Effect of densification on the practical properties of chemical and thermal modified poplar wood

For investigation on the effect of densification on the physical and mechanical properties of the chemically and thermally modified poplar wood (Populus deltoides), thermal modification at 170°C, chemical modification with glutaraldehyde, and compression at three levels of 10, 25, and 40% at the hot pressing time of 2h were carried out. With increasing compression ratio from 25 to 40%, the density of thermally and chemically modified samples increased by 13% and 8%, respectively. Spring back and moisture absorption of the thermally modified/compressed samples was more than chemically modified/compressed ones. Water absorption and thickness swelling for 10% compression ratio were more than the chemical and thermal control samples but significantly decreased with increasing compression ratio. The mechanical properties of both thermally and chemically modified samples were improved with increasing compression ratio. From 25 to 40% compression, improvement of bending modulus for both modified samples were more than 10 to 25%, which was more significant for the thermally modified samples. Bending strength was also improved with increasing compression ratio, but the intensity of improvement decreased by 40% compression. Increasing of compression ratio also led to a significant improvement of the compression strength parallel to grain and hardness, which was more obvious for glutaraldehyde modified specimens than the thermally modified ones.