Dalbergia odorifera T. Chen is a first-grade state protected plant in China. However, it is difficult to distinguish it from the closely related species Dalbergia tonkinensis Prain, which is less important in economic value, by wood anatomical features. In this study, three potential DNA barcode sequences, namely rpoC1, trnH-psbA and internal transcribed spacer (ITS), were used to differentiate wood of D. odorifera from D. tonkinensis. The average quantities of DNA extracts from twigs, sapwood and heartwood were 16.3, 11.5 and 6.0 ng mg^-1, respectively. The success rates for polymerase chain reaction (PCR) amplification for three loci, namely ITS, trnH-psbA and rpoC1, were 62.5, 100 and 81.25%, respectively. The success rate for bidirectional sequencing of amplified products was 100% for all the three loci. The identification power of the three proposed DNA barcodes has been calculated by the BLAST, tree-based method and the TAXONDNA method. The interspecific differences of the trnH-psbA region were greater than intraspecific variations. Moreover, the identification power of trnH-psbA was higher than that of ITS and rpoC1 regions at the species level. Finally, the trnH-psbA region is proposed as a DNA barcode for wood identification between D. odorifera and D. tonkinensis.

The industrial utilization of natural bamboo has been plagued by cracking that are closely related to the relationship between the moisture content (MC) and drying shrinkage. To reveal the cracking mechanism, three relationships between environmental factors and drying rate (DR), MC and shrinkage strain, strain variation and cracking were investigated during the air seasoning (AS) of the 6-meter-long bamboo in free state. The DR decreased significantly affected by hygroscopicity, and a model considering hygroscopicity and environmental factors was proposed for estimating the DR. Natural bamboos were prone to cracking between 42% and 12% MC. The top cracking was earlier and more than other parts, which is caused by initial lower MC and absence of end diaphragm. There were significant differences in shrinkage strain between different tissues and sites. This work reveals the drying characteristics, the law of strain variation, and cracking mechanism in bamboo AS process, which is vital to the prevention and control of drying defects.

To promote the application of polyamide 6 (PA6) in wood–plastic composites, the negative effects associated with the thermal degradation of plant fibers must be overcome. In this study, waste bamboo fibers were subjected to pyrolysis and ball milling to afford nano bamboo-based biochar (BC), which was subsequently used as reinforcement to prepare PA6/BC nano composites by injection molding. In addition, the processing fluidity, water absorption, mechanical properties, and interface compatibility of PA6/BC composites were discussed. Results revealed that a BC content of less than 30 wt% is beneficial to improve the processing fluidity of the composites. With the increase in the BC content, the density of the PA6/BC composites gradually increased, while the water absorption of the PA6/BC composites gradually decreased, and the maximum decrease was 46%. Compared to that of pure PA6, the mechanical strength of PA6/BC composites was improved by the addition of BC, and the maximum tensile/flexural strength and modulus of PA6/BC composites increased by 41%/72% and 195%/244%, respectively. However, the impact strength decreased by 27%. After immersion treatment, the dimensional stability and mechanical strength of the composites decreased, while toughness improved. At a BC content of less than 40 wt%, BC particles exhibited good dispersibility and wettability in the PA6 matrix, and the rough surface and rich pore structure of BC rendered strong mechanical interlocking effects and good interface compatibility, thereby enhancing the mechanical properties of the composites.

To enhance compression stability and fire retardancy of densified wood, a new modification method i.e., combined nitrogen–phosphorus (NP) fire retardant pre-impregnation with surface thermo-mechanical densification is used to fabricate a certain thickness of functionalized surface layer on poplar. This combined treated wood is investigated via vertical density profile (VDP), and the compression stability is revealed by both soaking test and cone analysis. Results demonstrate that the combined treatment hardened the surface of wood and reformed the interface combination of the NP with the wood cell wall, thus making the surface tissue more close-grained. Fire retardancy was also enhanced; the total heat release and CO generation values decreased by 21.9% and 68.4%, respectively, when compared with that of solely NP-treated wood. Moreover, surface hardness increased by 15.8%, and the recovery of surface hardness and thickness were 56.8% and 77.2% lower than that of simply densified wood. It appears that this NP-involved thermal densification could be considered as an alternative approach to enhance both the compression stability and fire resistance of wood.