Evaluating efficacy of different UV-stabilizers/absorbers in reducing UV-degradation of lignin

Susceptibility of wood to UV degradation decreases the service life of wood products outdoors. Organic UV absorbers (UVAs) and hindered amine light stabilizers (HALSs), as well as inorganic UVAs, are added to coatings to improve the UV stability of coated-wood products. Although about 85% of UV radiation is absorbed by lignin in the wood, it is unclear which UV stabilizers can minimize lignin degradation. In this study, the photodegradation of softwood organosolv lignin was monitored over 35 days of UV exposure. Changes in lignin properties were assessed using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and phosphorus-31 nuclear magnetic resonance spectroscopy (31P NMR). It was found that the aromatic rings of lignin underwent significant degradation, resulting in increased glass transition temperature and molecular weight of lignin. Subsequently, 18 different additives were mixed with lignin and exposed to UV irradiation. The analysis of samples before and after UV exposure with FTIR revealed that inorganic UVAs (cerium oxide and zinc oxide) and a mixture of organic UVAs and HALSs (T-479/T-292, T-5248, and T-5333) were the most effective additives in reducing lignin degradation. This study can help coating scientists to formulate more durable transparent exterior wood coatings.

COMPREHENSIVE APPROACH TO ENSURE DURABILTY OF EXTERNAL WOODEN STRUCTURES

The article deals with durability of wood, durability of wooden structures and surface modification of wood. We are trying to eliminate the factors causing degradation of wood with the use of photocatalytic materials. Those materials are efficient UV absorbers and they are able to destroy biological aggressors also. The planar particles of titanium oxide TiO2 were chosen for the purpose of our research and applied on a wooden surface. In our case, we used a water solution of TiO2. The main goal of our work was to study the interaction between planar particles of TiO2 and wood matter. The samples of pine wood (Pinus sylvestris) were monitored for 255 days and subsequently evaluated using an electron microscope. The use of TiO2 was compared with reference material and a reference commercial coating.

The Feasibility of Utilizing Cultured Cordyceps militaris Residues in Cosmetics: Biological Activity Assessment of Their Crude Extracts

Solid-based residues (SBRs) left from harvesting the fruiting bodies of cultured Cordyceps mushrooms are a challenge to sustainability. Therefore, in this study, the SBRs from the cultivation of Cordyceps militaris (C. militaris) via solid-state fermentation (SSF) were employed to prepare crude extracts, with the aim of considering their possible use in cosmetics. The SBRs obtained from cultivation with solid media containing defatted rice bran mixed with barley, white rice, Riceberry rice, and wheat were named SBR-B, SBR-R, SBR-Rb, and SRB-W, respectively. They were extracted with solvents of differing polarity and then evaluated for their total phenolic content (TPC), total flavonoid content (TFC), and total carbohydrate content (TCC). In addition, antioxidant and tyrosinase inhibitory activities, photoprotection, and cytotoxicity were also assessed. The results revealed that the total bioactive contents and biological capacities of crude SBR extracts were significantly influenced by the types of SBR and extraction solvent (p < 0.05). The SBR-B extracted with hot water exhibited the highest antioxidant activity (66.62 ± 2.10, 212.00 ± 3.43, and 101.62 ± 4.42 mg TEAC/g extract) when assayed by DPPH, ABTS, and FRAP methods, respectively, whereas tyrosinase inhibitory activity (51.13 ± 1.11 mg KAE/g extract) with 90.43 ± 1.96% inhibition at 1 mg/mL was excellently achieved by SBR-Rb extracted by 50% (v/v) ethanol. Correlations between bioactive contents in the crude extracts and their biological activities were mostly proven at a strong level (p < 0.01). The capability of the crude extracts to absorb UV over the range of 290–330 nm disclosed their potential roles as natural UV absorbers and boosters. Cytotoxicity analysis using fibroblast cell lines tested with hot water and 50% (v/v) ethanolic SBR extracts demonstrated safe use within a concentration range of 0.001–10 mg/mL. Interestingly, their fibroblast proliferative capacity, indicating anti-aging properties, was highly promoted. The chemical composition analyzed via LC–MS/MS techniques showed that seven phenolic acids and four flavonoids were identified in the crude SBR extracts. Furthermore, the other compounds present included nucleosides, nucleobases, amino acids, sugars, phospholipids, alkaloids, organic acids, vitamins, and peptides. Therefore, it is emphasized that SBRs from C. militaris can be a prospective source for preparing crude extracts employed in cosmetics. Lastly, they could be further utilized as multifunctional ingredients in cosmetics and cosmeceuticals.

