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Wood is a renewable resource that has been used as a material in appearance products for years. Despite its acceptable mechanical resistance, different modification processes were developed to enhance wood’s hardness and make it an even more durable material. Impregnating wood pores with monomers under vacuum-pressure cycle is a common method for that purpose. However, most implemented processes are long and mostly submerge wood into a monomer formulation (Bethell’s full-cell process). For that, they can be considered wasteful on the quantity of materials used, energy consumed and on process duration. The objective of this paper was to evaluate the parameters that influence the penetration of monomers into the tangential surface of Yellow birch (Betula alleghaniensis Brit.) samples. The analyzed factors were the monomer formulation’s viscosity, the surface temperature, the vacuum level applied to the process, the anatomy of samples, and the absorption time. After impregnation, the weight gain of the samples was calculated. Monomer penetration depth was calculated and visualized using density profiles and micro X-ray tomography imaging. Results showed that using a low viscosity monomer formulation allied to a certain level of vacuum and absorption time can considerably increase the impregnation into the wood.

Density of wood can be increased by filling its porous structure with polymers. Such densification processes aim to increase hardness of wood and are particularly interesting for flooring applications. This study aims to evaluate efficiency of different polymers for chemical densification based on the polymer properties. Yellow birch (Betula alleghaniensis Britt.) was chemically densified with seven monomer mixtures through acrylate monomer impregnation and electron beam in-situ polymerization. Chemical retention and polymer content of densified woods were recorded. Hardness of treated and untreated Yellow birch was measured and compared to hardness of Jatoba (Hymenaea courbaril L.). All densified woods showed higher or comparable hardness to Jatoba. Hardness of densified wood was analyzed in relation to initial density of wood and polymer content of the material using multivariable linear mixed models. Efficiency of polymers for chemical densification was evaluated through effect of polymer content on hardness with interaction coefficients. Polymer films corresponding to monomer impregnating mixtures were prepared through low energy electron beam and characterized by their glass transition temperature, micro hardness, indentation modulus and crosslinking density. Polymers showed statistically significantly different efficiencies and were separated in two main groups. Overall, polymer efficiency increased with increasing glass transition temperature of polyacrylates.

Wood is increasingly used in construction for the benefits it brings to occupants and for its ecological aspect. Indoor wood products are frequently subject to mechanical aggressions, their abrasion and scratch resistance thus need to be improved. The coating system ensures the wood surface protection, which is, for wood flooring, a multilayer acrylate UV-curable 100% solid system. To increase the service life of wood flooring, a new property is studied: self-healing. The objective of this study is to observe the impact of monomer structure on self-healing efficiency and the effect of self-healing parameters. A previous formulation was developed using hydrogen bond technology to generate the self-healing property. In this paper, the assessment of the formulation and the self-healing parameters’ impact on self-healing efficiency as well as the physicochemical properties are presented. The composition of the monomer part in the formulations was varied, and the effect on the conversion yield (measured by FT-IR), on the Tg and crosslinking density (measured by DMA) and on mechanical resistance (evaluated via hardness pendulum, indentation, and reverse impact) was analyzed. The self-healing efficiency of the coatings was determined by gloss and scratch depth measurements (under constant and progressive load). It was proven that monomers with three acrylate functions bring too much crosslinking, which inhibits the chain mobility necessary to observe self-healing. The presence of the AHPMA monomer in the formulation permits considerably increasing the crosslinking density (CLD) while keeping good self-healing efficiency. It was also observed that the self-healing behavior of the coatings is different according to the damage caused. Indeed, the self-healing results after abrasion and after scratch (under constant or progressive load) are different. In conclusion, it is possible to increase CLD while keeping self-healing behavior until a certain limit and with a linear monomer structure to avoid steric hindrance. Moreover, the selection of the best coatings (the one with the highest self-healing) depends on the damage.

