Автор: Viktor Savov
- STUDY ON POSSIBILITY FOR THE UTILIZATION OF TECHNICAL, HYDROLYSIS, LIGNIN IN COMPOSITION OF MEDIUM DENSITY FIBERBOARD
In the present report is presented a study on the possibility for utilization of hydrolysis lignin in the composition of Medium Density Fiberboard. For the purpose of the study in laboratory conditions were produced boards with five percentages technical lignin in their composition and different quantity of phenol-formaldehyde resin. The main physical and mechanical properties of boards were determined, and they have been compared with those of boards without technical lignin. It is compared the visual appearance of MDF with and without technical lignin. On that base was accomplished an analysis of the results with proper conclusions.
Ключови думи: Medium Density Fiberboard, technical, hydrolysis, lignin, Phenol-formaldehyde resin
- EFFECT OF PARTICIPATION OF VINE FIBRES ON SOME PHYSICAL AND MECHANICAL PROPERTIES OF FIBREBOARDS
Wood is a raw material in short supply both in Bulgaria and worldwide. In Bulgaria, vine twigs are widespread lignocellulosic waste from agricultural production.
In this study, the effect of inclusion of vine fibres in the composition of fibreboards on their properties is presented. Vine fibres were obtained by means of defibration with a defibrator laboratory mill. For the purpose of the study, fibreboards were produced under laboratory conditions with inclusion of vine fibres at a content from zero to twenty percent in increments of five percent. The main physical and mechanical properties of the boards were determined. On this basis, analysis was made and respective conclusions were drawn.
Ключови думи: fibreboards, lignocellulosic waste, vine fibres
- SELECTED PHYSICAL AND MECHANICAL PROPERTIES OF COMBINED WOOD BASED PANELS FROM WOOD FIBERS AND SAWDUST
The production of wood fiber mass is a very energy-intensive process This is also one of the reasons for the higher cost of this material in comparison of that at particleboards. One possibility to partially solving this problem is the inclusion of industrial wastes, which has not undergone a refining process, in MDF composition.
There is a significant amount of industrial wastes resulting from logging – these are mainly the sawdust resulting from the processing of solid wood with a band saw. It should be pointed out that this method of obtaining solid wood materials is widespread, both globally and in Bulgaria.
This report presents a study on the influence of the content of coniferous sawdust on the properties of combined panels from wood fiber and sawdust. Produced panels were with variation of sawdust content from 0 to 50% and respectively the fiber content was from 100 to 50%. The increase in sawdust content was with a step of 10%. The main physical and mechanical properties of panels were determined and experimentally-statistical equations for the influence of coniferous sawdust content on the properties of the panels were derived. It was determined at what percentage of sawdust the panels have properties that meet the requirements of the relevant standards for MDF.
Ключови думи: MDF, refining, combined wood based panels, coniferous sawdust
- PHYSICAL AND MECHANICAL PROPERTIES OF COMBINED WOOD-BASED PANELS WITH PARTICIPATION OF PARTICLES FROM VINE STICKS IN CORE LAYER
The growing needs for wood and the impact of forest ecosystems on the climate of the planet require the rational use of wood raw material. One possible way to "save" forests is to increase the use of agricultural lignocellulosic residues. The research efforts of scientists around the world are aimed at improving the properties of wood-based panels and to increase the share of agricultural residues in that production.
In laboratory conditions were produced three-layer combined wood-based panels with a face layer of wood fibers and a core layer of wood and vine sticks particles. The participation of vine stick particles in the core layer was: 0; 15; 30 and 45%. As binder was used urea-formaldehyde resin. The content of resin in core layer was 8; 10; and 12%. The properties of the panels with and without participation of vine particles were compared. The final data for physical and mechanical properties of the panels, with participation of vine particles, were processed by the methods of regression analyze.
In the result of conducted study was established and analyzed the influence of the participation of particles from vine stick and resin content on the physical and mechanical properties of combined wood-based panels.
Ключови думи: combined tree-layered wood-based panes, wood fibres, vine sticks particles, physical and mechanical properties
- ENGINEERING OF SELECTED PROPERTIES OF LIGHT MEDIUM DENSITY FIBREBOARDS PRODUCED FROM HARDWOOD TREE SPECIES
In this paper are presented results from study for the influence of hot-pressing temperature and press factor on some properties of light Medium Density Fibreboards (MDF) from hardwood tree species. MDF were produced from under laboratory conditions with phenol-formaldehyde resin as binder. The press factor varied from 45 to 90 s.mm-1 and the hot-pressing temperature was from 150° to 190 °C.
For the engineering of selected properties of the boards were applied the methods of regression analyze. Experimentally-statistical models that describe the studied relations and the optimal values of the factors were deduced. It has been established that by adjustment of the studied factors the properties of MDF from hardwood tree species can be significantly improved. It was also found that in the studied range, the temperature of hot pressing has a significantly greater influence on properties of MDF than the press factor.
