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Vpliv vrednosti pH termično modificiranega lesa na utrjevanje lepil : diplomsko delo - univerzitetni študij
Čop, Matjaž (Author), Šernek, Milan (Mentor) More about this mentor... This link opens in a new window, Pohleven, Franc (Reviewer)

URLURL - Presentation file, Visit http://www.digitalna-knjiznica.bf.uni-lj.si/dn_cop_matjaz.pdf This link opens in a new window

Abstract
Termična modifikacija lesa vpliva na znižanje vrednosti pH, kar lahko povzroča težave pri lepljenju modificiranega lesa z različnimi lepili. Da bi raziskali dejanski vpliv pH vrednosti lesa na utrjevanje lepil, smo v raziskavi zlepili 2 vrsti termično obdelanega lesa ter kontrolni, nemodificiran les. Iz lesa smo pripravili lamele, ki smo jih zlepili z urea-formaldehidnim (UF) in fenol formaldehidnim (FF) lepilom. Mehanske lastnosti lepilnega spoja smo preskušali s strižnim testom (SIST-TS CEN/TS 13354:2004). Spreminjanje reoloških lastnosti lepila med utrjevanjem smo spremljali z reometrom, stopnjo utrjenosti lepila pa z dielektrično analizo. Strižni moduli sistema les-lepilo se pri lepljenju z UF niso bistveno razlikovali, večje razlike pa so se pokazale pri lepljenju s FF lepilom. Dielektrična analiza je pokazala večjo začetno hitrost utrjevanja UF in FF lepila pri lepljenju modificiranega lesa, a je končna utrditev v obeh primerih najprej nastopila pri kontrolnem lesu. Največjo strižno trdnost lepilnega spoja smo ugotovili pri termično modificiranem lesu. Strižna trdnost se pri lepljenju s FF, v primerjavi z UF, ni zmanjšala, temveč se je v večini primerov celo nekoliko povečala. Izkazalo se je tudi, da sprememba vrednosti pH, zaradi termične modifikacije, ni vplivala na utrjevanje FF lepila, saj je bilo lepilo dovolj bazično in ni dopustilo večje spremembe vrednosti pH.

Language:Slovenian
Keywords:lepljenje, termično modificiran les, vrednost pH, reologija, utrjevanje, dielektrična analiza, mehanske lastnosti
Work type:Undergraduate thesis (m5)
Tipology:2.11 - Undergraduate Thesis
Organization:BF - Biotechnical Faculty
Year:2009
Publisher:[M. Čop]
Number of pages:X, 65 f., [5] f. pril.
Place:Ljubljana
UDC:630*824.86
COBISS.SI-ID:1782409 Link is opened in a new window
Views:778
Downloads:259
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Secondary language

Language:English
Abstract:
Thermal modification of wood causes decrease of pH value, causing problems while gluing such wood with different types of glues. To research the actual influence we have glued lamellas of 2 different stages of modification and one non-treated sample with 2 different glues, (UF and PF). A shear test (SIST-TS CEN/TS 13354:2004) has been used to test the mechanical properties, rheometer to test the rheological properties and dielectric analysis to measure glue curing. The results show that shear modules of a system (wood-glue) do not differ essentially when gluing with UF. However, gluing with PF shows bigger differences. Dielectric analysis results show higher curing velocity at the beginning of the test at heat treated samples. Shear strength is the best at heat treated wood and does not decrease when gluing with PF; in most samples it even increases. In our case the pH decreased while thermal treatment did not have any influence on curing capacity of PF glue. The glue used was too alkaline, so we could not influence the pH of the curing medium.

Keywords:gluing, thermally modified wood, pH value, rheology, curing, dielectric analysis, mechanical properties

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