Effects of adding nano-clay (montmorillonite) on performance of polyvinyl acetate (PVAc) and urea-formaldehyde (UF) adhesives in Carapa guianensis, a tropical species

Abstract

The aim of this study was to improve the bond strength resistance of polyvinyl acetate (PVAc) and ureaformaldehyde (UF) adhesives modified with nano-clay (montmorillonite) with a tropical species of wood known to exhibit adhesion related problems. These adhesives were evaluated with 1.0 and 1.5 wt% nanoclay concentrations with lap shear strength (SS), and the percentage of wood failure (PWF) in dry and wet conditions being evaluated. An additional aim of this study was to observe the presence of nano-clay within both adhesive types using Atomic Force Microscopy (AFM) and the Transmission Electron Microscopy (TEM). Color, viscosity and the thermostability of these adhesives with nano-clay were also evaluated. First, AFM and TEM studies showed adequate dispersion and impregnation of nano-clay. The viscosity of PVAc adhesive was not affected by the incorporation of nano-clay, whereas the UF adhesive was. With both PVAc and UF adhesives, the presence of nano-clay increased the L n and b n color parameters, especially when 1.5 wt% nano-clay was used. The incorporation of the nano-clay improved thermostability, as determined by thermogravimetric analysis (TGA). Finally, it was shown that the nano-clay incorporation improved SS and PWF. The highest values of SS were obtained when nano-clay was added at 1.5 wt% concentration in the PVAc adhesive under dry conditions. SS was not affected by nano-clay addition in the UF adhesive under dry conditions. However, under wet conditions, both 1.0 and 1.5 wt% loadings of nano-clay increased SS with both adhesive types. The addition of nano-clay in both proportions increased PWF by approximately 15% and between 20-30% in dry and wet conditions, respectively, for the PVAc adhesive. For the UF adhesive, PWF increased by approximately 10% under dry conditions and 25-50% in wet conditions.

Effects of adding TiO2 nanoparticles to a water-based varnish for wood applied to nine tropical woods of Costa Rica exposed to natural and accelerated weathering

“…The species used to test the varnish with the added nanoparticles were Acacia mangium, Cedrela odorata, Cordia alliodora, Enterolobium cyclocarpum, Gmelina arborea, Goethalsia meiantha, Ochroma pyramidale, Tectona grandis, and Vochysia ferruginea, which are species traditionally employed in Costa Rica for fabrication of wooden doors and other products, as well as engineering products which demand intensive use of varnishes. [27][28][29] These lumbers were obtained from different markets of sawn wood.…”

Enhancement of Polyvinyl Acetate (PVAc) Adhesion Performance by SiO2 and TiO2 Nanoparticles

“…PVAc is good adhesive for paper, plastics, metal foil, leather, cloth and wood, but it is also used as a general building adhesive [1,7,8]. PVAc sets through evaporation and to enhance their barrier, mechanical and rheological properties, fire retardancy, as well as their liquid infusion resistant properties [24,25]. Addition of NC or CNFs can cause an increase in viscosity [19,25].…”

“…Addition of NC or CNFs can cause an increase in viscosity [19,25]. Moreover, addition of NC can cause yellowing [24]. The mentioned changes are not desirable when using PVAc adhesive in graphic post press processes, regardless of the application methods and appearance of the final product.…”

Effects of diatomite inorganic fillers on the properties of a melamine–urea–formaldehyde resin

“…The elevated wet shear strength could be explained by the fact that the MUF resin molecules permeated into the diatomite pores and formed an embedding structure after curing. The confinement of polymer chains within the diatomite pores affected the local chain dynamics to a certain extent, and this reduced the volume shrinkage in the cured glue line and improved the wet shear strength of the resulting plywood. The embedding structure also effectively prevented glue‐line swelling during the 3 h of the soaking process at 63 °C.…”