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Owing to the abundance of raw material reserves and low cost, Na-ion batteries (NIBs) have successfully gained widespread attention from academic and industrial communities in the past few decades. However, the insufficient cathode energy density is still one of the critical bottlenecks restricting the development of NIBs. Following a strategy of inducing Li+ into the transition-metal (TM) layer to enhance the oxygen redox reaction, a novel layered cathode material P2-Na0.6Li0.11Fe0.27Mn0.62O2 (NLFMO) was designed and successfully synthesized. This NLFMO cathode not only delivers a large initial reversible capacity of 207.3 mAh g-1, but also showing a good cyclic performance (104.2 mAh g−1 after 80 cycles) and rate capability (126.2 mAh g−1 at 1C). The ultrahigh capacity is contributed by both cationic (Fe3+/Fe4+, Mn3+/Mn4+) and partially reversible anionic redox (O2-/On-) reactions, revealed by in situ X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) techniques. Moreover, no detrimental P2-O2 phase transition was observed through ex situ X-ray diffraction (XRD) patterns, confirming the high structural stability during Na+ deintercalation/intercalation processes. These results provide valuable information about the high-energy density layered cathode materials based on anionic redox reaction for NIBs.

A highly stretchable and sensitive multifunctional piezoresistive sensor was reported. These sensors contain micro-cracked and hollowed-out polyaniline (PANI) foams which are supported by polydimethylsiloxane (PDMS). The cracked-PANI foam/PDMS (C-PF/PDMS) strain sensor shows high sensitivity with a gauge factor of ∼10 and excellent linearity and high durability over 500 stretching-releasing cycles. The fabricated C-PF/PDMS pressure sensor exhibits a sensitivity of ∼0.055 kPa−1 in the pressure range of 0–5.0 kPa, a low detection limit of 4 Pa, a fast response time (∼60 ms), recovery time (∼90 ms) and the capability of detecting and distinguishing various mechanical stimuli including compression, shear and torsion forces. When the sensor is attached to the human body, it can function as a health-monitoring device by detecting various human motions such as the bending of fingers and wrist, phonation and the wrist pulse.

An anisotropic conductor with graphene nanoplatelets (GNPs) well planar aligned in PP matrix has been obtained in this work through multi-melt multi-injection molding (M3IM). In this method, a second composite melt penetrated the first melt and products with three layers (skin layer, intermediate layer and core layer) were obtained. The GNPs in the three layers was entirely planar oriented along machine direction (MD) owing to the second shear flow and confined interface between intermediate layer and core layer. The finely aligned structure drastically elevated in-plane thermal conductivity of intermediate layer to as high as 7.32 W m−1 K−1 and highlighted an average thermal conductive anisotropy of 20.86 under 25 wt % GNPs loading, as well as provided a good electric conductivity of 0.03 S m−1 in MD while insulativity in perpendicular direction. Additionally, the M3IM composite performed well in mechanical properties with tensile strength (40.33 MPa) and Young's modulus (1.15 GPa). This M3IM manufacturing provides outstanding anisotropic properties to the injection products which possess a considerable potential application in unilateral conduction field.

Rare earth luminescent material CaAlSiN3:Eu2+ (CEu) was applied and modified with (3-Aminopropyl) triethoxysilane (KH550) to obtain two types of rare earth conversion agents, CEu and KH550-modified CEu (KCEu). Two kinds of polylactide (PLA) conversion films were successfully prepared through solution blending. The results showed that the addition of rare earth complex increases the crystallinity of PLA. More importantly, both PLA/CEu and PLA/KCEu films showed good red-light conversion ability, which can accelerate plant growth.

In the present work, micropores and a low filler content of Ag@SiO2 nanoparticles (NPs) are synchronously introduced into polydimethylsiloxane (PDMS) film to obtain porous dielectric elastomeric composites. The morphology and dielectric and mechanical properties of the composites are investigated. The resulting composites possess high dielectric permittivity, low dielectric loss and low Young’s modulus, which is beneficial to the requirements of a dielectric elastomer actuator. This study provides an effective method to prepare high-performance PDMS-based dielectric porous dielectric elastomeric composites filled with low filler contents of Ag@SiO2 NPs.