Study on Microstructure and Properties of the UV Curing Acrylic Epoxy/SiO2 Nanocomposite Coating

This study is aimed at exploring the effects of SiO2 nanoparticles on the crosslinking and mechanical and thermal properties of UV curing acrylic epoxy coating. The curing polymerization process and thermal and mechanical properties of UV-curable acrylate epoxy system have been evaluated with or without the presence of SiO2 nanoparticles. To fabricate the UV curing acrylic epoxy/SiO2 nanocomposite coating, nano-SiO2 particles (0.5–5 wt.% by weight of resin) were added in the photo-curable system using sonication for 3 h. Various techniques for characterization have been used, such as FESEM (field emission scanning electron microscope), FTIR (Fourier-transform infrared spectroscopy), TGA (thermogravimetry analysis), gel fraction, and swelling degree analyses. FESEM data indicated that at the content of 2.5 wt.%, nanosilica was homogeneously dispersed in the coating procedure. However, once added 5 wt.%, large aggregation portions were found inside the coating matrices. Surprisingly, nano-SiO2 could play dual roles, as both UV absorbers and nanoreinforcers, in this nanocomposite coating. Besides, data from FTIR, gel fraction, and swelling degree analyses confirmed the role of SiO2 nanoparticles as UV absorbers that reduced the conversion performance of acrylate double bonds, thus increased slightly the swelling degree of coating. In addition, incorporation of SiO2 nanoparticles (as nanofillers, at content of 2.5 wt.%) in the polymer matrix enhanced significantly the abrasion resistance and thermal stability of the coating, by 60% (from 98.3 to 158.4 lite/mil) and 9°C (from 348°C to 357°C), respectively.

Material Monitoring of a Composite Dome Pavilion Made by Robotic Coreless Filament Winding

A hemispherical research demonstration pavilion was presented to the public from April to October 2019. It was the first large-scale lightweight dome with a supporting roof structure primarily made of carbon- and glass-fiber-reinforced composites, fabricated by robotic coreless filament winding. We conducted monitoring to ascertain the sturdiness of the fiber composite material of the supporting structure over the course of 130 days. This paper presents the methods and results of on-site monitoring as well as laboratory inspections. The thermal behavior of the pavilion was characterized, the color change of the matrix was quantified, and the inner composition of the coreless wound structures was investigated. This validated the structural design and revealed that the surface temperatures of the carbon fibers do not exceed the guideline values of flat, black façades and that UV absorbers need to be improved for such applications.

An all-sputtered photovoltaic ultraviolet photodetector based on co-doped CuCrO2 and Al-doped ZnO heterojunction

We propose and fabricate a heterojunction between Al-doped ZnO and (Mg, N)-doped CuCrO2 thin films using the sputtering deposition method. These materials possess wide bandgap that makes them transparent in the visible light but excellent UV-absorbers. On the other hand, the high conductivity of these materials, respectively as n-type and p-type transparent conducting oxides, facilitates the charge transport. We show that the p–n junction fabricated from these materials has the potential to act as a high-performance UV photovoltaic photodetector. The proposed structure, demonstrates fast responses in order of sub seconds, photosensitivity of ~ 41,000, responsivity of 1.645 mA/W, and a detectivity of 3.52 × 1012 Jones that are significantly improved in comparison with the Al-doped ZnO photoconductor. This excellent improvement is attributed to the capability of the photovoltaic configuration that creates a built-in voltage and facilitates the charge separation and collection rather than recombination in the photoconductor configuration.