Abstract
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.
Highlights
Aerogels were first described by Kistler in 1931 utilizing a novel sol-gel and drying process [1].This family of materials typically exhibit bulk densities ranging from 0.005 to 0.1 g/cm3 [2,3,4], and have attracted a great deal of attention because of their low densities, high specific surface areas, high porosities and low thermal conductivities
Due to its large number of hydroxyl groups resulting in extensive hydrogen bonding, tannic acid (TA) would be expected to serve as a crosslinking agent in Poly(vinyl alcohol) (PVA) aerogels [28,29,33]
PVA aerogels with TA or TA/NaOH were prepared through a simple and environmentally friendly freeze-drying process
Summary
Aerogels were first described by Kistler in 1931 utilizing a novel sol-gel and drying process [1]. Poly(vinyl alcohol) (PVA), as a hydrophilic and water soluble polymer, is an ideal candidate for fabricating polymer aerogels because of its low toxicity, good chemical stability, and favorable mechanical properties [14]. Such PVA aerogels can be prepared using a sustainable, freeze-drying method [15]. Incorporation of flame retardants, such as ammonium polyphosphate, potassium carbonate and silica gel reduced PVA aerogel flammability but at the cost of reducing mechanical properties [22,23]. TA and NaOH were incorporated into the PVA aerogel system to provide flame retardancy and improve mechanical properties. The resultant mechanical properties, morphologies, thermal stabilities, and combustion behaviors were investigated
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
