Dizajniranje svojstava ekološki prihvatljivih ploča vlaknatica srednje gustoće proizvedenih uporabom lignosulfonatnog ljepila

Free formaldehyde emissions from wood-based panels, especially in indoor applications, pose serious risks to human health at certain concentrations. Prolonged exposure to formaldehyde can cause adverse health effects including eye, nose and throat irritation, other respiratory symptoms and cancer. As a consequence, new formaldehyde emission limits for composite wood products were established in Europe, USA and Japan. This, together with the stricter environmental legislation are the main driving factors for shifting the scientific and industrial interest from the traditional formaldehyde-based synthetic resins to the new bio-based adhesives for production of eco-friendly wood-based panels. The lignin-based products are one of the most prospective ecological alternatives to the traditional formaldehyde resins. The main interest in lignin is due to its phenolic structure with several favourable properties for the formulation of wood adhesives such as high hydrophobicity and low polydispersity. The present article is aimed at studying the possibilities for using lignosulfonate as an adhesive for the production of eco-friendly MDF. Regression models describing the impact of lignosulfonate concentration and hot pressing temperature on the exploitation properties of MDF panels were developed. The individual and combined impact of both factors was analysed in order to determine the optimal exploitation properties of the panels.Emisija slobodnog formaldehida iz ploča na bazi drva, posebice primijenjenih u unutarnjim prostorima, u određenim je koncentracijama ozbiljan rizik za zdravlje ljudi. Dulja izloženost formaldehidu može uzrokovati znatne zdravstvene probleme, uključujući iritaciju očiju, nosa i grla, druge respiratorne simptome i rak. Stoga su u Europi, SAD-u i Japanu određene nove granice emisije formaldehida za kompozitne proizvode od drva. To je, zajedno sa strožim zakonodavstvom o okolišu, bio glavni poticaj za prebacivanje znanstvenoga i industrijskog fokusa s tradicionalnih sintetičkih smola temeljenih na formaldehidu na nova prirodna ljepila za proizvodnju ekološki prihvatljivih ploča na bazi drva. Proizvodi na bazi lignina jedna su od najperspektivnijih ekoloških alternativa tradicionalnim formaldehidnim smolama. Glavni razlog zanimanja za lignin jest njegova fenolna strukturas nekoliko povoljnih svojstava za formulaciju ljepila za drvo poput visoke hidrofobnosti i niske polidisperznosti. Cilj ovog rada jest proučavanje mogućnosti uporabe lignosulfonata kao ljepila za proizvodnju ekološki prihvatljivih ploča vlaknatica srednje gustoće (MDF ploča). Razvijeni su regresijski modeli koji opisuju utjecaj koncentracije lignosulfonata i temperature prešanja na svojstva MDF ploča. Analiziran je pojedinačni i kombinirani utjecaj obaju elemenata kako bi se odredila optimalna svojstva ploča

Optimization of the Hot-Pressing Regime in the Production of Eco-Friendly Fibreboards Bonded with Hydrolysis Lignin

This research was aimed at studying the potential of using residual lignin from acid hydrolysis as a binder in manufacturing eco-friendly, dry-process fibreboards. For that purpose, a modification of the adhesive system and hot-pressing regime was conducted. The adhesive system applied was composed of 2 % phenol-formaldehyde (PF) resin and 10 % hydrolysis lignin (based on the dry fibres). The PF resin does not only act as a binder but generally contributes to the even distribution and good retention of the main binder – hydrolysis lignin. A specific hot-pressing cycle was used. In the first stage, the pressure was 1.0 MPa, followed by an increased pressure of 4.0 MPa, and subsequent cooling. The purpose of the initial lower pressure was softening the lignin and reduction of the material moisture content. The effect of the second stage of hot-pressing on the properties of eco-friendly fibreboards was investigated. It was determined that the fibreboards produced with 2 % PF resin and 10 % hydrolysis lignin have similar physical and mechanical properties to those of the control panels, produced with 10 % PF resin at a standard hot-pressing cycle. The findings of this work demonstrate that residual hydrolysis lignin can be effectively utilized as a binder in the production of eco-friendly, dry-process fibreboards with acceptable physical and mechanical properties

Eco-Friendly Wood Composites: Design, Characterization and Applications

The ongoing transition from a linear to a circular, low-carbon bioeconomy is crucial for reducing the consumption of global natural resources, minimizing waste generation, reducing carbon emissions, and creating more sustainable growth and jobs, the prerequisites necessary to achieve climate neutrality targets and stop biodiversity loss [...

Effect of the content of corn stalk fibres and additional heat treatment on properties of eco-friendly fibreboards bonded with lignosulphonate

This study aims to find the possibility of producing eco-friendly thin Medium Density Fibrepanels (MDF) with the participation of corn stalk fibres and using lignosulphonate as a bio-based binder. The main novelty in the research is the establishment of the effect of additional heat treatment on the properties of MDF manufactured with the participation of non-wood lignocellulosic raw materials and bonded with bio-based adhesive – lignosulphonate. Panels with 15% lignosulphonate content and variation of the content of corn stalk fibres from 0% to 30% were manufactured. Previous experiments showed that when only lignosulfonate is used as a binder, the manufactured panels generally have low waterproofness. To reduce the effect of this main disadvantage, the panels were subjected additionally to heat treatment. The properties of the MDF with and without additional heat treatment were compared. The effect of both the content of corn stalk fibres and the additional heat treatment was found. As a whole, the additional heat treatment improves the properties of MDF produced with lignosulphonate. Still, in case of increased content of corn stalk fibres, it is necessary to apply softened regimes than the ones selected for this study

Sustainable Development and Forest-Based Industries: Main Considerations and Policy Measures. The Bulgarian Example

