The uncertainties of the environment and the emission levels of nonrenewable resources have compelled humanity to develop sustainable energy savers and sustainable materials. One of the most abundant and versatile bio-based structural materials is wood. Wood has several promising advantages, including high toughness, low thermal conductivity, low density, high Young's modulus, biodegradability, and non-toxicity. Furthermore, while wood has many ecological and structural advantages, it does not meet optical transparency requirements. Transparent wood is ideal for use in various industries, including electronics, packaging, automotive, and construction, due to its high transparency, haze, and environmental friendliness. As a necessary consequence, current research on developing fine wood is summarized in this review. This review begins with an explanation of the history of fine wood. The concept and various synthesis strategies, such as delignification, refractive index measurement methods, and transparent lumber polymerization, are discussed. Approaches and techniques for the characterization of transparent wood are outlined, including microscopic, Fourier transform infrared (FTIR), and X-ray diffraction (XRD) analysis. Furthermore, the characterization, physical properties, mechanical properties, optical properties, and thermal conductivity of transparent wood are emphasized. Eventually, a brief overview of the various applications of fine wood is presented. The present review summarized the first necessary actions toward future transparent wood applications.
The textile industries need an alternative to cotton since its supply is unable to keep up with the growing global demand. The ramie (Boehmeria nivea (L.) Gaudich) fiber has a lot of potential as a renewable raw material but has low fire-resistance, which should be improved. In this work, the objectives were to investigate the characteristics of lignin derived from black liquor of kraft pulping, as well as the properties of the developed lignin-based non-isocyanate-polyurethane (L-NIPU), and to analyze ramie fiber before and after impregnation with L-NIPU. Two different formulations of L-NIPU were impregnated into ramie fiber for 30, 60, and 90 min at 25 × 2 °C under 50 kPa. The calculation of the Weight Percent Gain (WPG), Fourier Transform Infrared Spectrometer (FTIR), Rotational Rheometer, Dynamic Mechanical Analyzer (DMA), Pyrolysis Gas Chromatography Mass Spectrometer (Py-GCMS), Universal Testing Machine (UTM), and hydrolysis test were used to evaluate the properties of ramie fibers. The result showed that ramie fiber impregnated with L-NIPU produced higher mechanical property values and WPG than non-impregnated ramie fiber. There is a tendency that the longer impregnation time results in better WPG values, FTIR intensity of the urethane group, thermomechanical properties, crystallinity, and mechanical properties of ramie fiber. However, the use of DMC and HMT cannot replace the role of isocyanates in the synthesis of L-NIPU because it produces lower heat resistance than ramie impregnated using pMDI. Based on the results obtained, the impregnation of ramie fiber with L-NIPU represents a promising approach to increase its wider industrial application as a functional material.
The rising environmental concerns and the growing demand for renewable materials have surged across various industries. In this context, lignin, being a plentiful natural aromatic compound that possesses advantageous functional groups suitable for utilization in biocomposite systems, has gained notable attention as a promising and sustainable alternative to fossil-derived materials. It can be obtained from lignocellulosic biomass through extraction via various techniques, which may cause variability in its thermal, mechanical, and physical properties. Due to its excellent biocompatibility, eco-friendliness, and low toxicity, lignin has been extensively researched for the development of high-value materials including lignin-based biocomposites. Its aromatic properties also allow it to successfully substitute phenol in the production of phenolic resin adhesives, resulting in decreased formaldehyde emission. This review investigated and evaluated the role of lignin as a green filler in lignin-based lignocellulosic composites, aimed at enhancing their fire retardancy and decreasing formaldehyde emission. In addition, relevant composite properties, such as thermal properties, were investigated in this study. Markedly, technical challenges, including compatibility with other matrix polymers that are influenced by limited reactivity, remain. Some impurities in lignin and various sources of lignin also affect the performance of composites. While lignin utilization can address certain environmental issues, its large-scale use is limited by both process costs and market factors. Therefore, the exact mechanism by which lignin enhances flame retardancy, reduces formaldehyde emissions, and improves the long-term durability of lignocellulosic composites under various environmental conditions remains unclear and requires thorough investigation. Life cycle analysis and techno-economic analysis of lignin-based composites may contribute to understanding the overall influence of systems not only at the laboratory scale but also at a larger industrial scale.