Untreated Panels Research Articles

Properties of patula pine plywood using phenolic resin-impregnated veneers

Having observed the need for structural panels for external use, it is important to study methods of treating wood from new forest species, with less harmful products. In this sense, veneers of Pinus patula wood were subjected to immersion treatment in phenolic resin diluted in water at 5% solids content for one minute, and subsequently used to produce plywood panels using phenol-formaldehyde resin, with a weight of 160 g /m² in single line. The experimental design included four types of panels: fresh veneers glued with 35% resin solids content, treated veneers glued with 12%, 23% and 35% resin solids content. The physical-mechanical properties of the panels were compared with the parameters defined by the Brazilian Association of the Mechanically Processed Wood Industry (ABIMCI) and the Brazilian Association of Technical Standards (ABNT). The panels produced presented apparent density and bonding quality results below the minimum recommendations established in these technical parameters, in addition to water absorption higher than the values found in research with other pine species. However, veneer panels treated with phenolic resin showed better bonding quality than untreated panels for the same resin solids content. In less severe conditions, such as in the wet bonding test, the use of 23% resin solids content maintained bonding quality compared to 35% untreated wood. Therefore, further studies are suggested on the use of wood veneers treated with phenol and to reduce the resin solids content for to reduce costs and harmful effects on the environment.

Cellulose nanofibrils as a bio-based binder for wood fiber composite insulation panels with enhanced thermo-mechanical properties for structural wall sheathing applications

A low-density wood fiber insulation panel (WIP) composite was developed with 100 % petrochemical-free, bio-based binder with high mechanical strength, water resistance and thermal insulation properties. This study investigated the manufacturing process of composite WIPs made with mechanical pulp fibers with cellulose nanofibrils (CNFs), lignin-containing CNFs (LCNFs), hybridized CNFs-LCNFs, and CNFs-starch as a binder on different scales and evaluated the effects of binder type and content on the panels’ physical, mechanical, and thermal properties. All panels had excellent thermal resistivity values, which increased with the decrease in density. The WIPs made with LCNFs as binder had lower mechanical properties, but it was possible to replace 20 % CNFs with LCNFs to obtain the same performance as neat CNFs as the binder. Untreated panels had poor water resistance but the water absorption properties were significantly improved with the addition wax. The WIPs made with 5 % and 7.5 % binder content and 2 % wax addition could fulfill the criteria of regular and structural wall sheathing applications, respectively. Overall, the results confirm the potential of CNFs and LCNFs to be used as 100 % bio-based adhesives to produce eco-friendly composite WIPs with excellent thermo-mechanical properties to be used for regular and structural wall sheathing applications.

Properties of Plywood Made of Thermally Treated Veneers Bonded with Castor Oil-Based Polyurethane Adhesive

Wood industries use thermal and thermomechanical treatments as ecological approaches to increase the durability of wood products, avoiding the need for chemical additives. In this regard, the aim of this study was to compare the physical and mechanical properties of plywood made from veneers treated at different temperatures using thermal and thermomechanical processes, with untreated panels serving as a control. The treatment process involved Pinus taeda veneers submitted to treatment in a hot press at 1.0 MPa in a laboratory oven at temperatures of 160 °C, 180 °C, and 200 °C for 30 min. For bonding the veneers, a vegetable-based polyurethane resin derived from castor oil with a grammage of 395 g/m2 was used, applying pressing conditions at 90 °C, 0.6 MPa, and 10 min. Our results indicate that temperature significantly influences plywood properties, playing a key role in the choice of equipment for the treatment process. Regardless of the method employed, the treatment resulted in an improvement in the hydrophobicity of the veneers due to the decrease in hemicellulose content. Notably, the reduction in strength and stiffness caused by the loss of cell wall polymers was not statistically significant. The treatment was successful in softening the wood material, reducing roughness, and increasing wettability. Despite a minimum of 20% reduction in glue line tension, the samples still surpassed the 1 MPa mark, showing satisfactory results. This demonstrates the feasibility of adjusting treatment variables to ensure the proper use of this adhesive.

