Engineered Wood Flooring Research Articles

Assessing environmental burdens of China's wooden flooring production based on life-cycle assessment

After over 30 years of rapid development in the wooden flooring industry in China, there is an imperative need to address the resulting environmental impacts. Therefore, this study analyzed the environmental impacts of the four most common types of wooden flooring in China, such as solid wood flooring, multi-layer engineered wood flooring, three-layer engineered wood flooring, and laminated flooring, utilizing the life-cycle assessment approach. This study assessed 12 environmental indicators, the comprehensive index of energy conservation and emission reduction (ECER), and the eco-efficiency of the four wooden flooring types. A trade-off was observed among the various impact categories, making it challenging to rank the environmental performance of the four types of wooden flooring. Contribution analysis revealed that woody raw materials and electricity consumption in the production process were the primary environmental hotspots of wooden flooring. The ECER index indicated that the multi-layer engineered wood flooring exhibited the highest environmental impacts, followed by laminated flooring, three-layer engineered wood flooring, and solid wood flooring. The eco-efficiency of solid wood flooring was 237%, 767%, and 1454% higher than that of three-layer engineered wood flooring, multi-layer engineered wood flooring, and laminated flooring, respectively. Sensitivity analysis revealed that enhancing the environmental performance of wooden flooring lies in reducing power consumption and woody raw material consumption during the production process. These findings contribute to a comprehensive understanding of the environmental impacts associated with wooden flooring manufacturing, while also serving as a reference for further improvements in reducing their environmental impacts.

The Impact of Top-Layer Sliced Lamella Thickness and Core Type on Surface-Checking in Engineered Wood Flooring

Surface-checking is a significant quality issue of veneer and sliced lamellae-based wood products. This study explores how surface-checking in sliced lamellae-based engineered wood Flooring (EWF) is influenced by two key structure parameters: core type and top-layer thickness. The core types assessed were a standard solid wood lamellae with a veneer back-end layer (S), a standard solid wood lamellae core with veneer back-end layers on the two sides (DS), and a single-layer oriented strand board (OS) core. The EWF element’s top-layer lamellae were plain sliced at nominal dimensions of 1.5, 2.5, 3.5, and 4.5 mm from freshly sawn slabs of European oak (Quercus spp.). The surface-checking of EWF specimens was quantified based on a digital image correlation (DIC) method, which outputs a surface-checking index. The surface-checking results were evaluated using a Tweedie compound Poisson data distribution to fit a general linear model. The model evaluated the impact of individual factors, sliced lamellae thickness and core type, and their interaction. The checking index confidence intervals were estimated using a bootstrapping technique. Findings reveal a significant interaction between studied factors and provide insight into optimizing top-layer thickness and core construction to diminish surface-checking. A low sliced lamella thickness on standard solid wood lamellae core resulted in low surface-checking, deemed relevant for further research.

Deformation rate of engineered wood flooring with response surface methodology and adaptive network-based fuzzy inference system.

Controlling the deformation rate is the key to improving the product quality of engineered wood flooring. In this work, the changes in the deformation rate of engineered wood flooring were in focus with cold-pressing, response surface methodology, and adaptive network-based fuzzy inference system were used to explore the relationship between deformation rate and processing parameters, including adhesive spreading rate, pressing time, and pressing pressure. According to the results, the deformation rate was positively related to pressing time, while it increased first and then decreased with both the increase of adhesive spreading rate and pressing pressure. Meanwhile, a mathematical model was developed, and the significant influence of each term on the deformation rate was analyzed. This model had high feasibility and can be used to describe the relationship between the deformation rate and processing parameters. Furthermore, an adaptive network-based fuzzy inference system model was established. It has higher accuracy than that of the response surface methodology model, and it can be used for predicting deformation rate and optimizing processing parameters. Finally, an optimal processing conditions with the lowest deformation rate was determined as follows: 147 g/m2 adhesive spreading rate, 12s pressing time, and 1.2 MPa pressing pressure, and it hope to be adopted in the industrial processing of engineered wood flooring with respective of the higher product quality and lower production costs.

