Vacuum-induced lyophilization for ultra-light PVA foams with enhanced crystallinity and functional properties

Key Words:CLAY AEROGEL COMPOSITES; THERMAL-CONDUCTIVITY; CELL-SIZE; DENSITY

Abstract:Lightweight polymer foams have found extensive applications across diverse fields. However, integrating ultralight property with high robustness is still a huge challenge. In this study, a vacuum-induced cryogenic crystallization and lyophilization strategy was introduced to fabricate ultra-light polyvinyl alcohol (PVA) foams featuring exceptional properties. Initially, a PVA solution was air-emulsified by mechanical stirring and then gelatinized through a cyclic freeze-thaw process. The PVA hydrogel, uniform bubbles, was subjected to vacuum at room temperature, causing bubble expansion and stretching of the PVA molecular chains during rapid depressurization. This process enhanced PVA crystallization while expelling ice crystals formed by vacuuminduced water freezing. The resulting high-porosity structure was stabilized, yielding PVA foams with an ultra-light density as low as 4.3 mg/cm3 and a Young's modulus reaching 347.28 kPa, a porosity of 99.65 %, and low thermal conductivity of 0.026 W/(m & sdot;K). Furthermore, solution foaming facilitated the incorporation of diverse functional fillers (e.g., magnetic nanoparticles, conductive materials, and flame retardants) into the PVA foams. Notably, the composite PVA foam containing 50 wt% carboxylated nitrile latex (XNBRL) exhibited a coldstorage capacity of up to 319.2 J/g, suggesting its potential for cold-chain applications. This study proposed a novel and efficient method for developing ultra-light, high-performance foam materials.

Volume:515

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Translation or Not:no