The Effect of Inorganic Preservatives in the Norway Spruce Wood on Its Wettability and Adhesion with PUR Glue

Recycled recovered wood, for example, from historic buildings, containing biocides, fire retardants or anti-weather paints is an attractive material manufacturing composite wood panels which can be used decoration as well load-bearing walls with a typical patina. This paper investigates the effect of four inorganic preservatives—CuSO4·5H2O, ZnCl2, H3BO3 and (NH4)2SO4—commonly in past, focus on their quality bonding. The milled surfaces Norway spruce (Picea abies Karst L.) were treated 0.5, 1 2% aqueous solutions these preservatives. preservatives was evaluated: (1) by its wettability drops redistilled water, measuring contact angles; (2) shear strength “spruce wood—polyurethane (PUR) Kestopur 1030 glue” interphases according to standard EN 205; (3) microscopic analysis “wood—PUR” interphases. worsened when using maximum 28.2%, but contrary, it improved due other mainly (NH4)2SO4, at 22.9%. In general, glued joints continually decreased higher concentrations all most significant decrease adhesion “wood—PUR”, 19.8% 10.66 MPa 8.55 MPa, caused ZnCl2 treatment both specimens interphase PUR glue. On less 2.5%, 0.5% (NH4)2SO4 applied only one surface two inter-bonded specimens. effects glue partly confirmed analysis.