Measurement of surface-checking in sliced lamellae-based engineered wood flooring using digital image correlation

The lack of quantitative methods for surface-checking measurements may hinder improving the product characteristics of engineered wood flooring products built with sliced top-layer lamellae. This study evaluated the digital image correlation method for its applicability to surface checking measurements in engineered wood flooring elements with the top-layer comprising the plain sliced lamellae of oak (Quercus spp.) species with nominal thicknesses of 1.5–4.5 mm. The method involves observing full-field surface displacements of the sliced lamellae-based wood flooring specimens subjected to an accelerated sorption/desorption cycle. Detection of surface checks relates to discontinuities in surface displacements which can be interpreted from the output strain data as strain peak regions. Additionally, a surface-checking index was defined to describe the extension of surface-checking. Exposure tests were performed on a combination of coating presence and a different number of testing cycles. The main findings provide insight into the method procedure parameters, such as exposure duration, climate conditions, analysis parameters and recommendations regarding the digital image correlation setup settings and specimen manufacturing.

Dimensional Stabilization of Engineered Wood Floor Using Linseed Oil and Paraffin Wax Impregnation

Abstract: Engineered wood flooring comprises three or more layers of wood veneer adhered together to create a plank. The surfaces were coated to scale back water absorption. However, as wood is a hygroscopic substance, it loses and gains moisture from the atmosphere. This affects the dimensional stability of the floor badly, which emanates wide gaps between boards, cupped edges, crowning edges, and bulking of boards. Hence, the main intention of this study was to stabilize the engineered wood flooring by filling the wood cavity with linseed oil, paraffin wax, and a mixture of both, and evaluate the physical, mechanical property of treated and non-treated engineered wood flooring boards. The treatments were conducted at different temperature and durations. Keywords: Dimensional stabilization, Wood modification, Wood floor, Linseed oil, Paraffin wax, Impregnation

Effects of working time on properties of a soybean meal-based adhesive for engineered wood flooring

ABSTRACT Soybean meal-based adhesives (SMAs) commercially applied in wood-based composites require stable bonding properties. However, the structure and properties of SMAs are not as stable as synthetic resins, which significantly affect their performances. In this study, the structure–property evolution of a SMA with working time was systematically investigated. The findings revealed that the secondary structure, microstructure, crosslinking density, zeta potential, nitrogen solubility index, viscosity, wood permeability, and bonding properties of SMA considerably vary with working time. The changes in adhesive properties were correlated with the dissolution of SM particles in crosslinker solution and the increased pre-curing of liquid SMA with working time resulting from the crosslinking reactions between the dissolved SM and the crosslinker. Preferably, SMA at the working time between 0.5 h and 3 h since the mixing of soybean meal flour with crosslinker solution, should be used in order to ensure the desired water resistance of plywood panels for engineered wood flooring. And an application strategy was proposed to ensure the required water resistance of plywood panels for manufacturing engineered wood flooring.

Drying of oak wood lamellas: Part 1. Analysis of the process in a dehumidification kiln

The subject of this paper is to analyse the drying process of oak lamellas, which are the solid wood top layer of engineered wood flooring. The focus of the first part of the paper is on dehumidification kilns. Drying in a dehumidification kiln is an interesting alternative to conventional drying of thin solid oak wood with the aim of reaching high drying quality in a reasonable time. Drying tests were done in an industrial dehumidification kiln, and drying parameters were compared with the drying in the conventional kiln. Simultaneously, a drying test at a higher temperature was done in the programmable climate chamber. It was demonstrated that thin oak lamellas (approx. 5 mm thick) could be successfully dried in a dehumidification kiln in a relatively short time and with high drying quality. With the applied drying schedule (initial temperature of 36?C, final temperature of 46?C), the drying cycle will last 2 to 5 days, depending on the amount of wood and the initial MC. Due to the high rate of water evaporation and the inability of the kilns to remove it fast enough, the drying of lamellas in both dehumidification and conventional kilns takes place at a higher equilibrium moisture content than the set values.