A free-standing unidirectional graphene aerogel/polyaniline (UGA/PANI) composite possessing the oriented PANI nanowire arrays on highly aligned and interconnected graphene network is obtained, through a facile in-situ polymerization of PANI on a unidirectional graphene aerogel scaffold. The resulted novel hierarchical structure can reduce the internal resistance and facilitate ion diffusion, which allows this electrode material to exhibit better electrochemistry performances. The UGA/PANI composite subsequently displays an enhanced specific capacitance of 538 F g-1 at 1.0 A g−1 with appreciable rate capability (keeps 73% even at 10 A g−1) as well as fine cycle stability (remains 74% of its initial specific capacitance after 1000 cycles at 3 A g−1). Besides, the electrochemical performances of UAG/PANI composite reported far excel that of conventional graphene aerogel/polyaniline (GA/PANI) composite with random graphene network and tortuous pores (345 F g-1 at 1.0 A g−1, 39% retention at 10 A g−1), demonstrating that proper construction of oriented structure is beneficial for achieving potential of PANI.

Soft materials with controlled surface patterns are useful for a range of applications, including microdevices, sensors and adhesives. In this work, the spontaneously wrinkled morphologies on the surfaces of crosslinked polydimethylsiloxane (PDMS) microspheres were observed. These wrinkled microspheres may have great potentials for construction of high-performance functional materials. They were fabricated in curable PDMS/water emulsions stabilized by surfactants. After curing and drying, the PDMS droplets in the emulsions formed microspheres with different surface wrinkling morphologies, including dimples and labyrinth patterns. The buckling patterns could be well tuned by the surfactant concentration, curing temperature, evaporation and compositions of PDMS phase. A power-law dependence of the wrinkling wavelength on microsphere radius was also observed. Furthermore, the wrinkling morphologies showed good reversibility by simply drying after wetting with water. It is speculated that the evaporation of dissolved water in the PDMS phase triggers interfacial instabilities and result in the wrinkled morphologies. This work gives new insights into the surface wrinkling behavior of soft microspheres, and provides a simple, efficient and environmentally friendly route to fabricate microspheres with complex surface patterns.

The biggest issues in the preparation of carbon nanotube (CNT)-reinforced composites reside in efficient dispersion of CNT into polymer matrix. In our work, a simple acid treatment method was adopted to obtain carboxylic functionalized multiwalled nanotubes (MWNTs), thus improving the dispersion of CNT and interaction between particles and polymer matrix. X-ray photoelectron spectroscopy and Fourier transform infrared showed that the carboxylic groups were introduced onto the surface of MWNTs. The Raman spectroscopy showed that the amorphous carbon materials and impurities decreased after acid treatment. The electrical and dielectric properties of the Polyamide-11 (PA11)-based composites filled with pristine multiwalled nanotubes (p-MWNTs) and carboxylic functionalized multiwalled nanotubes (c-MWNTs) were investigated. The biggest dielectric constant of PA11/c-MWNTs composites, which was about twice as high as that of PA11/p-MWNTs composites at room temperature and 103 Hz (345–610), was obtained, accompanied by a lower dielectric loss. The formation of abundant microcapacitors and improved interfacial polarization effect by improving the dispersion of MWNTs in the composites via carboxylic functionalization was the main reason for the excellent dielectric properties of PA11/c-MWNTs composites.

Achieving the desired sensors possessing multimodal sensory abilities and robust environmental degradability is critical for the practical applications of flexible wearable electronic devices. Herein, a facile and efficient strategy for preparing multifunctional sensors with a dual conductive network by sequential decoration of reduced graphene oxide and polyaniline onto the air-laid paper fibers is proposed. Such a design provides the fabricated sensor with dual-modal responsive capabilities, reaching an ultrahigh pressure sensitivity of 143.41 kPa−1 and an ammonia sensitivity of 0.036 ppm−1. The as-prepared sensor also exhibits a remarkable durability (5000 cycles), rapid pressure response time (70 ms), gas response time (30 s) and wide pressure-working range (0.005–40 kPa). The degradation experiment shows that the sensor possesses an excellent degradability, implying that it is free of environmental pollution. It can be utilized to perceive the human activities and surrounding status, thereby paving a valid path for constructing high-performance electronic devices.

