The effect of natural aging on the selected properties of wood of Norway spruce and sweet chesnut

Les vedno bolj pridobiva na pomenu. Ker bo lesa predvidoma že okoli leta 2020 pričelo zmanjkovati, ga bomo vedno pogosteje reciklirali ali tudi ponovno uporabljali. Želeli smo določiti vpliv naravnega staranja na izbrane lastnosti smrekovine in kostanjevine. Uporabili smo več 10 let star kostanjev drog (Castanea sativa) in 6 let star smrekov nosilec (Picea abies). Staremu lesu smo določili odpornost na glive, pri čemer smo uporabili izolate 5 različnih gliv razkrojevalk lesa: Gloeophyllum trabeum, Antrodia vaillantii, Hypoxylon fragiforme, Pleurotus ostreatus in Trametes versicolor. Mehanske lastnosti smo določali s tritočkovnim upogibnim testom (modul elastičnosti) in tlačnim obremenjevanjem vzorcev. Spremembe v navzemu vode smo določevali na tenziometru. Zanimal nas je tudi delež ekstraktivov v lesu, pri čemer smo za izpiranje uporabili 3 različna topila: vodo, 70 % metanol in cikloheksan. Numerično smo ovrednotili barve staranega lesa po CIE – L*, a*, b* sistemu. Rezultati testiranj kažejo na to, da se relevantne lastnosti kostanjevine niso bistveno spremenile. Tudi po več desetletjih rabe je les ohranil odpornost proti glivam razkrojevalkam lesa, za razliko od lesa smreke. Pri kostanju so prav tako opazne ohranjene mehanske lastnosti in nizek kapilarni navzem vode. Pri ekstrakciji se je kot najučinkovitejše topilo izkazala voda, tako pri kostanjevini in smrekovini. Po drugi strani se je 6 let stara smrekovina izkazala za manj odporno lesno vrsto, z višjo izgubo mase, večjim kapilarnim navzemom vode in manjšim deležem ekstraktivov. Obe lesni vrsti sta z leti spremenili naravno barvo lesa, ki s starostjo potemni.Wood is more and more important material. Since the availability of wood will presumably be scarce by year 2020, it will be more frequently reused and recycled. We tried to determine the effect of natural ageing on the selected properties of spruce and chestnut. The tested wood was a several decades old chestnut pole (Castanea sativa)and a 6 year old spruce beam (Picea abies). The resistance to the different wood decay fungi: Gloeophyllum trabeum, Antrodia vaillantii, Hypoxylon fragiforme, Pleurotus ostreatus, and Trametes versicolor was determined. Mechanical properties were measured by a 3-point bending test (modulus of elasticity) and compressive strength of samples. Changes in water uptake were defined with the use of tensiometre. Extractives in wood were determined by using 3 different solvents: water, 70 % methanol, and cyclohexane. The colour of the aged wood was numerically evaluated by the CIE L*, a*, b* system. The test results show that the relevant properties of chestnut did not change significantly. In comparison to the spruce, even after several decades of use, wood kept the resistance against the wood decay fungi. Preserved mechanical properties and low capillary water uptakewere also observed with chestnut. The most effective solvent for extraction is water, the same with chestnut and spruce. On the other site the 6 year old spruce has turned out to be a less susceptible wood species, with higher weight loss, higher water capillary uptake, and lower amount of extractives. Over the years, the both wood species changed natural colour which turned darker with age