Temperature-sensitive microcapsules modification treatment to reduce formaldehyde emission from wood-based panels

ABSTRACT The formaldehyde emission performance of wood-based panels treated with temperature-sensitive microcapsules was evaluated in this study. Formaldehyde scavenger-filled microcapsules were synthesized by the emulsion-solvent method using ethylcellulose and poly(N-isopropylacrylamide) (PNIPAM) as shell materials containing urea. The results demonstrated that the temperature-sensitive microcapsules exhibited perfect core–shell structures at a core/shell/PNIPAM ratio of 2:2:1. The loading capacity and loading efficiency of the functional core material of the microcapsules reached 33% and 59%, respectively. Compared with untreated panels, panels based on the temperature-sensitive microcapsule scavenger had better performance in controlling free formaldehyde emissions, the formaldehyde emission of treated panels decreased by 42% and 41% at room temperature and 40°C, respectively. The results indicated that the reason why the wood-based panels had a long-term low-level emission was that the microcapsules showed different release behaviour at different temperature, so they have different release paths and release principles.

Structural performance of sandwich wall made of concrete cast in between GFRP facings

The structural performance of concrete walls reinforced with pultruded glass fibre-reinforced polymer (GFRP) ribbed plates on either side has been experimentally investigated. The GFRP plates were used as a stay-in-place (SIP) structural formwork replacing internal steel reinforcement. The pultruded flat plates incorporated 51 mm deep T-shape ribs on one side, spaced at 100 mm, which provided interlocking with concrete. Six 3000 × 616 mm panels, either 150 or 200 mm thick, were tested in bending ( M), under axial compression ( N) and under combined loads to establish the completed ( M- N) failure envelope of the wall. The effect of surface treatment of the GFRP forms was also investigated. It resulted in full composite action with no concrete slip, reaching 30% higher flexural strength than untreated panels. The effect of reinforcement ratio was studied by varying wall thickness. In all panel tests, diagonal concrete shear cracking occurred and propagated into a horizontal delamination above the GFRP ribs. Slenderness effect and secondary moments were accounted for in developing the ( M- N) interaction curve. Initially, M increased by 25% as N increased from zero to 17% of pure axial strength. Then, M reduced linearly to zero at pure N as concrete crushing occurred when the GFRP compression plate separated from the ribs and buckled outwards at midspan. A simplified design approach is also presented.

Finishing performance of Acacia mangium wood surface-treated with methanol

ABSTRACT Evaluation of the effects of 8% methanol (MeOH) pretreatment on the finishing performance of Acacia mangium wood was carried out using different coating systems, i.e., nitrocellulose (NC), acid catalysed (AC) and polyurethane (PU). The coated surfaces were tested for adhesion test-cross cut, scratch resistance test, abrasion test, impact resistance test, surface roughness, and gloss measurements test according to the relevant standard. The results have shown that A. mangium wood surface treated with 8% methanol resulted in a superior finished surface compared to untreated panels except gloss. Among coating systems, AC and PU appear to be more compatible with MeOH than with NC. Applying 8% of methanol to A. mangium surface before coating, application of AC or PU improved the quality of finished A. mangium wood and meeting the minimum requirements outlined in the standards.

Effect of ozone pretreatment on the physical and mechanical properties of particleboard panels made from bagasse

Abstract The main objective of this study was to investigate the applied properties of particleboard panels made from bagasse, which were either treated or not treated with gaseous ozone (O 3 ). Variable parameters were ozone exposure time (1–3 min) at 9 ppm and storage period (1–5 months). Other parameters such as resin content (12 wt%), hardener content (1 wt%), type of hardener (NH 4 Cl), press closing time (5 mm/s), board density (0.70 g/cm 3 ), and press pressure (30 kg/m 2 ) were held constant. The experimental panels were tested for their mechanical properties including modulus of elasticity (MOE), modulus of rupture (MOR); and internal bonding strength (IBS) and physical properties in terms of water absorption (WA) and thickness swelling (TS) according to the procedures defined by EN standards. Overall results showed that all panels made from treated bagasse exceeded the EN standards for MOE, MOR, and IBS. However, WA and TS values decreased after ozone pretreatment compared to the un-treated (control) panels. Application of Duncan’s Multiple Range Test for the mean values of the results showed that the effects of both variables, except their interactions, on the mechanical and physical properties were highly significant ( p ⩽ 0.01%). All the mechanical properties of the panels decreased when the treatment duration increased from 1 to 5 months.

