Uticaj hemijskih tretmana na dimenzionalnu stabilnost drveta poljskog jasena - prvi deo - tangencijalno bubrenje

Abstract

Promena dimenzija drveta događa se pri promeni sadržaja higroskopne vlažnosti, a posledica je prisustva hidroksilnih grupa u građi drveta koje su pristupačne za ostvarivanje vodoničnih veza sa molekulima vode. Predtretmani drveta, koji se sve češće primenjuju u procesima prerade drveta, kao jedan od efekata imaju hidrolizu hemicelulozne komponente drveta, koja je nosilac najvećeg dela slobodnih hidroksilnih grupa u drvetu. U ovom radu ispitan je uticaj tretmana vodom i sirćetnom kiselinom koncentracije 3% i 6% u trajanju od 1h, 2h, 3h i 4h na dimenzionalnu stabilnost drveta poljskog jasena. Dimenzionalna stabilnost kontrolnih i tretiranih grupa uzoraka ispitivana je posle sušenja do apsolutno suvog stanja, potapanjem uzoraka u destilovanu vodu u trajanju od 32 dana. Kod sve tri vrste tretmana postignuto je povećanje dimenzionalne stabilnosti drveta poljskog jasena u odnosu na kontrolne grupe uzoraka. Istovremeno, ustanovljeno je da dužina trajanja tretmana nije imala značajan uticaj na iznos upijanja vode i tangencijalnog bubrenja.

Dimensional change in wood occurs with the change in hygroscopic moisture content, as a consequence of available hydroxyl groups in wood constituents, allowing for the hydrogen bonding with water molecules. Various pretreatments of wood material are being frequently applied in the wood processing industry. One of the main effects of such processes is the hydrolysis of hemicelluloses, which is the main carrier of the free hydroxyl groups in wood material. Hence, the influence of water treatment and the acetic acid treatment on dimensional stability of narrow-leaved ash (Fraxinus angustifolia Vahl. ssp. Pannonica Soó & Simon) were examined in this paper. Duration of treatments was 1h, 2h, 3h and 4h for both solvents. In addition the acetic acid was separately used in concentrations of 3% and 6%. Dimensional stability of the control (referent) and treated sample groups were tested on oven dried samples which were consequently submerged in the distilled water during 32 days. The increase of dimensional stability of narrow-leaved ash was achieved with all of the three treatments (one treatment with water and the two with acetic acid solutions). Simultaneously, it was noticed that the results of water uptake and tangential swelling were not significantly affected by the duration (length) of the treatments.