In this work, intumescent coatings were prepared for protection of wood from fire. The fire-retardant chemical ammonium polyphosphate (APP) is known to have poor resistance to water and high humidity as it is hygroscopic in nature. To improve the water resistance, durability and fire resistance of the intumescent coating, APP was modified using a hybrid organic-inorganic polysiloxane encapsulation shell prepared by the sol–gel method. The physical and chemical properties of the intumescent mix containing microencapsulated ammonium polyphosphate (EAPP) particles were characterized by X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), water absorption, dynamic vapor sorption (DVS) and thermogravimetric analysis (TGA). The EAPP mix showed 50% reduction in water absorption, 75% reduction in water vapor sorption and increased thermal stability when compared to the APP mix. The intumescent coatings were applied on wood samples, and their fire performance was evaluated using a cone calorimeter test. The intumescent coatings containing EAPP mix showed better fire retarding properties with longer time to ignition, lower heat release rate and shorter heat release peak when compared to the coating without EAPP mix. The prepared intumescent coating shows higher resistance to water and moisture, and it has great potential to be used in bio-based construction industry for enhancing the fire resistance of wood.

Wood products, especially those used in outdoor conditions, can be damaged by dimensional changes and decay fungi. It is therefore advised to use impregnation treatments to mitigate these hazards. While the potency of the chemicals employed in the treatments is important, characterization of the treatments is also crucial to ensure deep and durable protection. In this study, eastern white pine (Pinus strobus L.) and white spruce (Picea glauca (Moench) Voss) were impregnated with propiconazole and 3-iodo-2-propynyl butylcarbamate (IPBC) through diffusion. Instead of using pressure treatments, the samples were dipped in solutions containing amine oxides, which can diffuse into the wood. The treatments were characterized by the mass of fungicide impregnated, fungicide leaching, and the impregnation depths of both the fungicides and the amine oxides. It was found that the treatment impregnated slightly more than 0.040 kg/m3 of both fungicides, meeting EU standards. It was also shown that the presence of amine oxides slightly prevented the leaching of the fungicides in white pine. The penetration of the amine oxides was several millimeters deep in all directions, but the penetrations of the fungicides were much shorter and only longitudinal.

In this study, UV cured bio-nanocomposite coating systems were developed. An acrylated epoxidized soybean oil (AESO) and cellulose nanocrystals (CNCs) were used to make these coating systems. The CNC surface was modified by two different methods so as to achieve good compatibility between the CNC and AESO. Thermal stability, glass transition temperature, optical clarity (transparency), and curing behavior of the coating systems were assessed. The addition of CNC altered the thermal stability of the bio-nanocomposites slightly. Addition of CNC increased glass transition temperature of AESO. This increase was a function of the CNC surface modification method and CNC loading level. The transparency of the bio-nanocomposites was reduced by the addition of CNC. The curing behavior of these coating systems was not significantly different from that of a pure cured AESO matrix. A study of the morphology of the nanocomposite films by AFM demonstrated that the modified CNC had good compatibility with the AESO matrix.

Wood is an environmentally friendly material for the construction of buildings, and it possesses great physical and mechanical properties. However, under certain circumstances, it needs to be protected from degradation. This can be achieved either by proper design or treatment. In this study, eastern white pine (Pinus strobus L.) and white spruce (Picea glauca (Moench) Voss) were impregnated with propiconazole and 3-iodo-2-propynyl butylcarbamate, which are two organic fungicides. Unlike most impregnation techniques, no pressure treatment was needed. Instead, an aqueous buffered amine oxide system was used to allow the fungicides to diffuse rapidly into the wood. Many combinations of fungicides and amine oxides, as well as different diffusion times were tested to study the effect of the treatment on the dimensional stability and resistance to decay fungi. It was found that only the amine oxide affected the dimensional stability of the treated wood, with anti-swelling and anti-shrinking efficiencies values up to 30%. Amine oxides and fungicides both had an impact on the weight loss caused by the brown rot fungi. The weight loss after 10 weeks of exposure to Rhodonia placenta was reduced by half when using amine oxides or fungicides, and it was completely inhibited when they were combined.

