In order to reduce the dependency of resin synthesis on petroleum resources, vanillyl alcohol which is a renewable material that can be produced from lignin has been used to synthesize bioepoxy resin. Although it has been widely reported that the curing reaction and properties of the cured epoxies can be greatly affected by the molecular structure of the curing agents, the exact influence remains unknown for bioepoxies. In this study, four aliphatic amines with different molecular structures and amine functionalities, namely triethylenetetramine (TETA), Tris(2-aminoethyl)amine (TREN), diethylenetriamine (DETA), and ethylenediamine (EDA), were used to cure the synthesized vanillyl alcohol–based bioepoxy resin (VE). The curing reaction of VE and the physicochemical properties, especially the thermomechanical performance of the cured bioepoxies with different amine functionalities, were systematically investigated and compared using different characterization methods, such as DSC, ATR–FTIR, TGA, DMA, and tensile testing, etc. Despite a higher curing temperature needed in the VE–TETA resin system, the cured VE–TETA epoxy showed a better chemical resistance, particularly acidic resistance, as well as a lower swelling ratio than the others. The higher thermal decomposition temperature, storage modulus, and relaxation temperature of VE–TETA epoxy indicated its superior thermal stability and thermomechanical properties. Moreover, the tensile strength of VE cured by TETA was 1.4~2.6 times higher than those of other curing systems. In conclusion, TETA was shown to be the optimum epoxy curing agent for vanillyl alcohol–based bioepoxy resin.

In recent years, China is increasingly dependent on imported wood. Afrormosia and Newtonia are some of the imported species with good utilization potential. However, both of them also have problems with poor dimensional stability. In order to make better use of these two types of wood, the influence of heat treatment under air and palm oil conditions on the color, dimensional stability, and hygroscopicity of Afrormosia and Newtonia was investigated. The Afrormosia and Newtonia wood samples were heated in air or palm oil medium for two hours at 160 °C, 180 °C and 200 °C, respectively. Then, the color, weight changes, swelling, moisture absorption and chemical structure were evaluated for each case. As results, the heat treatments with air or palm oil increased the dark color of Newtonia and Afrormosia wood and this increase was proportional to the treatment temperature. The tangential and radial swelling coefficient for air heat treatment of Afrormosia wood at 200 °C were, respectively, reduced by 24.59% and 19.58%, while this reduction for Newtonia was 21.32% and 14.80%. The heat treatment in palm oil further improved the stability and hygroscopicity of the wood, showing that the Afrormosia samples treated by palm oil at 200 °C underwent a decrease of its tangential and radial swelling coefficient, respectively, by 49.34% and 45.88%, whereas the tangential and radial swelling coefficient of Newtonia treated under the same conditions were reduced by 42.85% and 33.63%, respectively. The heat treatments of Afrormosia and Newtonia samples under air at 200 °C diminished the water absorption by 21.67% and 22.12%. The water absorption of Afrormosia and Newtonia heat-treated under palm oil at 200 °C was reduced, respectively, by 39.40% and 37.49%. Moreover, the FTIR analysis showed the decrease of hydroxyl groups in proportion to the wood treatment temperature.

With China's increasing dependence on foreign wood, African wood has gradually become a potential imported species, but its use is seriously affected by problems such as unpleasant odors. In this study, we investigate the effect of heat treatment medium on odor-causing VOCs, decomposition of structural polymers, Modulus of Rupture (MOR) and Modulus of Elasticity (MOE) of hardwood. Samples of “Afrormosia” and “Newtonia” wood were heated under air and palm oil for two hours at 160 °C, 180 °C, and 200 °C, respectively. Then, the nature of the odor of each VOC emitted by the wood before and after heat treatment was identified using the GCMS method. The decomposition of hemicelluloses, cellulose and lignin in wood samples was examined using a ThermoGravimetric Analyzer coupled to Fourier Transform InfraRed spectrometry (TGA-FTIR). The 3-point bending test was used to evaluate MOR and MOE. The results indicate that the main VOCs responsible for unpleasant smells are acetic acid and hexanal; the reduction in hexanal emissions after heat treatment is mainly due to the treatment temperature, while the reduction in acetic acid emissions depends on the heat treatment medium and is due to the chemical interactions between palm oil and acetic acid; thus, the heat treatment under palm oil reduces the percentage area of VOCs with unpleasant odors in Afrormosia and Newtonia wood better than the heat treatment under air. Based on TGA-3D FTIR analysis and mechanical results, the reduction in MOR is greater in heat treatment under air because the said treatment induces a greater loss of woody matter, which was characterized by higher H₂O and CO emissions during heat treatment of wood under palm oil than during heat treatment of wood under air. On the other hand, palm oil more than air, promotes lignin deacetylation, which is characterized by the fact that the 1050 cm⁻¹ wavelength peak was far higher in samples treated with palm oil than in those treated under air; and this might explain why heat treatment under palm oil reduces MOE more than heat treatment under air.

