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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]

The electro-mechanical response of conductive carbon-nanotube(CNT)-polymer composites is vital when they are used as smart-sensing materials. Clarifying the variation trend of resistance with strain is the key to design and regulate the piezoresistive property of such material. Here, we present some finite element simulations to predict the electro-mechanical response using a geometrical model comprising two hollow cylindrical CNTs and a cuboid matrix. The electrical contact between CNTs is represented by some elements which account for quantum tunnelling effects and capture the sensitivity of conductivity to separation. Different from classical simulations using solid model or one-dimensional beam model, in which the tunnelling resistance between two CNTs changes monotonously with strain, the results in this work show that the trend is non-monotonic in some cases, i.e. it increases at first and then decreases with the uniaxial compressive strain when the elastic modulus of the matrix is high. In addition, factors affecting the different variation trends are discussed in details, which include geometric model, elastic modulus and Poisson’s ratio of the matrix, and orientation angle. [ABSTRACT FROM AUTHOR]

Superhydrophobic conductive rubber band with synergistic dual conductive layer was designed and prepared for high-performance strain sensor, showing great potential for full-range monitoring of human motion and physiological signal, especially in the water environment. [Display omitted] Wearable electronic devices have received increasing interests because of their excellent flexibility, stretchability, and human friendliness. As the core components, flexible strain sensors integrated with wide working range, high sensitivity, and environment stability, especially in moisture or corrosive environments, remain a huge challenge. Herein, synergistic carbon nanotubes (CNTs)/reduced graphene oxide (rGO) dual conductive layer decorated elastic rubber band (RB) was successfully developed and treated with hydrophobic fumed silica (Hf-SiO 2) for preparing superhydrophobic strain sensor. As expected, stable entangled CNTs layer and ultrasensitive microcracked rGO layer endow the sensor with extremely low detection limit (0.1%), high sensitivity (gauge factor is 685.3 at 482% strain), wide workable strain range (0–482%), fast response/recovery (200 ms/200 ms) and favorable reliability and reproducibility over 1000 cycles. Besides, the constructed Hf-SiO 2 coating also makes the sensor exhibit excellent superhydrophobicity, self-cleaning property, and corrosion-resistance. As a proof of concept, our prepared high-performance strain sensor can realize the full-range monitoring of human motions and physiological signals even in the water environment, including pulse, vocalization, joint bending, running, and gesture recognition. Interestingly, it can also be knitted into a tactile electronic textile for spatial pressure distribution measurement. Thus, this study provides a universal technique for the preparation of high-performance strain sensors with great potential applications in the field of next-generation intelligent wearable electronics. [ABSTRACT FROM AUTHOR]

Benefitting from the wearability, ductility and portability, flexible and stretchable strain sensors display a more extensive field of applications than traditional sensors in terms of medical diagnosis, smart home, environmental monitoring and so on. However, the critical sensing performances, such as sensitivity, sensing range, stability and detection limit of flexible strain sensors still need to be improved. Microstructural optimization has been considered as an efficient strategy for tuning the performances. In this work, a carbon nanotubes (CNTs)/carbon black (CB)/thermoplastic polyurethane (TPU) fibrous film (CCTF) is prepared through electrospinning, spraying and ultrasonic anchoring technique. Synergetic conductive layers by combining CNTs/CB and CB are constructed on both sides of CCTF. In virtue of the optimization of microstructures and the synergetic conductive network, the obtained CCTF possesses an ultrawide response range (up to 500 % strain), high sensitivity (gauge factor, GF up to 1516), short response/recovery time (80/80 ms), low detection limit (0.05 % strain), favorable sensing stability and long-term durability. CCTF with excellent strain sensing performances is assembled as a strain sensor, which accounts for full range human biological signal acquisition, including joint movements, muscle tension, and facial micro-expressions. This paper provides a certain reference significance for the preparation and fabrication of next-generation flexible strain sensors with high performances. A flexible strain sensor based on carbon nanotubes (CNTs)/carbon black (CB)/thermoplastic polyurethane (TPU) film (CCTF) is fabricated through electrospinning, spraying and ultrasonic anchoring technologies. CCTF possesses excellent sensing performance due to the optimization of the microstructure, achieving a wide sensing range (up to 500 % strain), high sensitivity (GF up to 1516), low detection limit (0.05 % strain), and short response/recovery time (80/80 ms). [Display omitted] • A fibrous strain sensor with synergetic conductive networks of CNTs/CB and CB is fabricated. • The sensor possesses both a wide sensing range (500 % strain) and high sensitivity (GF up to 1516). • Low detection limit (0.05 % strain) and short response/recovery time have also been achieved. • The sensor is demonstrated to precise full range human biological signal acquisition. [ABSTRACT FROM AUTHOR]

