Tailored waterborne polyurethane aerogels for construction: Role of polyol molecular weight and nanoclay additive

The development of sustainable insulation materials requires advanced polymers with improved fire resistance, stability, and moisture control. In this work, waterborne polyurethane (WPU) aerogels were synthesized using polyethylene glycol (PEG) with molecular weights ranging from 600 to 4000 g mol -1 to investigate the influence of polyol size on aerogel performance. The materials were characterized in terms of physical stability, flame retardancy, and hydrophilicity. Aerogels containing PEG 4000 g mol -1 were excluded due to polymerization instability, while PEG 3350 g mol -1 yielded the most stable structures, reducing combustion rates from 1.60 to 0.35 mm s -1 and preventing shrinkage over time. However, increased hydrophilicity at higher PEG molecular weight raised concerns for outdoor use. To overcome this, nanoclay (0.5–4 wt.%) was incorporated, which significantly enhanced hydrophobicity without impairing flame-retardant behavior, as confirmed by contact angle measurements. Overall, the combined use of PEG 3350 and nanoclay enabled the design of WPU aerogels with long-term stability, high flame resistance, and tunable moisture resistance. These findings highlight the potential of PEG–nanoclay aerogels as multifunctional and scalable insulation materials for both indoor and outdoor building applications. • PEG molecular weight tunes aerogel porosity and mechanical performance • WBPU3350 aerogels improve flame resistance and thermal insulation efficiency • Nanoclay additive increases hydrophobicity without reducing flame-retardant behavior • PEG–nanoclay aerogels enable versatile indoor and outdoor insulation uses