Покращення властивостей деревинно-солом'яних плит модифікуванням карбамідоформальдегідного клею етанолом

Improvement of wood-straw board properties using urea formaldehyde (UF) glue modified by ethanol was examined in this study. Wheat straw, wood particles, UF resin, ammonium chloride and ethanol were used for board production. Three-layer wood-straw boards with thickness 16 mm and density 650, 750 and 850 kg/m3 were produced. Wood particles and mixture of wood-straw particles were used respectively in the outer and inner layers of the board. The ratio between the layers of the board was 20:60:20 (outer: inner: outer). For the outer layers of board the glue without ethanol was used. For the inner layer of board the content of ethanol was 10 mass units on 100 mass units of resin. The same boards were produced using unmodified UF glue for the determination of ethanol effect on wood-straw board properties. We found that wood-straw boards with modified glue have better properties compared with control boards. The most significant increase of the MOR and is equal to 53 %. Slightly less is increase of the IB, namely 33 %. Water absorption and thickness swelling reduce slightly and these changes do not exceed 10 %. Consequently, ethanol which is contained in glue, effects on the fat-wax layer of straw, dissolving it, for a period from mixing particles with glue and till the finishing of boards pressing. As a result, in the points of straw surface contact with the glue the hydrophobic effect of fat-wax layer on their adhesive interaction decreases. The remaining hydrophobic surface straw is not changed. During the pressing the ethanol evaporates from the boards together with the moisture. Mechanical performance of wood-straw boards bonded with the modified glue meet the requirements of standard EN 312–2 at density of 650 kg/m3. With further increasing of board density their mechanical properties increase. In particular, while board density increases from 650 to 750 kg/m3 the MOR increases by 15 %, and IB – by 9 %. During board density increasing from 650 to 850 kg/m3 these mechanical performances grow by 52 % and 18 % respectively. Thickness swelling and water absorption of wood-straw boards decrease using the modified glue with increasing their density, which also points on improve of the adhesion interactions of the glue and the straw surface. During board density increase from 650 to 750 kg/m3 the thickness swelling index is reduced by 4 % and by 31 % – from 650 to 850 kg/m3. During the density increasing from 650 to 750 kg/m3 and from 650 to 850 kg/m3 the boards water absorption decreases by 9 % and 52 % respectively.