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