Improvement in dispersion and ionic conductivity of polyether/freeze-dried clay composites using supercritical carbon dioxide as treatment medium

Kitajima, Shunsuke; Tominaga, Yoichi

doi:10.1007/s11581-012-0731-y

Cited by 5 publications

(5 citation statements)

References 24 publications

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“…Freeze-drying (FD) has been widely used to prepare highly porous materials, such as carbon and polymer aerogels. − In a high-rate freezing process, the solute molecules in the solutions do not have enough diffusion time to form large aggregates, giving rise to micron- or even nanometer-sized aggregates separated by tiny ice crystals . The aggregates could be in sheet or even fiber forms depending on the templating effect of the ice crystals.…”

Section: Introductionmentioning

confidence: 99%

Sheet-Like Lignin Particles as Multifunctional Fillers in Polypropylene

Chen

Liu

Shahabadi

et al. 2016

ACS Sustainable Chem. Eng.

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Lignin is an attractive renewable reinforcing agent for polyolefins and also a promising low-cost antioxidant for polymers. It, however, exhibits poor compatibility with nonpolar polymers. In this work, alkali lignin was freeze-dried to achieve sheet-like morphology and then incorporated into polypropylene (PP) by melt compounding. Owing to the significantly increased interfacial area and improved dispersion, with the addition of only 2 wt % freeze-dried lignin, the PP/ lignin composites show much enhanced tensile mechanical properties, including a moderately improved Young's modulus and almost doubled elongation at break compared with those of neat PP. The enhancements brought by the sheet-like lignin are far more impressive than those achieved with the same amount of as-received lignin. The composites with the freezedried lignin also have rough fractured surfaces with fiber pull-out near the interface, revealing a significant toughening effect of the lignin, which can be attributed to the crazing near the interface, and enhanced relaxation in PP-lignin interphase as evidenced by the reduced T g . Furthermore, the large interfacial area also drastically improves the antioxidant effect of lignin, greatly slowing the UV-induced and thermo-oxidative degradation of PP. After 2 weeks of intense UV exposure, neat PP becomes very brittle with its yield strain reduced to about 37% of its original value, whereas the yield strain of the composite with 2 wt % sheet-like lignin is almost unchanged, demonstrating the excellent free-radical scavenger effect of the lignin.

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Section: Introductionmentioning

confidence: 99%

Sheet-Like Lignin Particles as Multifunctional Fillers in Polypropylene

Chen

Liu

Shahabadi

et al. 2016

ACS Sustainable Chem. Eng.

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“…In previous studies, we reported that the treatment with supercritical CO 2 is an effective method to improve the conductivity of polyether-clay composites. 16,17 As observed in Fig. 7, the s DC and s ID values rapidly decrease from the initial state as the CO 2 treatment time is less than 10 hours.…”

Section: Electric Measurements Of P(eo/em)-sa Under Co 2 Treatmentsmentioning

confidence: 54%

“…[13][14][15] In previous studies, we found that supercritical carbon dioxide as a treatment medium can be effective in enhancing further the conductivity of polyether-clay composites. 16,17 The enhancement in the conductivity is attributed to the improvement in the dispersion state of clay, which increases the number of mobile cations dissociated from the negatively-charged layers. The BES spectra provide crucial information on molecular dynamics and ionic conduction behavior of the investigated materials.…”

Section: Introductionmentioning

confidence: 99%

Dielectric relaxations and conduction mechanisms in polyether–clay composite polymer electrolytes under high carbon dioxide pressure

Kitajima

Bertasi

Vezzù

et al. 2013

Phys. Chem. Chem. Phys.

