Utjecaj namakanja i sušenja u sušioniku na mehanička i fizička svojstva furnirske ploče od brezovine (Betula spp.)

Autor: Silver Kruus, Regino Kask, Mihkel Kiviste, Johann Olaf Lääne, Harri Lille
Jazyk: angličtina
Rok vydání: 2021
Předmět:
Zdroj: Drvna industrija
Volume 72
Issue 2
ISSN: 1847-1153
0012-6772
Popis: The objective of this study was to explore some of the physical and mechanical properties of 9-layer birch (Betula spp.) plywood with the addition of phenol-formaldehyde glue, in cases in which the cutting edges of the samples are coated with the damp-proof mastic Fibergum, and in case in which they remain unprocessed (uncoated), following a total of ten cycles of soaking/oven-drying. The properties to be determined were the bending strength (BS), modulus of elasticity in bending (MOE), thickness swelling (TS) and restore dimensions (RD), which were tested according to the European standards (EN). A linear-fractional equation and linear relationship were used for the approximation of any change in the physical and mechanical properties of the samples depending upon the number of soaking/oven-drying cycles. It was shown that the values of the properties investigated were most affected by the first soaking and drying cycle. Thereafter, BS and MOE levels decreased smoothly at a low rate, but the values of TS became stabilised. The BS and MOE values for the wet samples with coated cutting edges were higher than when they were uncoated, as the moisture levels in the former case were lower. After the first soaking of the samples with coated cutting edges, the retention values were as follows: BS at 52.8 % and 66.7 % for the major and minor axes, respectively, with the same applying to MOE at 61.9 % and 64.2 %, while TS was at 105.2 %. To clarify the phenomenon that causes a decrease of the properties, the face plies and edge structures of the initial dry samples and of the samples after the first, second and ninth soaking/oven-drying cycles were studied using the X-Ray technique.
Cilj ovog istraživanja bio je odrediti neka fizička i mehanička svojstva furnirske ploče od brezovine (Betula spp.) izrađene od devet slojeva furnira i uz dodatak fenol-formaldehidnog ljepila. Uzorci čiji su rubovi premazani za vlagu nepropusnim premazom Fibregum i uzorci s nepremazanim rubovima namakani su i sušeni u sušioniku tijekom deset ciklusa. Prema europskim standardima, ispitivana su ova svojstva ploče: čvrstoća na savijanje, modul elastičnosti, debljinsko bubrenje i vraćanje dimenzija uzoraka. Za aproksimaciju promjena fizičkih i mehaničkih svojstava uzoraka ovisno o broju ciklusa namakanja i sušenja u sušioniku primijenjeni su linearna frakcijska jednadžba i linearni odnos. Utvrđeno je da je na vrijednost ispitivanih svojstava najviše utjecao prvi ciklus namakanja i sušenja. Nakon tog ciklusa namakanja i sušenja čvrstoća na savijanje i modul elastičnosti polako su se smanjivali, dok su se vrijednosti debljinskog bubrenja stabilizirale. Vrijednosti čvrstoće na savijanje i modula elastičnosti vlažnih uzoraka s premazanim rubovima bile su veće nego za uzorke s nepremazanim rubovima zbog manjeg sadržaja vode u uzorcima premazanih rubova. Nakon prvog namakanja uzoraka s premazanim rubovima zadržane su ove vrijednosti: čvrstoća na savijanje na 52,8 i 66,7 % te modul elastičnosti na 61,9 i 64,2 % za glavnu odnosno sporednu os, dok je debljinsko bubrenje iznosilo 105,2 %. Za objašnjenje fenomena smanjenja ispitivanih svojstava, lica slojeva furnira i rubne strukture uzoraka nakon prvoga, drugoga i devetog ciklusa namakanja i sušenja u sušioniku primijenjena je rendgenska metoda.
Databáze: OpenAIRE
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