Merging flexibility with superinsulation: Machinable, nanofibrous pullulan-silica aerogel composites
Freeze-dried nanofibrous scaffolds are flexible, but typically have high thermal conductivities. Conversely, silica aerogel has an ultra-low thermal conductivity, but is brittle. Here, the impregnation of pullulan/PVA nanofiber scaffolds with hydrophobic silica aerogel decreased the thermal conducti...
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doaj-04285b955aed4a1d98a22a0fb092a2f52020-11-25T01:17:09ZengElsevierMaterials & Design0264-12752018-12-01160294302Merging flexibility with superinsulation: Machinable, nanofibrous pullulan-silica aerogel compositesShanyu Zhao0Olivier Emery1Anja Wohlhauser2Matthias M. Koebel3Christian Adlhart4Wim J. Malfait5Laboratory for Building Energy Materials and Components, Empa, Überlandstrasse 129, 8600 Dübendorf, Switzerland; Corresponding authors.Laboratory for Building Energy Materials and Components, Empa, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandInstitute of Chemistry and Biotechnology, Zurich University of Applied Sciences ZHAW, Einsiedlerstrasse 31, CH-8820 Wädenswil, SwitzerlandLaboratory for Building Energy Materials and Components, Empa, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandInstitute of Chemistry and Biotechnology, Zurich University of Applied Sciences ZHAW, Einsiedlerstrasse 31, CH-8820 Wädenswil, SwitzerlandLaboratory for Building Energy Materials and Components, Empa, Überlandstrasse 129, 8600 Dübendorf, Switzerland; Corresponding authors.Freeze-dried nanofibrous scaffolds are flexible, but typically have high thermal conductivities. Conversely, silica aerogel has an ultra-low thermal conductivity, but is brittle. Here, the impregnation of pullulan/PVA nanofiber scaffolds with hydrophobic silica aerogel decreased the thermal conductivity from 31.4 to 17.7 mW/(m·K). The compatibility between the silylated nanofibers and the silica aerogel promotes the overgrowth of silica particles onto the fiber surfaces and the fiber incorporation. The composites display improved compressive and tensile properties compared to the neat pullulan scaffold and silica aerogel. The composite's E-modulus is 234 kPa compared to 4 kPa for the pullulan scaffold and 102 kPa for the silica aerogel. The composite's tensile strength is five times higher than that of the silica aerogel. Because of its reduced brittleness, the pullulan-silica aerogel composites can be shaped using a sharp blade. The composites can sustain uniaxial compression up to 80% strain, but the decompressed composites display two times higher densities because the strain is partially irreversible. This densification reduces thermal conductivity to 16.3 mW/(m·K) and increases final compressive strength by a factor of seven. Both the as prepared and densified composites demonstrate unique material properties in terms of thermal conductivity, mechanical strength and machinability. Keywords: Nanocomposite, Polysaccharide, Nanofibers, Hybrid aerogels, Densificationhttp://www.sciencedirect.com/science/article/pii/S0264127518307044 |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Shanyu Zhao Olivier Emery Anja Wohlhauser Matthias M. Koebel Christian Adlhart Wim J. Malfait |
spellingShingle |
Shanyu Zhao Olivier Emery Anja Wohlhauser Matthias M. Koebel Christian Adlhart Wim J. Malfait Merging flexibility with superinsulation: Machinable, nanofibrous pullulan-silica aerogel composites Materials & Design |
author_facet |
Shanyu Zhao Olivier Emery Anja Wohlhauser Matthias M. Koebel Christian Adlhart Wim J. Malfait |
author_sort |
Shanyu Zhao |
title |
Merging flexibility with superinsulation: Machinable, nanofibrous pullulan-silica aerogel composites |
title_short |
Merging flexibility with superinsulation: Machinable, nanofibrous pullulan-silica aerogel composites |
title_full |
Merging flexibility with superinsulation: Machinable, nanofibrous pullulan-silica aerogel composites |
title_fullStr |
Merging flexibility with superinsulation: Machinable, nanofibrous pullulan-silica aerogel composites |
title_full_unstemmed |
Merging flexibility with superinsulation: Machinable, nanofibrous pullulan-silica aerogel composites |
title_sort |
merging flexibility with superinsulation: machinable, nanofibrous pullulan-silica aerogel composites |
publisher |
Elsevier |
series |
Materials & Design |
issn |
0264-1275 |
publishDate |
2018-12-01 |
description |
Freeze-dried nanofibrous scaffolds are flexible, but typically have high thermal conductivities. Conversely, silica aerogel has an ultra-low thermal conductivity, but is brittle. Here, the impregnation of pullulan/PVA nanofiber scaffolds with hydrophobic silica aerogel decreased the thermal conductivity from 31.4 to 17.7 mW/(m·K). The compatibility between the silylated nanofibers and the silica aerogel promotes the overgrowth of silica particles onto the fiber surfaces and the fiber incorporation. The composites display improved compressive and tensile properties compared to the neat pullulan scaffold and silica aerogel. The composite's E-modulus is 234 kPa compared to 4 kPa for the pullulan scaffold and 102 kPa for the silica aerogel. The composite's tensile strength is five times higher than that of the silica aerogel. Because of its reduced brittleness, the pullulan-silica aerogel composites can be shaped using a sharp blade. The composites can sustain uniaxial compression up to 80% strain, but the decompressed composites display two times higher densities because the strain is partially irreversible. This densification reduces thermal conductivity to 16.3 mW/(m·K) and increases final compressive strength by a factor of seven. Both the as prepared and densified composites demonstrate unique material properties in terms of thermal conductivity, mechanical strength and machinability. Keywords: Nanocomposite, Polysaccharide, Nanofibers, Hybrid aerogels, Densification |
url |
http://www.sciencedirect.com/science/article/pii/S0264127518307044 |
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