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The composite material P(EO/EM)-Sa consisting of synthetic saponite (Sa) dispersed in poly[ethylene oxide-co-2-(2-methoxyethoxy)ethyl glycidyl ether] (P(EO/EM)) is studied by "in situ" measurements using broadband electrical spectroscopy (BES) under pressurized CO2 to characterize the dynamic behavior of conductivity and the dielectric relaxations of the ion host polymer matrix. It is revealed that there are three dielectric relaxation processes associated with: (I) the dipolar motions in the short oxyethylene side chains of P(EO/EM) (β); and (II) the segmental motion of the main chains comprising the polyether components (αfast, αslow). αslow is attributed to the slow α-relaxation of P(EO/EM) macromolecules, which is hindered by the strong coordination interactions with the ions. Two conduction processes are observed, σDC and σID, which are attributed, respectively, to the bulk conductivity and the interdomain conductivity. The temperature dependence of conductivity and relaxation processes reveals that αfast and αslow are strongly correlated with σDC and σID. The "in situ" BES measurements under pressurized CO2 indicate a fast decrease in σDC at the initial CO2 treatment time resulting from the decrease in the concentration of polyether-M(n+) complexes, which is driven by the CO2 permeation. The relaxation frequency (fR) of αslow at the initial CO2 treatment time increases and shows a steep rise with time with the same behavior of the αfast mode. It is demonstrated that the interactions between polyether chains of P(EO/EM) and cations in the polymer electrolyte layers embedded in Sa are probably weakened by the low permittivity of CO2 (ε = 1.08). Thus, the formation of ion pairs in the polymer electrolyte domains of P(EO/EM)-Sa occurs, with a corresponding reduction in the concentration of ion carriers.

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“…13,24 Freeze-drying (FD) method has been widely used to prepare highly porous materials, such as carbon and polymer aerogels. [25][26][27][28] In the FD step, the sublimation of the ice crystals leads to a highly porous material with high specic surface area (SSA). Therefore, alkali lignin with three-dimensionally branched macromolecular structure aer FD exhibits smaller lignin particles in the form of sheets, which signicantly increases its interfacial area and improves the dispersion in non-polar polyolen, and therefore drastically enhances the reinforcing and antioxidant effect of lignin.…”

Section: Introductionmentioning

confidence: 99%

Nanostructured thin lignin-derived carbon sheets as excellent reinforcement fillers in polypropylene

et al. 2018

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In this article, natural alkali lignin was freeze-dried and then annealed at different temperatures to achieve lignin-derived carbons (LCs) with mesh-shape or sheet-like morphology, which were incorporated into polypropylene (PP) matrix by melt compounding. Owing to the significantly increased interfacial area and improved dispersion of the carbons in the polymer matrices, with the addition of only 2 wt% relatively low temperature annealed freeze-dried lignin-derived carbon (FD-LC), the obtained PP/LC composites show notably enhanced tensile mechanical properties, including markedly improved Young's modulus and remarkably increased elongation at break compared with those of neat PP. The enhancements brought by the nano-structured thin FD-LC sheets are far more impressive than that with the same loading of particulate as-received lignin-derived carbon (AR-LC). The FD-LC filled PP composites also have rough fractured surfaces with fiber pull-out near the interface, revealing the non-negligible toughening effect of the LC. In addition, the higher temperature annealed FD-LC filler induces the further reinforcement of the composites. For the FD-LC annealed at 900 C, the corresponding composite possesses the highest Young's modulus of 668 MPa. † Electronic supplementary information (ESI) available: SEM image of as-received and freeze-dried lignin, BET SSA and BJH pore volume results of lignin and the corresponding LCs, DSC of PP/LC composites are included. See

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Improvement in dispersion and ionic conductivity of polyether/freeze-dried clay composites using supercritical carbon dioxide as treatment medium

Cited by 5 publications

References 24 publications

Sheet-Like Lignin Particles as Multifunctional Fillers in Polypropylene

Sheet-Like Lignin Particles as Multifunctional Fillers in Polypropylene

Dielectric relaxations and conduction mechanisms in polyether–clay composite polymer electrolytes under high carbon dioxide pressure

Nanostructured thin lignin-derived carbon sheets as excellent reinforcement fillers in polypropylene

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