Nanocellulose-Reinforced Polyurethane for Waterborne Wood Coating

Abstract

With the enhancement of people’s environmental awareness, waterborne polyurethane (PU) paint—with its advantages of low release of volatile organic compounds (VOCs), low temperature flexibility, acid and alkali resistance, excellent solvent resistance and superior weather resistance—has made its application for wood furniture favored by the industry. However, due to its lower solid content and weak intermolecular force, the mechanical properties of waterborne PU paint are normally less than those of the traditional solvent-based polyurethane paint, which has become the key bottleneck restricting its wide applications. To this end, this study explores nanocellulose derived from biomass resources by the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation method to reinforce and thus improve the mechanical properties of waterborne PU paint. Two methods of adding nanocellulose to waterborne PU—chemical addition and physical blending—are explored. Results show that, compared to the physical blending method, the chemical grafting method at 0.1 wt% nanocellulose addition results in the maximum improvement of the comprehensive properties of the PU coating. With this method, the tensile strength, elongation at break, hardness and abrasion resistance of the waterborne PU paint increase by up to 58.7%, ~55%, 6.9% and 3.45%, respectively, compared to the control PU; while the glossiness and surface drying time were hardly affected. Such exploration provides an effective way for wide applications of water PU in the wood industry and nanocellulose in waterborne wood coating.

Application of Eco-Friendly Waterborne Polyurethane Composite Coating Incorporated with Nano Cellulose Crystalline and Silver Nano Particles on Wood Antibacterial Board

“…But when one of the NCC has a hydrogen bond with a chemical group on the wall of a wood cell, NCC is not only affected by this hydrogen bond, but also wrapped in WPU. Under the pull of these two forces, many NCCs in WPU appear almost perpendicular to the surface of the plate state [21,25,26]. This also explains why the addition of NCC increases the adhesion of paint film.…”

Application of Nanotechnology in Wood-Based Products Industry: A Review

“…Nanocellulose was surface modified due to the issue of incompatibility with the polymer matrix. The addition of TEMPO-oxidised cellulose nanofibres improved the mechanical properties of the WPU coating [ 144 , 166 ]. In the case of the non-polar polymer matrix [ 167 ], nanocrystalline cellulose was modified by two methods, with acryloyl chloride or a cationic surfactant [ 167 ].…”

Effect of Urea-Formaldehyde (UF) with Waterborne Emulsion Microcapsules on Properties of Waterborne Acrylic Coatings Based on Coating Process for American Lime

“…However, due to the low molecular weight and a large number of hydrophilic groups, the mechanical properties of waterborne wood coatings decrease to some extent [4,5]. In addition, due to the change in environmental factors (temperature, humidity, light), insufficient toughness of the coatings, and poor self-adaptation, microcracks will occur inside the paint film, and even damage the overall structure of the paint film, thus affecting the service life of the paint film and woodwork [6][7][8]. Therefore, it is an urgent problem to improve the mechanical properties of the paint film and inhibit the generation of microcracks.…”