New Process for Peanut Husks Panels: Incorporation of Castor Oil Polyurethane Adhesive and Different Particle Sizes

New materials are being developed for architectural and design purposes. The recycling of waste is presented as an opportunity for new applications based on increased industrial waste and raw material shortages. Seeking an alternative to wooden panels, regional waste without sustainable disposal is being used as inputs in the production of lignocellulosic panels. We present the results of two experiments. The first one consists in the development of peanut husks ground-treated and untreated panels made in order to determine the influence of different particle sizes, shapes and their combinations, aiming to the physical and mechanical characterization of compact panels properties. In the second experiment, compact panels with whole peanut husks were made with polyurethane resin using castor oil painting. The object of this study was to analyze the influence of this new resin, without formaldehyde emissions, in the resulting panels physical and mechanical properties. It was concluded that the smaller particles had a positive influence in the panels physical-mechanical properties, and that the property characterization of panels made with castor oil resin was satisfactory for use in interior furniture. Peanut husks panels show good prospects for their integration in the field of design and architecture.

Water Cooling Method to Improve the Performance of Field-Mounted, Insulated, and Concentrating Photovoltaic Modules

The installation rate of crystalline silicon photovoltaic (PV) modules worldwide is at an all-time high and is projected to continue to grow as the cost of PV technology is reduced. It is important to note that PV power generation is heavily influenced by the local climate. In particular, for crystalline silicon-based PV devices, as the operating temperature of the panel increases, the efficiency decreases. Higher operating temperatures also lead to accelerated material and mechanical degradation, potentially compromising system effectiveness over the lifetime of the panels. In addition, atmospheric pollution can cause particle deposition on the surface of PV modules (soiling), reducing the amount of solar irradiance that reaches the PV material and reducing panel efficiency. Various cooling and cleaning methods have been proposed in the literature to mitigate these problems. In this study, a uniform film of water was continuously recirculated by pumping over the surface of a solar panel using an emitter head attached to the top of the panel. The water cooling technique was able to maintain panel temperature below 40 °C while adjacent untreated panels were operating near 55 °C. Besides the efficiency improvements due to cooling, the film of water also kept the panels clean, avoiding any reduced power output caused by panel soiling. Additional studies were carried out with artificially chilled cooling fluid, insulating materials, and side mirrors to examine the cooling system performance under different installation scenarios. Water cooling is concluded to be an effective means of increasing the efficiency of monocrystalline silicon photovoltaic panels. Under normal operating conditions, the increased energy output from the panels is more than sufficient to compensate for the energy required to pump the water.

Performance of clear coatings on modified wood exposed to the weather for 2 years in Australia

We examine the performance of clear coatings on wood treated to improve its photostability. The treatments tested were: benzoyl chloride; chromic acid; modified PF resins; vinyl benzoate; and primers containing different photostabilisers. Treated panels were finished with clear coatings containing different types/levels of photostabilisers and exposed outdoors in Australia for 2 years. The coatings performed better on treated than untreated panels, except for coatings on panels treated with a primer containing cerium oxide nanoparticles. Clear coatings performed best on wood treated with chromic acid, vinyl benzoate or PF resin containing a hindered amine light stabiliser. However, the performance of the coatings was also strongly influenced by coating type. We conclude that the performance of clear coatings can be increased if they are applied to photostable wood substrates. However, coating performance is also dependent on coating flexibility, its propensity to form surface defects, and the level/types of photostabiliser in the coatings.

HEAT APPLIED CHITOSAN TREATMENT ON HARDWOOD CHIPS TO IMPROVE PHYSICAL AND MECHANICAL PROPERTIES OF PARTICLEBOARD

High-heat treatment after surface application of chitosan was used in an effort to improve physical and mechanical performances of particleboard. Particleboard is mainly used in the furniture industry and also used as a home decoration material; however, it has a poor dimensional stability. In this work, hardwood chips were obtained from a commercial plant; half of the chips were used for the control panels without chitosan treatment, and the other half were treated with chitosan acetate solutions (2% wt). Those chitosan-treated particles were also exposed to extra high-heat (140°C) treatment for 90 minutes to convert chitosan acetate back to chitin. Liquid phenol-formaldehyde resin was sprayed onto dry particles at a level of 6 and 7% (wt) based upon oven-dry weight. The mat was pressed (200°C) for 11 minutes to form 19 mm thickness and a target of 0.63 g cm-3 density panels. Thickness swelling, linear expansion, and water gain of the treated panels were reduced over untreated panels during a 24-hour water-soak test. In addition, chitosan-treated panels showed better internal bond strength than control panels. Static bending test results showed a negative effect for the chitosan treated particleboard.