In this study, a renewable reinforcement, namely cellulose nanocrystals (CNC), was used to develop a bio-based nanocomposite UV-cured coating system with improved performance. CNC was modified in order to be compatible with the nonpolar polymer matrix (acrylated epoxidized soybean oil (AESO)). The CNC was modified by two methods, with acryloyl chloride or a cationic surfactant (HDTMA). The mechanical properties and structure of bionanocomposites were evaluated. The addition of CNC increased modulus of elasticity (MOE) and tensile strength of the cured film coatings. Use of CNC modified by HDTMA and acrylated CNC led to a higher increase in tensile strength and MOE, relative to un-modified CNC. Best performance enhancement was in hardness and reduced elastic modulus (Er), measured by the nanoindentation technique, which were improved several fold by CNC addition. Hardness, Er, MOE and tensile strength increased with CNC loading level in the matrix. Hardness measurements of cured film coating by pencil hardness test methods confirmed that CNC improved the hardness of the films. Studying the morphology of the nanocomposites revealed that surface modification method of CNC affected nanocomposite film structure and thus the mechanical properties.

Intumescent fire retardant (IFR) coatings are nowadays considered as the most effective flame retardant (FR) treatment. Nevertheless, the principal compound in an IFR system, ammonium polyphosphate (APP), is highly sensitive to moisture and IFR coating effectiveness decreases quickly. The main objective of this study is to encapsulate APP in a hybrid silica-based membrane by sol-gel process using alkoxysilane tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) precursor. The morphology and structure of APP and microencapsulated ammonium polyphosphate (MAPP) were assessed by scanning electron microscopy and Fourier transforms infrared spectroscopy (FTIR). X-ray photoelectron spectroscopy (XPS) results revealed that APP was well encapsulated inside the polysiloxane shells. The thermal degradation of APP and MAPP was evaluated by thermogravimetric analysis. At 800 °C, the MAPP had higher char residue (70.49 wt%) than APP (3.06 wt%). The hydrophobicity of MAPP increased significantly with the water contact angles up to 98°, in comparison to 20° for APP.

UV-curable coatings are attractive for a wide range of applications due to several advantages, including rapid polymerization rates, increased production rate, and low environmental impact (from limited use of volatile organic compounds). In the present work, UV-curable formulations were prepared from various acrylate oligomers and monomers and modified silica as a matting agent. To improve compatibility between the acrylate-based coating and silica, the surface of the silica particles was modified in two steps. First, to introduce amino-reactive groups to the surface, (3-aminopropyl) triethoxysilane (APTES) was grafted onto the silica. Subsequently, the second step consisted of grafting an acrylate monomer, dipropylene glycol diacrylate (DPGDA), via the aza-Michael reaction. The functionalization with acrylate chains promotes compatibility with the acrylate-based coating formulation and results in a very low gloss surface. The modified silica was characterized through a variety of techniques, including thermogravimetric analysis (TGA), 29Si and 13C NMR and laser diffraction particle size analysis. The matte UV-curable coatings were characterized using viscometry, photo-DSC (kinetic analysis) and real-time FTIR (conversion rate determination), gloss measurements, profilometry (surface roughness analysis), as well as scratch testing (abrasion resistance). This silica modification allows the formation of coatings with low gloss levels at loadings as low as 10% wt modified silica.

Over the last few decades, wood modification has been performed to improve wood product technical performance. Using renewable based chemicals for wood modification is an innovative alternative to the non-renewable petrochemicals commonly used. However, it should be kept in mind that having the raw material from renewable sources does not guarantee zero environmental impacts. In this study, the treatment considered uses citric acid and glycerol mixture; two chemical products derived from renewable sources. In the residential building context of Quebec-Canada, the cradle-to-grave life cycle assessment for untreated and treated lodgepole pine wood siding was performed and compared. The results obtained show that the treated wood siding has higher environmental impacts than the untreated wood siding, in spite of its longer service life. This is partially caused by the high contribution of citric acid production used for treatment. The current service life expectancy of treated wood siding was estimated to be 2.8 times longer than the one of untreated wood siding based on standardized durability test and classification (AWPA E 10–12 and ASTM D 2017-05). Sensitivity analysis showed that life cycle impacts of treated wood siding become lower than those from untreated wood siding when service life expectancy reaches 5-times that of untreated wood siding. Life cycle assessment could be used for guidance in developing better treatments to improve their environmental impacts.

