In sustainable construction and packaging, the development of novel bio-based materials is crucial, driving a re-evaluation of traditional components. Lightweight, biodegradable materials, including xerogels, have great potential in architectural and packaging applications. However, reinforcing these materials to improve their mechanical strength remains a challenge. Alginate is a promising matrix material that may be compatible with inorganic fibrous or particulate materials. In this study, biocomposite xerogel-structured foam materials based on an alginate matrix with expanded perlite reinforcement are improved using certain additives in different weight ratios. The plasticizers used include glycerol and gum arabic, while chitosan was added as an additional reinforcement, and iota carrageenan was added as a stabilizer. The tested specimens, with varying weight ratios of the added components, showed good mechanical behavior that highlights their potential use as packaging and/or architectural materials. The influence of the presence of different components in the composite material specimens on the modulus of elasticity was investigated using SEM images and FTIR analyses of the specimens. The results show that the specimen with the largest improvement in the elastic modulus contained a combination of chitosan and glycerol at a lower percentage (1.96 MPa), and the specimen with the largest improvement in tensile strength was the specimen containing chitosan with no plasticizers (120 kPa), compared to cases where combinations of other materials are present.

Biopolymer-based porous materials are attracting increasing interest as sustainable alternatives to conventional thermal insulation foams; however, achieving low thermal conductivity together with adequate mechanical performance and fire response remains challenging. Building on previous formulation screening, this study investigates alginate-expanded perlite xerogel foams modified with chitosan and glycerol for thermal insulation applications. Foams were prepared via in situ CO₂ foaming and Ca²⁺ crosslinking, followed by mild oven drying. The effects of expanded perlite (9–12%), glycerol (0–10%), and chitosan (0–1%) were systematically investigated. All formulations exhibited low thermal conductivity (0.0467–0.0525 W m⁻¹ K⁻¹) and UL-94 V-0 self-extinguishing behavior. Incorporation of dispersed chitosan significantly enhanced compressive strength, reaching 263 kPa at 10% strain, within the range of commercial polymer foams. Image analysis and SEM showed that chitosan suppressed bubble coalescence, reduced large-pore fractions, and improved particle coverage, yielding structurally coherent matrices. Glycerol primarily acted as a plasticizer, improving the dimensional stability, but contributing less to pore refinement. The developed foams combine competitive thermal insulation performance, self-extinguishing behavior, and mechanical properties suitable for self-supporting insulation applications through a simple, water-based manufacturing route, highlighting their potential as sustainable alternatives to conventional fossil-based insulation materials for building applications.

The 16th-century wall paintings of Monastery Crna Reka in Serbia are visibly deteriorating. Extensive wall degradation causes these frescoes to fall from their original positions and shatter into fragments. To address the proper restoration and conservation procedures, we examine the structure and morphology of the fragments. Micro-Raman spectroscopy and XRF revealed that the blue color on the wall paintings does not originate from blue pigments but results from the layer-by-layer technique of hematite and carbon black pigments by the artist, which, in combination with the mortar, gave a blue color sensation. Cross-sectional profiles and 3D maps obtained by profilometry show the surface morphology of these fragments, and can be consider as guidelines for further understanding of the various aspects of the painting’s creation, monitoring future degradation process, and developing or applying protective coatings for Serbian frescoes.