To evaluate the influence of ultrasound-assisted extraction (UAE) on the physicochemical characteristics of wood, UAE and Soxhlet extraction (SE) were used to treat Eucalyptus. In UAE, ultrasound with a frequency of 40 kHz and an intensity of 360 W was performed at 60 °C for 30 min. Comparison of UAE samples with Soxhlet-extracted and untreated samples indicated that both the extraction and cavitation effects of ultrasound played a significant role in the efficient alteration of wood characteristics. Identification of extractives by gas chromatography-mass spectrometry (GC/MS) suggested the presence of more low- and high-volatility components in UAE, whereas SE mainly consisted of moderate-volatility components. In thermogravimetry (TG) analysis, UAE samples obtained the highest maximum mass-loss rate (-52.1%/min) at the lowest temperature (378.4 °C). Volatile profiles obtained by thermogravimetry-infrared spectroscopy (TG-FTIR) indicated that CO and CH4 increased, whereas CO2 and formic acid decreased during pyrolysis after UAE. The release of CO and methanol components was mainly influenced by extraction; however, the emission of CO2, CH4, and formic acid responded more strongly to the effects of ultrasound. Scanning electron microscopy (SEM) images revealed that the fracture of pit membranes and small protuberances on the surface of the residues reflected the effects of ultrasound.

The objective of this work was to study the influence of palm oil on the VOCs emitted during the heat treatment of Afromosia (Pericopsis Elata Van Meeuwen) and Newtonia (Newtonia paucijuga Harms) wood by comparing to the VOCs emitted during the heat treatment under air. Two batches of Afrormosia and Newtonia wood samples were heated under air and palm oil at temperatures of 160 °C, 180 °C, and 200 °C for 2 h. Then, the VOCs were collected by Solid Phase Micro Extraction (SPME) and measured using a Gas Chromatograph and Mass Spectrometer (GC-MS). The results showed that the temperature, the wood species, and the treatment medium have a great influence on the categories and percentages of VOCs emitted. In the air heat treatment, ethers were the most emitted VOCs from Afrormosia and Newtonia when these woods were thermally treated at 160 °C. Newtonia treated under air at 180 °C emitted more esters, while Afrormosia continued to emit more ethers under the same conditions. Moreover, Afrormosia and Newtonia treated at 200 °C emitted more ketones and aldehydes, respectively. Regarding the heat treatment of Afrormosia and Newtonia wood under palm oil, a similarity of the VOCs emitted from Newtonia with those emitted from Afrormosia under the same conditions was observed. Furthermore, palm oil was the main factor conditioning the nature of the VOCs emitted during the heat treatment. In general, for the treatment of Afrormoshia wood with palm oil, the VOCs emitted, such as alcohols, alkanes, and ethers, decreased with the treatment temperature. Ethers and ketones increased with the processing temperature. At 160 °C and 180 °C, the percentage of aldehydes was highest, while, at 200 °C, the percentage of esters was highest. Similarly, for Newtonia treated under palm oil, adehydes, ethers, and alcohols were the most abundant VOCs emitted at 160 °C. However, their percentages decreased with the increase in the treatment temperature; on the contrary, esters and ketones were weakly emitted at 160 °C and became abundant with the increase in temperature. Additionally, the ethers formed during the heat treatment of Afrormosia and Newtonia wood treated under air carry acetyl groups, while those formed during the treatment of the said wood under palm oil carry hydroxyl groups.