RESUMEN
Poly(vinyl alcohol) (PVA), tannic acid (TA) and sodium hydroxide (NaOH) were used to prepare low-flammability, mechanically-strong aerogels via an environmentally-friendly freeze-drying method. Because of the strong interaction between TA and PVA through hydrogen bonds, PVA/TA/NaOH aerogels exhibited compressive moduli as high as 12.7 MPa, 20 times that of the control PVA aerogel. The microstructure of the aerogels in this study showed that the addition of NaOH disrupted the typical "card of house" aerogel structure, while the samples with TA showed a stereoscopic uniform structure. The thermal stabilities of aerogels were tested by thermogravimetric analysis, showing both a decrease on the onset of decomposition temperature, and a reduction in decomposition rate after initial char formation. The peak heat release rate and total heat release, as measured by cone calorimetry, dropped by 69% and 54%, respectively, after adding TA and NaOH.
RESUMEN
Biobased gelatins were used to improve the compressive properties and flammability of poly(vinyl alcohol)/montmorillonite (PVA/MMT) aerogels, fabricated using a simple and environmentally friendly freeze-drying method. Because of the excellent compatibility and strong interfacial adhesion between PVA and gelatin, the compressive moduli of aerogels were enhanced dramatically with the incorporation of gelatin. PVA/MMT/porcine-gelatin aerogels exhibit compressive modulus values as much as 12.4 MPa, nearly 300% that of the control PVA/MMT aerogel. The microstructure of the PVA/MMT/gelatin aerogels shows a three-dimensional co-continuous network. Combustion testing demonstrated that with the addition of gelatin, the self-extinguishing time of the aerogel was cut by half and the limiting-oxygen-index values increased to 28.5%. The peak heat-release rate, obtained from cone calorimetry, also decreased with the incorporation of gelatin. Thermogravimetric analysis demonstrated that the gelatins slowed the sharp decomposition of the PVA matrix polymer and increased the thermal stability of the aerogels at the major decomposition stage of the composite aerogels. These results indicate that as a green, biobased material, gelatin could simultaneously improve the mechanical properties and the properties of flame retardancy.