Modelling of Impact Falling Ball Test Response on Solid and Engineered Wood Flooring of Two Eucalyptus Species

In this study, dynamic hardness tests on solid and engineered wood flooring specimens of Eucalyptus globulus Labill. and Eucalyptus grandis W. Hill ex Maiden hardwoods were performed because nowadays, these fast-growing hardwoods are still scarcely employed for this use. Furthermore, another two examples of hardwood commonly applied on wood flooring, Quercus robur L. and Hymenaea courbaril L., were also tested. To compare their properties, a dynamic impact hardness test based on the impact of steel balls, with several diameters, and drop heights was developed. Accordingly, 120 solid wood flooring specimens and 120 engineering wood flooring specimens were producing with these four hardwood species. Dynamic impact tests were made with three steel balls of different diameters (30–40–50 mm), and they were carried out from five different drop heights (0.60–0.75–0.90–1.05–1.20 m). The impact of the steel ball drew the size of the footprint on the surface and this mark was measured with a digital caliper for both dimensions, diameter and depth, as footprint diameter (FD) and indentation depth (ID). Data from 3000 samples, corresponding to 120 different individual groups (4 species × 3 ball diameters × 5 drop height × 2 floor type) were analyzed. Results indicated that the variability of ID (CV between 19.25–25.61%) is much greater than the values achieved for FD (CV between 6.72–7.91%). Regarding the fast-growing hardwood species tested, E. globulus showed a similar behavior to traditional hardwood applied on wood flooring in Europe, Q. robur, and it could be a promising growth in the flooring industry. However, E. grandis showed the worst values compared to traditional hardwood in all test configurations.

Effect of the Layer Structure of Wooden Floorings on Dimensional Mobility under Different Relative Humidity and Water Retention Conditions

Abstract This study aimed to determine the effect of different wood flooring layer structures and surface features on water intake, shrinkage, and swelling rates under different relative humidity and water retention conditions. Nine wood flooring sample types were tested: solid wood beech (Fagus orientalis L.) flooring covered with polyurethane varnish, four engineered wood flooring types having different core-layers (solid-wood poplar (Populus nigra L.), 2× medium-density fiberboard, and plywood) covered with ultraviolet dried polyurethane varnish on beech veneer, and four laminated wood flooring types having different core layers (high-density fiberboard, medium-density fiberboard, particleboard, and plywood). The results showed the lowest water retention increase rates for 2 and 24 hours in the high-density fiberboard and medium-density fiberboard core-layered laminated wood floorings. The lowest thickness swelling rate occurred in the laminated wood flooring with a plywood core layer during exposure to high relative humidity, whereas the lowest swelling rate in the width dimension occurred for laminated wood flooring compared with other product types. The lowest thickness shrinkage rate was in the poplar core-layered engineered wood flooring, whereas the lowest shrinkage rate in the width direction was in the medium-density fiberboard core-layered engineered wood flooring and plywood core-layered laminated wood flooring at lower relative humidities. In conclusion, high-density fiberboard and medium-density fiberboard core-layered laminated wood floorings are advisable for flooring exposed to a humid environment. All laminated wood flooring types provided good resistance to swelling. The plywood core-layered laminated wood floorings, poplar, and medium-density fiberboard core-layered engineered wood flooring types performed the best for low-humidity environments.

