EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

The demand for sustainable high-performance materials is constantly growing. Biological materials such as wood demonstrate a sophisticated composite design by hierarchical structuring based on various building blocks. For example, supramolecular structuring of β-D-Glucose results in strong and stiff semi-crystalline cellulose fibrils, which are embedded in soft matrix polymers. In bottom-up approaches, wood is disassembled to cellulose nanocrystals and cellulose nanofibrils for application as reinforcement in synthetic nanocomposites. Yet, it remains challenging to achieve the structural intricacy of biological materials. Structure-retaining delignification of wood has attracted interest as a starting point for composite design over the last years (1). This top-down approach preserves the high-strength cellulosic scaffold of wood by retaining its fiber alignment and directionality. By combining this scaffold with polymer matrices, new functionalities such as transparency can be induced. However, the often used combination of delignified wood with fossil-based or thermosetting matrices (2) challenges the targeted sustainability of wood-based composites by insufficient recyclability.

As a sustainable alternative, we present a green and facile method for the production of bio-based and biodegradable cellulose-polymer composites with tunable mechanical properties and gradients. For example, gelatin can be infiltrated into the micro- and mesoporous system of delignified wood by water-based impregnation. Subsequent diffusion-controlled cross-linking of the cellulose-gelatin composite in aqueous solution leads to composites with tunable mechanical strength and stiffness. Moreover, controlled mechanical gradients can be implemented.

1. Frey M et al. Delignified and Densified Cellulose Bulk Materials with Excellent Tensile Properties for Sustainable Engineering. ACS Applied Materials & Interfaces. 2018;10(5):5030-7.
2. Frey M et al. Delignified Wood–Polymer Interpenetrating Composites Exceeding the Rule of Mixtures. ACS Applied Materials & Interfaces. 2019;11(38):35305-11.