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Simultaneous photopolymerization of radical and cationic systems is one strategy to generate polymer network architectures named interpenetrating polymer networks (IPNs). In these hybrid systems, phase separation and final polymer morphology are ultimately governed by thermodynamic incompatibility and polymerization kinetics. This behavior is quite complex, as numerous factors can affect polymerization kinetics including monomer/oligomer viscosity and structure, light intensity, photoinitiator content and absorbance, cross-linking, vitrification, etc. In this work, the impact of photoinitiator concentration and monomer fraction on surface morphologies in a hybrid radical/cationic phase-separated system was examined. Wrinkles formed on the surface of photopolymerized films depend on the polymerization rate and acrylate/epoxy ratio. This phenomenon is partially explained by the rapid polymerization rate associated with the development of an epoxy matrix and a smaller acrylate domain. The size and shape of the wrinkles can be controlled by varying formulation parameters (mainly, composition) and photoinitiator content. It was possible to create surface roughness and consequently decrease the gloss by controlling the polymerization kinetics and phase-separated morphology. This study demonstrates that the morphology, polymerization kinetics, and film properties (e.g., gloss, transparency) can be manipulated with the ratio of the acrylate/epoxy mixture and the photoinitiator content.

Wood is a biosourced material with unique aesthetic features due to its anatomy and chemical composition. White oak wood surface color can be modified with the use of iron salts, which react with wood phenolic extractives, present as free molecules in wood porous structure. The impact of modifying wood surface color with iron salts on the final appearance of wood, including its color, grain contrast and surface roughness, was evaluated in this study. Results showed that following the application of iron (III) sulphate aqueous solutions on white oak wood surface, its roughness increased, which is due to grain raising after wetting of wood surface. The color modification of wood surface with iron (III) sulphate aqueous solutions was compared with a non-reactive water based blue stain. The contrast associated to wood grain that was expressed by the standard deviation of luminance values in wood images, also increased after application of the iron (III) sulphate aqueous solution on white oak wood surface. The comparison of contrast changes showed that wood samples stained with iron (III) sulphate on their curved surface had the highest increase in grain contrast compared to iron-stained wood showing the straight grain and to wood surfaces colored by a non-reactive water-based stain for both curved and straight grains.

The application of a flame retardant coating is an effective solution to enhance the fire retardancy of wood flooring. However, finding the right balance between reducing the flame propagation and good overall coating properties while conserving wood appearance is complex. In order to answer this complex problem, transparent ultraviolet (UV)-curable flame retardant wood coatings were prepared from an acrylate oligomer, an acrylate monomer, and the addition of the tri(acryloyloxyethyl) phosphate (TAEP), a phosphorus-based monomer, at different concentrations in the formulation. The coatings’ photopolymerisation, optical transparency, hardness, water sorption and thermal stability were assessed. The fire behaviour and the adhesion of the coatings applied on the yellow birch panels were evaluated, respectively, using the cone calorimeter and pull-off tests. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) analyses were performed on the collected burnt residues to obtain a better understanding of the flame retardancy mechanism. Our study reveals that phosphorus monomer addition improved the coating adhesion and the fire performance of the coated wood without impacting the photopolymerisation. The conversion percentage remained close to 70% with the TAEP addition. The pull-off strength reached 1.12 MPa for the coating with the highest P-monomer content, a value significantly different from the non-flame retarded coating. For the same coating formulation, the peak of heat release rate decreased by 13% and the mass percentage of the residues increased by 37% compared to the reference. However, the flame-retarded coatings displayed a higher hygroscopy. The action in the condensed phase of the phosphorus flame retardant is highlighted in this study.

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.

