Автор: Borche Iliev

Статии

WATER RESISTANCE OF PLYWOOD BONDED WITH ALCOHOL-SOLUBLE PHENOL-FORMALDEHYDE RESIN

Автори: Violeta Jakimovska Popovska, Borche Iliev, Юлия Михайлова

Резюме

Тhe aim of the research presented in this paper is to study the water resistance of experimental plywood bonded with alcohol-soluble phenol-formaldehyde resin. The evaluation of water resistance is made on the basis of the obtained data for the changes of the physical properties of plywood after exposure to prolonged water treatment. Tests for the thickness swelling, volume swelling and water absorption are made after immersion in water for prolonged period in controlled laboratory conditions. The measuring of thickness, length, width and mass of plywood specimens for determination of these properties is made after immersion in water for the period of 1 day (24 hours) to 52 days (1248 hours).

The experimental plywood model was made from peeled beech veneers. Pure alcohol-soluble phenol-formaldehyde resin is used as plywood binder.

The research results showed that the plywood model has uniform density; it is dimensionally stable during and after prolonged water treatment, without any deformations of the shape of the test specimens. The changes of the values of thickness and volume swelling, as well as the values of water absorption in the analyzed period are proportional to change of the duration of the period of water treatment. According to the obtained data from the tests of these properties the plywood model meets the requirements of the standard for load-bearing plywood for use in construction.

Ключови думи: plywood, alcohol-soluble phenol-formaldehyde resin, water resistance, thickness swelling, water absorption, dimensional stability

EN Version

TENSILE STRENGTH IN DIFFERENT DIRECTIONS OF LAMINATED PLYWOOD MADE FROM BEECH VENEERS

Автори: Violeta Jakimovska Popovska, Borche Iliev

Резюме

Тhe aim of the research presented in this paper is to study the tensile properties at different directions of experimental plywood.

For this research nine-layered plywood is made. The model is made from peeled beech veneers with thickness of 1,2; 1,5; 2,2 and 3,2 mm.

Pure water-soluble phenol-formaldehyde resin is used as plywood binder.

The tensile strength of the plywood panel is tested in five directions, i.e., parallel and perpendicular to the face grain, and at the angles of 22,5º; 45º and 67,5º to the face grain of the panel.

Coefficients of the equality of the tensile strength in different directions of the plywood model is calculated trough polar diagram made on the basis of the obtained data for the tensile strength at different angles to the face grain of plywood. The coefficient of mass quality is calculated too.

The research results showed that the experimental plywood model meet and exceed the defined values of tensile strength in accordance with the requirements of the standard for load-bearing plywood for use in construction.

Ключови думи: laminated plywood, beech veneers, tensile strength, coefficient of equality of tensile strength, coefficient of mass quality

EN Version

PHYSICAL CHARACTERISTICS OF MULTILAYERED PLYWOOD MADE FROM BLACK PINE VENEERS

Автори: Violeta Jakimovska Popovska, Borche Iliev, Julia Mihajlova

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.

Ключови думи: multilayered plywood, black pine veneers, phenol formaldehyde resin, physical properties, resistance to water and heat

EN Version

IMPACT OF VENEER LAYOUTS ON PLYWOOD BENDING PROPERTIES

Автори: Violeta Jakimovska Popovska, Borche Iliev

Резюме

The research presented in this paper includes the study of the plywood bending properties through a change of the position of the layers in the structure of the panel around the central axis, without changing the number and the thickness of the veneers.
For studying this impact, experimental models of nine-layer plywood are made. The models are made from peeled beech veneers with thickness of 1,2; 1,5; 2,2 and 3,2 mm.
The modeling is made on the basis of changing the position of veneers with thickness of 3,2 mm around the central axis (axis of symmetry).
Pure water-soluble phenol-formaldehyde resin is used as plywood binder.
The bending strength and modulus of elasticity in bending of the plywood panels is test-ed in two directions, parallel and perpendicular to the face grain.
The research results showed that the tested plywood models meet the defined values of bending properties in accordance with the requirements of the MKS standard for structural plywood for use in construction. The different layouts of veneer sheets in panel structure gives opportunities for production of panels with different strength characteristics.

Ключови думи: plywood, veneers, bending properties, changes, position, layers

EN Version

SCREW WITHDRAWAL RESISTANCE OF WOOD-BASED COMPOSITE PANELS (PART I)

Автори: Violeta Jakimovska Popovska, Borche Iliev, Julija Mihajlova

Резюме

This research includes the screw withdrawal resistance of wood-based composite panels for use in the construction.

Three experimental wood-based composite panels were prepared by combining particleboards and peeled beech, black pine and poplar veneers with thickness of 3.2 mm. The core layer of the wood-based composite panels was made of single-layer particleboard with the thickness of 16 mm, which was overlaid on both sides with the veneers.

Water-soluble phenol-formaldehyde resin was used for particle bonding and veneering. The screw withdrawal tests were performed according to the principles of the standard MKS D.C8.112/82. The screw withdrawal resistance was tested in two directions: perpendicular to the plane of the panel, and in plain of the panel.

The results from the research showed that the different veneer species used for particleboard overlay significantly affected the screw withdrawal resistance perpendicular to the plain of the wood-based composite panels.

According to the obtained the screw withdrawal resistance values, wood-based composite panels tested in this study could be recommended for utilizing in the construction of wooden structures.

Ключови думи: Composite wood-based panels, particleboard, veneer, beech, black pine, poplar, phenol formaldehyde resin, screw withdrawal resistance

EN Version