In this study, the impact of incorporating cellulose nanofibrils (CNF) and carboxylated organo‐montmorillonite (OMMT), separately or in combination, into a UV‐curable wood coating was evaluated for ...performance enhancement. This study investigated the influence of nanoparticle loading percentage on the mechanical properties and thermal behavior of the coating, as well as the surface properties of digitally printed decorative wood‐based panels. The results indicated that the addition of CNF or OMMT increased the viscosity of the polymer solutions. Although CNF randomly oriented within the matrices, OMMT adhered to the surface of the polymer matrix. Chemical crosslinking was observed between CNF/OMMT and the coating. The addition of CNF and OMMT improved the thermal stability of the neat UV curing coating. The tensile strength of nanocomposite films with a 6 wt% loading of CNF increased significantly from 7.63 MPa to 12.73 MPa compared to pure films. The reinforcing effect of CNF on the tensile performance was significantly better than that of OMMT. Adding CNF to the matte coating slightly improved the clarity of the printed decorative panels. When CNF and OMMT were added together in the coating, there was a synergistic enhancement in the low gloss and high pencil hardness of the panels.
Highlights
Both CNF and OMMT were chosen to achieve performance improvements
A simple filling method was adopted for preparation of reinforced coating
The nanocomposite films exhibited fine thermal and mechanical properties
The better integrated property was obtained from the C + CNF3 + OMMT0.8 sample
The physicochemical interaction of nanofiller with polymer molecule existed
Fabrication process of digital printing decorative panel. Enhancement mechanism of UV‐curable wood coatings by cellulose nanofibrils and carboxylated organo‐montmorillonite.
The prospective applications of wood in the furniture industries and building sector are constrained owing to its inherently flammable nature. The application of coatings with flame retardants (FRs) ...onto the wood substrate is a well-recommended approach to mitigate the risk of fire. Non-halogenated FRs, on the other hand, have gained popularity over halogenated FRs, as halogenated FRs are under regulatory scrutiny due to their carcinogenicity and bio-accumulation issues despite offering excellent FR performance. Furthermore, given the green chemistry principles, it is also recommended to use solvent-free or environmentally benign solvents to make such coatings. The ultraviolet (UV)-assisted curing process is advantageous as it can in practice avoid the use of solvents. A few relevant pieces of literature were found in the bibliographic search databases from January 2015 to December 2022 on UV-curable, non-halogenated FRs for wood coating applications. The current review focuses on the design strategies of reactive and non-halogenated FRs with UV-curable functionalities adapted in recent years, and their applications in various UV-curing polymeric systems such as epoxy acrylate, polyurethane acrylate, thiol-ene systems, and oligomeric systems obtained from bio-based oils'. The significant findings of several research groups, the major insights gained and perspectives are covered.
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•Summarizes the effectiveness of UV-curing chemistry in designing FR wood coatings.•Highlights the importance of non-halogenated FRs under declared SDGs set globally.•The documented reports of various reactive FRs over the last decade are covered.•Discusses the reactive and non-halogenated FRs with UV-curable functionalities•The underlying mechanism of FR action is outlined as guide to design strategies to be adopted.
Wood is an ever more demanded material for sustainable construction. However, to perform accordingly, most of the material has to be coated, usually with a petroleum-based polymeric lacquer. Due to ...difficult removal of the coating layers, coated wood is usually discarded at its end-of-life, resulting in lost value and environmental issues. To tackle this challenge, we aim to establish an integral recycling process, based on the principles of circular economy. As a first step, we herein introduce a novel technique for efficient and feasible separation of wooden substrate and coating at end-of-life. To this end, we developed a thermally triggerable primer based on nitrocellulose (NC) which enables debonding on demand specifically for coating layers on wood. The debonding mechanism is triggered at temperatures of 160–170 °C and results in complete loss of adhesion, while having no negative impact on the coating during use. The effect can be applied on large substrates with ease. It can also be used site-specifically which leaves adhesion of non-primed areas fully intact. Additional mechanistic investigations show that decomposition of NC is observed mainly at the interface between primer and coating.
•Topcoat layers were removed from wooden substrates, using a primer made of nitrocellulose.•Before triggering the system, unimpaired adhesion was found. After triggering at 160-170 °C, the adhesion was reduced to a minimum.•The debonding mechanism was investigated by IR and microscopical analysis.•Based on this process, recycling procedures for high value wood can be implemented.