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]

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]

Poly(ε-caprolactone)/poly(lactic acid) (PCL/PLA) blends are promising biomaterials with biodegradable characteristics. However, poor compatibility of the two components may lead to undesirable mechanical properties. In this work, the effect of combining carboxyl multi-walled carbon nanotubes (CNTs) and organically modified montmorillonite (MMT) on the morphology and properties of PCL/PLA blend was investigated. The morphological observations and rheological analysis showed that exfoliated MMT platelets enhanced interfacial adhesion of the two phases, whereas CNTs formed a percolating network in PCL matrix. The addition of CNTs/MMT (0.5 wt%: 0.5 wt%) led to an increase by 137.4% in elongation at break, 79.6% in tensile strength, and 14 °C in decomposition temperature without sacrificing its rigidity apparently for the PCL/PLA matrix. Obvious synergistic effect was demonstrated in comparison to the blends containing single nanofiller. This study demonstrated that combining CNTs and MMT is a facile way to preparing immiscible PCL/PLA blends based nanocomposites with interesting structure and properties. [ABSTRACT FROM AUTHOR]

Polylactic acid (PLA) is a biodegradable and biocompatible polyester derived from renewable resources like corn starch, presenting great potential in clinical applications like tissue engineering, implants and drug delivery systems. However, the intrinsic brittleness restricts its real applications. In this work, PLA nanocomposites were prepared by incorporating a small amount of carboxyl functionalized multi-walled carbon nanotubes (CNTs) and surface compatabilized montmorillonite (MMT) via technologies of freeze-drying and masterbatch-based melt blending. In the resulting nanocomposites, a well-distributed nano-filler network with microstructures of 1-D CNTs/2-D MMT platelets is formed favored by the enhanced interfacial interaction between the organic modified fillers with PLA matrix. Thanks to the well dispersed organic modified nanofillers, a large number of microcracks and extremely stretched PLA matrix are induced during tensile process, dissipating amounts of energy. As a result, the filler networks reinforce PLA with increment of 19% in modulus, remarkably increase by 13.8 times in toughness relative to PLA control without sacrificing strength. Thus, the PLA nanocomposites with excellent properties prepared through the facile and effective route possess broad prospect in biomedical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Flexible polymer PENGs were prepared with interface-engineered PVDF/CNTs nanofibers. • PVDF- g -MA stabilized electrospinning flow to yield defect-free composite nanofibers. • Interfacial anchoring of PVDF- g -MA promoted electroactive β -phase in PVDF matrix. • A small amount of PVDF- g -MA boosted piezoelectric outputs (10.6 V, 3.15 µW/cm2) • Our strategy enhanced PENG with preserved flexibility avoiding excessive filler use. Polymeric piezoelectric nanogenerators (PENGs) hold great promise for flexible energy harvesters and self-powered sensors. However, achieving high piezoelectricity in inherently piezoelectric polymers while maintaining their flexibility remains a challenge. Herein, we propose a simple yet effective approach to fabricate flexible and cost-effective PENGs based on interface-engineered composite nanofibers of poly(vinylidene fluoride) (PVDF)/carbon nanotubes (CNTs) using electrospinning. Our strategy involves the incorporation of a tailor-made interfacial coupling agent, maleic anhydride grafted PVDF (PVDF- g -MA), onto PVDF/CNTs interfaces. This mild interface-engineering strategy not only promotes interfacial interactions within composites but also stabilizes electrospinning flow jets, yielding defect-free nanofibers. More importantly, the interfacial anchoring of PVDF- g -MA molecules promotes the preferential crystallization of electroactive β -phase within PVDF matrix. By incorporating a small quantity of PVDF- g -MA (up to 1.0 wt%), our approach significantly enhances piezoelectric outputs while preserving flexibility. This eliminates the need for excessive nanofiller usage that can sacrifice the flexibility associated with conventional methods. Remarkably, the resulting composite nanofiber-based PENGs exhibit excellent piezoelectric performance, generating high output voltages (10.6 V) and remarkable power density (3.15 µW/cm2) under tiny force stimuli. Our findings open new avenues for efficient and scalable fabrication of polymeric piezoelectric nanogenerators for flexible and wearable energy harvesting and self-powered sensing applications. [ABSTRACT FROM AUTHOR]

