Лесотехнически Университет

Резюме

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.

Резюме

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.

Резюме

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.

Резюме

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.

Резюме

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%.

Резюме

The present study aims to establish the mechanical properties of three-layered particleboards with a face layer entirely from beech and oak particles. Three compositions of the panels were studied, with the corresponding content of the face layers as follows: 30%, 40% and 50%. To analyse the possibility of reducing the content of pinewood particles in the core layer, it is replaced with sunflower stalk particles with the participation of 30%, 40% and 50%. This research determined the effect of those factors on the main mechanical properties of particleboards.

As a result of the study, it was found that the increase in the percentage of the face layers leads to a significant increase in the mechanical properties of the panels. It was found that by using the hardwood in the face layers of the panels, the share of this raw material can be increased to 50%, and sunflower stalks are a suitable raw material as an alternative raw material for the core layer of the particleboards.

Резюме

The production of particleboard is influenced by various technological and technical factors that affect both quality and economic performance. Among these, board density is particularly important-higher density enhances mechanical properties but increases production costs. Therefore, medium-density particleboards are typically manufactured from softwood species, whose low density provides favorable strength characteristics. In contrast, hardwood species often reduce mechanical performance, limiting their proportion in the mixture to 20–30%. However, in the Republic of Bulgaria, 32% of forested areas are covered with oak species, including 9% with turkey oak (Quercus cerris L.), making its exclusion from production impractical. This study explores the potential for greater use of turkey oak in three-layer particleboards made from aspen. Layers of turkey oak particles were added to the face layers at 10%, 20% and 30%. In two additional panels, turkey oak was included in the core layer at 10% and 20%, resulting in a total content of 40% and 50%. The panels were manufactured under laboratory conditions at 180°C, 2.3 MPa and 330 seconds, with a target density of 640 kg·m⁻³. The results showed consistently high values of modulus of rupture and modulus of elasticity at all levels of turkey oak inclusion.