The durability of clear coatings is an important problem in the coatings industry. This problem can be partly solved with the addition of UV absorbers (UVAs) in the coating formulation. UVAs can absorb part of the UV radiation and convert it into harmless heat. Organic UVAs are prone to photodegradation and can migrate in the binder of a coating formulation. In this study, commercial UVAs have been encapsulated in poly(methyl methacrylate) microspheres using the internal phase separation method. Microspheres have been incorporated into a clear acrylic binder. The acrylic was then applied on wood panels and was placed into an artificial UV chamber. Efficiency of coatings after aging as well as chemical and physical properties were monitored using a colorimeter, FTIR spectroscopy and transmission electron microscopy. This study presents a comparison between the efficiency of free and encapsulated Tinuvin 1130 and 292 commercial absorbers. Results have shown that the coating efficiency is slightly improved when using the encapsulated products.

The development of wood treatments is of increasing industrial importance. A novel technique for improving the properties of lodgepole pine and white pine through modification of the microstructure is described. The present investigation is devoted to the synthesis and determination of in situ parameters of citric acid and glycerol based polymers for wood impregnation. This solvent free approach is environmentally friendly and achieved through an esterification condensation reaction under acidic conditions. Crude glycerol and citric acid reactants were cross-linked via a curing process at 160 °C creating a polymer with only water as the byproduct. The ester bonds and crosslinking levels were controlled using different catalysts and citric acid contents and related to the reaction time and temperature. The nature of bonding within the polymers and at the wood cell walls was determined by FT-IR analysis. The thermal properties such as glass transition temperature (Tg) were studied using TGA/DSC and the effect of citric acid content and catalyst type determined. Dimensional stability of impregnated wood samples improved above 50% for each sample with HCl and p-TSA catalysts compared to control samples. FTIR spectra were studied to show the presence of the ester linkages of the polymer in situ at the wood cell walls. Bonding between the polymer and wood macromolecules were observed by scanning electron microscopy and interpreted as evidence of chemical bonds at the wood cells. When prepared using a catalyst, the polymer was intimately incorporated into wood structure significantly improving the substrate dimensional stability. Enhanced stability makes this approach of particular interest for exterior wood products especially as a green renewable option for the wood industry.

In this study, the feasibility of improving the mechanical properties of a high solid content UV-curable acrylic coating system through the addition of cellulose nanocrystal (CNC) was examined. The CNC was rendered hydrophobic by using a cationic surfactant, hexadecyltrimethylammonium bromide (HDTMA), to make it compatible with the matrix polymer and facilitate proper dispersion. Two different amounts (1 and 3%) of modified CNC were added to the coating system. Tensile strength and modulus of elasticity (MOE) of coating films were affected positively by the addition of CNC. Hardness, measured both by Konig pendulum and pencil methods, was found to increase as CNC loading increased in the coatings. Mass loss due to abrasion resistance tests was reduced by the addition of CNC. The results of this research showed that CNC is an ideal reinforcing nanoparticle which can positively affect the mechanical performance of coating systems.

The photodegradation of white spruce by artificial ageing was studied by several techniques: colourimetry, FTIR-ATR and FT-Raman spectroscopy. Samples were exposed at a xenon lamp for 2000h. Two distinct colour changes were found by colourimetric analysis, yellowing and silvering. These colour modifications indicate the formation of chromophoric structures which supports previous FTIR-ATR experiments. The degradation of lignin to generate the first chromophoric group for yellowing and then the appearance of surface layer cellulose. New carbonyl compounds conjugated with double bond at 1615cm(-1) are probably the second chromophoric group. The crystallinity index was also calculated and showed an increase of cellulose crystallinity by prior degradation of amorphous cellulose. The FT-Raman analysis confirms the wood sensitivity to photodegradation but the most remarkable results is the increase of fluorescence as a function of time. In softwood lignin, the compound able to produce fluorescence is a free rotating 5-5' linkage of one biphenyl structure. At native state these linkages are not free rotating, this phenomenon means the release of 5-5' linkage of lignin structure by cleavage of both α carbon linkages (Norrish type I reaction). These data confirm also the photosensitivity of α and β carbon in lignin and the resistance of 5-5' linkages.