In this paper, a carbon nanotube (CNT)/polydimethylsiloxane (PDMS) conductive composite foam (CCF) was fabricated via a dual-solvent ice template (DSIT) process, whose structure features the conductive filler CNT "embedded" in the cell wall surface, and this CCF was applied to the field of flexible piezoresistive sensing. Benefiting from the sensitive conductive network constructed by the DSIT process, the CNT/PDMS CCF-based piezoresistive sensor can effectively detect compression strains down to 0.1% and exhibits excellent and stable response at compression strains up to 90%. In addition, the CCF shows fast response and recovery times (54 ms and 65 ms), as well as excellent durability and stability (2000 cycles). An electronic skin assembled from the CCF into 5 × 5 pixels was applied to detect the magnitude and spatial distribution of forces and strains. The CCF was also applied for roughness recognition, optical and thermal sensing responses, which shows its potential applications in personalized medical monitoring, electronic smart skin fabrication, external environment monitoring and other fields. [Display omitted] • The CNT/PDMS conductive composite foam (CCF) was prepared via the dual-solvent ice template (DSIT) process. • The CNT/PDMS CCF shows superior piezoresistive sensing capacity. • The CNT/PDMS CCF also possesses good optical and thermal response. • The CNT/PDMS CCF shows great potential for human motion detection and E-skin. [ABSTRACT FROM AUTHOR]

Abstract In this work, linear low-density polyethylene (LLDPE) nanocomposites with different loading levels of multi-walled carbon nanotube (MWCNTs) were prepared by microinjection molding. Interestingly, a similar network structure featured with oriented nanohybrid shish-kebab structure was formed in all the LLDPE/MWCNTs composites. Importantly, the composites with improved strength and modulus in parallel with enhanced toughness were obtained. For example, the tensile strength, modulus and toughness of the composites with 1 wt% MWCNTs were increased by 64.1%, 100% and 134.6%, respectively. This work offers a simple approach to achieve high-performance composites molded by microinjection molding (MIM) together with nanohybrid shish-kebab structure. Graphical abstract Image 1 Highlights • LLDPE/MWCNTs composites were prepared by microinjection molding. • A network structure featured with oriented nanohybrid shish-kebab structure was formed. • Composites with improved strength and modulus in parallel with enhanced toughness were obtained. [ABSTRACT FROM AUTHOR]

Abstract Thermal and rheological behaviors have a significant impact on the properties and applications of polymer blends and their composites. In this work, multi-walled carbon nanotubes (MWCNTs) filled poly (ethylene oxide)/poly (methyl methacrylate) (PEO/PMMA 60/40) blends with various MWCNTs concentrations were prepared via melt mixing. The DSC results indicate that the incorporation of MWCNTs not only raise the crystallization temperature but also increase the crystallinity. According to the results of dynamical oscillatory measurements, the storage modulus in accordance with the typical terminal behavior at low-frequency region for the blank PEO/PMMA blends, due to the well miscibility between PEO and PMMA. As the MWCNTs increase, the slope of storage modulus versus angular frequency plots in the low-frequency is lower than neat blend. Moreover, the melt viscosity of high concentration composites increases at low frequencies. The creep-recovery experiments results show that when the nanofiller concentration reaches 4%, the zero-shear viscosity of the composites does not exist. These suggest that the composites exhibit a transformation from liquid-like to solid-like states when the MWCNTs concentration is up to 4 wt%. Highlights • PEO/PMMA/MWCNTs composites were prepared by melt blending. • Addition of MWCNTs increases the crystallization temperature and crystallinity. • No zero-shear viscosity was found at high MWCNTs concentration. [ABSTRACT FROM AUTHOR]

