Plant-Fiber and Wood-Based Functional Materials

Plant-fibers are attractive compared to synthetic fibers, since they exhibit beneficial properties like low cost, good specific mechanical properties, and low energy consumption during production. Relevant plant fibers are categorized, and important processes (i.e., retting) and properties such as fiber structure and chemistry, aspect ratio, microfibril angle, fiber damages, fiber surface energy, and mechanical performance are shown. When it comes to plant fiber materials and composites, issues such as filler effectiveness, rule of mixtures, critical fiber length, interfacial compatibility and its modification, and material selection criteria are presented. The most important manufacturing technologies for bio-based composites covered in this chapter include pultrusion, filament winding, hand lay-up, compression molding, resin transfer molding, injection molding and extrusion, and non-wovens. Various applications of plant fiber composite materials are reviewed as well. In the future, design for disassembly, or single-component materials, may play a more prominent role. Moving from the plant fiber level to higher resolutions, nanocellulose is today considered as crucial for novel added-value in biomedical, packaging, and composite applications. Cellulose as a bio-based and renewable material can be extracted from wood, algae, or is produced by bacteria. As the most abundant polymer on earth, cellulose can be processed at several length scales, making it suitable and versatile for many applications that require high mechanical properties at high biocompatibility. An overview is given on different nanocellulose types and their properties, functionalization, and their various processing techniques depending on the final application. Finally, the potential of wood as a platform for novel multifunctional materials is shown, highlighting new developments for wood functionalization and modification. Exemplarily, we show the possibility of transforming wood into mechanically high-performing materials or to utilize wood-based materials for filtration and energy applications. This illustrates that wood-based functional materials are at the forefront in green materials design, which is in line with the goal of transforming society toward sustainability.