Mineralization of Clay/Polymer Aerogels: A Bioinspired Approach to Composite Reinforcement

Johnson, J. E.; Spikowski, Jane; Schiraldi, David A.

doi:10.1021/am9001919

Cited by 51 publications

(45 citation statements)

References 29 publications

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“…The Young’s modulus achieved for the chitin aerogels (9.32–7.07 MPa) significantly improves upon those reported for polymer/clay aerogels29 (with a density of 0.07 g cm −3 and a modulus of 0.23 MPa) and polymer/clay/nanotube aerogels30 (with a density of 0.05 g cm −3 and a modulus of 0.63 MPa). Our chitin aerogels also displayed a higher modulus than microfibrillated cellulose aerogels19c of a similar density range (0.007–0.103 g cm −3 ) with a reported Young’s modulus range of 0.056–5.31 MPa.…”

Section: Resultssupporting

confidence: 62%

Chitin Nanowhisker Aerogels

2013

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Chitin nanowhiskers are structured into mesoporous aerogels by using the same benign process used previously in our group to make cellulose nanowhisker aerogels. The nanowhiskers are sonicated in water to form a hydrogel before solvent-exchange with ethanol and drying under supercritical CO2 (scCO2). Aerogels are prepared with various densities and porosities, relating directly to the initial chitin nanowhisker content. scCO2 drying enables the mesoporous network structure to be retained as well as allowing the gel to retain its initial dimensions. The chitin aerogels have low densities (0.043–0.113 g cm−3), high porosities (up to 97 %), surface areas of up to 261 m2 g−1, and mechanical properties at the high end of other reported values (modulus between 7 and 9.3 MPa). The aerogels were further characterized by using X-ray diffraction, BET analysis, electron microscopy, FTIR, and thermogravimetric analysis. Characterization showed that the rod-like crystalline nature of the nanowhiskers was retained during the aerogel production process, making the aerogel truly an assembled structure of chitin nanocrystals. These aerogels also showed the lowest reported shrinkage during drying to date, with an average shrinkage of only 4 %.

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Section: Resultssupporting

confidence: 62%

Chitin Nanowhisker Aerogels

2013

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“…The line shapes follow the classical foam behavior in which a linear elastic region is followed by a horizontal plateau, and finally a densification region, which is similar to the curve of previously reported aerogels. [7][8][9][10][11][12][13] As noted, after being compressed up to 90%, the majority of the samples did not recover to their original size, even when the NR concentration was increased up to 10 wt %. The neat 2.5 wt % NR aerogel showed a compressive modulus and toughness at 30% strain of 70 and 2 kPa, respectively.…”

Section: Resultsmentioning

confidence: 86%

“…13 As the pristine clay aerogels are fragile and lack an efficient energy dissipation mechanism in their frameworks, the addition of a polymeric component and/or reinforcing fibers is essential for optimizing their structural integrity and creating materials with mechanical properties similar to those of typical foamed polymers. [4][5][6][7][8][9][10][11][12][13] In previous studies, natural rubber (NR)/clay aerogel composites were produced by freeze-drying aqueous suspensions that were prepared using a sulfur-based cure system (conventional vulcanization). 14,15 Although the compressive moduli of conventionally vulcanized NR/clay aerogel composites increased as a function of clay volume fraction, those values were somewhat low (19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) kPa) compared to other aerogels reported to date.…”

Section: Introductionmentioning

confidence: 99%

Solution Cross-Linked Natural Rubber (NR)/Clay Aerogel Composites

et al. 2011

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Aerogels are structural materials with ultralow bulk densities (often less than 0.1 g cm -3 ), which stand out as good candidates for a variety of applications. In the present study, natural rubber (NR)/ clay aerogel composites were produced by freeze-drying of the aqueous aerogel precursor suspensions, followed by solution cross-linking of the aerogel samples in benzene using sulfur monochloride (S 2 Cl 2 ) as a cross-linking agent. The influences of cross-linking conditions, i.e., cross-linker concentration and reaction temperature, as well as polymer loading on the aerogel structure and properties were investigated. 1% (v/v) of S 2 Cl 2 and reaction temperature of -18°C were found to be the optimum conditions for producing a strong and tough rubber composite; the 2.5 wt % NR aerogel, for example, after being cross-linked, exhibited a compressive modulus of 1.8 MPa, 26 times higher than that of the neat control. These favorable mechanical properties are attributed to the high local concentration of rubber and S 2 Cl 2 in the freeze-dried structures, giving rise to the high cross-linking efficiency. Increasing the rubber concentration led to a substantial increase in the mechanical strength, in accord with the changes in microstructure and degree of cross-linking. The swelling capacity of the NR aerogels decreased with either increasing the cross-linker concentration or decreasing the weight fraction of rubber. Cross-linking of the rubber aerogels brought about increased thermal stability, consistent with restricted thermal motion of NR chains.

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“…Such polymer/clay aerogel composites can possess excellent thermal insulation properties [17], and can be modified to be electrically conductive [18], highly absorbant [19], or to exhibit environmentally responsive properties [20]. Further physical modifications which can substantially enhance the physical properties of polymer/clay aerogel composites include biomimetic mineralization [21], incorporation of rigid nanowhiskers [22], and reinforcement with fibers [23]. These aerogels can also be incorporated into traditional, fabric-reinforced composite structures, benefiting from adhesive penetration of both fabric and aerogel to produce materials whose mechanical properties and densities are reminiscent of balsa or cork [24].…”

Section: Introductionmentioning

confidence: 99%

Effects of Fiber Reinforcement on Clay Aerogel Composites

2015

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Novel, low density structures which combine biologically-based fibers with clay aerogels are produced in an environmentally benign manner using water as solvent, and no additional processing chemicals. Three different reinforcing fibers, silk, soy silk, and hemp, are evaluated in combination with poly(vinyl alcohol) matrix polymer combined with montmorillonite clay. The mechanical properties of the aerogels are demonstrated to increase with reinforcing fiber length, in each case limited by a critical fiber length, beyond which mechanical properties decline due to maldistribution of filler, and disruption of the aerogel structure. Rather than the classical model for reinforced composite properties, the chemical compatibility of reinforcing fibers with the polymer/clay matrix dominated mechanical performance, along with the tendencies of the fibers to kink under compression.

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Mineralization of Clay/Polymer Aerogels: A Bioinspired Approach to Composite Reinforcement

Cited by 51 publications

References 29 publications

Chitin Nanowhisker Aerogels

Chitin Nanowhisker Aerogels

Solution Cross-Linked Natural Rubber (NR)/Clay Aerogel Composites

Effects of Fiber Reinforcement on Clay Aerogel Composites

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