Graphical abstract This study reports an aligned wave-like carbon nanotubes (CNTs)/thermoplastic polyurethane (TPU) fibrous network based strain sensor with ultra-wide sensing range, low detection limit, fast response rate and excellent stability, which provides a good candidate for wearable devices and artificial intelligence (AI). Highlights • An aligned conductive fibrous mat based strain sensor with wave-like structure was fabricated. • The sensor possesses an ultrahigh stretchability of 900%, combining with an excellent stability. • An ultralow detection limit (0.5%) and a fast response time of 70 ms have both been achieved. • The sensing behaviors of the CNTs/TPU fibrous sensor agree well with the tunneling theory. • The designed wave-like structure and the joints structure caused the fine sensing performances. Abstract Recently, flexible strain sensors with large stretchability, high sensitivity and excellent stability have been widely concerned owing to their potential applications in wearable electronic devices. However, the challenge of narrow sensing range still remains for strain sensors with high performance. In this paper, we proposed a facile, cost-effective and scalable technology to manufacture the carbon nanotubes (CNTs)/thermoplastic polyurethane (TPU) fibrous strain sensor with aligned wave-like structure. Through electrospinning technique, we prepared an aligned TPU fibrous mat, then used a simple and effective assembly approach to induce CNTs to wrap TPU fibrous mat through ultrasonication. The sensing properties of CNTs/TPU mats in vertical and parallel directions were investigated, respectively. The sensing behaviors of the two sensors both agreed well with the tunneling theory. Compared with the random CNTs/TPU mats and parallel direction sample, the aligned CNTs/TPU fibrous mats in vertical direction possessed an ultra-high stretchability (900%) and excellent durability (10,000 cycles at the strain of 200%). An ultra-low detection limit (0.5%) and fast response time of 70 ms were also achieved, exhibiting a favorable sensitivity. The generation of the wave-like structure and the joints structure in the designed conductive network, which could affect the evolution of the conductive paths subsequently, led to these excellent sensing performances. The CNTs/TPU mats strain sensor was then assembled to monitor both subtle human motions, like cheek bulging and phonation; and vigorous human motions, like leg squatting and elbow bending, both showing excellent sensing performances. The present paper provides a good candidate for potential applications as artificial skins, human-activity monitoring and personal healthcare. [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]

The advantages of segregated conductive polymer composites are greatly hampered owing to its limited preparation technology, which seriously relies on hot compression with low efficiency. The plunger type injection molding (PTIM) is employed to fabricate segregated carbon nanotubes (CNTs)/high density polyethylene (HDPE)/ultra-high molecular weight polyethylene (UHMWPE) composites in this paper, which lowers the production cycle by 45%, compared with the conventional hot compression. The morphology and conductive properties are investigated in detail. Graceful segregated conductive network and a very low percolation threshold (0.45 vol%) of the polymer composites have both been achieved. The present processing technique with short production cycle provides a fancy idea to realize segregated conductive polymer composite in mass production. [ABSTRACT FROM AUTHOR]

The epoxy nanocomposites with ordered multi-walled carbon nanotubes (MWCNTs) were used to influence the micro-cracks resistance of carbon fiber reinforced epoxy (CF/EP) laminate at 77 K, Oxidized MWCNTs functionalized with Fe 3 O 4 (Fe 3 O 4 /O-MWCNTs) with good magnetic properties were prepared by co-precipitation method and used to modify epoxy (EP) for cryogenic applications. Fe 3 O 4 /O-MWCNTs reinforced carbon fiber epoxy composites were also prepared through vacuum-assisted resin transfer molding (VARTM). The ordered Fe 3 O 4 /O-MWCNTs were observed to have effectively improved the mechanical properties of epoxy (EP) matrix at 77 K and reduce the coefficient of thermal expansion (CTE) of EP matrix. The ordered Fe 3 O 4 /O-MWCNTs also obviously improved the micro-cracks resistance of CF/EP composites at 77 K. Compared to neat EP, the CTE of ordered Fe 3 O 4 /O-MWCNTs modified CF/EP composites was decreased 37.6%. Compared to CF/EP composites, the micro-cracks density of ordered Fe 3 O 4 /O-MWCNTs modified CF/EP composites at 77 K was decreased 37.2%. [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]

