Dry thermal treatments of wood samples were carried out at 160 and 200 °C. After each treatment, the samples were irradiated using a strong UV emitter mercury lamp, and the colour change was then evaluated. For control, untreated samples were also irradiated using the same mercury lamp. Results showed that the extractive content of the wood played an important role in the colour change not only during thermal treatment but also during light irradiation. It was found that, compared to the thermally untreated samples, the thermal treatment at 200 °C reduced the red colour change due to photodegradation. The yellow colour change of photodegradation was hardly affected by the applied thermal treatments, showing that thermal treatments were not able to reduce the light degradation of lignin. The applied treatments slightly stabilized the wood against the degrading effect of light. The wood treated at lower temperature (160 °C) had less colour change induced by the light source.

The colour change of wood has been the topic of numerous research activities worldwide. This study investigates the colour change of Robinia (Robinia pseudoacacia L.) and two hybrid poplars, namely Pannónia poplar (Populus x euramericana cv. Pannónia) and I-214 poplar (Populus x euramericana cv. I-214). The sapwood and heartwood were investigated separately for each of the poplars. The heartwood of Robinia was also investigated. The timbers were dried in a climate chamber at four different temperatures (20 °C, 40 °C, 60 °C, and 80 °C), as the relative humidity was reduced in 5 steps (95%, 80%, 65%, 40%, and 20%) at each temperature. The colour co-ordinates L*, a*, and b* were measured according to the CIELab system. Differences in terms of colour change between wood species and sapwood versus heartwood are discussed in the paper. The effect of wood moisture content and heat on the colour co-ordinates is provided. The colour of Robinia is more sensitive to heat than poplar.

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361 A terméket angol nyelvterületen Cross-Laminated Timber néven ismerik (rövidítése CLT, esetenként XLT vagy X-lam), Németországban korábban a KreuzlagenholzTM (KLHTM, jelenleg egy konkrét gyártó tulajdonában álló árujelző), újabban a Brettsperrholz (BSH) elnevezés terjedt el. Jól használható magyar neve nincsen, várhatóan hazánkban is a CLT rövidítés fog elterjedni, ezért cikkünkben is ezt használjuk. The applicability of I-214 hybrid poplar as Cross-Laminated Timber raw material Abstract Cross-Laminated Timber (CLT) is a relatively new construction material that has not gained popularity in Hungary yet. Producing such building elements using Hungarian raw materials may help to establish this technique. The purpose of our research was to examine the possibility of producing CLT using Hungarian grown I-214 hybrid poplar. One three-layer panel was produced using Hungarian hybrid poplar and polyurethane resin, and tested in bending. The MOR of the poplar CLT was found to be comparable to low-grade softwood CLT, but the MOE was lower than the requirement. Poplar raw material may be suitable for CLT production by selecting higher grade raw material using nondestructive testing, or as a secondary raw material mixed in with softwood. CLT hazai I-214 olasz nyár faanyagból Keywords: CLT, hybrid poplar, lightweight construction, nondestructive timber grading BevezetésA könnyűszerkezetes lakóépületek Európa-szerte egyre népszerűbbek, köszönhetően elsősorban az egyre szigorúbb energetikai szabályozásnak, amely a közel zéró kibocsátású épületek építését szorgalmazza. A bordavázas épületek különösen alkalmasak erre a célra, kitűnő hőszigetelő képességük, és alacsony beépülő energiatartalmuk miatt. Ugyanakkor többen kritizálják ezeket az épületeket alacsony hőtároló kapacitásuk miatt (Hacker és tsai. 2008), illetve a potenciálisan egészségtelen lakókörnyezet miatt, amely az alkalmazott szellőztetőrend-szertől függően kialakulhat (Hens 2012). A tömörfa falszerkezetek (pl. a gerenda-és rönkházak) egészségesebb és jobb hőtároló képességű alternatívát kínálnak, azonban építésük időigényesebb és komoly szakértelmet kíván.A többrétegű keresztirányú ragasztott tömörfa szerkezeti paneleket (CLT 1 ) a '90-es évek-ben fejlesztették ki Ausztriában, a grazi egyetemen (Technische Universität Graz, Kramer 2014).