Filling wood cells with polymeric materials offers great opportunities to improve wood strength. Some applications, such as flooring, may require densification on one side of the material only. Yellow birch (Betula alleghaniensis Britt.), sugar maple (Acer saccharum Marsh.) and red oak (Quercus rubra L.) were surface densified through lateral chemical impregnation of monomers under vacuum followed by in situ electron beam polymerization. Lateral impregnation led to low mean chemical retention of 4% for sugar maple, 11% for red oak and 12% for yellow birch. X-ray densitometry and microtomography revealed an asymmetric density profile comparable to mechanically surface densified wood due to polymer-filled vessels. Scanning electron microscopy images showed presence of polymer-filled fibers beneath the surface. Brinell hardness of all species increased significantly compared to untreated wood. Low chemical retention significantly improved hardness due to localized polymer beneath the surface. Density profile characteristics were extracted from densitometry curves and correlated to hardness. Deep monomer penetration was more favorable to hardness than high surface density peak.

International audience; In a high-rise building, due to the risk of flame spread and strict regulations associated, wood use is limited for interior finishes. This study aimed to evaluate the effect of a thin organosilicon layer (similar to 500 nm) prepared by atmospheric pressure plasma on the fire behavior of a wood substrate. The coating was deposited from hexamethyldisiloxane in argon on both untreated wood and wood with a preparatory coating of primer. The primer reduces the presence of cracks in the plasma layer and ensures more homogenous coverage of the substrates. Finally, the flame retardancy analysis highlights an improvement in fire behavior only when the primer is used. Our study suggests that plasma thin deposition has a synergic effect with primer to fireproof 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.

Metal salts application on wood surface is a simple and nontoxic method that can be used for wood color modification, which is induced by the formation of colored complexes between wood extractives...

Hybrid free-radical/cationic systems can generate phase-separated polymers or interpenetrating networks driven by photopolymerization. In this study, phase separation of a ternary mixture composed of a polybutadiene urethane diacrylate (PBUDA), a cycloaliphatic diepoxyde (CE), and hexanediol dimethacrylate (HDDMA) was investigated. Using systematic variations of the initial composition of the mixture, a miscibility phase diagram of the ternary mixture was established. Based on this diagram, a reactive copolymer (poly(butyl acrylate-co-glycidyl methacrylate) (PBGMA)) was introduced in a reference hybrid system to manipulate the crosslinking network, polymer morphology, and properties (e.g., roughness, gloss, strain at break, and glass transition temperature Tg). When cured as a coating, the ternary hybrid system showed a depthwise gradient of epoxy conversion, and thereby developed a mostly cured skin above a viscous sublayer of uncured monomer. This skin can develop compressive stress due to the swelling from the diffusion of unreacted monomers beneath, and if the compressive stress is significantly high, wrinkles appear on the coating’s surface. This work highlights how both skin thickness and elastic modulus impact wrinkle frequency and amplitude. It was demonstrated that these wrinkle parameters can be manipulated in the ternary system by the addition of PBGMA. We also demonstrated that by employing UV irradiation and varying the PBGMA content, it is possible to engineer coatings that range from smooth surfaces with high gloss to wrinkled topographies with a very low associated gloss.

Discoloration of wood coatings due to fungal growth negatively affects the aesthetic properties of the coatings, and new ways to control fungal growth on coatings are needed. For this reason, silver nanoparticles (AgNPs) have been incorporated in acrylic latexes as antifungal agents. Using miniemulsion polymerization, latexes were prepared with two types of initiators (hydrophilic and hydrophobic) to assess the influence of the initiator type on AgNPs dispersion, both within the latex particles and the dry film. In addition, the impact of NP dispersion on resistance to black-stain fungi (Aureobasidium pullulans) was also evaluated. Inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis indicates that acrylic latexes prepared with azobisisobutyronitrile (AIBN) as the initiator contain more AgNPs than those prepared with potassium persulfate (KPS). Cryo-TEM and SEM analyses show that the distribution of the AgNPs within the polymer particles is influenced by the nature of the initiator. When AIBN, a hydrophobic initiator, is used, the AgNPs appear to be closer to the surface of the polymer particles and more evenly distributed. However, the antifungal efficiency of the AgNPs-embedded latexes against A. pullulans is found to be higher when KPS is used, despite this initiator leading to a smaller amount of incorporated AgNPs and a less uniform dispersion of the nanoparticles.