• Waterproof conductive fiber with microcracked synergistic conductive layer was designed. • High sensitivity and wide working range were achieved for the conductive fiber strain sensor. • Tunable sensing performance was achieved for the conductive fiber strain sensor. • The sensor can precisely distinguish various human movements and physiological signals. With the rapid development of wearable smart electronic devices, flexible strain sensors with high sensitivity in a wide working range are urgently demanded. Meanwhile, good self-cleaning and anti-corrosion properties are also essential for daily use. Herein, a waterproof conductive spandex fiber strain sensor with microcracked synergistic Ag nanoparticles (AgNPs)-carbon nanotubes CNTs conductive layer was designed and fabricated via the solvent swelling, non-solvent-induced phase separation (NIPS), and low surface energy treatment process. Benefiting from the stable synergistic conductive network and the ultrasensitive microcrack structure, the sensor exhibits excellent overall strain sensing performances, including high sensitivity (gauge factor is 48,310 within 335–400% strain), wide working range (0–400%), ultralow detection limit (0.1%), fast response/recovery time (80 ms/100 ms), and long-term fatigue resistance over 10,000 cycles, making it reliably and precisely distinguish both violent human movements and subtle physiological signals. More importantly, strain sensing range and sensitivity of the sensor can also be effectively tunned through changing the AgNPs loading in the synergistic conductive network, enabling it to be applicable for different application scenarios. What's more, the waterproof surface with good self-cleaning and anti-corrosion properties also endows the sensor with great potential for real-time body motion monitoring under humid and underwater environments without being interfered. This study provides a facile one-step method for the fabrication high-performance flexible strain sensor. [ABSTRACT FROM AUTHOR]

A novel approach, i.e. manipulating the size of incorporated polymer matrix particles, was proposed to tune the positive temperature coefficient (PTC) characteristics of carbon nanotubes (CNTs)/polypropylene (PP) composites with a segregated microstructure. For the conductive properties of CNTs/PP composites, the percolation threshold decreased from 1.32 vol% to 0.44 vol% when the matrix particle size enlarged from 20 to 1200 µm, showing an inverse correlation effect. The controllable PTC characteristics in resistivity are attributed to the microstructure development of conductive pathways and the heat-induced volume expansion of polymer matrix particles. An extremely high PTC material has also been achieved through this method. The present work provides an effective route to acquire a tunable temperature-resistivity sensor. [ABSTRACT FROM AUTHOR]

Conductive polymer composites (CPCs) have found applications as eco-friendly vapor sensor. In this study, ramie fiber (RF) was incorporated into poly (lactic acid) (PLA), an eco-friendly polymer, through a premixing process of conductive fillers (carbon black (CB) and carbon nanotubes (CNTs)) and RF. The introduction of RF increases the crystallinity of composites without sacrificing electrical properties. The influence of RF on the vapor sensing behaviors of the CPC was investigated in detail. Compared with those systems with only conductive fillers, i.e. , CB/PLA and CNT/PLA, the RF embedded CPCs show higher electrical conductivity with lower percolation threshold, better shape stability toward ‘good solvent’ such as dichloromethane, and excellent reversibility upon ‘poor’ solvent. The increased crystallinity and the interaction between conductive fillers and RF are responsible for the phenomenon. To illustrate the conductive network evolution during tests, a schematic was proposed. The results suggest that conductive polymer composites containing RF can be applied as a promising eco-friendly vapor sensor. [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]

