1,721,012 research outputs found
Enzymatic modification of wood fibres for activating their ability of self bonding
No full textObjective is the use of phenoloxidases like laccases to activate the surfaces of fibres for making fibreboards without any adhesive. The concept of using lignin-oxidising enzymes for bonding applications is based on the reactivity of phenoxy radicals in the plant cell wall. A problem is that laccase can only oxidise the phenolic constituents of lignin, due to its lower oxidation potential, Therefore the use of appropriate low molecular-mass compounds (so-called mediators), in combination with laccase, makes this enzyme competent for the oxidation of nonphenolic substrates. The oxidised mediator can rely on an oxidation mechanism that is not available to the enzyme
Effects of Wheat Protein as a Biological Binder in the Manufacture of Particleboards Using a Mixture of Canola, Hemp, Bagasse, and Commercial Wood
No full textThis article deals with the feasibility of the use of wheat protein glue to produce general purpose particleboards from bagasse, canola, and hemp chips and of decreasing the formaldehyde emission by using a bioproduct adhesive. Three series of panels were produced using wood chips in the surface layers and a mixture of annual plants with industrial wood in the middle layers. Particleboards were manufactured using various annual plants. Wheat protein was used in combination with urea-formaldehyde (UF) resin in the surface layers. Pure UF was only used in the middle layer. Panels were tested for some physical and mechanical properties. In addition, the formaldehyde emission according to the perforator method and the bottle method was determined. The data were compared with the respective properties specified by the Deutsches Institut fur Normung EN 312-2 standard for commercial wood-based particleboard. The results showed that all mechanical properties greatly exceeded the standard requirements for wood particleboards. An increase of more than 50 percent canola particles in the core negatively affected the internal bond (IB) strength. All of the particleboards produced from hemp and bagasse had modulus of rupture and IB strength higher than required. With those containing up to 50 percent annual plant particles in the middle layer, thickness swelling values met the standard requirement. It was found that applying wheat protein as a bonding agent reduced the formaldehyde emission in comparison to when pure UF resin was applied. This study demonstrated that consistent, high-performance agricultural fiber composite panels with desirable environmental attributes can be successfully developed
Utilization of Date palm (Phoenix dactylifera L.) Pruning Residues as Raw Material for MDF Manufacturing
No full textFiber of Date Palm (Phoenix dactylifera L) pruning residues are a potential source for the production Medium Density Fiberboard (MDF). Dry process was employed to produce MDF in pilot plant scale using three categories of manufacturing parameters, i.e., two resin types, two resin content levels and three pressing times. Due to the availability of the materials in the pilot plant, Date palm and also soft wood fibers (Pinus silvestries L.) as reference were used for the MDF production under the same parameters. Three boards were manufactured with combination of variables, and samples of all boards were tested according to the methods of European (EU) standard. As main technological properties modulus of rupture (MOR), modulus of elasticity (MOE), internal bond strength (IB), and formaldehyde emission were determined. Also, samples of each board were tested for thickness swelling and water absorption after soaking in water for 2 h and 24 h respectively. In addition all the mechanical and physical properties of boards were derived from analysis procedures. The results of this study showed that boards made of Date Palm pruning residues fibers featured better properties than the MDF property requirements which was recommended by ASTM and EN standards particularly inspect of mechanical properties. In addition, the formaldehyde (HCHO) emission of the panels featured that almost all the boards met the minimum requirement according to EN 120 especially for the panel bonded with MUF resin. Therefore, Date palm could be proposed as an alternative material for the manufacture of MDF
Oxygen Consumption of Laccase-Mediator-Systems (LMS)