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.

Translucent coatings applied to wood that is used for exterior applications often fail because of photodegradation and colonisation by black-stain fungi. This paper reports the effect of silver nanoparticles on the black-stain resistance of acrylic latex coatings. Acrylic latexes that contained various concentrations of silver nanoparticles were mixed with a commercial acrylic resin. The formulations were then applied to red pine (Pinus resinosa) sapwood, which was later evaluated for fungal resistance to Aureobasidium pullulans, Sclerophoma pityophila, and Eppicoccum nigrum. Latexes with silver nanoparticle concentrations as low as 0.03% (total coating formulation weight) were able to limit S. pityophila and E. nigrum growth, while higher concentrations were needed to limit the growth of A. pullulans. The influences of silver nanoparticles on the optical properties of the coating (i.e., colour, opacity, and gloss) were evaluated. It was demonstrated that the addition of silver nanoparticles to the formulation does not compromise the development of a translucent coating.

International audience; Fire protection has been a major challenge in wood construction for many years, mainly due to the high flame spread risk associated with wood flooring. Wood fire-retardancy is framed by two main axes: coating and bulk impregnation. There is a growing need for economically and environmentally friendly alternatives. The study of polyelectrolyte complexes (PECs) for wood substrates is in its infancy, but PECs’ versatility and eco-friendly character are already recognized for fabric fire-retardancy fabrics. In this study, a new approach to PEC characterization is proposed. First, PECs, which consist of polyethyleneimine and sodium phytate, were chemically and thermally characterized to select the most promising systems. Then, yellow birch (Betula alleghaniensis Britt.) was surface-impregnated under reduced pressure with the two PECs identified as the best options. Overall, wood fire-retardancy was improved with a low weight gain of 2 wt.% without increasing water uptake.

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.

One of the major issues in the wood industry is the durability of clear coatings. The addition of organic ultraviolet absorbers (UVAs) improves coating resistance by the absorption and conversion of UV radiation into harmless heat. Organic UVAs are, however, easily degraded by free radicals produced by photodegradation inside the polymer matrix and are prone to migration in the coating. In this study, commercial UVAs and hindered amine light stabilizers (HALS) entrapped into poly(methyl methacrylate) (PMMA) microspheres and CaCO3 templates coated with UV-responsive polymers were added into clear acrylic water-based coating formulation. Artificial accelerated weathering experiments were performed on each formulation. Raman spectroscopy mapping was performed to visualize the concentration and distribution of UVAs and HALS. This study also presents a comparison of the mechanical properties of coatings obtained by dynamic mechanical analysis. Results showed that coating mechanical properties were improved when using encapsulated UVAs and HALS inside PMMA microspheres. The color change of the wood and coating system was minimized and the production of photo-oxidation compounds in the binder was also limited.

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.

In order to clarify the relationship between photodegradation and biological degradation, wood specimens finished with a semi-clear coating were degraded under a xenon lamp for different periods of time. The specimens were then inoculated one of two black stain fungi (Aureobasidium pullulans and Epicoccum nigrum). Colonization was monitored visually and by colorimetric analyses. The extent and the nature of the degradation were evaluated using different techniques. The chemical composition was studied by Fourier Transform Infrared Spectroscopy (FTIR) and the physical changes by both microscopic analyses and adhesion tests. The results obtained from FTIR did not provide relevant information. Coating thickness and adhesion were found to decrease as photodegradation increased. Microscope observations detected numerous bubbles trapped in the coating films. These bubbles were found to become holes following photodegradation and the decrease in coating thickness. It was established that more severe photodegradation led to more extensive colonization of the specimens. The fungi seemed to use transpressorium to go through the protective layer and take advantage of organic matter present at the wood/coating interface. Funguscolonization was also found to decrease the coating adhesion in the early stages of the exposure process.