The development of a multifunctional wood wax oil-based coating holds significant importance in meeting demands for wood protection and enhanced longevity of wood materials. Nevertheless, a simple ...method of developing such an integrated coating that possesses excellent durability, ultraviolet (UV) resistance, water resistance, and environmental friendliness remains a significant obstacle. In this paper, stearoyl chloride-grafted cellulose nanocrystals (SCNCs) with excellent compatibility with wood wax oil (WWO) coatings were prepared by combining cellulose nanocrystals (CNCs) with stearoyl chloride through a one-step non-homogeneous esterification reaction. Nanocomposite coatings were prepared by a simple one-step ultrasonic miscibility method using SCNCs as modified functionalized fillers. The prepared SCNC-WWO wood coatings had high hardness (grade H), strong adhesion (class 0, with no peeling), high abrasion resistance, good UV resistance, high hydrophobicity (water contact angle of 116°), and good water resistance (maintainable for 1 day). In addition, SCNCs with gas barrier properties can effectively inhibit the release of pollutants within the coatings, making this composite coatings environmentally friendly. Therefore, SCNC-WWO can be used as a high-performance coating for substantial protection of wood in harsh environments, and the strategy for developing it provides insight into the preparation of multifunctional wood paint.
•The prepared fillers SCNCs have cellulose type I structure and excellent organic compatibility.•SCNC-WWO composite coatings can be successfully prepared by a one-step ultrasonic miscibility method.•SCNC-WWO wood coatings have excellent durability, UV and water resistance.•SCNC-WWO wood coatings have excellent gas barrier properties, making the coatings environmentally friendly.
Abstract
Transparent wood (TW)‐based materials have increasingly become the focus of researchers worldwide owing to their superior physico‐chemical‐optical properties, sustainable nature, as well as ...the fact that they are highly accommodating frameworks that can act as building blocks to readily explore a vast range of potential functionalities, holding great potential to displace glass and plastics in their various respective applications. The integration of multiple functionalities into TW has been undertaken to fulfill the demands of prospective sophisticated applications through the utilization of functional fillers or coatings. Herein, the up‐to‐date foundational developments and reports concerning emergent TW composites and coatings from a perspective of fabrication‐functionality‐application are comprehensively summarized, with a particular focus on seven specific functionalities; i) solar control; ii) chromically‐responsive, iii) electrically‐conductive, iv) shape‐memory active; v) flame‐retardant; vi) electromagnetic interference shielding; and vii) aesthetics. The potential applications of TW with these functionalities are also discussed. Finally, the current challenge with TW is addressed, as well as the future developments required for eventual real‐world application.
Abstract
To address the issues of insufficient film smoothness, and flammability of aqueous polyurethane dispersions (PUD) prepared by adding matting agents, two hydrophilic chain extenders, ...dimethylolpropionic acid (DMPA) and sodium 2‐(2‐aminoethyl)amino ethanesulphonate (A95), were used to regulate the particle size of the emulsion while using FRC‐6 flame retardant as a small molecule chain extender to prepare a self‐matting and flame retardant PUD. Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscope, and atomic force microscopy were used to structurally characterize the latex films. The results showed that as the
R
‐value (NCO/OH molar ratio) and soft segment content decreased, the prepolymer viscosity increased, making it difficult to emulsify and reducing the glossiness of the film. Moreover, an initial increase in DMPA content led to a decrease in film glossiness, followed by an increase. Increasing the molar ratio of A95 sulfonic acid salt‐based chain extender to EDA affected the glossiness of the film, with a 2:8 molar ratio of A95: ethylenediamine (EDA) resulting in a glossiness of the film of 6.5%. The addition of reactive flame retardant diethyl bis (2‐hydroxyethyl) aminomethyl phosphonate (FRC‐6) increased the branching content in the prepolymer, improved the flame retardancy of the film, and reduced its glossiness. As a result, the self‐prepared PUD had a flat film with a glossiness as low as 6.0% and a flame retardancy rating of level 4.