Incidence and severity of marine borer attack at different depths at Mtongwe Jetty Pontoon Mombasa, Kenya

AbstractThe activity of marine borers was investigated at Mtongwe Jetty Pontoon, Mombasa, Kilindini harbour using untreated panels of Pinus patula (Schlecht) submerged to different depths. Twenty test panels replicated over 7 months were each strung in three ladder‐like frames using nylon twine and suspended vertically, in such a way that the top most panels were 25 cm below the water surface at low and high tide. Monthly observations were made between January and July for the vertical incidence and extent of marine borer attack following the technique of Bobat (1995). Marine borers were collected from test panels, identified and counted. In addition, the percentage weight loss for panels at different depths was determined at the end of 7 months. Teredo fulleri (Clapp) was dominant on panels near water surface while Martesia striata (Linne) and Lyrodus pedicellatus (Quatrefages) were predominant at the bottom. The results showed that attack began within the first month of exposure and was severest by the seventh month. The vertical incidence and extent of attack decreased with increasing depth of panel exposure and was negatively correlated with depth. This is attributed to changes in hydrographic conditions.

Establishment and Succession of an Epibiotic Community on Chromated Copper Arsenate-Treated Wood in Mediterranean Waters

Colonization and succession of an epibiotic animal community on chromated copper arsenate (CCA)-treated wood were studied for 18 months in the eastern Mediterranean (Saronikos Gulf, Aegean Sea). Pine wood panels, 200 x 100 x 25 mm, impregnated with CCA at retentions of 0, 12, 24, and 48 kg m(-3) were used. The abundance or surface coverage of the most characteristic taxa (polychaetes, mollusca, crustacea bryozoa, sponges, ascidians) was measured in situ, while 12 months after submersion two panels of each retention were removed and examined in the laboratory. A total of 26 taxa were identified, among which polychaetes of the family Serpulidae dominated. The controls carried the largest number of species (17) but the lowest number of individuals. On panels with CCA retentions of 12 and 24 kg m(-3), 14 and 16 species were observed, respectively, while at 48 kg m(-3), only 9 species were found. Only the controls were affected by boring bivalves of the family Teredinidae and started to break up within 3 months of submersion. Statistically significant differences in barnacle and polychaete abundance were found between treated and untreated panels. There were no significant differences among panels treated at the three CCA loadings. Ordination by nonmetric multidimensional scaling showed a seasonal effect on the colonization of the treated panels, with the highest recruitment during the warmer months of the study.

Weathering of uncoated and coated wood treated with methylated 1,3-dimethylol-4,5-dihydroxyethyleneurea (mDMDHEU)

Scots pine (Pinus silvestris L.) sapwood panels were treated with a methylated 1,3-dimethylol-4,5-dihydroxyethyleneurea (mDMDHEU) causing weight gains of approx. 25% and were exposed to weathering for 18 months. Compared to untreated panels, treatment with mDMDHEUreduced surface discoloration mainly caused by staining fungi. Panels treated with mDMDHEU clearly exhibited lower moisture content throughout the exposure time and lower water uptake in periodical submersion tests. The treatment also reduced deformation (cupping) and crack formation of the panels due to weathering (assessed as waviness and surface roughness).