The surface modification of nano particles is very important in nanotechnology. Grafting from (GF) and grafting to (GT) are two main methods to prepare surface modified nanoparticles like nanocellulose crystalline (NCC) grafted with polylactic acid (PLA) chains. In the GF method, the NCC can get high grafting degree but short side chains to improve its compatibility with the polymer matrix. The GT method can help obtain long side chains to increase the chain entanglements but owns low grafting density. To take the advantage of both methods, a mixed modification method combining GT and GF methods was put forward to synthesize comb-like NCC-g-PLA (NP) as a macromolecular modifying agent of PLA. Firstly, GT Method was used to obtain long side-chain NP to improve chain entanglement. Secondly, the GF method was applied to obtain NP-g-PLA (NPL) and NP-g-PDLA (NPD) with additional short side chains to improve its dispersion and compatibility in the PLA matrix. The products showed an enhanced nucleation effect, the degree of crystallinity (Xc) of PLA composites increased almost four times with only 1 wt% NPD or NPL. What's more, the storage modulus and loss modulus of the composite melts also increased with 1 wt% NPL or NPD. The NPD/PLA shows a higher effect than NPL/PLA owning to stronger interaction originated from the stereocomplex (SC) network of PLA matrix with PDLA short chains in NPD.

Distinct “island-bridge” structure was purposely designed by appointing carbon nanofiber (CNF) filled high density polyethylene (HDPE) and polyvinylidene fluoride (PVDF) blend, in which, very dense electrical conductive networks were formed in HDPE dispersion phase (islands) and these islands were then linked by CNF particles partly stretched out from HDPE phase or distributed in PVDF phase (bridges). The HDPE/PVDF/CNF composites with “island-bridge” electrical conductive network showed unique positive temperature coefficient (PTC) effect, namely, a two-step PTC effect companied extremely favorable PTC reproducibility. The first sharp increase and the second increase of resistivity could be attributed to the sequential volume expansion of HDPE and PVDF at their melting point, where the electrical conductive networks were broken twice. In addition, the existence of dense electrical conductive networks in HDPE phase and the additional compression on them by the volume shrinkage of PVDF phase during the cooling process resulted in the favorable PTC reproducibility.

The carboxylic acid functionalized multi-walled carbon nanotubes/polyaniline nanotubes (PANI-NTs)/carboxylic acid functionalized single-walled carbon nanotubes electrodes for the flexible supercapacitors are fabricated by the layer-by-layer vacuum filtration. This strategy is aimed to assist powdery PANI-NTs to form a binder-free electrode, and meanwhile avoid sufficient contact between PANI-NTs and carbon nanotubes, ensuring abundant channels with a low tortuosity for enhanced electrolyte permeation and ion diffusion as well as large ion available surface area. Consequently, the assembled all-solid-state device achieves a high areal capacitance (258 mF cm−2 at current density of 0.5 mA cm−2), a superior energy density (3.82 m Wh cm−3 at a power density 33 mW cm−3) and favorable cycle stability (75.1% capacitance retention after 5000 cycles). Furthermore, the supercapacitor possesses outstanding flexibility and can be 180° bended up to 1000 times without loss of capacitance. Our works reveal that electrode structure design and fabrication procedures are also significant factors that greatly dominates electrochemical performance of supercapacitors.

Flexible pressure sensors are increasingly required for their widely practical applications in health monitoring, humanoid robotics and wearable electronics. Although the geometric microstructure design or active material selection for sensor has been manipulated by many researchers, achieving the desired pressure sensor possessing high sensitivity over a broad linear detection range is still challenging. Herein, a flexible and wearable pressure sensor is demonstrated based on the polyaniline/polydimethylsiloxane (PANI/PDMS) composite with hollow structure and micro-protrude surface structure. The sensitivity and linearity of the as-fabricated sensor could be greatly enhanced through the construction of hollow structure and micro-protrude surface structure, reaching a sensitivity of 0.641 kPa−1 over a broad linear range (0.05–60 kPa), and the sensor also exhibits stable cycling performances (6000 cycles), fast response time (200 ms) and recovery time (150 ms). Importantly, the sensing mechanism of this sensor is theoretically studied, a sensing model based on tunneling effect and contact mechanic is proposed and its validity is experimentally verified. Finally, the pressure sensor demonstrates practical applications in object operations, answering mouse click and feet movements, thereby providing a significant guidance for constructing advanced electronic devices.