As the new coronavirus pneumonia swept the world in 2020, the demand for antibacterial products significantly increased. In this study, a soy protein isolate nano-silver hydrosol was prepared using ...an environmentally friendly Ag+ in situ reduction process, where the soy protein was ultrasonically blended with polyacrylic resin to obtain a polyacrylate-nano silver antibacterial wood coating. The structure of the soy protein isolate nano-silver hydrosol was assessed, and the structure and antibacterial and mechanical properties of the film were characterized. The results showed that the silver nanoparticles (AgNPs) exhibited good crystallinity and were evenly distributed in the emulsion. The composite film had good antibacterial properties against gram-negative bacteria represented by Escherichia coli and gram-positive bacteria represented by Staphylococcus aureus. With increased nano-silver content, the diameter of the inhibition zone increased from 0 to 30 mm, and from 18 to 50 mm for the two bacteria, respectively. Moreover, the elastic modulus of the film increased from 8.173 to 97.912 MPa, and the elongation at break decreased from 240.601 to 41.038% as the content of AgNPs changed from 0.1 to 1%, respectively. Thus, this study provides a new method for preparing waterborne polyacrylate coatings with excellent antibacterial properties.
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•Green preparation of soybean protein isolate nano-silver hydrosol.•Tyrosine from soy protein isolate was used to reduce silver ions and stabilize elemental silver.•waterborne polyacrylate coatings with excellent antibacterial properties were prepared.
The degree of crystallinity of cellulose was used for assessing the degradation level of coated and uncoated samples of pine wood after weathering. X-ray diffraction (XRD) and Fourier Transform ...Infrared (FT-IR) spectroscopy measured the changes in the surface crystallinity of cellulose resulting from weathering, both natural and artificial. Both techniques revealed an increase in the crystallinity index (CI) of cellulose when wood was subjected to weathering. An increase in the size of crystallites was also observed by XRD measurements. These results were related to the reduction of the amorphous fractions of wood, and, consequently, to the enrichment of the relative crystalline content. Thanks to FT-IR analysis, the degradation of hemicellulose was observed for uncoated samples after exposure to artificial weathering. The effect of weathering was less evident on coated samples because of the protective action of the coating. A good correlation between the crystallinity indexes obtained from FT-IR and XRD was found. The experimental results proved that the proposed method may be a very useful tool for a rapid and accurate estimation of the degradation level of wood exposed to weathering. This methodology can find application in the field of conservation and restoration of wooden objects or in the industry of wood coatings.
For improving the finishing performances of complicated three-dimensional coated wood products (e.g., furniture) with some shadow zones in the absence of ultraviolet (UV) light, resulting in ...incomplete curing of UV coatings, the aim of this study was to investigate the characteristics and effects of curing process on the properties of epoxy acrylate UV/PU dual-cured resin for wood coatings when compared with traditional UV and polyurethane (PU) coatings. The epoxy acrylate oligomer was synthesized for providing a double bond of acryloyl group and a secondary hydroxyl group. The UV/PU dual-cured coating was formulated with epoxy acrylate resin/tripropylene glycol diacrylate (TPGDA) monomer by the weight ratio of 80/20, 3% dosage of benzil dimethyl ketal as a photoinitiator, and the NCO/OH mole ratio of 1.0. The aromatic polymeric diphenylmethane diisocyanate was used as a hardener. The films of the dual-cured coating, obtained from UV-cured or room temperature-cured process, showed an excellent tensile strength, elongation at break, impact resistance, and lightfastness when compared with traditional UV and PU coatings; especially, the adhesion of UV/PU dual-cured coating by UV-cured process was better than that of traditional UV coating. It can therefore be concluded that the epoxy acrylate oligomer-based dual-cured coating could readily be used for complicated wood products finishing.
Timber and wood-based materials are considered sustainable building materials; however, as they are prone to degradation by biotic and abiotic factors, they often required the addition of protecting ...coatings. In this context, the preferred options are waterborne coatings since they are non-aggressive solvents (odor, toxicity, fire risk) and ultimately eliminate the emission of Volatile Organic Compounds (VOCs). Notwithstanding, these reductions imply lower durability and protection as compared to conventional organic coatings. This study demonstrates that incorporating nanocellulose produced from blueberry pruning residues and titanium dioxide and silica dioxide NPs into waterborne varnishes can improve wooden surfaces' mechanical performance and stability. Particularly the adhesion and abrasion properties are enhanced without significant changes in other properties such as optical transparency, color, and coating gloss. These results present a promising potential for different applications in the context of developing products for a circular economy in furniture, floors, and wood paneling.
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•CNCs from blueberry pruning residues were incorporated into a waterborne coating.•Nanocomposites improve the mechanical performance and stability of wooden surfaces.•Additives with TiO2, SiO2, and nanocellulose stabilize aesthetic wood properties.
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