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This study is concerned with establishing a uniform experimental protocol for the determination of phenolic extractives, which play an essential role in the durability of the wood of selected species included in the field tests. European larch (Larix decidua), Norway spruce (Picea abies), Scots pine (Pinus sylvestris), European oak (Quercus sp.), sweet chestnut (Castanea sativa), and black locust (Robinia pseudoacacia) were included in the study. Extraction yield data were collected for extraction in a Soxhlet apparatus using common polar extraction solvents (ethanol, acetone, methanol, water) and for single static extraction cycles in accelerated solvent extraction (ASE). The suitability of the solvents and the appropriate extraction conditions were evaluated based on the results of gravimetric analysis of hydrophilic extractives, spectrophotometric analysis of total phenols, and chromatographic analysis using high-performance liquid chromatography. Extraction in the ASE system with methanol proved to be a quick and accurate way to prepare samples for chemical analysis of extractives of selected wood species. With the chemical monitoring of targeted phenolic extractives in wood subjected to leaching, we propose a novel protocol suitable also for for measuring the effects of weathering on the natural durability of wood in future studies.

Hydrogels are classified as a three-dimensional network system, capable of retaining large amounts of water while preserving their shape and dimensional stability. Due to their natural origin and biocompatibility with human tissue, cellulose nanofibrils are often considered to be promising candidates for bioactive hydrogels preparation. For such applications, their responsiveness under different types of mechanical load, including multiple cyclic compressions, is of crucial importance. In the present study, cellulose nanofibril-based hydrogels were initiated though a simple alkali neutralization treatment. Structural, rheological and compressive features were investigated as a function of elevated NaOH concentration and physical gelling conditions. It was found that a sufficiently concentrated alkaline solution allows the formation of mechanically robust cellulose nanofibril hydrogels, which can be dried to the state of ultralight material, aerogel, of low density (0.057 g cm$^{−3}$), superior porosity (96.2%), super water absorbant capacity (1200%), and exceptional shear and compressive load resilience with elasticity modulus of 9.3 kPa. These outstanding characteristics can be predominantly attributed to the polymorphic conversion of cellulose I to cellulose II, which results from the mercerization of cellulose nanofibrils and creates a stable and firm hydrogels texture. 水凝胶被分类为三维网络系统, 能够保留大量水, 同时保持其形状和尺寸稳 定性. 由于其天然来源和与人体组织的生物相容性, 纤维素纳米纤维通常被 认为是生物活性水凝胶制备的有前景的候选材料. 对于此类应用, 它们在不 同类型的机械载荷(包括多次循环压缩)下的响应性至关重要. 在本研究中, 通过简单的碱中和处理引发纤维素纳米纤维基水凝胶. 研究了作为提高 NaOH浓度和物理胶凝条件的函数的结构、流变和压缩特性. 发现充分浓缩 的碱性溶液允许形成机械坚固的纤维素纳米纤维水凝胶, 其可干燥至超轻 材料、低密度(0.057 gcm) 气凝胶的状态−3) 具有优异的孔隙率(96.2%)、 超强吸水能力(1200%)以及优异的剪切和压缩载荷弹性, 弹性模量为9.3 kPa. 这些突出的特征主要归因于纤维素I向纤维素II的多晶型转化, 这是纤 维素纳米纤维丝光化的结果, 并产生稳定和牢固的水凝胶纹理.

The main goal of the investigation was to measure and estimate the thermal stability of pinosylvin, pinosylvin monomethyl ether, robinetin, and dihydrorobinetin, i.e., characteristic compounds of wood of Scots pine and black locust, respectively. The pure compounds were analyzed with chromatography before and after they were steam-sterilized and oven-dried. Detailed thermogravimetric analysis was followed to check the thermal decomposition of the stilbenes and flavonoids of wood. The tested phenolic compounds were susceptible to thermal degradation. After the steam-sterilization and oven drying, the amount of investigated phenolic extractives decreased by more than a half. The thermogravimetric analysis showed that stilbenes decompose differently than flavonoids, which can be attributed to the different chemical structures. Twenty minutes of steam sterilization followed by 24 h of oven drying decreased the amount of phenolic compounds in the vials; however, after the applied thermal treatments, the stilbenes and robinetins stayed available in such quantities that they can still provide sufficient bioactivity. Nasl. z nasl. zaslona. Opis vira z dne 28. 9. 2022. Bibliografija: str. 9-12. Abstract.