Binderless Panels Research Articles

Emissions of Volatile Organic Compounds (VOCs) as Safety Indicators in the Development of Wood-Based Binderless Boards

Wood-based panels are ubiquitous in our daily lives, both as building materials and as furnishing materials. Numerous studies have revealed that these materials emit volatile organic compounds, such as formaldehyde, into indoor air, which can be harmful to human health. These volatile organic compounds come both from the wood itself, more specifically cellulose, hemicellulose, and lignin, and from the resins used to bind the wood fibers or particles together. Today, new panels bonded with bio-based adhesives and binderless panels are emerging. The aim of this article is to highlight the importance of measuring VOC emissions from binderless wood-based panels, and more specifically, to identify the VOCs, originating from the wood and thermal transformation processes, likely to be emitted during the production of such panels, as well as how to sample them and measure their emissions. This work provides a useful approach to identifying and quantifying VOC emissions from these new materials. These methodologies should be applied more widely to gain knowledge about VOCs, which are relevant indicators for the development of environmentally friendly materials.

Microchamber Extraction and Analytical Pyrolysis to Explore Volatile Organic Compounds from Compression-Cooking Wood Materials Obtained under Different Conditions

Volatile organic compounds are species of concern for indoor air quality. They are emitted from a wide range of indoor sources and in particular from construction materials. Industrialized wood-based panels made from various types of wood bonded with thermosetting adhesive resins have been shown to emit volatile organic compounds over months or even years mostly due to the petrochemical binders. Some studies have been conducted on binderless panels, but they mainly focused on the pressing parameters to be applied to optimize the panel characteristics. The aim of this research is to document the emissions from binderless panels and to access the volatile composition of wood processing through the molding of materials. For this purpose, binderless boards were manufactured from hardwoods, known to emit less than softwoods with different thermopressing temperatures and times. Emissions were studied by placing the materials in microchambers. Volatile organic compounds were then sampled and analyzed by various chromatographic methods. On the other hand, materials were pyrolyzed and then analyzed by gas chromatography and mass spectrometry. The implemented protocols proved suitable for the determination of more than 40 organic compounds, among which are aldehydes, aromatics, furans and derivatives, and carboxylic acids.

Influence of Manufacturing Conditions on Binder-Less Boards from Steam-Exploded Hemp Shives and Wheat Straw.

In the current decade, based on the European Green Deal, new challenges of the wood-based panel industry have arisen, seeking for formaldehyde-free bio-based adhesives and broadening raw lignocellulosics. In order to contribute to the potential solution to the challenges, binder-less boards of steam-exploded (SE 220 °C/2 min) hemp shives and wheat straw were investigated. The objective of this study was to find out the optimal hot-pressing conditions in terms of temperature (150–200 °C) and time (5–16 min) for the boards with three density levels (800–1000–1200 kg·m−3). An experimental design was created and the influence of the variables on binder-less panels were evaluated using a randomized central composite design of the response surface methodology. Water absorption (WA) and thickness swelling (TS) during 24 h, modulus of elasticity (MOE), and modulus of rupture (MOR) in bending test, internal bonding (IB), and Fourier-transform infrared spectroscopy were determined for the obtained boards. Each detected physical-mechanical property of the obtained boards was described by statistical models being different at each density level. The optimal conditions of the obtained binder-less boards were different depending on the raw material and density. For example, the optimal conditions of the boards from SE wheat straw with a density of 800 kg m−3 were found at T = 220 °C and t = 15 min, with the achieved properties of WA = 53%, TS = 4%, MOE = 2750 N mm−2, MOR = 15.5 N mm−2, and IB = 0.64 N mm−2. Based on the achieved properties at the optimal conditions, the boards meet the requirements of the conventional particleboard Type P3 according to EN 312.

Analysis of the Manufacturing Variables of Binderless Panels Made of Leaves of Olive Tree (Olea europaea L.) Pruning Waste

While the construction industry consumes more raw materials than any other industrial sector, agriculture generates a large amount of waste that is not managed properly. The olive industry produces more than 7.5 million tons of waste that could be recovered. This paper presents a new method to valorize the leaves of olive tree pruning waste consisting of the manufacture of ecologic boards without adhesives by hot pressing. In order to analyze their influence, three manufacturing variables were varied to obtain the boards: leaf type (shredded and whole leaves), temperature (130, 140 and 150 °C) and time (4, and 12 min). Twenty-four boards were made and were then tested for their mechanical, physical and thermal properties according to the EN standards. The boards showed good results of thickness swelling (TS), water absorption (WA) and of thermal conductivity and can be used as an alternative for manufacturing thermal insulation boards. With a smaller particle size of shredded leaves, longer pressing times and higher pressing temperatures, the mechanical behavior of the boards could improve. The olive leaves are a low-cost renewable resource, and manufacturing products with a long, useful life can be beneficial to the environment.

