Alumina nanoparticles as formaldehyde scavenger for urea-formaldehyde resin: Rheological and in-situ cure performance

Formaldehyde emission in the environment from thermosetting resins, like urea-formaldehyde (UF), is one of the most negative aspects of wood-based composite panels. UF resins with low or zero formaldehyde emission and keeping or improving their remarkable properties have been designed by different approaches, with special attention to organic and inorganic nanofillers. Although formaldehyde emission can be mitigated, controlling of rheology kinetics, curing and thermal stability are essential to avoid restrictions for practical applications. Here, we investigated the incorporation of small percentages of Al2O3 nanoparticles into UF resin regarding its rheology, thermodynamic mechanics, thermal kinetics and morphology. Changes on formaldehyde emission was determined by desiccator method and qualitatively illustrated by thermogravimetry-mass spectrometry analysis. The Al2O3 incorporation without significant agglomerations changed the viscosity of UF resin, presenting a shear thinning behavior, especially for higher quantity of nanoparticles. Likewise, analysis of thermodynamic mechanisms shows Al2O3 as an effective additive for UF resin without changing important curing parameters like vitrification point and gel temperature. Al2O3 nanoparticles are also effective to reduce the formaldehyde emission during the UF resin cure reactions at high temperatures and up to 14% in MDF composite panels at environmental temperatures. •Al2O3 nanoparticles were added as reinforcement and formaldehyde scavenger for UF resin.•Al2O3 nanoparticles interacts with UF chains as was illustrated by thermal and thermodynamics analysis.•Al2O3 nanoparticles enhance viscoelastic properties of UF resin.•UF resin becomes pseudoplastic without changes on vitrification point and gel temperature.•Al2O3 reduces formaldehyde emission during UF curing and at environmental temperatures.