The impact of the quality of adhesiveness of building blocks on the swelling of particle- and fibreboards

Preučevali smo korelacijo med debelinskim nabrekom in razslojno trdnostjo pri lesnih kompozitih oziroma kakšen vpliv ima zlepljenost gradnikov na nabrekanje plošč. Preizkušali smo razslojno trdnost in debelinski nabrek LSB plošče, MDF plošče ter iverne plošče tipa P2 in P5. Debelinski nabrek smo določali s potapljanjem v vodo, izpostavitvijo okolju s povišano vlažnostjo (relativna zračna vlažnost 85 %, temperaturo 20 °C) ter ciklično izpostavitvijo (potopitev v vodo, zmrzovanje in sušenje). Po končanem preizkusu smo preizkušancem določili debelinski nabrek ter razslojno trdnost. Ugotovili smo, da imajo v suhem stanju najboljšo razslojno trdnost LSB plošče, najslabše pa so se obnesle iverne plošče tipa P2. Pri izpostavitvi vlažni klimi so imele najmanjši nabrek iverne plošče tipa P5, največji debelinski nabrek pa so imele MDF plošče. Pri potapljanju v vodo so imele najmanjši debelinski nabrek LSB plošče, največji pa pri iverni plošči tipa P2. Opravili smo tudi ciklični test. Ugotovili smo, da so po končanem cikličnem preizkusu razslojne trdnosti in debelinski nabreki v podobnem razmerju kot pri suhih ploščah, z izjemo MDF plošče, ki je imela po cikličnem preizkusu najmanjši nabrek, ker je zadnji korak pri ciklu sušenje v sušilniku, kjer vlaknene plošče hitreje oddajo vlago, kot druge plošče, ker imajo vlakna veliko sposobnost vpijanja in oddajanja vlage. Zato se plošča zelo hitro odziva na spremembo klime v okolici.We studied the correlation between the thickness swelling and the layer strength of wood composites, or what impact the adhesiveness of the building blocks has on the swelling of the boards. We tested LSB and MDF boards, particleboards type P2 and particleboards type P5. We tested layer strength and thickness swelling. Thickness swelling was determined by immersion in water, exposure to an environment with increased humidity (relative humidity 85 %, temperature 20 °C), and cyclic exposure (immersion in water, freezing and drying). When the test was completed, layer thickness swelling and sturdiness of the test samples were determined. We established that in the dry state, LSB panels have the best layer strength, whereas the particleboards type P2 have proven to be the least effective. When exposed to a humid climate, particleboards type P5 showed the smallest swelling, whereas MDF boards had the highest thickness swelling. When immerging under the water, LSB boards showed the smallest thickness swelling, while particleboard type P2 the largest. We also performed a cyclic test, where we found that the proportions of layer strengths were similar as those with the dry boards, as well as thickness swelling with the exception of MDF boards. The latter had smaller swelling due to the drying, which was the last step of the cycle. The fibreboard namely submits the moisture quicker than other boards because fibres have the great ability of absorption and dissipation of moisture, which is why the board very rapidly responds to a climate change of the surrounding area