Dimensional stability of wood modified by citric acid using different catalysts

Small wooden samples of fir (Abies alba Mill.) and beech (Fagus sylvatica L.) were chemically modified by citric acid (CA) as non-formaldehyde cross-linking system reagent and cured by convection heating at three different temperature regimes. Two different CA solutions were used, one with NaH2PO2 and the other with NaH2PO4 as a catalyst. The dimensional stability of the modified wood was determined by the anti-swelling efficiency (ASE) using the water soak/oven dry method. Almost equally large improvement of dimensional stability of wood was attained using NaH2PO4 as when NaH2PO2 was applied as a catalyst.