Ключови думи: light MDF, hardwood tree species, phenol formaldehyde resin, temperature of hot-pressing, press factor
- INFLUENCE OF HOT-PRESSING TEMPERATURE ON PROPERTIES OF ECO-FRIENDLY DRY-PROCESS FIBREBORDS WITH LIGNOSULFONATE ADHESIVE
A major challenge for the producers of wood-based panels is to achieve formaldehyde emissions at wood levels. For that purpose, various types of lignin have emerged as particularly promising substitutes for the traditionally used urea-formaldehyde resins.
Lignosulfonates are a by-product of the production of cellulose by the sulphite method. They are practically harmless to human health. The main functional groups of lignosulfonates are the hydroxyl groups and the connection with fibres is mainly through hydrogen bonds. To form these bonds, in addition to the surface with active hydroxyl groups, the temperature of hot-pressing is also essential.
This paper presents a study on the effect of hot-pressing temperature on the properties of eco-friendly dry-process fibreboards. As an adhesive was used calcium lignosulfonate in a content of 10% to absolutely dry fibres. In the experiment, the hot-pressing temperature varied from 150 to 200° C, with increments of 10° C. The main physical and mechanical properties of the panels were determined. On this basis, an analysis was made. It was found that the properties of dry-process fibreboards with only lignosulfonate as a binder are significantly affected by the temperature of hot-pressing, because of which the hot-pressing temperature should be at least 190°C.
Ключови думи: eco-friendly dry-process fibreboards, calcium lignosulfonate, hot-pressing temperature
- POSSIBILITIES FOR UTILIZATION OF WASTE WATER AND RESIDUAL WOOD FIBRES IN THE PRODUCTION OF HARDBOARDS
Despite the continuous introduction of new materials and technologies in the production of wood-based composites, hardboards (HB), remain in the range of wood products, due to their good consumer and exploitation properties. The production of these products is characterized by the intensive consumption of raw materials. In the wet production process, much of the raw material used is taken up by water involved in the formation of the wood-fibre mat. It forms a significant share in the value of the finished product, resulting in a smaller added value. At present, the utilization of wastewater from the production of the HB is unsatisfactory. Its high fibre content creates sludges that can be recycled or thermally utilized. The present study is aimed at reviewing the possible methods of utilizing the wastewater and fibre sludge in it. This will provide the Bulgarian producers with a means of enhancing production efficiency and applying the circular economy principles.
Ключови думи: utilization, wastewater, wood fibres, circular economy
- PROPERTIES OF HIGH-DENSITY FIBERBOARDS BONDED WITH UREA-FORMALDEHYDE AND PHENOL-FORMALDEHYDE RESINS
Urea-formaldehyde (UF) resins are the most common type of resins used in the production of wood-based panels. Despite their numerous advantages, the main drawbacks of these thermosetting aminoplastic resins are the deteriorated water resistance, emission of hazardous volatice organic compounds, and to a lesser extent, the reduced strength. Hence, for producing wood-based panels with increased quality, a modification or partial replacement of UF resins should be performed. There are many previous studies on the improvement of UF resins with melamine-formaldehyde (MF) resins. The partial replacement of UF resins with phenol-formaldehyde (PF) resins has been studied to a lesser extent.
The aim of this research work was to investigate the effects of replacing the UF resin with PF resins on the properties of high-density fiberboards (HDF). The panels were produced at a press factor of 15 s.mm-1 and a pressing temperature of 220 °C. The resin content in fiberboards was 6%, based on the dry weight of fibres. A complete replacement of UF with PF resin was performed with an increment of 1%. It was found that at 50% content of PF resin in the adhesive system, the panels meet the strictest requirements for load-bearing applications and use in humid conditions. For achieving further improvement of fiberboard properties, the PF resin content should be increased to 83.3%.
Ключови думи: wood-based panels; high-density fiberboards; adhesive system; urea-formaldehyde resin; phenol-formaldehyde resin
- RECYCLING OF MEDIUM DENSITY FIBREBOARDS – A REVIEW
Production of Medium Density Fibreboards (MDF) is one of the growing woodworking industries. It has been found that a quarter of the produced MDFs have a life cycle of up to five years, and by ten years, this amount has increased to fifty percent. There is no established industrial practice for recycling that type of waste. That, together with the fact that some countries have banned the dumping of these panels in landfills, poses significant challenges.
There are currently two main research directions on MDF recycling, namely with and without pre-treatment. In both cases, with an increase in the content of recycled fibres, a deterioration in the properties of the panels is observed. Still, the share of cut fibres and formaldehyde emissions from the boards are reduced during the preliminary treatment, mainly by hydrolysis.
In the present manuscript, a review and analysis of MDF recycling methods are performed. On that base, conclusions and recommendations are derived.