In the wood furniture and flooring industry, the protective and aesthetic properties of the final product often rely, at least partially, on the coatings applied to the wood surface. For flat surfaces, UV-cured coatings are often preferred due to their many advantages, such as fast curing times, low volatile organic compound (VOC) emissions, low energy consumption and high crosslinking densities. To increase the durability of interior wood products, the behavior of the protective coatings while subjected to wear and deterioration has to be understood in order to be enhanced. Depending on the type of solicitation, mar (i.e. shallow defects), scratches or indentations can be formed, which impact the coating's appearance and can shatter the perception of the whole product. In this work, formulations based on different monomer-oligomer couples were prepared and photo-polymerized to investigate their performances. First, the glass transition temperature and the crosslinking density were determined to understand the contribution of both components in the polymeric network formed upon UV-curing. Then, hardness, and abrasion, scratch and wear resistances were studied. The results showcased the importance of the monomer and oligomer structure, functionality and main physical properties. In scratch experiments, the hard and brittle coatings tend to display failures at lower loads than soft and ductile ones. The friction experiments also caused subsurface tearing and fissuring in the soft coatings and generated several fractures in the harder ones. Furthermore, the best overall mechanical resistance was obtained for the couples with high crosslinking density, and a correlation was found between the crosslinking density and the hardness of UV-cured coatings. Interestingly, the investigation of tracks after scratch and wear experiments revealed a significant amount of information about the coatings' behavior under various mechanical loads.

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.

In this study, sugar maple and white pine, two species of wood commonly used in indoor and outdoor applications, were treated by photo-initiated chemical vapor deposition to impart barrier properties. After treatment, wood wettability decreased significantly, as evidenced by water contact angle measurements (from 50° to 113° for sugar maple and 87° to 172° for white pine). Further, beyond being able to repel water, the coating shows the ability to breathe, evidenced by standardized vapor sorption tests. However, accelerated weathering via ASTM G155 testing determined that the treatment could not protect the wood from photo-degradation, or retain its properties post-weathering. This treatment could therefore be best suited for wood pre-treatment in combination with other coatings.

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.

As a previous study has shown, it is possible to increase by 50% the dowel bearing strength of black spruce with an acrylate formulation applied by impregnation. Three diameters of bolts and two orientations of loading were included in this study. The effect of treatment on the dowel-bearing strength appeared to increase while the diameter of bolt decreased. The orientation of loading was significant as the treatment had a major impact in the parallel to grain direction and no impact in the perpendicular direction. With the digital image correlation analysis, an expanded strain field perpendicular to the load direction was observed. The superior embedding capacity would help to reduce the dimensions of the timbers as well as the number of connections required in the building design. With an increase of ductility, wood connections show a safer yielding behavior.

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 esthetic durability of coatings on wood surfaces of components constituting wood furniture used in bathrooms is generally affected by high humidity. In this study, surfaces of yellow birch wood (Betula alleghaniensis Britton) were protected with three different types of transparent UV-cured multilayer coatings (MCs), namely MC1, MC2, and MC3. Each MC consisted of three layers: primer, sealer, and topcoat. MC1, MC2, and MC3 contained, respectively, 0, 1, and 3 wt% of nanoclay (NC) in the topcoat, while no nanoparticle was added in the primer and sealer. The surface roughness of coated wood surfaces was measured before accelerated aging and optical properties (color and gloss) were investigated before, during, and after accelerated aging. Statistical results have shown that: (1) all coated wood samples have a similar surface roughness and (2) NC in the topcoat does not have a significant effect on initial color, whereas its effect on initial gloss is significant. There is a significant effect on relative humidity (RH) on color changes, but not between the different types of MCs. With respect to gloss, a lowering of gloss retention with the increase in aging time and RH has been observed for all coatings on wood surfaces. Significant differences appear only at high RH between: MC1 vs MC3 and MC2 vs MC3.

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.