Penetracija urea-formaldehidnog adheziva u tkivo drveta, deo I - radijalna penetracija UF adheziva u drvo bukve

Abstract

Penetracija adheziva ima značajnu ulogu u adheziji drveta, pošto je drvo porozni materijal. Stepen penetracije najviše zavisi od faktora drveta, vrste i recepture adheziva i parametara presovanja. Za ovo istraživanje pripremljene su tangencijalno rezane daščice (bočnice) bukovog drveta (Fagus moesiaca) debljine 5 mm, dužine 100 mm (paralelno sa vlaknima) i širine 30 mm. Urea-formaldehidni adheziv je nanešen na površinu jedne pločice. Dve daščice su slepljene u uzorak tako da su im paralelna drvna vlakna. Uzorci su presovani u hidrauličnoj presi 15 min na temperaturi od 120°C i pritisku od 0,7 MPa. Poprečni mikrotomski preparati, debljine 20 μm isečeni su na klizećem mikrotomu. Evidentan je nedostatak iscrpnijih istraživanja penetracije ureaformaldehidnih (UF) adheziva u drvo. Pošto su UF-smole najvažnija vrsta adheziva u drvnoj industriji u poslednjih 60 godina, cilj ovog istraživanja je mikroskopsko određivanje UF-adhezivne penetracije u tkivo drveta. U svrhu ovog istraživanja korišćene su četiri UF-smole različitog stepena polikondenzacije. U veziva je dodat safranin pošto je za merenje dubine penetracije adheziva korišćen epi-fluorescentni mikroskop.

Adhesive penetration plays an important role in wood adhesion, since wood is a porous material. The degree of penetration mostly depends on the wood factors, resin type and formulation and processing parameters. Tangentially cut 5 mm thick beech wood (Fagus moesiaca) plies, 100 mm long (parallel to grain) and 30 mm wide, were prepared for this study. The urea-formaldehyde (UF) adhesive was applied to the surface of one ply. Two plies were assembled into sample so that the grains of two plies were parallel. Samples were pressed in a hydraulic press at 120°C and 0,7 MPa for 15 min. Microtome test-specimens were cut of each sample. 20 μm thick microtomes were cut by sliding microtome apparatus, exposing a bondline with a cross-sectional surface. The lack of more exhausting research on the penetration of urea-formaldehyde adhesives in wood is evident. Since ureaformaldehyde (UF) glue resins were the most important type of adhesives in the wood industry in the last 60 years (Dunky, 2000), the objective of this research was microscopic detection of UF adhesive penetration in wood tissue. Four types of UF resins with different levels of polycondensation were used in this research. Safranin was added in resins, since epi-fluorescence microscope was used in this research for measuring the adhesive penetration.