Moisture content distribution of densified wood and the impact of various heat post-treatments on Brinell hardness and set recovery

This research focused on the moisture content distribution of densified poplar (Populus Nigra L.) prior to a post-treatment and the impact of various heat post-treatments (200°C|3h, 180°C|10h and 180°C|7h) on the Brinell Hardness and set recovery on densified wood. Therefore, lamellas with an average density of 383 kg/m 3 and length of 500 mm (longitudinal) x 100 mm (width) x 10 mm (thickness) without specific orientation were densified in the thickness direction with a targeted density of approximately 1040 kg/m 3. The results of the moisture content distribution of the densified samples prior to the post-treatments showed a heterogeneous moisture content distribution (from 7% to 10.5%) right after the hot pressing. In order to reduce the local swelling during the post-treatment, additional pre-drying is needed. In addition, the posttreatment at 200°C for 3 h allowed to reach the best compromise, significantly lowering the set recovery on the densified samples below 10% whilst not impacting statistically the Brinell hardness (50 N/mm²) compared to the not posttreated samples (54.4 N/mm²).