Analisi della degradazione di schiume furaniche con tannini condensati e sviluppo di nuove schiume a base di tannino di castagno

Heating and cooling of buildings are major sources of energy consumption and emissions in the European Union, highlighting the need for more efficient insulation. However, petroleum-based foams, such as polyurethane and XPS foams, continue to dominate the market for insulation materials, raising concerns about their sustainability while generating interest in biobased alternatives, such as tannin foams. Tannin foams are versatile materials characterized by low thermal conductivity and good fire resistance. They are produced through the polymerization of plant tannins with various crosslinkers and have shown potential for many additional uses such as acoustic absorbers or as ammonia mitigator in cattle slurry. Tannins are natural polyphenolic compounds found in various plant parts that are traditionally used for leather tanning. Chemically, they can be classified into different groups such as hydrolysable and condensed tannins, with the latter being the preferred type for foam production due to their higher reactivity. However, the limited availability of commercially and locally produced condensed tannin and uncertainties regarding the general end-of-life degradability of tannin foams have been identified as potential challenges to their commercialization in the EU. This PhD project addressed these issues by formulating new foams from locally and commercially produced chestnut tannin (hydrolysable) supplied by the industrial partner of this project, and by examining the degradability of state-of-the-art tannin foams. An initial study investigated the effects of tannin–furanic foams compared to natural tannin extract on the in vitro growth of selected fungi and bacteria. The results showed that at low doses, the tannin–furanic polymer promoted the growth of both fungi and bacteria, while at higher doses, it inhibited fungal growth, exhibiting effects like or slightly weaker than those of the natural tannin extract. Building on these findings, a follow-up study focused on the degradation of these foams in soil, assessing their breakdown and impact on microbial activity through weight loss, FTIR analysis, and enzymatic activity measurements. Over 24 weeks, the foams showed approximately 10% mass loss, additionally indicating microbial breakdown based on changes in foam chemical composition. Enzymatic activities (β-glucosidase and FDA), which are indicators of overall microbial activity, tended to increase, suggesting no adverse—and potentially even positive—effects on soil microbial health at the tested concentration. These findings suggest relatively fast degradability but highlight the importance of concentration in the tested media. However, further long-term and detailed studies are required to ensure their environmental safety before considering their application as ammonia mitigators in agriculture. The studies on novel chestnut tannin foam formulations underscore the potential of hydrolysable tannins in mechanically foamed tannin-based production but also highlight challenges due to their lower reactivity. Chestnut tannin can be combined with various crosslinkers (furfuryl alcohol, hexamine/SPI, glyoxal) in a mechanical foaming approach, but stronger catalysts (e.g., higher temperatures, acids) are required to prevent foam collapse and ensure hardening. Compared with condensed tannins (mimosa, quebracho), foamability is lower, leading to increased material density. Usage of chestnut tannin further reduces compression strength at comparable densities and increased leaching. Despite these trade-offs, fire resistance and thermal conductivity remain largely unaffected by tannin type, being primarily determined by foam density. While higher-density foams may be suitable for other applications, they are undesirable for insulation due to increased thermal conductivity and higher raw material consumption...