Acrylated epoxidized soybean oil (AESO) is an interesting bio-based starting material for the development of biomaterials. Betulin, another bio-based product, can be extracted in large amounts from birch trees. Acrylated betulin (AB) was synthesized and added as a comonomer to the AESO at different loading levels (5 wt% and 10 wt%). AESO and AESO-AB mixture were cured photochemically to form films. The properties of the newly formulated coating systems were evaluated. The mechanical properties of cured AESO were affected by addition of AB comonomer. Modulus of elasticity (MOE) and tensile strength, hardness and abrasion resistance of the cured film increased, while strain at break was reduced. AB comonomer addition increased the glass transition temperature (Tg) of the cured AESO polymer while it yellowed AESO formulations and reduced optical clarity (transparency) of the cured film coating.

In this study, UV curable high solid content wood coating systems with high performance were developed by using cellulose nanocrystal (CNC). CNC modified by a cationic surfactant was added to the coating system at two loadings (1 and 3%). Water uptake and permeability, optical clarity and glass transition temperatures (Tg) of these new nanocomposite coatings were measured. The quality of CNC dispersion in the matrix was also studied. Results showed that CNC improved the barrier and optical properties of the nanocomposite coatings. Tg of the polymer matrix did not change significantly with the addition of CNC. The quality of CNC dispersion in the polymer matrix was a function of CNC loading. High CNC loading (3%) resulted in sizable agglomeration, but this agglomeration did not negatively impact coating performance.

The multiple advantages of UV-curable coatings, such as high curing speeds and cross-linking densities, low VOC and energy consumption led to a widespread interest for a wide range of applications. Free-radical photopolymerization constitutes one of the most used methods of polymerization. However, oxygen present in the atmosphere is able to inhibit radical formation and propagation, which is considered a major drawback. Among all the strategies developed for reducing the oxygen inhibition, the addition of reactive additives is often preferred. This method does not require major changes in the production lines of the industries or in the formulations compositions. The efficiency of reactive additives against oxygen inhibition has been investigated in multiple studies, but in different experimental conditions. The addition of the reactive additives can also influence coatings hardness and abrasion resistance which are considered important mechanical properties. The aim of this study is to evaluate additives overall performances. Eleven of the chosen additives were previously described in the literature. The four remaining are commercial products never used for that application, like a polyhedral oligomeric silsesquioxane bearing a thiol function, which later showed the best results. Reduction of oxygen inhibition was analyzed by photo differential scanning calorimetry (Photo-DSC) and Confocal Raman Micro-spectroscopy (CRM). Pendulum hardness and abrasion resistance measurements were used to determine the influence of the additives on the mechanical properties of the coatings. The results obtained show that most of the additives tested had reducing effect on the pendulum hardness, but helped in improving the abrasion resistance.

Wood used outdoor is subjected to different sources of degradation and should be protected properly. In this study, acrylic resins were added to a wood impregnation system using amine oxides and propiconazole, an organic fungicide, to create a two-part wood protection preservation treatment. Since amine oxides can diffuse readily into wood, this treatment protected both the surface and inner structure of the treated wood following a simple dipping. Many aspects of the treatment were studied: the adhesion of the acrylic coatings, their permeability to water, and the impregnation depth of the propiconazole. In each case, a particular attention was accorded to the interactions between the resins and the impregnation system. Adhesion and permeability tests were coupled with an artificial aging process simulating severely wet conditions. Amine oxides reduced the adhesion of the coatings but did not impair their aging properties. Because of their hydrophilic nature, they also increased the permeability to liquid water, although they did not affect the air moisture permeability. The penetration of the propiconazole, estimated with a dye, decreased with the resin. Overall, the two parts of the treatment lightly impaired each other, but the practical aspect of this treatment may overcome these disadvantages.