No full textCrude oil as a non-renewable resource is presenting challenges for the future in many industrial sectors. Due to the dwindling of these resources, costs are increasing negatively affecting the wood based panels industry, which uses mainly petrochemical resins as components for binding agents. In addition harmful formaldehyde emissions arising from conventionally produced wood composites are demonstrable. In order to substitute these conventional binding agents for wood based panels, in particular medium density fiberboards (MDF), Laccase-Mediator-Systems (LMSs) were investigated in several researches. A popular and reliable method used to test the suitability of LMSs is the measurement of their oxygen consumption on wood fibers in aqueous suspension. This enzymatic catalyzed oxidation was the object of this study. The mediators 4-hydroxybenzoic acid (HBA), vanillic acid (VanA), vanillic alcohol (VAl), ethylvanillin (EVan), acetovanillone (AVan), ferulic acid (FA), caffeic acid (CA) and guajacol (Gu) were tested as possible components of the LMSs. The study showed that all of the LMSs have oxidized wood fibers more efficiently than laccase on its own. Among the different mediators, vanillic alcohol, guajacol and caffeic acid in LMSs have shown the fastest O2 consumption
Laccase-Mediator Catalyzed Modification of Wood Fibers: Studies on the Reaction Mechanism and Making of Medium-Density Fiberboard
No full textOwing to the constant increase of prices of the process for petrochemical resin and the possibility of harmful formaldehyde emissions from industrial produced medium-density fiberboards (MDF), enzymatic binder systems are discussed as an environmentally friendly alternative for gluing lignocelluloses such as wood fibers. In this work laccase-mediator systems (LMSs) were used to activate the lignin on wood fiber surfaces. Two different mediators were tested, vanillic acid (VAN) and 4-hydroxybenzoic acid (}IBA), of which HBA performed best. Carbon-13 nuclear magnetic resonances (C-13-NMR) and electron spin resonances (ESR) of LMS-treated thermomechanical pulp (TMP) fibers were determined for qualitative and quantitative analysis of lignin activation. Analysis outputs were transferred to produce MDF using a dry process. 13C-NMR revealed more structural changes in the wood fibers using LMS with HBA than LMS with VAN. ESR spectroscopy indicated a higher amount of phenoxy radicals after treatment with LMS containing HBA as a mediator. The data correlated well with the quality of MDF. The best mechanical technological properties were achieved by using HBA within the LMS, so that the European Norms could be fulfilled. But VAN also performed well, which showed a high potential to produce ecofriendly MDF by using LMSs in the future.Deutsche Forschungsgemeinschaft (DFG) [EU 124/2-1
Use of MUF Resin for Improving the Wheat Protein Binder in Particle Boards Made from Agricultural Residues
No full textThis work was focused on the production and characterization of lightweight and water resistance particle boards with various lignocellulosic materials of the annual plants hemp (Cannabis sativa L.), canola (Brassica napus L.) and bagasse (Saccharum officinarum L.) in admixtures with industrial wood. Some chemical properties of these annual plants were investigated to find out their chemical characteristics in wood composites production. In all board variants 100% of the middle layers consisted of chips from one of the above annual plants. Reference boards were 100% beech wood. Laboratory manufacturing treatments included two panel density levels (500 and 600 kg/m3) and three resin types (urea-formaldehyde, melamine-urea-formaldehyde and wheat protein). Water absorption and thickness swelling of the laboratory manufactured boards were improved by adding melamine to urea-formaldehyde resin and by adding water repellent chemicals. The mechanical properties of the boards produced met the requirement for the general purpose product standards (EN 312-2) at both 500- and 600- kg/m3 densities. Decreasing the density, negatively affected the bending (modulus of rupture) and internal bond properties of canola boards. This decreasing trend was also observed for modulus of rupture values in bagasse boards of 500 kg/m3 density. Based on the results of the chemical analysis, it might be concluded that high values of ash content and lower values of hemicellulose and lignin content caused low physical properties and/or high water absorption of canola boards. The findings indicated that hemp and bagasse are valuable renewable natural resources for particleboard production and could be utilized as a substitute for wood in board production. In comparison with the reference boards, mixed variants boards showed surprisingly good results and generally conformed to European standards (EN 312-2) values
Manufacturing Medium-density Fiberboards and Wood Fiber Insulation Boards Using a Blood Albumin Adhesive on a Pilot Scale
