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Currently used humidity sensors have a large size which seriously hinders their applications in many special fields. Therefore, a facile way for fabricating miniaturized humidity sensors is desired. In this work a high-performance, nanofiber bundle sensor (NfBS) was fabricated through immersing nylon66 (PA66)/multiwall carbon nanotubes (MWCNTs) nanofiber bundles into a polyvinyl alcohol solution. In the PA66/MWCNTs nanofiber bundles the MWCNTs were absorbed on the surfaces of the PA66 nanofibers. The NfBS exhibited a wide range of 11–85% relative humidity (RH) sensitivity with a fast response-recovery time as well as small hysteresis and good repeatability, but had an extremely small size (about 0.1 mm in diameter and 2 mm in length) due to the unique advantages of nanofiber bundles. In addition, the NfBS showed good performance in monitoring human breath. The results in this study provide a promising opportunity and a good method for manufacturing mini-humidity sensors with smaller sizes for electronic products. [ABSTRACT FROM AUTHOR]

The strain-sensing behaviors of carbon black (CB)/polypropylene (PP) and carbon nanotubes (CNTs)/PP conductive composites prepared by the vacuum-assisted hot compression were studied and compared. When ten extension-retraction cycles were applied, it was found for CB/PP, the value of the maximum responsivity (Δ R/ R, Δ R-the instantaneous variation of the resistance during the test, R-the original resistance) decreased gradually with increasing the cycle number, but it began to rise from the seventh cycle. The value of the min Δ R/ R increased during the whole test. While for CNTs/PP, both the values of the max and min Δ R/ R decreased rapidly. It is suggested that the different behaviors mainly depend on the distinction in the dimension of the conductive fillers and the preparation technique. [ABSTRACT FROM AUTHOR]

Resistivity variations of carbon black (CB)/polypropylene (PP) and carbon nanotubes (CNTs)/PP conductive polymer composites subjected to different tensile speeds were studied with the same maximum strain 3%. With increasing tensile speed, the responsivity (ΔR/R0, R0is the original resistance, ΔR is instantaneous change in resistance) shows an obvious increase for both CPCs, although the increase degree is different. CB/PP has a higher responsivity than that of CNTs/PP during the tension and unloading process. It is proposed that the difference depends mainly on the distinction in the microstructure of conductive fillers and the interaction between the fillers and the matrix. [ABSTRACT FROM AUTHOR]

Abstract Given the advantages of polyethyleneimine (PEI) for interface modification of carbon fiber reinforced polyamide 66 composite (CF/PA66), an effective method was developed to fabricate CNT@PEI-CF. The XPS results confirmed CNT@PEI-CF was covered with a double grafted layer. Interface stability investigated showed thermal stability (under injection molding temperature, about 270 °C) and structural stability of CNT@PEI-CF/PA66 interface were both improved, but PA66 crystallization behavior affected by CNT@PEI-CF was identical with that of pure PA66. The contact angle tests exhibited that its compatibility with PA66 was also enhanced. Its interfacial shear strength, composite tensile strength and elastic modulus increased by 64.74%, 27.58% and 22.68% compared with that of untreated-CFs and composite, respectively. These best mechanical properties were ascribed to the formation of "fish-scale" layers on pull-out fibers resulted from CNT@PEI-CF modification. It could be concluded that CNT@PEI-CF would not only enhance its composite mechanical properties, but also exhibit much fiber pull-out and avoid the catastrophic failure for CNT@PEI-CF/PA66 composites. This CF surface modification study would be beneficial to expand application of thermoplastic composite with reusability. [ABSTRACT FROM AUTHOR]

Resistivity–temperature characteristics of conductive multi-walled carbon nanotubes (MWCNT)/epoxy (EP) composite were studied during a heating-cooling run (HCR) with different top test temperatures. The values of R e (room-temperature resistance at the end of a HCR) decrease with increasing the top test temperature. The fluctuation-induced tunneling conduction (FITC) and the hysteresis effect developing in MWCNT/EP composite are responsible for this fascinating phenomenon. In order to understand this result further, resistivity–temperature characteristic at different cooling rates was studied. The values of R e also decrease with rising the cooling rate. This paper provides an effective approach to acquire a tunable temperature sensor. [ABSTRACT FROM AUTHOR]