The limited durability of clear coatings is a major issue for the coating and wood industry. The addition of organic UV absorbers improves coating resistance by the absorption and the conversion of the UV radiation into harmless heat. Organic UVAs are prone to degradation and can migrate in the binder of coatings. In this study, commercial UVAs and HALS have been entrapped into CaCO3 templates coated with stimuli responsive polymers. Microspheres were incorporated into a clear acrylic water-based coating formulation. The formulation was applied on glass and wood panels and was placed into an artificial UV chamber. This study presents a comparison between the aesthetic behavior of coating formulations with free and encapsulated commercial UVAs and HALS during the accelerated ageing test. Encapsulation of UVAs was confirmed by XPS and TGA analysis. Results have shown that the coating&rsquo, s aesthetic was slightly improved when using the encapsulated products.

Ultraviolet light emitting diodes (UV-LEDs) have attracted great interest in recent years. They can be used to polymerize coatings, such as those used for prefinished wood flooring. In this project, two lamps were compared for their suitability to be used on a wood flooring finishing line: a UV-microwave and a UV-LED lamp. Low heat emission was found for the UV-LED lamp compared to the UV-microwave one. This study also reveals that the 4 W/cm2 UV-LED lamp used is not powerful enough to cure UV high solids acrylate coatings while satisfactory results can be obtained for UV water-based formulations. In fact, conversion percentages were found to be low for the high solids coatings, leaving the coatings tacky. Higher conversion percentages were obtained for the UV water-based formulations. As a result, mass loss, hardness, and scratch resistance found for the samples cured by UV-LED were closed to the ones found for the samples cured using the UV microwave lamp.

The coating industry is under increasing pressure to find and use renewable resources as a source of raw materials. Substituting products from crude oil by value-added wood products can have both positive environmental and economic aspects. Betulin, mainly found in the bark of white birch, is often left over following wood processing. Betulin has a very interesting molecular structure for the synthesis of polymers. Soybean oil is increasingly used to develop new coatings because of its unique properties. In this study, the properties of acrylated epoxidized soybean oil (AESO) were improved by combining it with a modified betulin sample. Betulin was modified using acryloyl chloride. Spectroscopic techniques were used to study the chemical structure of modified and unmodified betulin. FTIR and NMR analyses revealed that there were chemical reactions between betulin and acryloyl chloride. GCMS analysis showed that diacrylated betulin was the more abundant compound after the reaction. Photo-DSC analysis showed that the speed of polymerization of coatings was slowed down by adding modified betulin to AESO. Thermal stability studies showed that modified betulin developed a cross-linked and rigid structure with AESO. The results of this study confirmed that modification of betulin is possible and the resulting products can be used as a comonomer with AESO for coating formulation.

The combination of UV-curing technology and nanotechnology has been applied in this study to synthetize by in situ photopolymerization method, UV-cured topcoats based on acrylate matrix reinforced (1 and 3 wt%) individually with three different types of commercial organoclays, namely Cloisite 10A (C10A), Cloisite 15A (C15A) and Cloisite 30B (C30B). The morphological study was quantitatively and qualitatively performed by X-ray diffraction (XRD) and by transmission electron microscopy (TEM) respectively. Water vapor transmission rate (WVTR) and optical clarity of these nanocomposites were also assessed. TEM images obtained for those UV-cured coatings respectively reinforced with C10A and C30B showed that the absence of diffraction peaks in XRD patterns of these samples do not mean necessarily a possible exfoliation of their layered silicate nanoparticles by acrylate matrix (AM). Indeed, according to TEM images, we believe that C30B was not dispersible in the AM; while both UV-cured nanocomposites containing C10A and C15A respectively seemed to have an intercalated morphology regardless of the clay content (1 and 3 wt%). All the organoclays used in this study have had an effect on both WVTR and optical clarity. The tortuous path created by the organoclay dispersed into the AM, by retarding the progress of water vapor through a sample, best explain the decrease of WVTR whereas the decrease of optical clarity is due to the light scattering by organoclay particles. Based on the above mentioned results, among the three different reinforcing agents used in this study, C10A appears to be the ideal organoclay for practical application.