Industrial policy determines the industry's orientation for growth, in line with the economic development stage. The main objective of this article is to establish the sustainability of the relationship between the development of forest resources, on the one hand, and their use in wood and furniture products in the Republic of Bulgaria, on the other hand. The main tasks are to find out the sustainability in the production of timber and products from it, to assess the tendency of development and needs of policy measures. The methods used include statistical methods for trend analysis, descriptive methods and others. Forestry is a clear example of the transformation of natural resources into consumer products, where sustainability in the development of society can easily be disturbed. Forestry policies should support the use of tree resources in products with the highest possible added value

Eco-Friendly Wood Composites: Design, Characterization and Applications

The ongoing transition from a linear to a circular, low-carbon bioeconomy is crucial for reducing the consumption of global natural resources, minimizing waste generation, reducing carbon emissions, and creating more sustainable growth and jobs, the prerequisites necessary to achieve climate neutrality targets and stop biodiversity loss [...

Effect of the Adhesive System on the Properties of Fiberboard Panels Bonded with Hydrolysis Lignin and Phenol-Formaldehyde Resin

This study aimed to propose an alternative technological solution for manufacturing fiberboard panels using a modified hot-pressing regime and hydrolysis lignin as the main binder. The main novelty of the research is the optimized adhesive system composed of unmodified hydrolysis lignin and reduced phenol–formaldehyde (PF) resin content. The fiberboard panels were fabricated in the laboratory with a very low PF resin content, varying from 1% to 3.6%, and hydrolysis lignin addition levels varying from 7% to 10.8% (based on the dry wood fibers). A specific two-stage hot-pressing regime, including initial low pressure of 1.2 MPa and subsequent high pressure of 4 MPa, was applied. The effect of binder content and PF resin content in the adhesive system on the main properties of fiberboards (water absorption, thickness swelling, bending strength, modulus of elasticity, and internal bond strength) was investigated, and appropriate optimization was performed to define the optimal content of PF resin and hydrolysis lignin for complying with European standards. It was concluded that the proposed technology is suitable for manufacturing fiberboard panels fulfilling the strictest EN standard. Markedly, it was shown that for the production of this type of panels, the minimum total content of binders should be 10.6%, and the PF resin content should be at least 14% of the adhesive system

Eco-Friendly, High-Density Fiberboards Bonded with Urea-Formaldehyde and Ammonium Lignosulfonate

The potential of producing eco-friendly, formaldehyde-free, high-density fiberboard (HDF) panels from hardwood fibers bonded with urea-formaldehyde (UF) resin and a novel ammonium lignosulfonate (ALS) is investigated in this paper. HDF panels were fabricated in the laboratory by applying a very low UF gluing factor (3%) and ALS content varying from 6% to 10% (based on the dry fibers). The physical and mechanical properties of the fiberboards, such as water absorption (WA), thickness swelling (TS), modulus of elasticity (MOE), bending strength (MOR), internal bond strength (IB), as well as formaldehyde content, were determined in accordance with the corresponding European standards. Overall, the HDF panels exhibited very satisfactory physical and mechanical properties, fully complying with the standard requirements of HDF for use in load-bearing applications in humid conditions. Markedly, the formaldehyde content of the laboratory fabricated panels was extremely low, ranging between 0.7–1.0 mg/100 g, which is, in fact, equivalent to the formaldehyde release of natural wood

Eco-Friendly Fiberboard Panels from Recycled Fibers Bonded with Calcium Lignosulfonate

The potential of using residual softwood fibers from the pulp and paper industry for producing eco-friendly, zero-formaldehyde fiberboard panels, bonded with calcium lignosulfonate (CLS) as a lignin-based, formaldehyde free adhesive, was investigated in this work. Fiberboard panels were manufactured in the laboratory by applying CLS addition content ranging from 8% to 14% (on the dry fibers). The physical and mechanical properties of the developed composites, i.e., water absorption (WA), thickness swelling (TS), modulus of elasticity (MOE), bending strength (MOR), as well as the free formaldehyde emission, were evaluated according to the European norms. In general, only the composites, developed with 14% CLS content, exhibited MOE and MOR values, comparable with the standard requirements for medium-density fiberboards (MDF) for use in dry conditions. All laboratory-produced composites demonstrated significantly deteriorated moisture-related properties, i.e., WA (24 h) and TS (24 h), which is a major drawback. Noticeably, the fiberboards produced had a close-to-zero formaldehyde content, reaching the super E0 class (≤1.5 mg/100 g), with values, ranging from 0.8 mg/100 g to 1.1 mg/100 g, i.e., equivalent to formaldehyde emission of natural wood. The amount of CLS adhesive had no significant effect on formaldehyde content

Eco-Friendly, High-Density Fiberboards Bonded with Urea-Formaldehyde and Ammonium Lignosulfonate

The potential of producing eco-friendly, formaldehyde-free, high-density fiberboard (HDF) panels from hardwood fibers bonded with urea-formaldehyde (UF) resin and a novel ammonium lignosulfonate (ALS) is investigated in this paper. HDF panels were fabricated in the laboratory by applying a very low UF gluing factor (3%) and ALS content varying from 6% to 10% (based on the dry fibers). The physical and mechanical properties of the fiberboards, such as water absorption (WA), thickness swelling (TS), modulus of elasticity (MOE), bending strength (MOR), internal bond strength (IB), as well as formaldehyde content, were determined in accordance with the corresponding European standards. Overall, the HDF panels exhibited very satisfactory physical and mechanical properties, fully complying with the standard requirements of HDF for use in load-bearing applications in humid conditions. Markedly, the formaldehyde content of the laboratory fabricated panels was extremely low, ranging between 0.7–1.0 mg/100 g, which is, in fact, equivalent to the formaldehyde release of natural wood