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ABSTRACT
This article is focused on the influence of coating thickness on colour changes of beech surface with transparent coating. The influence of following factors has been also observed: treatment of wood surfaces before coatings application, and the type of coating. The influence of thickness of the coating on the colour changes during artificial weathering in the Xenotest Q-SUN was also researched on selected specimens. The colour of the surface (the values L*a*b*) was measured by spectrum photometer BYK-Gardner GmbH in CIELAB system. The colour change ΔE* was evaluated. Two different transparent coatings were applied on specimens at three various thicknesses. In the next step, the colour changes were observed after artificial weathering. The specimens with coatings were compared with references without coatings.
The evaluation of the experiments has shown that technology of the surface treatment, type of the coating, and also its thickness much influenced the colour changes of beech wood treated with coatings. The influence of the thickness of the coating has been shown also by photo-stability measurements during artificial weathering; as the paint thickness was increased the colour changes also slightly increased.
Keywords: beech wood, colour changes, film thickness, mechanical working of wood surface, paints.
UVOD
Náterovy film je povlak, ktory vznikol nanesením kvapalného materiálu na povrch vyrobku a následnym vytvrdnutím sa vytvorila tenká pevná vrstva. Náterovy film na drevenÿch vyrobkoch má za úlohu tieto vyrobky chránif proti vlhkosti, mechanickému a chemickému namáhaniu, ale aj ich esteticky zhodnocovaf. Jednotlivé druhy náterovych látok vytvárajú filmy so specifickymi vlastnosfami, ktoré sú prevazne predurcené chemickym zlozením danej náterovej látky. Niektoré vlastnosti povrchovÿch úprav môzu byf ovplyvnované interakciou náterového filmu s drevom, ako aj hrúbkou náterového filmu.
Hrúbka náterového filmu ovplyvnuje konecnú drsnosf povrchovej úpravy. S narastajúcou hrúbkou náterového filmu drsnosf klesá (Slabejová - Moza 2010). Zároven ovplyvftuje aj lesk a v tekutom stave aj mnozstvo prchavych organickych zlúcenín (VOC), ktoré prchajú do prostredia (Lee et al. 2003, Tesarová et al. 2010).
Na zmenu farby povrchu dreva alebo povrchovÿch úprav vplÿvajù rozne faktory. Chou et al. (2008) sledovali farebné zmeny polyuretânovÿch transparentnÿch povrchovÿch úprav. Sledovali vplyv UV-stabilizátora na degradáciu lignínu v dreve ako aj na samotné zltnutie nâterového filmu. Scrinzi et al. (2011) hodnotili zivotnosf vodou rieditel'nÿch a syntetickÿch polyuretânovÿch povrchovÿch úprav na základe zmeny...