Author: Ján Matyašovský
Articles
- WOOD-BASED PANELS WITH LOW FORMALDEHYDE EMISSION BY COLLAGEN AND KERATIN BIOPOLYMERS
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Summary
Urea formaldehyde (UF) adhesives are the most commonly used for wood-based panels, but their main disadvantage is an intensive formaldehyde emission. The aim of the investigation was to reduce the release of formaldehyde from UF bonded wood materials by developing and testing new and more efficient modifiers that bind formaldehyde and form more stable methylene bonds resistant to hydrolysis of the adhesive. Methylol pre-condensate additives with varying ratios of glutaraldehyde and urea modified by fibril proteins based on collagen and keratin were tested. The measurements confirmed the decrease of formaldehyde at all concentrations of methylol pre-condensate compared to the reference sample. Formaldehyde emissions were evaluated from five-layer plywood according to JIS A 1460 (2001): "Building boards. Determination of formaldehyde emission. Desiccator method". The most significant decrease of formaldehyde emission up to 37% was achieved with the application of 5% methylol pre-condensate into UF adhesive standard. The gluing quality has been assessed according to standards EN 314-1 and EN 314-2 and the tested plywood meet the requirements of the standard for Class 1 – suitable for application in the interior.
Keywords: wood-based panels, urea-formaldehyde resin, collagen, keratin, plywood
- INVESTIGATION OF PLASTIC/WOOD COMPOSITES
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Summary
Polyolefin (linear low-density polyethylene, LLDPE) was blended with date palm wood (DPW) powder to prepare composites with concentrations of filler ranging from 10 to 70 wt.%. The Young´s modulus of the composites significantly increased with an increase in the filler content in the entire concentration range. The presence of the filler improved the flexural strength, which was represented by the flexural stress at peak. The water absorption test revealed that the composites had a strong tendency to absorb water, which was dependent on the filler content. The experimental data were compared with several theoretical models.
Keywords: LLDPE, date palm wood, composites, mechanical properties, water absorption, adhesion
- REDUCTION OF FORMALDEHYDE EMISSION FROM WOOD-BASED PANELS BY MODIFICATION OF UF ADHESIVES WITH NATURAL BIOPOLYMERS
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Summary
At present, polycondensation urea-formaldehyde (UF) resins are the most widely used wood gluing adhesives, but their main disadvantage is their low resistance to water and moisture, which causes the subsequent release of formaldehyde emissions from finished products. The aim of the study was to reduce the release of formaldehyde from wood materials by developing and testing new, more effective modifiers that bind formaldehyde or form more stable methylene bonds during polycondensation. Research was focused on the biopolymer collagen and keratin. For this study collagen samples were modified with hardener RODA M 210 (manufacturer Duslo Šaľa) and sulphur additive. From biopolymer keratin, which can be found in hair, feather, wool, nails, hoofs, horns, etc., were prepared samples by thermal heating during for 1 hour at various temperatures from 150°C to 197°C. XPS Ray photoelectron spectroscopy analyse was used to identify changes in their surface chemical structure. The XPS spectrum of keratin samples has been shown to depend on the temperature of their thermal degradation, with the total amount of carbon, nitrogen and sulphur increasing with increasing temperature. For sulphur, the total amount of its reduced form expressed as sulphide also increases, while the total amount of oxygen decreases with increasing temperature. Technical applications have focused on the application of keratin samples to modify mixtures of UF resins to reduce the release of formaldehyde from glued wood-based panels. Formaldehyde emissions were assessed from five-layer plywood according to EN ISO 12460-4. Measured values of extinctions of tested samples confirmed the decrease of formaldehyde emissions for each concentration of collagen and keratin samples in comparison with the reference sample.
Keywords: UF adhesive, modifier, keratin, collagen, UF resin, plywood, gluing, formaldehyde emission
- BEECH WOOD MODIFIED BY RADIO-FREQUENCY DISCHARGE PLASMA
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Summary
The radio-frequency discharge plasma (RFDP) has been used to improve the wetting and adhesive properties of beech (Fagus Sylvatica L.) wood. The pre-treatment of wood surface using discharge plasma is attractive for various wood applications, mainly because of its high efficiency and low production cost. Moreover, a significant increase of the polar component of wood surface energy after modification by RFDP has been identified, while the polar component of the surface energy is associated with the presence of acid-base forces (electron donor–acceptor bonds). The surface energy of beech wood pre-treated by RFDP during 120 s in air significantly decreased. The shear strength of adhesive joint beech wood-polyurethane adhesive increased non-linearly from 5.2 MPa (native beech wood) up to 7.8 MPa. FTIR-ATR results confirm the increase of the beech wood polarity during RFDP treatment due to growth in –OH polar groups amount. The enhancement of the wood wettability is a necessary condition to promote a better adhesion with a water-based adhesives and coatings, which is currently being studied.
Keywords: adhesion, beech wood, plasma treatment, surface chemistry, hydrophilicity
- MODIFICATION OF VARIOUS WOOD SPECIES BY BARRIER DISCHARGE PLASMA
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Summary
The barrier discharge plasma (BDP) modification represents an appropriate method for the polarity increasing of the wood surfaces. The surface properties of various wood species (beech, maple, birch) were pre-treated using BDP at atmospheric pressure in air were evaluated by contact angle measurements. The FTIR spectrum of the three tested species of wood is a mixed spectrum (composition) of cellulose and lignin with characteristic peaks corresponding to –OH bonds (with a maximum at about 3400 cm-1) and fingerprints assigned to the –CO, –COO and –CH2– bonds typical for polysaccharides.
Keywords: barrier discharge plasma, beech, maple, birch, chemical composition