• Synergistic MXene/CNTs based multifunctional TPU fabric (MCT-fabric) was prepared. • The MCT-fabric strain sensor shows both high sensitivity and broad sensing range. • The MCT-fabric shows superior EMI shielding effectiveness. • The MCT-fabric shows high efficient and long-term stable Joule heating capability. High-performance electronic textile with outstanding strain sensing, electromagnetic interference (EMI) shielding, and Joule heating performances are highly desirable for modern integrated smart wearable electronic devices. Herein, multifunctional electronic textile based on hybrid Ti 3 C 2 T x MXene and carbon nanotubes (CNTs) conductive nanomaterials coated thermoplastic polyurethane (TPU) non-woven fabric (MCT-fabric) is fabricated via a facile dip-coating approach. Based on the synergistic MXene/CNTs conductive coating and pre-stretching induced ultrasensitive microcrack structure, tunable conductive MCT-fabric strain sensor with high sensitivity (GF is as high as 9022), wide sensing range (∼210 %), rapid response/recovery time (140/160 ms), excellent long-term stability and reliability (∼1000 cycles) is successfully constructed. Besides, benefiting from the perfect synergistic conductive network and porous fibrous network structure, the MCT-fabric displays superior EMI shielding effectiveness (∼43 dB for the MCT-fabric with a thickness of 600 μm) and excellent thermal management performance including high Joule heating temperature at relatively low applied voltages, rapid Joule heating response, sufficient heating stability and reliability. This work indicates that the high-performance multifunctional electronic textile has attractive potential for strain sensing, EMI shielding and thermal management applications in artificial intelligence and emerging wearable electronics. [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]

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]

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]

The present work proposes a facile method to fabricate elastic micropatterned array, which can be further assembled into multifunctional interlocked e-skin. The as-prepared e-skin can simultaneously recognize pressure–temperature stimuli, monitor multiple arterial pulses waveform. Moreover, human physiological signals can be real-time wirelessly monitored by a remote mobile phone. • Elastic micropatterened array is fabricated via a cost-effective method. • Interlocked e-skin exhibits superior sensing stability in a wide working range. • Such interlocked e-skin can simultaneously recognize pressure–temperature stimuli. • Such interlocked e-skin can discriminate multiple arterial pulses waveform. • Human physiological signals can be wirelessly monitored by a remote mobile phone. Electronic skin (e-skin) based on elastic piezoresistive sensor is considered to be one of the most important components for future wearable electronic devices, whose performances can be substantially improved by shaping patterned surface. However, most patterned surfaces are generally fabricated via some tedious methods. Obviously, it is still a huge challenge to realize high sensing performance via facile fabrication process. Here, an efficient but facile method named hot-air-gun assisted preparation is proposed, which enable quasi-hemispherical micropatterned array to be directly fabricated on the single-walled carbon nanotubes (SWCNTs)/thermoplastic polyurethane (TPU) film. The interlocked micropatterns can significantly improve the sensing performance of the as-prepared e-skin based on such micropatterned film, endowing it with very fast response time (<46 ms), wide working range (0.055–254.8 kPa) and excellent durability (>20000 cycles). Interestingly, the interlocked e-skin exhibits multifunction to simultaneously discriminate pressure–temperature stimuli. Moreover, it can monitor a variety of human physiological signals (e.g., arterial pulse waveform, voice recognition and human breathing behavior), indicating a promising application in human–machine interaction. Furthermore, the as-prepared interlocked e-skin could be connected to a wireless transmitter for wireless monitoring respiratory rates. Considering the facile preparation process and the low-cost raw materials, this approach can be easily scaled up for practical production. [ABSTRACT FROM AUTHOR]

• Friction and wear of glass fabric reinforced epoxy composites. • MoO 3 /CNTs modified glass fabric reinforced epoxy composites. • Friction and wear of MoO 3 /CNTs modified glass fabric reinforced epoxy composites. A hybrid material composed of MoO 3 nanobelts and oxide multi-walled carbon nanotubes (MoO 3 -CNTs) was prepared via a one-step hydrothermal method. A modified vacuum filtration technique was used to prepare uniform MoO 3 -CNTs films (f -MoO 3 -CNTs). These MoO 3 -CNTs and f -MoO 3 -CNTs were used to enhance the tribological properties of a glass fabric-reinforced epoxy (GF/EP) composite prepared using the vacuum-assisted resin transfer molding (VARTM) method. Wear tests were carried out by using a ball-on-disc ("steel-on-polymer") configuration under dry sliding conditions. The hybrid material acted as both the lubrication and reinforcement to improve the friction and wear performance of the GF/EP composite. The frictional coefficient decreased from 0.61 for the neat GF/EP composite to 0.50 for MoO 3 -CNTs/GF/EP and to 0.32 for f -MoO 3 -CNTs/GF/EP. The wear resistance of the GF/EP composite improved by about four times with the addition of f -MoO 3 -CNTs. The morphologies of the worn surfaces of the composites and their possible wear micro-mechanisms were investigated. [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]