Controlled Study of Mold Growth and Cleaning Procedure on Treated and Untreated Wet Gypsum Wallboard in an Indoor Environment

The basis for some common gypsum wallboard mold remediation practices was examined. The bottom inch of several gypsum wallboard panels was immersed in bottled drinking water; some panels were coated and others were untreated. The panels were examined and tested for a period of 8 weeks. This study investigated: (a) whether mold growth, detectable visually or with tape lift samples, occurs within 1 week on wet gypsum wallboard; (b) the types, timing, and extent of mold growth on wet gypsum wallboard; (c) whether mold growth is present on gypsum wallboard surfaces 6 inches from visible mold growth; (d) whether some commonly used surface treatments affect the timing of occurrence and rate of mold growth; and (e) if moldy but dried gypsum wallboard can be cleaned with simple methods and then sealed with common surface treatments so that residual mold particles are undetectable with typical surface sampling techniques. Mold growth was not detected visually or with tape lift samples after 1 week on any of the wallboard panels, regardless of treatment, well beyond the 24–48 hours often mentioned as the incubation period. Growth was detected at 2 weeks on untreated gypsum. Penicillium, Cladosporium, and Acremonium were early colonizers of untreated panels. Aspergillus, Epicoccum, Alternaria, and Ulocladium appeared later. Stachybotrys was not found. Mold growth was not detected more than 6 inches beyond the margin of visible mold growth, suggesting that recommendations to remove gypsum wallboard more than 1 foot beyond visible mold are excessive. The surface treatments resulted in delayed mold growth and reduced the area of mold growth compared with untreated gypsum wallboard. Results showed that simple cleaning of moldy gypsum wallboard was possible to the extent that mold particles beyond “normal trapping” were not found on tape lift samples. Thus, cleaning is an option in some situations where removal is not feasible or desirable. In cases where conditions are not similar to those of this study, or where large areas may be affected, a sample area could be cleaned and tested to verify that the cleaning technique is sufficient to reduce levels to background or normal trapping. These results are generally in agreement with laboratory studies of mold growth on, and cleaning of, gypsum wallboard.

Contact thermal post-treatment of oriented strandboard to improve dimensional stability: A preliminary study

The oriented strandboard (OSB) has less dimensional stability than plywood, but they are competitive panels and have been used for similar ends. The wood-water relation variables, such as thickness swelling and water absorption, express this OSB dimensional instability and can be explained by two main factors: wood hygroscopicity and imposed hot-pressing stresses. The objective of this present paper was to propose a thermal post-treatment as a method to improve OSB dimensional stability by decreasing wood hygroscopicity and releasing hot-pressing stress. OSB panels from Pinus taedawood were produced in laboratory, and their characteristics were: single layer, 0.8 g/cm3; 8% phenolic resin and without wax. The OSB panels were treated in a laboratory press at 250 °C for about 4, 7 and 10 minutes. The wood-water relation variables, thickness swelling (TS), water absorption (WA), equilibrium moisture content (EMC) and springback or permanent thickness swelling (PTS) were determined and compared with untreated panels. The results showed that the proposed thermal treatment was effective to reduce TS, EMC and PTS, but didn’t affect WA which was affected by panel density reduction. The longer the treatment the higher the dimensional stability, and panel weight loss could be used as predictive variable for the efficiency of the treatment.

Assessment of effects of chromated copper arsenate (CCA)-treated timber on nontarget epibiota by investigation of fouling community development at seven European sites.

To assess the effect of the anti-marine-borer timber preservative CCA (a pressure-impregnated solution of copper, chromium, and arsenic compounds) on nontarget epibiota, fouling community development was investigated. Panels of Scots pine treated to target retentions of 12, 24, and 48 kg CCA per m3 of wood (covering the range of retentions recommended for marine use) plus untreated controls were submerged at seven coastal sites (Portsmouth, UK; La Tremblade [two sites], France; Ria Formosa, Portugal; Sagres, Portugal; Kristineberg, Sweden; Athens, Greece). The fouling community on the surfaces of the panels was assessed both qualitatively and quantitatively after 6, 12, and 18 months of exposure. Multivariate statistical methods were used to compare community structure between panel treatments. Panels treated to the three CCA loadings supported very similar fouling assemblages, which in most cases had higher numbers of taxa and individuals than assemblages on untreated panels. No detrimental effects on epibiota due to CCA preservatives were detected at any of the treatment levels at all seven exposure sites, suggesting that the range of environmental conditions at the sites had no bearing on preservative impact on fouling biota. Differences in community structure between CCA-treated and untreated panels may be due to enhanced larval settlement on CCA-treated timber by some species as a result of modifications to the surface properties of the timber by the preservative. Possible reasons for the higher numbers of certain species on the surface of CCA-treated panels are discussed.

