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- ItemMultifilament fibres of poly(ε-caprolactone)/poly(lactic acid) blends with multiwalled carbon nanotubes as sensor materials for ethyl acetate and acetone(Amsterdam [u.a.] : Elsevier, 2011) Rentenberger, Rosina; Cayla, Aurélie; Villmow, Tobias; Jehnichen, Dieter; Campagne, Christine; Rochery, Maryline; Devaux, Eric; Pötschke, PetraConductive poly(ε-caprolactone) (PCL) + 4% multiwalled carbon nanotubes (MWCNTs)/poly(lactic acid) (PLA) = 50/50 wt% blend multifilament fibres were melt-spun and a woven textile was made by a handloom with the conductive fibres in weft direction. The fibres were tested for cyclic liquid sensing in ethyl acetate and acetone as two moderate solvents and in ethanol as a poor solvent. The liquid sensing responses, namely the relative resistance changes Rrel relating the resistance change to the initial resistance of the samples on contact with ethyl acetate and acetone, were fast (R rel higher than 16 after 100 s), with high amplitudes (R rel higher than 23 after 500 s), and well reproducible. At the same time, the fibres were resistant against these solvents. The response to ethanol was also reproducible, however, very slow and with low amplitude. PLA was found to crystallize during the immersion process, whereas in PCL the crystalline domains transformed into amorphous ones as studied by Wide Angle X-ray Diffraction. The crystallization of PLA does not influence negatively the liquid sensing properties which can be assigned to the finding that the MWCNT are predominantly localized in the PCL phase as confirmed by Scanning Electron Microscopy. In the final step, a textile based on those fibres was prepared and its sensing behaviour was investigated on ethyl acetate and acetone clearly showing that such textiles are suitable to detect these solvents.
- ItemVapor sensing properties of thermoplastic polyurethane multifilament covered with carbon nanotube networks(Amsterdam [u.a.] : Elsevier, 2011) Fan, Qingqing; Qin, Zongyi; Villmow, Tobias; Pionteck, Jürgen; Pötschke, Petra; Wu, Yongtao; Voit, Brigitte; Zhu, MeifangThe volatile organic compound (VOC) vapor sensing properties of a novel kind of thermoplastic polyurethane multifilament - carbon nanotubes (TPU-CNTs) composites is studied. And the sensing is based on changes in the electrical resistance of the composites due to vapor contact. The composites were readily obtained by adhering CNTs on the surface layer of TPU by means of simply immersing pure TPU multifilament into CNT dispersion. The uniformly formed nanotube networks on the outer layer of composite multifilament are favorable for providing efficient conductive pathways. The resulting TPU-CNTs composites show good reproducibility and fast response (within seconds) of electrical resistance change in cyclic exposure to diluted VOC and pure dry air. The vapor sensing behaviors of the composites are related to CNT content, vapor concentration, and polar solubility parameters of the target vapors. A relatively low vapor concentration of 0.5% is detectable, and a maximum relative resistance change of 900% is obtained for the composite with 0.8 wt.% CNT loading when sensing 7.0% chloroform. It is proposed that both the disconnection of CNT networks caused by swelling effects of the TPU matrix and the adsorption of VOC molecules on the CNTs are responsible for the vapor sensing behavior of TPU-CNTs composite, while the former effect plays the major role.
- ItemDuctile-to-semiductile transition in PP-MWNT nanocomposites(Weinheim : Wiley-VCH, 2007) Satapathy, Bhabani K.; Ganß, Martin; Weidisch, Roland; Pötschke, Petra; Jehnichen, Dieter; Keller, Thomas; Jandt, Klaus D.A ductile-to-semiductile transition in the crack resistance behaviour of PP/MWNT composites is discussed, using an essential work of fracture approach based on a post yield fracture mechanics concept and its possible interrelation to the structural attributes studied by TEM, SEM, and WAXD. A maximum in the non-essential work of fracture is observed at 0.5 wt-% MWNT content, which demonstrates the enhanced resistance to crack propagation compared to pure PP, followed by a sharp decline with the increase in MWNT content to 1.5 wt.-%, which reveals a ductile-to-semiductile transition. Fracture kinetic studies present a qualitative picture of the nature of such a transition in terms of a) switch over from non-steady (in pure PP) to steady-state crack tip opening displacement rate (in nanocomposites), and b) a ductile-to-semiductile transition largely as a result of delayed- yielding of the nanocomposites.
- ItemAttenuation of electromagnetic waves by carbon nanotube composites(Amsterdam [u.a.] : Elsevier, 2008) Hornbostel, Björn; Leute, Ulrich; Pötschke, Petra; Kotz, Jochen; Kornfeld, Daniela; Chiu, Po-Wen; Roth, SiegmarExperiments on polycarbonate/single-walled carbon nanotube composites were performed to explore the potential of carbon nanotubes in attenuating electromagnetic waves. According to the results of these experiments a distinct effect is present. The effect is dependent on the tubular filler properties and on the morphology of the composite. At a loading of 5.4 wt% single-walled carbon nanotubes in polycarbonate an attenuation of the field of 47 dB could be detected, which corresponds an attenuation of the power of 99.998%.
- ItemLiquid sensing of melt-processed poly(lactic acid)/multi-walled carbon nanotube composite films(Amsterdam [u.a.] : Elsevier, 2008) Kobashi, Kazufumi; Villmow, Tobias; Andres, Timo; Pötschke, PetraLiquid sensing properties of poly(lactic acid) (PLA)/multi-walled carbon nanotube (MWNT) composites were studied on the basis of the change of electrical properties on solvent contact. The composites were prepared by melt processing using a twin screw extruder. The MWNT loading differed between 0.5 and 2.0 wt%, and an electrical percolation threshold below 0.5 wt% MWNT content was obtained. TEM observations revealed that the nanotubes form a conductive network structure in the PLA matrix, which is the key for liquid sensing. Electrical resistance of the composites was monitored in solvent immersion/drying cycles on samples prepared from thin pressed composite sheets. The resistance reversibly changed upon the cycles with good reproducibility. Lower MWNT loadings resulted in larger resistance changes, indicating that the conductive MWNT network tends to readily disconnect due to the less dense structures as compared to higher loadings. Various solvents (n-hexane, toluene, chloroform, tetrahydrofuran, dichloromethane, ethanol, and water) were successfully detected, showing different degrees of the resistance changes (ca. 4-1.0 × 103 Ω) and the relative resistance changes (ca. 0.003-3.0 × 103). The solubility parameters of the solvents were found to be good indicators to estimate liquid sensing properties of these PLA/MWNT composites for the poor and good solvents.