An investigation of thermal conductivity and sound absorption from binderless panels made of oil palm wood as bio-insulation materials

Oil palm wood is one of the solid wastes available in large quantities, which has been used as non-structural material. Many researchers focus on their material strength and binder selection. However, limited studies investigate oil palm wood as insulation materials. Therefore, this study aimed to evaluate the thermal and sound characteristics of oil palm wood binderless panels as insulation materials. Panels were manufactured from oil palm wood using hot presses with different particle sizes and pressing times. The results indicated that the particle size had a significant effect on the characteristics of the binderless panels but not on pressing times. The coarser particle size enhanced the thermal and sound resistance but decreased density, water resistance, and flexural strength. In addition, the panels with large particles had the least thermal conductivity (0.050 W/mK) and the highest sound absorption coefficient of 0.33. The study also showed that the flexural strength and water absorption of the panels ranged from 4.21 to 8.18 MPa and 84.51%–119.06%, respectively. The findings of this study indicate the feasibility of binderless panels from oil palm wood as insulation materials.

Binderless boards made of milled coconut husk: an analysis of the technical feasibility and process restraints

ABSTRACTThe possibility of producing binderless panels made of milled coconut husk, a largely available by-product of the coconut oil industry, has been shown in previous researches. Long pressing times and a high risk of blisters have however hindered the industrial implementation of the process. In this study, a more energy-efficient manufacturing process, involving a tailored degassing step, was developed on a laboratory scale and then validated at an industrial size (2 × 1 m2). To achieve mechanical properties close to the European and Japanese standards for fibreboards and to avoid the delamination of the boards, final densities between 900 and 1000 kg m−3 had to be targeted. Similarly, a successful board production was only possible if the moisture content of the husk was between 10 and 25%. The need for a suitable mat-forming technology to avoid the risk of warping of the panel was highlighted.

Preliminary Study of the Biorefinery Concept to Obtain Furfural and Binder-less Panels from Hemp (Cannabis Sativa L.) Shives

Abstract The objective of the study was to investigate the preliminary technological parameters for obtaining furfural and binder-less panels depending on hydrothermal pre-treatment temperature, steam explosion treatment and pressing conditions. If the pre- treatment temperatures were 160–180 °C and the time 90 min, the yield of furfural was 64.8–67.2% from that which was theoretically possible. The furfural obtaining dynamics significantly increases in the first 10 minutes, when the yield of furfural at 180 °C is almost twice as high as at 160 °C. The obtained maximal MOE value (3250 N mm -2 ) and good enough surface of some panels demonstrate that all prepared hemp shives materials can be used for binder-less panel production. The obtained excellent correlation between MOE and MOR values (r = 0.9) demonstrates that the strength of the composites could be predictable.

A review of wood thermal pretreatments to improve wood composite properties

The objective of this paper is to review the published literature on improving properties of wood composites through thermal pretreatment of wood. Thermal pretreatment has been conducted in moist environments using hot water or steam at temperatures up to 180 and 230 °C, respectively, or in dry environments using inert gases at temperatures up to 240 °C. In these conditions, hemicelluloses are removed, crystallinity index of cellulose is increased, and cellulose degree of polymerization is reduced, while lignin is not considerably affected. Thermally modified wood has been used to manufacture wood–plastic composites, particleboard, oriented strand board, binderless panels, fiberboard, waferboard, and flakeboard. Thermal pretreatment considerably reduced water absorption and thickness swelling of wood composites, which has been attributed mainly to the removal of hemicelluloses. Mechanical properties have been increased or sometimes reduced, depending on the product and the conditions of the pretreatment. Thermal pretreatment has also shown to improve the resistance of composites to decay.

Properties of binderless particleboard from oil palm trunk with addition of polyhydroxyalkanoates

This study evaluated the properties of binderless particleboard made from oil palm trunk with addition of polyhydroxyalkanoates in the form of freeze dried and pure samples. Modulus of rupture, internal bonding strength, thickness swelling and water absorption of the boards were evaluated based on Japanese Industrial Standards. Modulus of rupture and internal bonding strength increased as the amount of polyhydroxyalkanoates were increased. Thickness swelling and water absorption decreased with increasing percentage of polyhydroxyalkanoates. The surface roughness, gas chromatography, thermogravimetric analyses, Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy and differential scanning calorimetry were also investigated. Based on the findings in this work, it appears that the addition of polyhydroxyalkanoates enhanced overall properties of such binderless panels.

