214, in Google Scholar

Gindl, W., Sretenovic, A., Vincenti, A., and Müller, U. (2005). Direct measurement of strain distribution along a wood bond line. Part 2: effects of adhesive penetration on strain distribution. Holzforschung 59: 307–310, in Google Scholar

Gindl, W., Schoberl, T., and Keckes, J. (2006). Structure and properties of pulp fiber-reinforced composite with regenerated cellulose matrix. Appl. Phys. A 83: 19–22, in Google Scholar

Groom, L., So, C.L., Elder, T., Pesacreta, T., and Rials, T. (2004). Proceedings of the seventh Pacific Rim Bio-Based Composites Symposium, October 31th-November 2nd, 2004: Effect of refining pressure and resin viscosity on resin flow, distribution and penetration of MDF fibers. Science & Technique Literature Press, Nanjing, China.Search in Google Scholar

He, G. and Riedl, B. (2004). Curing kinetics of phenol formaldehyde resin and wood-resin interactions in the presence of wood substrates. Wood Sci. Technol. 38: 69–81.10.1007/s00226-003-0221-5Search in Google Scholar

Herzele, S., Van Herwijnen, H.W.G., Griesser, T., Gindl-Altmutter, W., Rößler, C., and Konnerth, J. (2020). Differences in adhesion between 1C-PUR and MUF wood adhesives to (ligno)cellulosic surfaces revealed by nanoindentation. Int. J. Adhesion Adhes. 98: 102507, in Google Scholar

Huang, Y.X., Lin, Q.Q., Yang, C., Bian, G.M., Zhang, Y.H., and Yu, W.J. (2020). Multi-scale characterization of bamboo bonding interfaces with phenol-formaldehyde resin of different molecular weight to study the bonding mechanism. J. R. Soc. Interface 17: 20190755, in Google Scholar PubMed PubMed Central

Jakes, J.E., Hunt, C.G., Yelle, D.J., Lorenz, L., Hirth, K., Gleber, S.C., Vogt, S., Grigsby, W., and Frihart, C.R. (2015). Synchrotron-based X-ray fluorescence microscopy in conjunction with nanoindentation to study molecular-scale interactions of phenol-formaldehyde in wood cell walls. ACS Appl. Mater. Interfaces 7: 6584–6589, in Google Scholar PubMed

Jakes, J.E., Frihart, C.R., Hunt, C.G., Yelle, D.J., and Nayomi, Z.P. (2019). X-ray methods to observe and quantify adhesive penetration into wood. J. Mater. Sci. 54: 705–718, in Google Scholar

Jeong, B. and Park, B.D. (2019). Effect of molecular weight of urea–formaldehyde resins on their cure kinetics, interphase, penetration into wood, and adhesion in bonding wood. Wood Sci. Technol. 53: 665–685, in Google Scholar

Jiang, Z.H., Yu, Y., Qin, D.C., Wang, G., Zhang, B., and Fu, Y.J. (2006). Pilot investigation of the mechanical properties of wood flooring paint films by in situ imaging nanoindentation. Holzforschung 60: 698–701, in Google Scholar

Johnson, S.E. and Kamke, F.A. (1992). Quantitative analysis of gross adhesive penetration in wood using fluorescence microscopy. J. Adhes. 40: 47–61, in Google Scholar

Kamke, F.A. and Lee, J.N. (2007). Adhesive penetration in wood - a review. Wood Fiber Sci. 39: 205–220.Search in Google Scholar

Konnerth, J. and Gindl, W. (2006). Mechanical characterisation of wood-adhesive interphase cell walls by nanoindentation. Holzforschung 60: 429–433, in Google Scholar

Konnerth, J., Gierlinger, N., Keckes, J., and Gindl, W. (2009). Actual versus apparent within cell wall variability of nanoindentation results from wood cell walls related to cellulose microfibril angle. J. Mater. Sci. 44: 4399–4406, in Google Scholar PubMed PubMed Central

Konnerth, J., Eiser, M., Jäger, A., Bader, T.K., Hofstetter, K., Follrich, J., Ters, T., Hansmann, C., and Wimmer, R. (2010). Macro and micro-mechanical properties of red oak wood (Quercus rubra L.) treated with hemicellulases. Holzforschung 64: 447–453, in Google Scholar

Lippke, B.B., Wilson, J., Garcia, J.P., Bowyer, J., and Meil, J. (2004). CORRIM: life-cycle environmental performance of renewable building materials. For. Prod. J. 54: 8–19.Search in Google Scholar

Liu, M.H., Lyu, S.Y., Peng, L.M., Cai, L.P., Huang, Z.H., and Lyu, J.X. (2021). Improvement of toughness and mechanical properties of furfurylated wood by biosourced epoxidized soybean oil. ACS Sustain. Chem. Eng. 9: 8142–8155, in Google Scholar

Marra, A.A. (1992). Technology of wood bonding: principles in practice. Springer, New York.Search in Google Scholar

Modzel, G., Kamke, F.A., and De Carlo, F. (2010). Comparative analysis of a wood: adhesive bondline. Wood Sci. Technol. 45: 147–158, in Google Scholar

