Influence of biocides in glue line on mechanical and fungicidal properties of glued timber

Zaradi težav pri lepljenju impregniranega lesa in nezadostne zaščite lepljenega lesa s premazovanjem smo v lepilno mešanico pred lepljenjem dodali biocid. Biocid je difundiral iz lepilnega spoja v strukturo lesa in tako zaščitil lamele, pri tem pa je moral lepilni spoj ohraniti svoje mehanske lastnosti. Lesene lamele smo lepili z MUF in PU lepilom, ki smo jima dodali 0,5 in 0,1 % bora oz. bakra v obliki borove kisline oz. bakrovega hidroksid karbonata. Mehanske lastnosti lepilnih spojev smo preskušali s strižnim testom (SIST EN 392) in testom delaminacije (SIST EN 391). Pred tem smo utrjevanje lepil spremljali z dielektrično analizo, reološke lastnosti pa z reometrom. Difundiranje bora in bakra smo spremljali vizualno in z ICP ablacijo. Učinkovitost zaščite lepljenih vzorcev pred glivami smo preverjali s testom izpostavitve glivam (SIST EN 113). Ugotovili smo, da je utrjevanje hitreje potekalo pri lepilnih mešanicah z dodanimi biocidi, reološke lastnosti slednjih pa se niso bistveno poslabšale. Strižna trdnost se ob dodanem biocidu ni bistveno znižala oziroma se je v določenih primerih celo izboljšala. Podobno velja za delež delaminiranih spojev. Ugotovljena je bila povezava med vlažnostjo vzorcev in difundiranjem bora. Najhitreje in najintenzivneje so prodirale borove učinkovine iz spojev, ki smo jim dodali 0,5 % bora. Žal pa se je izkazalo, da je količina dodanih aktivnih učinkovin prenizka, da bi zaščitila lepljen les pred najpomembnejšimi glivami razkrojevalkami.Problems related to bonding of impregnated timber and insufficient protection of glued wood with surface treatment were the main reasons for adding biocides to adhesives before bonding. To protect lamellas biocide diffused from the glue line into the wood structure: at the same time the glue lines should have preserved their mechanical properties. Tested samples were glued with MUF and PU adhesives with addition of 0.5 or 0.1 % of boron or copper in form of boric acid and copper hydroxide carbonate. The shear test (SIST EN 392) and delamination test (SIST EN 291) were used to test the mechanical properties of glue lines and dielectric analysis was used to measure glue hardening, while the rheometer to test the rheological properties. Boron and copper diffusion was measured visually and by ICP ablasion. Fungal decay was tested according to SIST EN 113 standard. Results show that glue line hardening was more efficient when using adhesive with added biocidesč the rheological properties of the glues with addition of boric acid did not significantly differ from the glues without biocides. Shear strength prepared with the glues with biocides did not decrease, in contrary, in some cases it even increased. Similar influences of added biocides were observed at the delamination test of glue lines as well. Furthermore, there is a significant correlation between sample moisture content and boron diffusion. The quickest and most intensive diffusion of boron compounds was measured from glue lines with boron concentration of 0.5 %. Unfortunately, it turned out that the amount of added compounds was too low to protect glued timber against fungal decay