Nanocellulose-reinforced phenol-formaldehyde resin for plywood panel production

Elaine Cristina Lengowski,José Guilherme Prata,Rafael Dallo,Eraldo Antonio Bonfatti,Silvana Nisgoski,Jorge Luís Monteiro De Mattos

doi:10.4067/s0718-221x2021000100405

Abstract

The search for new technologies to improve adhesives and the properties of reconstituted wood panels is constant, and nanotechnology is a tool for this purpose. The aim of this study is investigating the effect of adding nanocellulose in the formulation of the adhesive phenol-formaldehyde on the physico-mechanical properties of Pinus taeda plywood panels. Three ratios of nanofibrillated cellulose (NFC) were added to the adhesive formulation used to produce plywood panels: 0,026 %, 0,038 % or 0,064 %. The panels were tested according to the European standards; apparent density, resistance to parallel and perpendicular flexure and glue line shear strength were determined after 6 hours of boiling and after the boiling cycle for the 1st glue line (face) and 2nd line (core). The use of NFC in the adhesive caused an increase of viscosity and reduction of the gel time of the adhesive. The apparent density of the panels was not influenced by the addition of NFC, but the properties of parallel bending, perpendicular flexing and glue line shear were sensitive to the addition of NFC. The NR2 treatment (0,038 % NFC) presented the best results in the mechanical tests

Highlights

The use of solid wood presents some disadvantages because it is heterogenous and anisotropic (Torquato 2002, Fratzl and Weinkamer 2007, Buligon 2015), and in many cases the mechanical properties of wood are unsatisfactory for certain uses (Song et al 2018)
The addition of nanocellulose to the adhesives affected significantly the physico-chemical properties, except for pH, which remained practically constant for all adhesives (p-value = 0,0521)
Means followed by the same letter in the column are statistically the same by the Tukey test at 95 % confidence; values in parentheses indicate the coefficient of variation

Summary

Introduction

The use of solid wood presents some disadvantages because it is heterogenous and anisotropic (Torquato 2002, Fratzl and Weinkamer 2007, Buligon 2015), and in many cases the mechanical properties of wood are unsatisfactory for certain uses (Song et al 2018). The production of wood panels can be a more rational use of this raw material (Carvalho 2016). Wood panels are composites that use wood and adhesives as bonding agents, to improve the characteristics of the raw material (Lengowski et al 2019). Resin represents the third highest industrial cost, which leads to constant research for improved adhesives in terms of performance and economy (Eichhorn et al 2010, Gindl-Altmutter and Veigel 2014). Resin reinforced with nanocellulose has been identified as promising, among various improvements offered by nanotechnology in the forest products industry (Candan and Akbulut 2015). Various applications have provided improvement in both the physical and mechanical properties of panels (Gindl-Altmutter and Veigel 2014)

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Conclusion