Ключови думи: waste Medium Density Fibreboards, natural fibres, recycling, refining hydrolysis, electrolysis
- PROPERTIES OF PARTICLEBOARDS WITH THE PARTICIPATION OF HEMP AND VINE PARTICLES IN THE CORE LAYER – PART I: EFFECT OF THE COMPOSITION
Increasing deforestation worldwide, on the one hand, and the increased production of wood-based panels, on the other hand, lead to the need for alternative lignocellulosic raw materials. In this context, it should be said that significant amounts of lignocellulosic biomass remain annually from agricultural production, and unfortunately, that biomass is generally burned. However, individual types of lignocellulosic non-wood raw materials can hardly cover the needs of wood-based panel manufacturers, which necessitates their combination.
For the aim of the study, particleboards with a core layer of vine and hemp particles were produced. The contents of vine and hemp particles varied from 0 to 100% in steps 20%. A control panel composed only of wooden raw material was also fabricated, and the face layers of the panels were from hardwood particles.
As a result of the study, it was found that the variation in the composition of the core layer does not affect the waterproof properties of the panels. In contrast, with the increased content of hemp particles, the mechanical properties of particleboards improved significantly.
Ключови думи: particleboards, non-wood lignocellulosic raw material, vine particles, hemp particles
- EFFECT OF LIGNOSULFONATE CONTENT ON THE ADHESIVE STRENGTH AT VENEERING OF MEDIUM DENSITY FIBREBOARDS
The transition to a circular bio-oriented industry requires the search for alternative raw materials, sources and binders in producing materials for the furniture industry.
Lignosulfonates (sulphite lignins) are by-products, residues, of cellulose production, and they are bio-based materials with adhesive properties.
This work presents a study evaluating lignosulfonates as binders in the veneering of Medium Density Fibreboards (MDF). An adhesive composition of urea-formaldehyde (UF) resin and ammonium lignosulfonate was used in the veneering. Preliminary experiments have been carried out that show a significant reduction in the adhesion strength when the lignosulfonate content in the adhesive system passes 60%. Therefore, the study used the substitution of UF resin with lignosulfonate from 0 to 60%, with a step of variation from 10%. It is carried out at the gelling time of the various adhesive systems.
An analysis of the adhesive strength in veneering at adhesive systems with different lignosulfonate content was performed. Based on this, conclusions and recommendations were derived.
Ключови думи: veneering, Medium Density Fibreboards, adhesive system, ammonium lignosulfonate, urea-formaldehyde resin
- PROPERTIES OF PARTICLEBOARDS WITH THE PARTICIPATION OF HEMP AND VINE PARTICLES IN THE CORE LAYER – PART II: OPTIMISATION OF THE COMPOSITION
Volarization of agro-industrial residues into value-added materials such as particleboards will increase the utilisation of natural bio-resources and support the transition to a circular economy.
In the first part of the publication, research was presented regarding the effect of the content of vine, hemp and wood particles in the core layer of three-layered particleboards on the properties of these panels. It was established that the variation in the content of vine and hemp particles does not affect the waterproof properties.
The present part represents the results of the optimisation of the core layer of the panels, given their mechanical properties. Data are delivered with accompanying analysis regarding the screw withdrawal resistance of particleboards. This property is of primary importance in using particleboards as a structural element in furniture production.
As a result of the conducted research, it was established that the panels fabricated with a core layer entirely of hemp particles have the best exploitation properties. It was also found that when using vine particles for the core layer of particleboards, their content is not recommended to be over 30%.
Ключови думи: particleboards, vine particles, hemp particles, mechanical properties, optimisation
- SUNFLOWER STALKS AND LIGNOSULFONATE – ALTERNATIVE RAW MATERIALS FOR THE PRODUCTION OF ECO-FRIENDLY MEDIUM DENSITY FIBREBOARDS
The main advantages of the technology for producing Medium Density Fibreboards (MDF) are the reduced requirements for wood raw material, the possibility of fabricating that type of product from sawmill residues and the potential of including other non-wood lignocellulosic raw materials in the composition of the panels.
Such lignocellulose raw materials are residues from agriculture. In our country and worldwide, there are many successful studies for at least partial replacement of wood raw material with agricultural residues. Sunflower plantations are the second largest in our country, which is why they would be a significant source of non-wood lignocellulosic raw material.
Another significant problem in MDF production is the presence of formaldehyde emissions from the panels. One of the main directions for solving this problem is replacing the traditional binders with alternative ones without formaldehyde emissions. These alternative binders should not significantly increase the cost of board production, maintain their performance, and, most importantly, not be hazardous to human health. This binder includes the so-called bio-based binders, of which lignin-based products are the most promising. A typical representative of such an alternative bio-based binder is lignosulfonate (methylated lignin).
That leads to the relevance of a study on the possibility of partially replacing wood raw material with sunflower stalks and reducing the number of synthetic binders used in MDF by adding lignosulfonate in the adhesive system.
As a result of the research on the influence of urea-formaldehyde resin content, lignosulfonate content, and pulp from sunflower stalks on the properties of thin MDF, the main conclusions were deduced, and recommendations were made on the practical use of these alternative raw materials.
Ключови думи: eco-friendly MDF, sunflower stalks, lignosulfonate, urea-formaldehyde resin