Development of a cornstarch adhesive for laminated veneer lumber bonding for use in engineered wood flooring

To produce aldehyde-free engineered wood flooring, we developed a cornstarch-based adhesive for laminated veneer lumber bonding. Polyvinyl alcohol was used as the tackifier, wheat flour as the filler, and polyisocyanate prepolymer as the reinforcing agent. After the application of the cornstarch adhesive to the engineered wood flooring, we found that the cornstarch adhesive had excellent adhesion in the laminated wood parquet. The properties of the cornstarch-based adhesive met the requirements of GB/T 14074–2006, GB/T 20241–2006, and GB/T 18103–2006 for non-structure interior adhesives. When lumber veneer (thickness, ≤2.2 mm) was used, the engineered wood flooring showed good dimensional stability after 1–2 min of hot-pressing pretreatment (temperature, 100–120 °C; pressure, 0.83 MPa). The main physical and chemical properties also met the requirements of GB/T18103-2000, Engineered Wood Flooring. The emission of formaldehyde during production was ≤0.05 mg/l, lower than the GB/T18103-2000 requirement of ≤0.124 mg/l. The results of this study provide practical and forward-looking guidelines for expanding the application of biomass-based adhesives in the manufacture of laminated veneer lumber.

Preparation of a Fast Water-Based UV Cured Polyurethane-Acrylate Wood Coating and the Effect of Coating Amount on the Surface Properties of Oak (Quercus alba L.).

A fast water-based ultraviolet light (UV) curing polyurethane-acrylate (PUA) wood coating was prepared in the laboratory, and applied on oak (Quercus alba L.) at different coating amounts. The PUA wood coating can be fast cured within 22 min, which highly improved the drying speed compared to normal water-based wood coatings (often higher than 35 min). The coating amounts affected the coating properties after curing on oak. With the increase of coating amount, the adhesion, hardness and gloss value of surface increased to different extents. Meanwhile, the surface of sample became smooth gradually because the voids of the oak were filled. Thus, higher coating amount resulted in better coating properties. However, no significant increase of penetration depth was found. During curing, the hydroxyl groups of the wood reacted with the coating. The optimal parameter in this study was the coating amount of 120 g/m2, where the adhesion reached 1 (with 0–5% cross-cut area of flaking along the edges), with the hardness of 2H and the gloss of 92.56°, which met the requirement of Chinese standard GB/T 18103–2013, and could be used for engineered wood flooring.

Method of Stabilizing Heavily Spalted Big Leaf Maple as a Decorative Coating Veneer Layer for Engineered Wood Flooring

Spalted wood, wood colored by fungi, has been popular in woodcraft for centuries. Most spalted wood, however, is found in an advanced state of decay and cannot be utilized. This project describes the use of viscoelastic thermal compression (VTC) to investigate the potential increase in spalted woods’ strength and stiffness, with the main objective of converting so-called “punky” wood into the top layer (veneer layer or “coating”) on commercial flooring. Spalted Acer macrophyllum logs were cut into veneers of size 7 mm × 7.8 cm × 25 cm and were then VTC-treated at 150 °C and 50 psi for 11.5 min. Statistical analysis on the mixed linear models showed significant increases for both the density and hardness of spalted wood (p < 0.0001). Density and Brinell hardness increased by 84% and 209%, respectively. FTIR analysis revealed that the wood polymers present in spalted wood were more susceptible to degradation imposed by the heat of the VTC treatment compared to sound wood. Additionally, the color analysis of the wood specimens showed statistically significant changes in color after the VTC treatment (p < 0.0001), which turned the wood surface darker and redder. The use of the VTC technology to transform spalted wood into wood flooring is viable. However, when exposed to moisture, the VTC-treated spalted wood showed a high percentage of set recovery (78%), which was significantly different from the set recovery of the sound wood (71%, p = 0.004). Successful use of VTC-treated spalted wood for flooring will require addressing of the swelling issue, and additional studies are needed to fully characterize the anatomy of VTC-treated spalted wood.