Effects of Chromated Copper Arsenate (CCA) Wood Preservative on Early Fouling Community Formation

The effects of the anti-marine-borer timber preservative CCA (a pressure impregnated solution of copper, chromium and arsenic compounds) on early fouling community formation were investigated during a number of field trials. The formation of a biofilm on the surface of CCA-treated and untreated timber panels of Scots pine was examined by scanning electron microscopy following submersion in Langstone Harbour, Portsmouth, UK for periods of 2, 7, 14 and 28 days. Results indicated a slightly faster rate of biofilm formation after 2 and 7 days of exposure on untreated timber compared to CCA-treated timber, although no differences were visible between panels after 14 and 28 days exposure, or between panels treated to different CCA loadings after all exposure periods. Settlement of the serpulid Ficopomatus enigmaticus and two species of barnacles ( Elminius modestus and Balanus crenatus) onto the surface of untreated and CCA-treated panels of Scots pine was examined following 4 weeks exposure in a brackish water millpond at Emsworth, West Sussex. Numbers of individuals were higher on CCA-treated panels than on untreated panels, and in the case of F. enigmaticus abundance of individuals increased with increasing preservative loadings. Early colonization by macroalgal species on the surface of CCA-treated and untreated panels of Scots pine was examined following submersion of panels in Langstone Harbour for a period of 4 weeks. Percentage cover of most species of algae was similar on the surface of CCA-treated and untreated panels, with the exception of Hincksia granulosa and Ceramium nodulosum which had significantly higher percentage cover on untreated panels. Possible explanations for the recruitment patterns are discussed.

Toxicity of Chromated Copper Arsenate (CCA)-Treated Wood to Non-Target Marine Fouling Communities in Langstone Harbour, Portsmouth, UK

The effect of the anti-marine-borer timber preservative chromated copper arsenate (CCA) (a pressure impregnated solution of copper, chromium and arsenic compounds) on non-target marine fouling animals was investigated during a subtidal exposure trial. Panels of Scots pine treated to target retentions of 12, 24 and 48 kg CCA per m −3 of wood, plus untreated controls were submerged at a coastal site on the south coast of the UK for 6, 12 and 18 months. After each exposure period the fouling communities that formed on the surface of panels were assessed both qualitatively and quantitatively. Community structure was similar on panels treated to the three CCA loadings, but was significantly different from community structure on untreated panels. The total number of species (species richness) was similar on all panels, although the number of individual organisms attached to the surface of panels was significantly higher on CCA-treated panels than on untreated panels. k-dominance curves revealed that the difference in numbers of individuals between CCA-treated and untreated panels was caused by higher numbers of the dominant species ( Elminius modestus, Hydroides ezoensis, and Electra pilosa) on CCA-treated panels. Other species were present in similar numbers on panels of all treatments. Results indicate that there are no detrimental toxic effects to epibiota caused by the presence of CCA preservative within the matrix of the wood at any of the treatment levels. Differences in community structure between CCA-treated and untreated panels may be due to enhanced larval settlement on CCA-treated timber by some species as a result of modifications to the surface properties of the timber by the CCA preservative.

Long‐term natural weathering of coated ThermoWood

Heat treatment reduces hygroscopicity and accompanying dimensional changes in wood. Prior to coating, pine and spruce boards were heat treated at 225°C for six hours under steam, in order to achieve dimensional stability and durability of wood substrate. The panels were coated surface finishes which are commonly used on exterior cladding, joinery and fences in Finland. Performance of the coated heat‐treated and untreated panels was monitored during five years’ outdoor exposure. Without coating the heat‐treated wood is not weather resistant. The original dark brown colour of the uncoated heat‐treated wood panels was not stable when exposed to weather, turning grey. Cracking of the heat‐treated wood without coating was at the same level as that of the untreated wood despite the lower moisture content of the heat‐treated wood. The unpigmented or low build stains and oils did not prevent cracking of the heat‐treated wood. Weather resistance of the heat‐treated wood was improved by the water‐ or solvent‐borne paints. Wood heat treated by means of this process is comparable to untreated wood as a substrate for coatings and no alterations in coating recommendations are needed when considering coating of heat‐treated wood.