The present study is aimed at obtaining self-binding (without any additional binders) medium density board samples from steam-exploded grey alder (alnus incana (L.) Moench) chips. The chips used for steam explosion pre-treatment (SEP) were fractionated by crushing to different size from 0.4 mm to 20 mm. The SEP was done in a batch reactor at constant temperature and pressure (235 °C and 3.2 MPa) varying the time from 0.5 to 3 minutes. The pre-treated fibrous mass was air dried to different water content and hot-pressed under various conditions part of the fibrous samples being additionally milled before hot-pressing. The pressing temperature of boards was set at 150 – 170 ˚C, the pressure – at 0.4 – 2.1 MPa for 6 – 8 min during the hot-pressing and for 10 – 15 min during the cooling of the press plates to 80 °C. The density range of the produced boards is 0.5 – 0.8 g cm-3.
To find the effect of the used pre-treatments and of the pressing conditions on the boards various physical properties were tested according to the relevant EN standards. Except for thickness swelling varying from 6 to 19 % regardless of the density, all the other determined properties are found to improve with increasing the board density. Contrary to expectations the tested mechanical properties do not meet the requirements of EN standards.
Keywords: grey alder, steam explosion treatment, fibreboard, medium density, mechanical properties
Authors
Tupciauskas R.
Wood Materials and Technology, Department of Wood Processing, Latvia University of Agriculture, Jelgava
Veveris A.
Latvian State Institute of Wood Chemistry, Riga, Latvia
Gravitis J.
Latvian State Institute of Wood Chemistry, Riga, Latvia
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