Welding of solid wood/Zavarivanje masivnog drva

This paper presents the up-to-date knowledge and results of the application of wood welding techniques at the Faculty of Forestry University of Zagreb. Wood welding technologies have been developed as a new way of bonding timber by using high temperature generated by friction and pressure. Timber is assembled without any adhesives. During the process the surface layer of timber (lignin), which is in direct contact with its counterpart, melts due to high pressure and temperature, which is usually generated by mechanical friction of the elements being connected. The cell structure in the interface area of timber is completely destroyed, while in the welding area the density is increased due to the destruction of wood cells. The cell walls are broken, as a result of exposure to high temperatures, mechanical pressure and chemical process, which occur during the cooling stage. Only natural materials are used in wood welding, which makes these products eco friendly. In case of recycling, welded products may be disposed of just as natural timber, without the release of toxic substances. Keywords: solid wood, welding wood, dowels, adhesion Uradu su prikazane dosadasnje svjetske spoznaje o novijoj metodi spajanja drva, a rezultati eksperimentalnog zavarivanja drva dobiveni su no Sumarskom fakultetu Sveucilista u Zagrebu. Tehnika zavarivanja drva razvijena je kao nov nacin spajanja drvenih dijelova uz pomoc topline koja se razvija zbog trenja i tlaka. Drveni se elementi spajaju bez upotrebe ljepila. Tijekom procesa zavarivanja rastale se povrsinski slojevi drva (lignin) u medusobnom kontaktu, a to se dogada zbog utjecaja tlaka i topline, koja se najcesce postize trenjem elemenata koje zavarujemo. U medupovrsinskoj zoni stanicna je struktura drva u potpunosti unistena, a u zoni zavarivanja znatno je povecana gustoca drva jer su drvne stanice sasvim unistene. Stijenke stanica popucaju zbog utjecaja topline, tlacne sile i kemijske reakcije tijekom hladenja drva. Zahvaljujuci upotrebi iskljucivo prirodnih materijala, tako spojeni proizvodi ekoloski su prihvatljivi. Pri recikliranju ili spaljivanju zavareni proizvodi, kao ni prirodno drvo, ne oslobadaju toksiMe tvari. Kljucne rijeci: masivno drvo, zavarivanje drva, mozdanici, adhezija