Thermal modification is an environmentally friendly process that does not utilize chemical agents to enhance the stability and durability of wood. The use of thermally modified wood results in a significantly extended lifespan compared with untreated wood, with minimal maintenance requirements, thereby reducing the carbon footprint. This study examines the impact of varying modification temperatures (160, 180, and 210 °C) on the lignin of spruce wood using the ThermoWood process and following the accelerated aging of thermally modified wood. Wet chemistry methods, including nitrobenzene oxidation (NBO), size exclusion chromatography (SEC), thermogravimetry (TG), differential thermogravimetry (DTG), and Fourier transform infrared spectroscopy (FTIR), were employed to investigate the alterations in lignin. At lower modification temperatures, the predominant reaction is the degradation of lignin, which results in a reduction in the molecular weight and an enhanced yield of NBO (vanillin and vanillic acid) products. At elevated temperatures, condensation and repolymerization reactions become the dominant processes, increasing these traits. The lignin content of aged wood is higher than that of thermally modified wood, which has a lower molecular weight and a lower decomposition temperature. The results demonstrate that lignin isolated from thermally modified wood at the end of its life cycle is a promising feedstock for carbon-based materials and the production of a variety of aromatic monomers, including phenols, aromatic aldehydes and acids, and benzene derivatives.

• Keywords
• infrared spectroscopy, life cycle, lignin, nitrobenzene oxidation, size exclusion chromatography, spruce wood, thermal treatment, thermogravimetry, vanillin,
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• Journal Article MeSH

Thermal modification is an environmentally friendly process in which technological properties of wood are modified using thermal energy without adding chemicals, the result of which is a value-added product. Wood samples of three tropical wood species (meranti, padauk, and merbau) were thermally treated according to the ThermoWood process at various temperatures (160, 180, 210 °C) and changes in isolated lignin were evaluated by nitrobenzene oxidation (NBO), Fourier-transform infrared spectroscopy (FTIR), and size exclusion chromatography (SEC). New data on the lignins of the investigated wood species were obtained, e.g., syringyl to guaiacyl ratio values (S/G) were 1.21, 1.70, and 3.09, and molecular weights were approx. 8600, 4300, and 8300 g·mol-1 for meranti, padauk, and merbau, respectively. Higher temperatures cause a decrease of methoxyls and an increase in C=O groups. Simultaneous degradation and condensation reactions in lignin occur during thermal treatment, the latter prevailing at higher temperatures.

• Keywords
• meranti, merbau, padauk, thermal treatment, wood lignin,
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• Journal Article MeSH

Biodegradable packaging materials represent one possible solution for how to reduce the negative environmental impact of plastics. The main idea of this work was to investigate the possibility of utilizing grape seed lignin for the modification of polyhydroxyalkanoates with the use of its antioxidant capacity in packaging films. For this purpose, polymeric films based on the blend of high crystalline poly(3-hydroxybutyrate) (PHB) and amorphous polyhydroxyalkanoate (PHA) were prepared. PHB/PHA films displayed Young modulus of 240 MPa, tensile strength at a maximum of 6.6 MPa and elongation at break of 95.2%. The physical properties of PHB/PHA films were modified by the addition of 1-10 wt% of grape seeds lignin (GS-L). GS-L lignin showed a high antioxidant capacity: 238 milligrams of Trolox equivalents were equal to one gram of grape seeds lignin. The incorporation of grape seeds lignin into PHB/PHA films positively influenced their gas barrier properties, antioxidant activity and biodegradability. The values of oxygen and carbon dioxide transition rate of PHB/PHA with 1 wt% of GS-L were 7.3 and 36.3 cm3 m-2 24 h 0.1 MPa, respectively. The inhibition percentage of the ABTS radical determined in PHB/PHA/GS-L was in the range of 29.2% to 100% depending on the lignin concentration. The biodegradability test carried out under controlled composting environment for 90 days showed that the PHB/PHA film with 50 w/w% of amorphous PHA reached the degradability degree of 68.8% being about 26.6% higher decomposition than in the case of neat high crystalline PHB film. The degradability degree of PHA films in compost within the tested period reflected the modification of the semi-crystalline character and varied with the incorporated lignin. From the toxicological point of view, the composts obtained after biodegradation of PHA films proved the non-toxicity of PHB/PHA/GS-L materials and its degradation products showed a positive effect on white mustard (Sinapis alba L.) seeds germination.

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• Journal Article MeSH