Impregnation of Wood with Microencapsulated Bio-Based Phase Change Materials for High Thermal Mass Engineered Wood Flooring

Wood is a porous material that can be impregnated and have enhanced properties. Two species of hardwood, red oak (Quercus rubra L.) and sugar maple (Acer saccharum Marsh.), were impregnated in a reactor with a microencapsulated phase change material. The objective was to enhance the thermal mass of wood boards used as surface layers for engineered wood flooring manufacturing. Preliminary experiments were conducted on small samples in order to define suitable impregnation parameters, based on the Bethell cycle. Thin wood boards were impregnated with a microencapsulated phase change material dispersed into distilled water. Several cycles of pressure were applied. Heating storage of the impregnated wood boards was determined using a dynamic heat flow meter apparatus method. A latent heat storage of 7.6 J/g over 3 °C was measured for impregnated red oak samples. This corresponds to a heat storage enhancement of 77.0%. Sugar maple was found to be harder to impregnate and thus his thermal enhancement was lower. Impregnated samples were observed by reflective optical microscopy. Microcapsules were found mainly in the large vessels of red oak, forming aggregates. Pull-off tests were conducted on varnished samples to assess the influence of an impregnation on varnish adhesion and no significant influence was revealed. Engineered wood flooring manufactured with impregnated boards such as characterized in this study could store solar energy and thus improve buildings energy efficiency. Although wood is a material with a low-conductivity, the thermal exchange between the PCM and the building air could be good enough as the microcapsules are positioned in the surface layer. Furthermore, flooring is an area with frequent sunrays exposure. Such high thermal mass EWF could lead to energy savings and to an enhancement of occupant’s thermal comfort. This study aimed to characterize the potential of impregnation with MPCM of two wood species in order to make high thermal mass EWF.

Investigation of Shear Strength of Engineered Wood Flooring Bonded with PUR by Response Surface Methodology

The effects of process parameters (adhesive spreading rate, pressing time, and applied pressure) on the response parameter (shear strength) of engineered wood flooring bonded with polyurethane (PUR) were studied by response surface methodology. A mathematical model was established to provide a satisfying prediction for the experimental results observed. The model indicated a high degree of fitting. The results also showed that the major factors were adhesive spreading rate and pressing time. The optimized parameters for highest shear strength of engineered wood flooring were 98 g/m2 adhesive spreading rate with pressing time of 24 s and applied pressure of 1.2 MPa, respectively, within certain ranges.

Proteinska lepila na osnovi soje, krvi in kazeina nekoč in danes

This paper reviews the development of protein adhesives, specifically soy, blood, and casein adhesives. It addresses the formulations and bonding technologies of these protein adhesives from 1930 to 1960, and current commercial formulations. Between the 1930s and 1960s the consumption and technological refinements of protein adhesives were at their peak. Addressing current formulations and bonding technologies, the emphasis is on the soy adhesives, since they are used in industry of decorative plywood, particleboard, fibreboard, and engineered wood flooring. Today, casein is used only in adhesives for fire-resistant wood doors, while animal blood is no longer utilised in adhesives. Although the formulations from 1930 to 1960 do not meet current standards and are no longer used today, all described technologies are still usable and may be reintroduced if the world's crude oil resources are dried up.

Warping and Surface Checking Analysis of Engineered Wood Flooring for Heating Systems

The objective of this paper was to investigate the warping and surface checking of engineered wood flooring that was exposed to a heating system. The effects of decorative veneer type, wood structure, and wood shape on warping and surface checking were studied in a laboratory with a simulated heating system. Poplar/seven layer plywood engineered hardwood (structure C) or a 9 mm think poplar substrate layer wood was used, which contained the two veneer surface layers, structure A and structure B. For each structure, two shapes (mono-block or three splice) were tested, and a total of eight different veneer wood types were used. The highest degree of warping was seen in Eucalyptus or sapele veneer types. The degree of warping was the greatest for structure C with mono-block, followed by structure A with mono-block, structure C with three splice, and structure A with three splice. According to the surface checking tests for wood type, American ash, eucalyptus, maple, or birch exhibited the easiest wear, whereas, eastern black walnut exhibited the hardest wear. The surface checking tests revealed that the ranking from easiest to hardest wear was structure B, structure A, and structure C.