Conductive elastomeric materials of multi-walled carbon nanotube (MWCNT) filled thermoplastic vulcanizate (TPV) based on polypropylene (PP)/ethylene-propylene-diene rubber (EPDM) blends were fabricated via different processing procedures, i.e., one-step and two-step methods, to control strain sensitivity aiming at applications from strain sensors to stretchable conductors. The phase size of cross-linked EPDM could be effectively tuned and the average diameter of EPDM particles was 550 nm for one-step TPV and 230 μm for two-step TPV. Uniform dispersion of MWCNTs in two-step TPV and serious aggregations of MWCNTs in one-step TPV were observed. Both TPVs showed excellent strain-resistance repeatability for 50 tensile and recovery cycles. The one-step-TPV showed a potential to be used as strain sensor due to a high gauge factor (GF) of 1004 at a strain of 100%, while the resistance for the two-step TPV composite was independent with strain even at a strain of 200%, resulting in a stretchable conductor with excellent resistance memory effect. The different strain sensitivity can be explained by the orientation of PP matrix. Moreover, the two-step TPV showed much lower electrical conductivity percolation threshold, 0.65 wt.%. This work provided a simple route to tune the strain sensitivity of MWCNTs filled TPVs based on PP/EPDM blends for applications from strain sensors to highly stretchable conductor through different processing procedures to control the morphologies and MWCNT dispersion.

A nanocomposite with a giant dielectric constant and suppressed dielectric loss was obtained from the high-density polyethylene (HDPE)/polyamide-11 (PA11)/multiwalled carbon nanotube (MWCNTs) composites, by tailoring the selective localization of MWCNTs in the PA11 phase and improving the interfacial interaction between HDPE and PA11 through the addition of high density polyethylene grafted maleic anhydride (HDPE-g-MAH). The effect of the addition of the polar component compatibilizer (HDPE-g-MAH) and PA11 on the dielectric properties of the HDPE/MWCNT composites was systematically studied. Through the addition of the polar phase (PA11) into the HDPE/MWCNT composites as the dispersed phase, with MWCNTs selectively localized in it, the dielectric properties were improved. Subsequently, as the compatibilizer (HDPE-g-MAH) was added into the HDPE/PA11/MWCNT composites, the interface between HDPE and PA11 became indistinct and PA11 in the form of dispersed phase coated MWCNTs could generate some degree of combination, to cause the size of the dispersed phase to get larger. Therefore, the dielectric constant of HDPE/PA11/MWCNT composites containing compatibilizer was up to 4000 at 3 wt% MWCNT and 103 Hz, which was attributed to the selective localization of MWCNTs to reduce the distance between the MWCNTs and the formation of larger sized microcapacitors (PA11 coated MWCNTs), and dielectric loss was still maintained at a low value (∼2 at 103 Hz), which was due to the stronger interfacial interaction between HDPE and PA11. The composites displayed advantages of excellent dielectric properties and good processability, which are suitable for the development of dielectric materials for energy storage.

Flexible sensing materials have attracted tremendous attention for the practical applications in humanoid robotics and wearable electronics. However, achieving flexible sensors possessing high sensitivity and multifunctionality via a facile and robust manufacturing strategy is still challenging. Herein, a scalable and efficient fabrication strategy is employed to yield conductive textile with a hierarchical architecture as high performance piezoresistive sensing element, by assembling reduced graphene oxide and polyaniline nanorod arrays onto fabric fibers in sequence (PANI/rGO/textile). The pressure sensor, which is prepared by multilayer PANI/rGO/textile, exhibits ultrahigh sensitivity (97.28 kPa−1) and linear response over a wide pressure regime (0.0005–40 kPa), excellent durability (11000 cycles), wide working bandwidth (1–10 Hz), fast response time (≈30 ms) and recovery time (≈25 ms), and low detection limit (0.5 Pa). In practical applications, the pressure sensors are used to detect various human motions. Additionally, pressure sensor arrays could successfully perceive the magnitude and spatial distribution of diverse pressure stimuli. Moreover, the PANI/rGO/textile can be used for strain sensor directly, confirming a negative resistance variation and anisotropic strain response behavior. The strain sensor exhibits a high negative sensitivity (−78) and excellent durability (1000 cycles), which could be woven on clothing for human activities monitoring, thereby marking a significant progress for constructing high-performance wearable electronics.