No full textAn albumin adhesive derived from animal blood was used for the first time for the production of two kinds of fiberboard in a dry process: medium density fiberboard (MDF) and wood fiber insulation board (WFI). Additionally, the curing for WFI was completed using an innovative hot-air/hot-steam (HA/HS) process. There is a general importance to develop alternatives to substitute common binding agents, such as urea formaldehyde (UF) or polymeric methylene diphenylene diisocyanate (pMDI) resins, and to develop value-added opportunities for such waste material from slaughterhouses. An adhesive analysis was performed to understand the curing reaction of these protein adhesives, which showed good properties in regards to viscosity or gel time. The physical mechanical results showed on the one hand that the albumin adhesive could compete with UF-bonded MDF regarding tensile strength and modulus of rupture in conformity to the European Standard, but it failed to meet requirements for thickness swelling. The albumin adhesive also can compete with pMDI bonded WFI regarding tensile and compression strength, but it showed non-viable results for short-term water absorption
Effects of Wheat Protein as a Biological Binder in the Manufacture of Particleboards Using a Mixture of Canola, Hemp, Bagasse, and Commercial Wood
No full textThis article deals with the feasibility of the use of wheat protein glue to produce general purpose particleboards from bagasse, canola, and hemp chips and of decreasing the formaldehyde emission by using a bioproduct adhesive. Three series of panels were produced using wood chips in the surface layers and a mixture of annual plants with industrial wood in the middle layers. Particleboards were manufactured using various annual plants. Wheat protein was used in combination with urea-formaldehyde (UF) resin in the surface layers. Pure UF was only used in the middle layer. Panels were tested for some physical and mechanical properties. In addition, the formaldehyde emission according to the perforator method and the bottle method was determined. The data were compared with the respective properties specified by the Deutsches Institut fur Normung EN 312-2 standard for commercial wood-based particleboard. The results showed that all mechanical properties greatly exceeded the standard requirements for wood particleboards. An increase of more than 50 percent canola particles in the core negatively affected the internal bond (IB) strength. All of the particleboards produced from hemp and bagasse had modulus of rupture and IB strength higher than required. With those containing up to 50 percent annual plant particles in the middle layer, thickness swelling values met the standard requirement. It was found that applying wheat protein as a bonding agent reduced the formaldehyde emission in comparison to when pure UF resin was applied. This study demonstrated that consistent, high-performance agricultural fiber composite panels with desirable environmental attributes can be successfully developed
Preparation of a canola-based polyethyleneimine-crosslinked bioadhesive for particleboards production
No full textOver the past decades, consistent efforts have been dedicated to addressing the challenge of low performance of protein-based wood adhesives. This study explored the potential of polyethyleneimine (PEI) as a crosslinker for improving the bonding strength of canola protein isolate (CPI) and canola meal (CM) bio-adhesive. Simultaneously, the effect of the pH value of the slurry was investigated. Three-layer particleboards were manufactured using the canola-based adhesives and subjected to testing for their internal bonding strength (IB), bending strength (BS), and modulus of elasticity (E-modulus). Results showed that, despite the low PEI ratio utilized, notable enhancements in the mechanical properties of the boards were observed. The IB values increased by 17% and 15% for CPI and CM-based adhesive formulations, respectively; while the BS exhibited rose by 13% and 9%, respectively. It was observed that an increase in pH contributed to enhanced bonding properties of the bio-based adhesive. By enhancing the denaturation of the protein and increasing the free reaction group in the protein chain, this improves the crosslinking mechanism of PEI, leading to improved mechanical properties.Open-Access-Publikationsfonds 202
Enzymatic modification of wood fibres for activating their ability of self bonding
No full textObjective is the use of phenoloxidases like laccases to activate the surfaces of fibres for making fibreboards without any adhesive. The concept of using lignin-oxidising enzymes for bonding applications is based on the reactivity of phenoxy radicals in the plant cell wall. A problem is that laccase can only oxidise the phenolic constituents of lignin, due to its lower oxidation potential, Therefore the use of appropriate low molecular-mass compounds (so-called mediators), in combination with laccase, makes this enzyme competent for the oxidation of nonphenolic substrates. The oxidised mediator can rely on an oxidation mechanism that is not available to the enzyme
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