Effect of nanoclay-treated UF resin on the physical and mechanical properties of plywood manufactured with wood from tropical fast growth plantations

Freddy Muñoz,Roger Moya

doi:10.4067/s0718-221x2018005001202

Abstract

Physical and mechanical properties were evaluated on cross-laminated panels (plywood) fabricated with three plantation species (Cordia alliodora, Gmelina arborea and Vochysia ferruginea) from tropical climates in Costa Rica. The panels were glued with urea-formaldehyde resin modified with nanoclay at four concentrations (0.75, 1.00, 1.50 and 2.00 per cent) and unmodified resin. It was determined that addition of nanoclay to urea-formaldehyde adhesive positively decreased moisture absorption and swelling of the plywood panel with statistical significance. However, nano-modification did not have a significant effect on the density and specific weight of plywood. Nano-modification of urea-formaldehyde resin with nanoclay at 0.75 per cent improved the Module of rupture and Modulus of elasticity in flexure parallel to surface in the three species, also increasing mechanical resistance to strains in parallel tension, shear and compression. By means of electronic microscopy, it was evidenced that the nano-modified adhesive became diffused at the inside of the cellular structure of wood in a better way, allowing for the generation of a transition zone that increased the mechanical properties at the macro level. According to the properties evaluated, it was determined that 0.75 per cent is the optimal percentage to use of nanoclay on urea-formaldehyde resin.

Highlights

Cross-laminated panels of the plywood type are wood derivatives made with an odd number of veneers, each with their fibres perpendicular to the other
Addressing the physical properties evaluated, density at 12 % (DEN12) and specific gravity at 12 % (SG12) (Table 1), it was reported for the particular case of C. alliodora plywood-type panels that the effect of nanoclay is not statistically significant
For panels using V. ferruginea, the effect of adding nanoclay was rather varied; for example, in UF-1,50 and UF-2,00 formulations, DEN12 values increased significantly in relation to the control, whereas in the UF-0,75 treatment the DEN12 value decreased and, no effect was observed in the UF-1,00 treatment

Summary

Introduction

Cross-laminated panels of the plywood type are wood derivatives made with an odd number of veneers, each with their fibres perpendicular to the other. The veneers oriented along the fibres equate tension, reduce ruptures and minimise dimensional change and warping of the panel (Bodig and Jayne 1993) This technology makes it possible to obtain a product with good stability and mechanical strength. The adhesion properties of veneers are essentially similar to those of solid wood; plywood panel manufacturing processes that include shearing, drying and lamination can change the physical and chemical properties of the veneer surface. These are factors to take into account in order to ensure good moistening and penetration of the adhesive (Frihart and Hunt 2010)

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Discussion

Conclusion