Nanocrystalline cellulose (CNC) is a renewable material with high potential in many applications. Due to its unique self-assembly and optical properties, CNC tends to behave as an iridescent pigment. The aim of this research was to explore the potential of CNC as an effect pigment in wood coatings. CNC-based coatings were developed from an aqueous CNC solution, a UV-curable water-based clear coating formulation, several colorants, and specialized additives. In this paper, the morphology of the resulting CNC films was investigated through circular dichroism and optical microscopy under polarized light. The effect of the CNC surface charge changes was monitored through zeta potential measurements. Color changes, or travel, and flop index were used to assess the iridescent effect of the coatings containing CNC. The experimental wood coatings contained CNC showed that the enhancement of the iridescent effect depends on the distribution and alignment of the CNC rod-like particles in order to generate the right pitch in the helical structure and their interaction with the polymer matrix as well with the additives. In conclusion, CNC could be successfully used as effect pigment in finishing systems, which can enhance the attractiveness and bring out the special grain of various types of wood., ISRN nanomaterials, 2013, ISSN:2090-8741

Wood is a renewable material widely used in many applications due to its unique properties and distinctive look. However, as wood is organically constituted, it is slowly destroyed by the long-term impact of oxygen, UV radiations, water, and biological attacks (Mahltig et al., 2008). Therefore, protective treatments are necessary to improve the mechanical, thermal, and chemical properties of wood. In order to improve the mechanical properties of sugar maple (Acer saccharum Marsh.), as this species is widely used in the wood products industry, samples of sugar maple were impregnated with sols of metal oxides (AlO(OH), SiO2, and ZrO2). The weight gain and two different techniques of microscopy were used to evaluate the efficiency of the impregnation in the wood samples. The mechanical properties were evaluated using hardness test, scratch test, and impact test. It was shown that the maple samples impregnated with ZrO2 led to the greatest improvement of the mechanical properties.

PVDF-acrylic opaque coating systems were applied onto two different wood species; Black spruce and White pine. Weathering resistance of these products was compared to the one of industrial water-based acrylic coatings used for exterior siding. ATR-FTIR results have shown that the PVDF portion of the coatings resist easily to the UV light, even at the extreme surface. At the opposite, the acrylic portion of the coatings was strongly affected by the UV light. This degradation has led to significant color change. Contact angles were also measured before and after the accelerated aging test in order to assess the recoatability of these coatings. Wettability was found to be slightly lower for the PVDF-acrylic coatings. The morphology of the different coating systems was finally assessed. Results have shown that the PVDF-acrylic coatings are strongly affected by the White pine resin exudation.

The purpose of this study was to investigate the performance of a semitransparent PVDF–acrylic coating on two wood species: Black spruce and White pine. An accelerated aging test was performed on the PVDF–acrylic coating and the results obtained were compared with those obtained for a water-based acrylic coating. Color changes were found to be more significant for the acrylic coating, especially after 1000 h of exposure, and for the White pine panels. Infrared spectroscopy revealed that the acrylic resin was more affected by the accelerated aging test than the PVDF resin, although X-ray photoelectron spectroscopy revealed that PVDF was slightly affected at the extreme surface (first 10 nm). Star-shaped defects were found at the surface of the White pine panels finished with the PVDF–acrylic coating. Experiments revealed that the PVDF–acrylic coating does not seem to be flexible enough to sustain resin exudation or other stresses.

Clay-based nanocomposites have already shown their great potential. In this study, clay–acrylate nanocomposite formulations, for wood finishes, were prepared in four differents ways. High-speed mixing, ball milling, bead milling and three roll milling were used to disperse clay into the neat acrylate formulation. The viscosity of the formulations was determined. Small angle X-ray scattering and transmission electron microscopy experiments were performed on these samples in order to study the quality of the dispersion. Then, photo-calorimetry and real-time infrared spectroscopy were used in order to investigate the effects of clay loading and clay dispersion on the ultraviolet curing. These studies have shown that UV curing is related to the quality of clay dispersion. Presence of large clay aggregates decreases the conversion of the acrylate functional groups, even at a small clay loading. However, a small amount of clay, well dispersed, can help UV curing.

