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3 Annals of Warsaw University of Life Sciences - SGGW. Forestry and Wood Technology

3 2018

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Oak wood pre-treated by cold plasma

Novák I., Kleinová A., Sedliačik J., Matyašovský J., Jurkovič P.

Annals of Warsaw University of Life Sciences - SGGW. Forestry and Wood Technology

2018

No. 104

163--168

The cold plasma was used to improve the hydrophilicity of oak wood. A significant increase of the polar component of oak wood surface energy after modification by cold discharge plasma has been observed. The polar component of the surface energy is associated with the presence of acid-base forces (electron donor-acceptor bonds). FTIR spectra confirm the changes in C=O and C–O–C bonds that occur on the cold plasma modified wood. The integrated intensities ratios of oxygen function absorption with the majority of polar –OH groups contribution with a maximum at 3400 cm-1 and a maximum of non-polar CH2-groups with a maximum at 2985 cm-1 (–CH2 groups)sym shows an increase of the ratio P(OH)/P(– CH2) during plasma treatment of the oak wood.

Environmentally friendly natural polymers for modification of wood adhesives

Matyašovský J., Duchovič P., Jurkovič P., Sedliačik J.

Annals of Warsaw University of Life Sciences - SGGW. Forestry and Wood Technology

2018

No. 104

174--181

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 methyl-ol pre-condensate additives with varying ratios of glutaraldehyde and urea. Pre-condensates were modifying by hydrolysates collagen and keratin, polymer polyphenolic molecules of vegetable tannins. Results of laboratory tests confirmed, that natural bio-polymers are suitable additives for lowering of formaldehyde emission from wood products glued with UF adhesive. Methylol pre-condensate additives and their modifications with antioxidant properties significantly reduced formaldehyde emissions from urea-formaldehyde adhesives. The most significant decrease of formaldehyde emission up to 34.7% was achieved with the application sample No. 9 – UF resin + 20% technical flour + 2% (methylol pre-condensate MOD-II+ keratin) + 4% hardener into UF adhesive standard. Formaldehyde emissions were assessed from five-layer plywood according to JIS A 1460 (2001).“Building boards. Desiccator method” Quality of gluing was tested according to standards EN 314-1 and EN 314-2. Tested plywood fulfils the requirements of the standard for class of gluing 1 – they are suitable for application in normal interior environment.

Discharge plasma treatment of wood surfaces

Novák I., Kleinová A., Sedliačik J., Matyašovský J., Jurkovič P.

Annals of Warsaw University of Life Sciences - SGGW. Forestry and Wood Technology

2018

No. 104

169--173

The water contact angle of various wood species treated by radio-frequency discharge (RFD) plasma in air decreased with activation time from 75 up to 40 deg. The growth of water contact angle of plasma-treated wood from 37 up to 68 deg during aging was faster within 2 days after the plasma pre-treatment. The water contact angles of tested wood species showed a steep decrease after activation by RFD plasma in air. Water contact angles were markedly increased during the first 2 days of aging. RFD plasma-treated wood surfaces should be treated up to 2 days after modification by plasma. The unmodified beech wood sample shows lower roughness compared to wood surface treated by RF-plasma. Higher roughness of the plasma-treated wood samples is related to the ablation of amorphous lignin on the surface of the beech wood.