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The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/mame.201900525. Over the past decade, flexible strain sensors have been of tremendous interest due to their wide application in robotics, medical diagnostics, human motion detection, and healthcare. Herein, a fiber strain sensor is fabricated by continuously coating a layer of ultrathin multi-walled carbon nanotube (MWCNT)/thermoplastic polyurethane (TPU) nanocomposites onto the surface of commercial spandex fiber. The effect of noncovalent functionalization of MWCNTs using 1-pyrenecarboxylic acid (PCA) on the electrical conductivity as well as the sensing performance of the fiber sensor is investigated. The low-cost strain sensor possesses a large workable strain (up to 200% strain), high sensitivity (gauge factor is 14 191.5 under 170-200% strain), and excellent stability (up to 1000 cycles), and regular signal responses within a wide measuring frequency range of 0.01-1 Hz are achieved with the introduction of PCA via enhanced nanotube dispersion and polymer-nanofiller interactions.Additionally, the resistance response to strain is fitted with a model based on tunneling theory to understand the sensing mechanism, and to prove that the fitted results are in agreement with the experimental results. Furthermore, the developed sensor is successfully applied in human motion detection, such as joint movement, facial microexpressions, and speech recognition. Conflict of InterestThe authors declare no conflict of interest.

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Diglycidyl ethers of bisphenol-A (DGEBA)/methyl tetrahydrophthalic anhydride/polyethersulphone (PES) blends are prepared as matrix resins for thermally conductive composites using graphite nanoplatelets (GNPs) as the conductive component. The epoxy/PES blends form a network structure via reaction-induced phase separation (RIPS) during the curing process, and the GNPs are selectively localized in the PES phase and at the interface leading to a three-dimensional continuous filler network. With this unique structure, the thermal conductivity of the epoxy/PES/10 wt% GNPs composite is increased to 0.709 W m-1 K-1 , which is nearly 3.5 times that of the pure epoxy or a 52% increase compared to the epoxy/GNP composite without PES. In addition, it is found that the impact strength of the composite relative to the unfilled material is also improved.

Poly(lactic acid) (PLA)/poly(propylene carbonate) (PPC)/mica composites with different amount of chain extender (CE) were melt compounded and then processed via two routes (compression molding and uniaxial stretching) into sheets and films. The tensile, thermal, and oxygen barrier properties of all the samples were investigated.Tensile test showed that the tensile strength and elongation at break of all films were much higher than that of all sheets, especially for PLA/PPC/mica with 0.9-wt% CE composite (CM 3 (CE) 0.9 ) film. The crystallinity of all films increased significantly after uniaxial stretching of sheet samples. The Fourier transform infrared spectroscopy (FTIR) results proved the chemical reactions occurred between PLA/PPC and CE.Scanning electron microscope (SEM) analysis revealed that compatibility and interfacial adhesion of all samples were improved after adding mica and CE, and they were further enhanced after uniaxial stretching. The addition of CE was not favorable to improve the oxygen barrier performance of PLA/PPC/mica sheet samples. However, the oxygen barrier performance of film samples was significantly improved after uniaxial stretching. In particular, the CM 3 (CE) 0.9 film had the lowest oxygen permeability coefficient (1.4 × 10 −15 cm 3 ·cm/(cm 2 ·s·Pa)), and this was the best oxygen barrier properties reported in the literature for PLA-based composites, which was comparable with PA film. This study demonstrated the high efficiency of uniaxial stretching on improvement of properties of composites, which would promote the application of biodegradable polymers in oxygen sensitive food packaging.