Effect of Citric Acid on the Properties of Sapwood of Pinus sylvestris Submitted to Thermomechanical Treatment

The present study aimed to evaluate the effect of citric acid on the properties of solid pine wood, which were submitted to thermomechanical treatment. A preliminary test was performed in a previous study to evaluate the influence of different temperatures of pressing and concentrations of citric acid on the physical properties of wood. After choosing the best treatments (170 C-degrees and 5% and 10% of citric acid), the effect of these on the chemical properties (SEM, FTIR and pH); on the density profile using an X-ray microtomography and on the resistance to aging through an abrasion test were evaluated. The result of the chemical analysis showed an increase of the presence of ester functional groups, as well as better coverage and higher acidity of the surface. The density profile technique allowed us to observe the formation of peaks of density on the surface where the acid was applied. Lastly, it was also possible to verify an increase in the resistance to abrasions because of the application of citric acid.