Effects of Decorative Veneer and Structure on the Thermal Conductivity of Engineered Wood Flooring

This paper explores the thermal conductivity of engineered wood flooring, which is widely used in world market. The effects of decorative veneer type and structure on the thermal conductivity of engineered wood flooring were studied. Four decorative veneer types and three different structures of engineered wood flooring served as test specimens. All samples were placed in a laboratory simulating a heating system environment, of which the temperature should be measured three times every five minutes. The temperature differences between the upper and lower surfaces were as follows: cherry > maple > birch > eastern black walnut. Three types of structures also showed differences in temperature changes, based on five-minute observations. The larger the decorative veneer’s density, the higher the thermal conductivity, and the faster the heat transferred, meaning less heat was lost. The thermal conductivity of three-layer engineered wood flooring, with decorative veneer made of sawn wood, exhibited the best properties. The second best of the three samples was the three-layer engineered wood flooring with decorative veneer made of thick veneer and plywood. Finally, a multilayered engineered wood flooring performed the worst. The engineered wood flooring for use in heating systems should be chosen for its larger density of decorative veneer made of sawn wood.

Combustion Performance of Composite Floor with Different Radiant Heat Flux

The combustion performance of engineered wood flooring and intensive composite floor under the different radiation heat flux were experimented by cone calorimeter. Fire parameters were measured including the ignition time and heat release rate. Experimental results show that the ignition time of engineered wood flooring is much lower than intensive composite floor, and the ignition time are decreased with the increase of radiation heat flux. The heat release rate (HRR) curve has two peaks under the same radiation heat flux, and the first peak of the heat release rate of engineered wood flooring occurs significantly earlier than intensive composite floor. The heat release rate is increased and the first peak significantly ahead of time with the increase of the radiation intensity

Produção de lamelas em serra de fita horizontal múltipla para fabricação de piso engenheirado de madeira

Este trabalho teve como objetivo estudar a relacao da velocidade de avanco de um modelo de serra fita horizontal na qualidade final das lamelas de quatro especies de madeira utilizadas na producao de pisos engenheirados: jatoba (Hymenaea courbari L.), muiracatiara (Astronium lecointei), amendoim (Pterogyne nitens) e sucupira (Bowdichia nitida). Foram estudadas as distribuicoes das espessuras das lamelas com relacao a velocidade de avanco, considerando-se o tipo de madeira, a especificacao do controle de qualidade e a existencia de marcas na superficie. Os resultados mostraram que o amendoim apresentou maior aproveitamento na producao de lamelas, enquanto que o jatoba foi a especie que sofreu maior perda no processo de producao. A velocidade de avanco que apresentou os menores indices de desclassificacao de lamelas foi de 8 m/min, sendo a mais indicada para producao de lamelas.

ENGINEERED WOOD FLOORING WITH A DENSIFIED SURFACE LAYER FOR HEAVY-DUTY USE

High-density wood is required in wood flooring, especially in engineered wood flooring (EWF) designed for heavy-duty applications. However, high-density wood resources are limited and their cost is high. A densification treatment makes it possible for low- or moderate-density woods to replace harder species by modifying them into high-performance and high-value products, such as engineered wood flooring for heavy-duty applications. The general objective of this study was to develop a prototype of engineered wood flooring using sugar maple hygro-thermally densified surface layers. The results showed that thin sugar maple lumber densified at 200 °C under the combined effects of steam, heat, and pressure with a heat-resistant fabric had great potential for the manufacturing of engineered wood flooring for heavy-duty use. As a result of treatment, it acquired high density, improved mechanical properties, and it had a relatively high dimensional stability and an attractive color. Tests in conditioning rooms showed that the EWF with a densified sugar maple (Acer saccharum March.) surface layer presented the lowest amplitude distortion between the dry and humid conditions compared with the standard EWF (0.15 mm vs. 0.17mm and 0.25 mm).