Obersriebnig, M., Konnerth, J., and Gindl-Altmutter, W. (2013). Evaluating fundamental position-dependent differences in wood cell wall adhesion using nanoindentation. Int. J. Adhesion Adhes. 40: 129–134, in Google Scholar PubMed PubMed Central

Oliver, C.D., Nassar, N.T., Lippke, B.R., and Mccarter, J.B. (2014). Carbon, fossil fuel, and biodiversity mitigation with wood and forests. J. Sustain. For. 33: 248–275, in Google Scholar

Oliver, W.C. and Pharr, G.M. (1992). An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments. J. Mater. Res. 7: 1564–1583, in Google Scholar

Paris, J.L. and Kamke, F.A. (2015). Quantitative wood–adhesive penetration with X-ray computed tomography. Int. J. Adhesion Adhes. 61: 71–80, in Google Scholar

Pizzi, A., Mtsweni, B., and Parsons, W. (1994). Wood-induced catalytic activation of PF adhesives autopolymerization vs. PF/wood covalent bonding. J. Appl. Polym. Sci. 52: 1847–1856, in Google Scholar

Pizzi, A. (2015). Synthetic adhesives for wood panels: chemistry and technology. In: Mittal, K.L. (Ed.), Progress in adhesion and adhesives. John Wiley & Sons, New York, pp. 85–123.10.1002/9781119162346.ch4Search in Google Scholar

Qin, L.Z., Lin, L.Y., Fu, F., and Fan, M.Z. (2017). Microstructure and quantitative micromechanical analysis of wood cell-emulsion polymer isocyanate and urea-formaldehyde interphases. Microsc. Microanal. 23: 687–695, in Google Scholar

Rao, F., Ji, Y.H., Huang, Y.X., Li, N., Zhang, Y.H., Chen, Y.H., and Yu, W.J. (2021). Influence of resin molecular weight on bonding interface, water resistance, and mechanical properties of bamboo scrimber composite. Construct. Build. Mater. 292: 123458, in Google Scholar

Resnik, J., Sernek, M., and Kamke, F.A. (1997). High-frequency hating of wood with moisture content gradient. Wood Fiber Sci. 29: 264–271.Search in Google Scholar

Serrano-Ruiz, J.C., West, R.M., and Dumesic, J.A. (2010). Catalytic conversion of renewable biomass resources to fuels and chemicals. Annu. Rev. Chem. Biomol. Eng. 1: 79–100, in Google Scholar PubMed

Stoeckel, F., Konnerth, J., and Gindl-Altmutter, W. (2013). Mechanical properties of adhesives for bonding wood — a review. Int. J. Adhesion Adhes. 45: 32–41, in Google Scholar

Wang, W.Q. and Yan, N. (2005). Characterizing liquid resin penetration in wood using a mercury intrusion porosimeter. Wood Fiber Sci. 37: 505–513.Search in Google Scholar

Wang, X.Z., Deng, Y.H., Li, Y.J., Kjoller, K., Roy, A., and Wang, S.Q. (2016). In situ identification of the molecular-scale interactions of phenol-formaldehyde resin and wood cell walls using infrared nanospectroscopy. RSC Adv. 6: 76318–76324, in Google Scholar

Wang, X.Z., Zhao, L.G., Deng, Y.H., Li, Y.J., and Wang, S.Q. (2018). Effect of the penetration of isocyanates (pMDI) on the nanomechanics of wood cell wall evaluated by AFM-IR and nanoindentation (NI). Holzforschung 72: 301–309, in Google Scholar

Wang, X.Z., Chen, X.Z., Xie, X.Q., Yuan, Z.R., Cai, S.X., and Li, Y.J. (2019). Effect of phenol formaldehyde resin penetration on the quasi-static and dynamic mechanics of wood cell walls using nanoindentation. Nanomaterials 9: 1409, in Google Scholar PubMed PubMed Central

Wimmer, R., Lucas, B.N., Tsui, T.Y., and Oliver, W.C. (1997). Longitudinal hardness and Young’s modulus of spruce tracheid secondary walls using nanoindentation technique. Wood Sci. Technol. 31: 131–141, in Google Scholar

Yu, Y., Tian, G.L., Wang, H.K., Fei, B.H., and Wang, G. (2011). Mechanical characterization of single bamboo fibers with nanoindentation and microtensile technique. Holzforschung 65: 113–119, in Google Scholar

Yusof, N.M., Tahir, P.M., Lee, S.H., and Khan, M.A. (2019). Mechanical and physical properties of cross-laminated timber made from acacia mangium wood as function of adhesive types. J. Wood Sci. 65: 20, in Google Scholar

Zhang, Y., Liu, C., Wang, S.Q., Wu, Y., Meng, Y.J., Cui, J.Q., and Zhou, Z.B. (2015). The influence of nanocellulose and silicon dioxide on the mechanical properties of the cell wall with relation to the bond interface between wood and urea formaldehyde resin. Wood Fiber Sci. 47: 249–257.Search in Google Scholar

Received: 2021-10-14
Accepted: 2022-02-10
Published Online: 2022-03-10
Published in Print: 2022-06-27

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