Binderless panels made with black spruce bark

The bark of black spruce was thermo-mechanically refined and used to manufacture binderless bark-based fiberboard with various pressing temperatures, times, and panel structures in order to utilize an abundant bark resource for a better value-added application. The test results indicated that it is technically feasible to manufacture binderless fiberboard with refined black spruce bark through self-bonding under elevated temperatures over a reasonable period of pressing time. Binderless bark-based fiberboards with a homogeneous structure had very poor flexural properties due to the poor strength of bark itself; however, by using a sandwich structure with 30wt% wood fiber in the surface layers and 70wt% bark in the core layer it was possible to sufficiently improve panel flexural properties so that the manufactured binderless bark-based fiberboards was able to meet the mechanical property requirements of 115-grade fiberboard according to ANSI A208.2 (2009). Refining conditions had a great impact on the mechanical properties of binderless bark-based fiberboard.

Effect of particle geometry on the properties of binderless particleboard manufactured from oil palm trunk

Experimental binderless composite panels were manufactured using fine particles and strands of oil palm ( Elaeis guineensis) trunks. Modulus of rupture (MOR), internal bond strength (IB), dimensional stability, and surface roughness of the panels made with a target density of 0.80 g/cm 3 were evaluated. Strand type samples had MOR and IB values of 24.95 and 0.95 MPa, respectively. Corresponding values for the fine particle type samples were 4.04 and 0.49 MPa. Panels made from strands met MOR requirement stated in Japanese Industrial Standard (JIS). Enhanced bonding between strands observed by micrographs taken using scanning electron microscopy (SEM) also supported the findings. However, the samples having fine particles had lower MOR values than minimum requirement listed in JIS. Strand type panels had 41.6% thickness swelling which is only 4.6% lower than that of the panels made from fine particles. It appears that dimensional stability of both types of panels exhibited insufficient results according to JIS. Surface roughness quality of the samples made from fine particles had average surface roughness values comparable to those of panels made in past studies. Based on initial results of this work, raw material from oil palm trunks can have some potential to be used to manufacture binderless panels without using any adhesives. This study revealed that mechanical and physical properties of such experimental panels were influenced by the particle geometry. It would be important to consider possible addition of chemical or wax in the particles to improve their dimensional stability in further studies.

Manufacture and properties of low-density binderless particleboard from kenaf core

Low-density binderless particleboards from kenaf core were successfully developed using steam injection pressing. The target board density ranged from 0.10 to 0.30 g/cm3, the steam pressure used was 1.0 MPa, and the steam treatment times were 7 and 10 min. The mechanical properties, dimensional stability, and thermal and sound insulation performances of the boards were investigated. The results showed that the low-density kenaf binderless particleboards had good mechanical properties and dimensional stability relative to their low board densities. The board of 0.20 g/cm3 density with a 10-min treatment time produced the following values: modulus of rupture 1.1 MPa, modulus of elasticity 0.3 GPa, internal bond strength 0.10 MPa, thickness swelling in 24 h water immersion 6.6%, and water absorption 355%. The thermal conductivity of the low-density kenaf binderless particleboards showed values similar to those of insulation material (i.e., rock wool), and the sound absorption coefficient was high. In addition, the boards are free from formaldehyde emission. Kenaf core appears to be a potential raw material for low-density binderless panels suitable for sound absorption and thermally resistant interior products.

Suitability of steam exploded residual softwood for the production of binderless panels. Effect of the pre-treatment severity and lignin addition

A steam explosion pre-treatment was applied at various severities to softwood residual substrate to determine the most suitable pre-treatment for the manufacture of binderless panels. The effect of adding acid to the pre-treatment of fibres was also evaluated. The changes in the chemical composition and morphology of the original material were investigated by fractionation analyses and scanning electron micrographs. High severities caused defibrillation of the material allowing to build links to form the panels. Prehydrolysis with acid had a great effect on the structure of the material even at low acid concentration. The physical and mechanical properties of the panel improved as the severity of the pre-treatment increased up to a point where mechanical properties deteriorated. The composites with highest internal bond had a high cellulose content and a medium lignin content. All these factors suggested that steamed pre-treated residual could be improved by adding a natural binder to produce the panels. A test of producing panels with addition of several kinds of lignin (up to 20%) was performed. With no significant changes in density, water stability (thickness swelling and water absorption) internal bond and mechanical properties were greatly improved. Results after accelerated ageing test were also enhanced.