Mechanical Properties and Dimensional Stability of Poplar Wood Modified by Pre-Compression and Post-Vacuum-Thermo Treatments

Abstract

Fast-growing poplar wood has the bottleneck problems of inferior mechanical strength and poor dimensional stability. In this study, the wood was modified by combined treatments of pre-compression and post-vacuum-thermo modification to improve its mechanical strength and dimensional stability, simultaneously; in addition, the variation law of mechanical properties of the wood with compression ratio as well as the improvement effect of dimensional stability of the treated wood were mainly studied. The results show that the optimal temperature and time of the vacuum-thermo modification were 190 °C and 10 h, respectively. Under these conditions, the structure of pre-compressed and post-vacuum-thermally modified wood (CT wood) is gradually densified with the increase in the compression ratio, which results in the continuous enhancement of mechanical properties. Meanwhile, the anti-swelling efficiency (ASE) of the CT wood after water absorption is correspondingly better than that of the compressed wood before thermal modification, indicating that the dimensional stability of compressed wood was improved by the thermal modification. When the compression ratio was 70%, the modulus of rupture (MOR) and impact toughness of CT wood was 176 MPa and 63 KJ/m2, which was 125% and 59% higher than that of untreated wood, respectively. The ASE was also 26% higher than that of the wood with sole compression. Therefore, this method improves the mechanical strength and dimensional stability of wood simultaneously, and it provides a scientific basis for optimization of the reinforcing modification process of fast-growing wood.

Mobile technology of thermal modification of wood

“…In the study [14], wood was modified by a combined pre-compression treatment and post-vacuum thermal modification to simultaneously improve its mechanical strength and dimensional stability. The law of changes in the mechanical properties of wood with the degree of compression was investigated, as well as the effect of improving the dimensional stability of wood treated in this way.…”

Cell Wall Modification Based on Combination Reagents to Improve Dimensional Stability of Wood with High Efficiency

“…The wood obtained by using a 70% compression ratio and heat treatment at 190 °C showed 26% higher dimensional stability than compressed wood alone. 7 Compared with physical methods, chemical modification 10−12 is a more permanent and effective strategy to improve dimensional stability. On the one hand, the amount of hydroxyl groups in the wood cell wall would be reduced by graft modification.…”

“…Therefore, cell wall modification is the critical factor in improving wood dimensional stability. Generally, physical methods − are preferred in industry due to cost advantage. In physical modification, heat treatment and wax impregnation are reported to reduce the maximum swelling of the wood by 31 and 29%, respectively.…”

Preparation of Photochromic Wood Films Comprising Spiropyran-Based Wood Cellulose Scaffold Realized through Grafting and Densification

“…Thus, densified wood can replace hardwood as well as other precious wood species. After compression densification treatment, the wood undergoes significant changes in organization at the cellular level and in overall physical and mechanical properties [39][40][41][42]. Results have shown that the strength and toughness of compressed wood pretreated by delignification are considerably higher than those of natural wood [43], and the specific strength is even superior to that of some metals and alloys [44,45].…”