Aerogels are lightweight solid materials characterized by their low densities, highly interconnected pores, and large specific surface areas. These properties make them interesting for a wide range of applications, particularly as sustainable high-performance insulation materials. The biodegradability as well as biocompatibility of biopolymer-based aerogels enabling their applications in the food and pharmaceutical, for instance in controlled release systems and drug delivery.
The production of aerogels typically involves three major steps: (1) gelation of an aqueous biopolymer-sol to form a hydrogel network, (2) solvent exchange with an organic solvent, usually ethanol, and (3) supercritical CO2 drying to extract ethanol from the alcogel, converting it into a highly porous aerogel while preserving both the inner pore structure and the macroscopic shape.
Currently, batch-wise solvent exchange and supercritical drying of wet gel particles in packed beds represent a promising approach to meet the economic requirements of scaling up aerogel production. However, the mechanical behavior of the gel particles plays a critical role due to their soft and deformable nature, particularly in the case of biopolymer-based gels. During the process steps, mechanical stresses—caused by the self-weight of the particles and external forces such as fluid flow—can lead to deformation. This deformation affects the macroscopic shape and internal microstructure of the particles, thereby influencing the overall process performance and limiting the operational process window. In particular, during solvent exchange and supercritical drying, the mechanical properties of the particles — such as stiffness and compressive strength — change significantly due to varying solvent concentrations (water, ethanol, or CO₂ content within the pore structure).
This work aims to provide both experimental and theoretical insights into the mechanical behavior of aerogel particles, considering individual gel particles as well as multiple particles in packed beds. For single particles and small scale packed beds, the uniaxial compressive behavior is investigated, with a particular focus on how stiffness increases throughout the process, from hydrogel to aerogel (with changing solvent contents). The next stage of the research includes the study of permeability, compressibility, and pressure drop in packed beds during the process — starting at ambient conditions during solvent exchange and continuing at supercritical conditions using ethanol–CO₂ mixtures.
