Лесотехнически Университет

Резюме

The research presented in the paper is directed to creating possibilities for production of multilayered plywood that are resistant to prolonged water impact, as well as to mutual impact of water and heat.

The aim of the conducted research consists of the possibility for production of stable multifunctional plywood made from coniferous raw material. For that purpose experimental multilayered plywood panels are made from peeled black pine veneers bonded with water-soluble phenol formaldehyde resin.

The experimental panels were subjected to standard laboratory tests in conditions of water regimes in order to define the water resistance and dimensional stability under water impact and mutual impact of water and heat, as well as to determine the degree of adhesion between the veneers.

The research showed that panels were characterized by high stability during this kind of treatment. The panels showed consistency in form and dimensions, as well as consistency of the adhesion in glue lines.

Резюме

Raw materials and materials form a big part of the cost price of the end product. At the same time, the deviations from the requirements put forward to them impede the manufacturing processes, lead to additional expenditure for elimination and compensation of the discrepancies of the raw materials delivered, serious losses and lost profit for the manufacturer.

The provision of raw materials and materials of constant quality is not always achievable and that is why it is necessary to assess the deviations from the optimum requirements and to determine what it costs to us to eliminate / compensate them and at minimum expenditure at that.

In the report, methods for assessment of suppliers of urea-formaldehyde resin are presented. They reflect the relationship between manufacturing and financial indices (price, expenditure, lost profit) when assessing the losses from deviation in the raw materials quality.

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

To reduce pollution as well as energy consumption, new insulating and non-flammable bio-panels based on the combination of different reinforcements such as Miscanthus x giganteus particles and rice husk mixed with recycled textile fibres were prepared using Chitosan as a polysaccharide natural binder. Different formulations using one or more combined reinforcements and Chitosan (7 wt%) as an aqueous binder were prepared by a thermocompression process. Mechanical, thermal and fire behaviour of the panels were examined. Results showed that the mechanical properties vary according to the size and the nature of the used reinforcements. All the panels showed sufficient bending and compressive strength for thermal insulation uses, according to European construction specifications (DIN 4108-10). The highest mechanical strengths in bending and compression have been found for the formulation with small size miscanthus particles (0.48 MPa and 0.64 MPa respectively). Fireproof panels (E rating, according to standard NF EN ISO 11925-2) with an insulating behavior (thermal conductivity vary between 0.07 and 0.09 W/m/K) and a density range between 247 and 400 kg/m³ were successfully elaborated. The prepared bio-panels show promising results and great potential to compete with the conventional insulating materials used nowadays.

Резюме

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.