Poly(lactic acid)/poly(ε-caprolactone) (PLA/PCL) blends are among the most widely investigated biomaterials for tissue engineering scaffolds. Incorporating carboxylic multi-walled carbon nanotubes (MWCNTs) into the blend can further tune the microphase distribution and interface adhesion which conversely dominates the micromechanical properties. In this work, atomic force microscope (AFM) based quantitative nanomechanical measurements were applied on PLA/PCL/MWCNTs bionanocomposites for gaining knowledge at the nanoscale. Results show that MWCNTs are mainly dispersed in the PCL phase which is adjacent to the PLA phase. The microphase structures and the onsite microscopic Young's moduli distributions have significant changes with the introduction of MWCNTs. No obvious intermediate layer in the PLA/MWCNTs and PCL/MWCNTs interfaces is observed in the Young's moduli map, indicating weak interactions in the polymer/MWCNTs interface. Moreover, microscopic structure-property relationships of PLA/PCL/MWCNTs nanocomposites were discussed and correlated to the macroscopic mechanical properties. A better understanding of these properties would be helpful in tailoring the PLA/PCL based bionanomaterials for applications in tissue engineering scaffolds, where the nanomechanical information is critical. • The dispersion state of MWCNTs in PLA/PCL/MWCNTs composites was visualized by AFM. • The introduction of MWCNTs significantly affected the morphology of the nanocomposites. • New method nanomechanical mapping was presented to characterize the microscopic mechanical properties. • Microscopic Young's moduli distribution together with interface interactions of the nanocomposites was investigated. • The microscopic mechanical properties of the nanocomposites were related to their macroscopic mechanical properties. [ABSTRACT FROM AUTHOR]

A co‐coagulation method combined with hot pressing technique is successfully applied to fabricate thermoplastic polyurethane (TPU) nanocomposites with different contents of carbon nanotubes (CNTs). Obviously, the mechanical and thermal properties of the nanocomposites are improved with increasing the CNT content. In addition, the existence of hydrogen bonding between CNTs and polymer matrix is demonstrated. Furthermore, the influences of impact parameters on solid particle erosion behavior are investigated systematically. The surface roughness and line roughness are also investigated to illustrate the mechanism of solid particle erosion. As elastic nanocomposites, the maximum and minimum erosion rate (ER) occur at 30° and 90°. The ER is relatively small when the impact velocity is at 10 m s−1, then is increased rapidly between 20 and 30 m s−1. As the size of impact particles increases to 300 µm, a rapid increase of ER occurs between 10 and 20 m s−1. All these results indicate CNTs improve the erosion resistance of TPU matrix. [ABSTRACT FROM AUTHOR]

The agglomeration problem of nanofillers, for instance, carbon nanotubes (CNTs) in a poly(ether ether ketone) (PEEK) matrix, is still a challenging assignment due to the intrinsic inert nature of PEEK to organic solvents. In this work, organically modified montmorillonite (MMT) was introduced as a second filler for improving the dispersion of CNTs in the PEEK matrix and enhancing the mechanical properties, as well as reducing the cost of the materials. The nanocomposites were fabricated through melt-mixing PEEK with CNTs/MMT hybrids, which were prepared in advance by mixing CNTs with MMT in water. The introduction of MMT improved the dispersion stability of CNTs, as characterized by sedimentation and zeta potential. The CNTs/MMT hybrids were maintained in PEEK nanocomposites as demonstrated by the transmission electron microscope. The mechanical and thermomechanical measurements revealed that CNTs together with MMT had a strong reinforcement effect on the PEEK matrix, especially at high temperature, although it had a negative effect on the toughness. A maximum increase of 48.1% was achieved in storage modulus of PEEK nanocomposites with 0.5 wt% CNTs and 2 wt% MMT at 240 °C, compared to that of neat PEEK. The differential scanning calorimetry results revealed that CNTs accelerated the crystallization of the PEEK matrix while a further addition of MMT played an opposite role. The nucleation activity of the fillers was also evaluated by the Dobreva method. [ABSTRACT FROM AUTHOR]