Pressure-impregnation technique for wood chips

Abstract

In this paper, the pressure impregnation of wood chips is analyzed and a pressure-impregnation method is suggested, whereby the chips are impregnated at high pressures without causing the wood to collapse. This can be done by increasing the pressure slowly so that the pressure difference between the edge of the chip and the centre of the chip never exceeds the compression strength of the wood. To test the efficiency of the suggested method, penetration of copper sulphate into dry Norway spruce wood blocks was studied with a colour reagent for copper and with SEMEDXA. High pressures (1-10.5MPa), which were reached by increasing gradually the pressure (0.5-2.3 MPa/min), were tested in combination with short impregnation times (3-15 min). The experiments showed that the penetration was more thorough at a higher pressure than at ordinary pressure (1 MPa). After the impregnation, no collapsed wood cells could be observed.