Alkaline treatment of poplar wood

The alkaline treatment of milled poplar wood is studied by applying a face-centered three-dimensional experimental design considering temperatures between 50 and 90 degrees C, alkali concentrations between 0.4 and 10.0 g NaOH l(-1) and time between 15 and 60 minutes. Experimental data, i.e. treatment yield, chemical consumption, acid groups content and swelling measured by WRV are fitted to polynomial equations. The relationship between swelling and the chemical state of the wood is analysed. The evolution of swelling reaches maximum levels within the time period. The ionic content proves to be a non-determining factor of wood swelling. For the range of mild treatments, WRV correlates with acetyl groups content confirming our own previous results obtained at low temperature. Although the maximum in swelling can be obtained at any temperature, low and medium levels are more convenient since higher temperature causes important material loss together with higher chemical consumption.