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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]

Personalized rehabilitation training provides maximum help to stroke patients to alleviate the after-effects and restore the body to normal function. However, available monitoring devices have the disadvantages of being large, requiring professional guidance, and lacking intuitive signal display capabilities. Herein, a bio-inspired wearable high-performance strain sensor with a simple structure can simultaneous electrical signals and optical visualization in response to external stimuli. The sensor comprises a conductive layer with significant electromechanical behaviors of cellulose nanocrystals (CNC)/carbon nanotubes (CNTs)/MXene nanohybrid network, and a stretchable elastomer layer consisting of thermoplastic polyurethane and fluorescent agent. Benefiting from the designed microcracks and fluorescent material, the strain sensor exhibits ultra-high sensitivity (476800), ultra-low detection limit (0.005%), low response time (60 ms), wide working range (0–100%), and enables strain visualization for applications in visually rehabilitation training monitoring. Based on these sensing characteristics, the sensor shows great advantages in human motion and sound monitoring, with the integration of digital signals and visual images makes it show great potential in visually personalized rehabilitation training monitoring. [Display omitted] • Cellulose nanocrystals are introduced to modulate the sensitivity of the strain sensor. • CCMTPF has ultrahigh sensitivity of 476800 and ultralow detection limit of 0.005%. • CCMTPF achieves electric signals and visualization of optical images responses under strain. • CCMTPF has been demonstrated for visual rehabilitation training monitoring in real time. [ABSTRACT FROM AUTHOR]

Abstract Highly flexible and stretchable strain sensors play an important role in the wearable electronic systems. Up to now, it is still an enormous challenge to achieve a good balance between the wide response range and high sensitivity for a resistive-type flexible strain sensor. In this work, we prepared a fiber-shaped strain sensor based on thermoplastic polyurethane (TPU) and multi-walled carbon nanotubes (MWCNTs) via a simple and cost-efficient wet-spun method. The production process can satisfy continuous and large-scale preparation. The generation of the interesting porous structure is related to the solvent exchange in solidification process and beneficial to the improvement of the sensing range. In the uniaxial stretching test, the MWCNTs/TPU fiber-shaped sensor showed an ultra-wide workable strain range (320%), a high sensitivity (gage factor of 22.2 within 160% strain and 97.1 for strain of 160–320%) and a fast response time (<200 ms). The MWCNTs/TPU composite fiber sensor exhibited good reproducibility and excellent durability in multi-cycle test (9700 cycles at 100% strain). The mechanism of the response behavior was studied through the tunneling theory. The strain sensor shows potential applications in human motion detections including bending of the fingers, elbows and knee, squatting and squat-jumping. The present paper provides an effective strategy for the design of high performance fiber-shaped wearable electronic systems. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

In this paper, we used epoxy (EP) as a third component to tune the electromechanical performances of the conductive porous foam. A directional ice-template freezing method was utilized to fabricate a carbon nanotubes (CNTs)/EP/thermoplastic polyurethane (TPU) porous foam with a herringbone-like structure. CNTs were homogeneously distributed in the skeleton of the foam. The microstructure of the herringbone-like foam was studied in detail from both the directions perpendicular and parallel to the freezing front movement direction. An ultralow percolation threshold (0.088 vol%) of the conductive foam was achieved. The strength of the CNTs/TPU/EP foam was significantly enhanced with the increase of the CNTs and EP contents. When the foams were exposed to a compression strain from 0 to 70%, the resistance of the porous material decreased in a good linear manner. The foams showed a good differenciation capability towards different compression strain amplitude. Upon multiple cyclic compressive process, the change of the resistance tended to be stable after several compression loading-unloading cycles' measurement. After a pre-compression treatment, the resistance response also became much stable on the basis of the re-arrangement of the conductive network and the stabilized cells structure of the foam. The porous foam possesses a rapid response speed (about 160 ms). Our flexible porous foam with a good chemical resistance can be used in ethanol to sense the finger pressing, and it showed excellent sensing performances when applied to monitor human body motions. [ABSTRACT FROM AUTHOR]