Radiation curable coatings are presently the standard in wood flooring industries, although important improvements can still be brought to these coatings. In this work, nanocomposites coatings for wood flooring were prepared from various acrylate reactives. Nanoparticles were added in the neat acrylate formulation prepared from two acrylate monomers, two acrylate oligomers, a defoaming agent and a photoinitiator. Particle size characterization was performed by a dynamic light scattering technique. Reinforcing agents and coupling agents addition effects on acrylate resin conversion were studied by photo-calorimetry (photo-DSC). For each nanocomposite sample, heat of reaction and induction time were determined from exotherms and these datas were used to study the effects of reinforcing agents and coupling agents on curing kinetics of radiation curable nanocomposite coatings. Photo-DSC studies show that nanoparticles and coupling agent clearly affect coatings polymerization. In fact, zirconia nanoparticles tend to decrease polymerization. Alumina nanoparticles do not affect negatively curing coatings. Silane coupling agent affects positively the curing of acrylate coatings, although zirconate coupling agent tends to decrease it.

Wood material is a good reservoir for biogenic carbon storage. The use of wood material for outdoor products such as siding in the building construction sector presents limits. These limits are bound to the nature of wood material (hygroscopic property and anatomical structure). They are responsible for the dimensional variation associated with moisture content variations. Fungal attacks and coating layers adhesion on wood surface, are other problems. This research investigated the feasibility of impregnation with environmentally friendly chemicals, i.e., a citric acid-glycerol mixture (CA-G). The anti-swelling efficiency (ASE), hardness, biodegradation, and coating adhesion tests were performed on softwood specimens. ASE results were up to 53%. The equilibrium moisture content of the treated specimens was less than half of the untreated ones. FTIR spectroscopy showed bands at 1720 to 1750 cm-1, indicating the presence of ester bonds, and scanning electron microscopy images confirmed the polymerization and condensation of treatment solution inside the wood structure. Hardness and decay resistance were increased; however, treatment reduces coating adhesion. In conclusion, CA-G represents a promising eco-responsible solution for improving the technical performance of outdoor wood products.

Chemical impregnation of black spruce was conducted to enhance the wood embedment capacity. The formulation was made of 1,6 hexanediol diacrylate, trimethylpropane triacrylate, and a polyester acrylate oligomer. A second formulation, same as the first but with 1% wt of SiO2 nanoparticles, was selected to investigate the potential of nanoparticles and to improve the efficiency of the treatment. The wood embedment capacity was carried out by a dowel-bearing test, which was performed for the two treatments and for an untreated wood group. Both treatments showed an increase of strength of nearly 50% when compared to untreated samples. Micrograph views revealed that the impregnation solution penetrated into the wood only up to 100 μm. Hence, with low chemical consumption, the structural bearing capacity can be significantly increased.

Morphological, physical, thermal, and mechanical properties of nanocrystalline cellulose (NCC) were determined. Moisture content as well as oil absorption were also studied. The NCC was obtained from sulfuric acid hydrolysis of wood pulp. Transmission electron microscopy showed that NCC has a diameter of 10 nm and a length of 150 nm. Fourier transform–Raman spectroscopy and x-ray diffraction experiments both showed that NCC has a very high degree of crystallinity. Using an Abbe refractometer, the average refractive index of the NCC in different solvents was determined to be 1.499. Hardness and elastic modulus of the homogeneous, translucent NCC films were determined by nanoindentation technique. Oil absorption and moisture content were related to the particle size.

To improve technical performance of wood siding, treatment with maleic anhydride was applied. The effects on technical performance of drying time and esterification temperature parameters were analyzed. Wood samples of lodgepole pine and white pine were treated and tested. Results indicated that treatment improves technical performance of wood (dimensional stability, fungal degradation resistance, and accelerated aging). FTIR spectroscopy analysis showed spectra with peaks at 1750 to 1730 cm-1. These correspond to ester bonds formed between wood hydroxyl groups and MA carboxylic acid groups. SEM images indicate that the MA quantity in wood cavities was increased with decreasing esterification temperature. Weight percent gain (WPG) increased with decreasing time and temperature of esterification. Artificial aging and fungal degradation performances were monitored using FTIR analysis. Esterification temperature had no important effect on fungal degradation. Weight loss after fungal exposure of treated samples was not only due to fungal action but also due to evaporation of MA during the drying step. Regarding artificial aging, degradation of wood components and ester bonds were less for samples esterified at 180 °C than those esterified at 160 °C or 140 °C.