Compared to polymer fibers, it is still challenging for fabricating large-scale polymer products with superb mechanical properties. Herein, high density polyethylene (HDPE) films reinforced with carbon nanotubes (CNTs) were prepared via an ingenious high-speed melt stretching strategy. With employing a homemade two-drum extensional rheometer, the maximum 80 × stretch ratio of supercooled melt was realized within very short time of 220 ms. The achieved nanocomposite films present the highest tensile strength of 147 MPa in reported HDPE-based composites, while the Young's modulus keeps simultaneously a high level of 2300 MPa in spite of low filler fraction of 3 wt%. Furthermore, the nanocomposite films display an excellent erosion resistance, ensuring the durability in harsh using environments. Microstructural characterization indicates a strong synergy between high-speed melt stretching and CNTs in (1) forming the densely distributed shish-kebab superstructures, (2) making a nearly perfect orientation of shish-kebab crystal and (3) reinforcing the physical connectivity of shish-kebab network. The construction of such characteristic microstructures greatly improves the transfer of mechanical load and underlies a significant enhancement on the mechanical performance. Due to the ultrastrong nanocomposite films fabricated directly by melt processing, the current work is of guiding significance in engineering practice and lights a feasible path towards expanding applications of general plastics to some special occasions like collision protection and structural materials. [Display omitted] • PE/C nanocomposite films are fabricated by high-speed melt stretching. • Films show ultrahigh mechanical properties and excellent erosion resistance. • Dense shish-kebab superstructures with nearly perfect orientation are formed. • CNTs greatly reinforce physical connectivity of shish-kebab crystal network. [ABSTRACT FROM AUTHOR]

Polyvinyl alcohol-graphene oxide-oxidized carbon nanotube (PVA-GO-OCNT) hybrid coatings were adopted to modify glass fibers (GFs) and carbon fibers (CFs), and modified GF/CF-reinforced polyurethane hybrid composites (PVA-GO-OCNTs-HFs/PUs) with different concentric hybrid structures were prepared. The synergistic effect of the hybrid structure and surface modification of hybrid fibers (HFs) on the mechanical properties of hybrid composites was investigated systematically. The results show that the hybrid structure can optimize the comprehensive mechanical properties of HF-reinforced composites (HFRCs) by combining the performance advantages of the two types of fiber reinforcement, and the strength of the interface between HFs and polyurethane (PU) plays a crucial role in whether the advantages of the hybrid structure can be fully achieved. In addition, the mechanical properties of the composite were significantly enhanced, and the structural advantages of the hybrid structure were further improved after HFs were modified by PVA-GO-OCNT hybrid coating. The hybrid effect on the tensile strength of HFRCs with CF as the core and GF as the shell changes from a negative hybrid effect (−5.4%) before modification to a positive hybrid effect (4.3%). The hybrid effect in tensile failure strain of HFRCs with GF as the core and CF as the shell changes from a negative hybrid effect (−2.1%) before modification to a positive hybrid effect (2.1%). Moreover, the interlaminar shear strength of HFRCs modified by PVA-GO-OCNT hybrid coating is significantly higher than that of unmodified HFRCs. Image 1 • The surface of hybrid fiber was modified by PVA/GO/OCNTs. • Multi-scale structure and chemical activity contribute a lot in composite adhesion. • A comparison of hybrid effect before and after interfacial modification is performed. • The collaborative reinforcement of the hybrid interface modification and hybrid structure were analyzed. [ABSTRACT FROM AUTHOR]

Ultrathin flexible transparent film heaters (TFHs) with fast response time are fabricated by embedding single-wall carbon nanotubes (CNTs) into transparent poly(vinyl alcohol) (PVA) film using a green all-water based solution process. Typically, CNTs network was firstly constructed on the surface of commercial polycarbonate film by a continuous hot roll pressing and spraying technique. The obtained CNTs network was then transferred to the surface of ultrathin PVA film using a transfer spinning technique coupled with hot pressing approach. The resulting film not only shows well optical and electrical properties of 475 Ω/aq with a transmittance of 77.3%, but also exhibits strong interfacial adhesion (standing 100 repeated scratches with 3 M sticky tape) and good flexibility (allowing more than 1000 bending cycles). Very interestingly, the fabricated PVA/CNT TFHs presents a quick Joule heating effect with a very fast heating time and rate of 8 s and 11.4 °C/s, respectively, under low impressed voltage (<15 V). These results demonstrate that our TFH is therefore considered suitable for providing anti-fogging or de-icing in optics and optoelectronic devices, as well as for wearable heating systems. [ABSTRACT FROM AUTHOR]