In this work, polyethylene (PE)/silica microsphere composite melt is used to penetrate the ethylene-α-octene block copolymer (OBC) melt in multi-melt multi-injection molding (M3IM) process. Due to the viscosity difference between PE/silica composite melt and OBC melt, a disturbed flow interface of these two melts formed. Thanks to the “shear-induced migration” theory in suspended balance model (SB model) and the unique flow field in M3IM, silica microspheres can be designed to migrate from high shear rate layer to low shear rate layer in PE/silica core melt, further to intaglio micro-pits on the interface of PE/silica core and OBC skin melt. As a result, the migrated silica microspheres can be intuitively observed by peeling off the OBC layer, as well as a “lotus seedpod”-like structure consisting of quantity-adjustable asperities and micro-pits can be constructed on the peeled surface of OBC layer. This work sheds lights to rapidly fabricate multi-tier structures by polymer melt processing strategies, aiming to manufacture functional devices on a large scale.

The elastic properties and multi-level relaxation behavior of a filler network in isotactic polypropylene/carbon black (iPP/CB) nanocomposites were systematically investigated, which was instructive for the development and application of viscoelastic materials. Based on a two-phase model, master curves of the elastic modulus of composites with different CB concentrations were built to describe the elastic feature of CB networks in the composites. From the elasticity of the networks, it was found that the critical volume of particle for the formation of the elastic network is 2.4 vol% and that the value of critical exponents is 5.1 ± 0.3, indicating that the particle–particle interaction in the network is strong. Based on semi-dilute fractal theory, the value obtained for the fractal dimension of the filler network was df = 2.0 ± 0.1, which was in agreement with the reaction limited aggregation mechanism, namely that CB particles must overcome a great barrier to form a cluster. The relaxation behavior of the filler network was also studied. For composites with a CB content of 2.0 vol% (slightly lower than the elastic percolation threshold of 2.4 vol%), the relaxation behavior became slower with the extension of the annealing time. Furthermore, the CB particles aggregated to form a denser network or backbone and the distribution of relaxation units became narrower, leading to an increase of the relaxation modulus. For composites with a CB content of 13.6 vol%, 0.5 h annealing treatment brought a wider distribution of relaxation units, due to the formation of “short chains” of particles, while both relaxation time and relaxation modulus of the network increased. Further annealing treatment (>0.5 h) made no difference to the distribution of relaxation units and relaxation modulus of the network, but relaxation time of the networks kept increasing. The CB concentration dependence of the relaxation behavior of the network revealed that as CB content increased, the relaxation modulus of the filler network increased monotonously. However, both relaxation time and distribution of relaxation units decreased to a minimum value when CB content increased to 6.4 vol%, and then increased with CB content.

The electrical resistance change of highly extensible films consisting of a network of carbon blacks in high-density polyethylene, with different regularity of stacked lamellae, is investigated. The film was fabricated by melt mixing of high-density polyethylene (HDPE) and carbon black (CB) via cast film extrusion. The morphology of particle network and regularity of stacked lamellae were affected by draw ratio during the cast film extrusion process. Testing has shown that the regularly stacked lamellar structure furnishes the film with hard elastic behavior and is conducive to the enhancement of the reversible level for the conductive film, which correlates with the piezoresistance response during the stretching and strain recovery. A rebound peak of R/R0 is observed at the beginning of each loading cycle within the relatively low deformation level and a marked growth of the amplitude of R/R0, as the number of cycle increases, is observed within the high deformation level for the film with highly regular stacked lamellae. It indicates that the regularity of stacked lamellar structure of matrix has a significant influence on the piezoresistivity of the film. The results could be utilized for the development of smart sensing and structural health monitoring of CB composite materials.

The piezoresistive behavior of two kinds of films, cast film and pressed film, based on high-density polyethylene/carbon-black composites is investigated for specimens loaded in axial tension. The tests are performed under a low number of cycles and different levels of applied strain. The normalized electrical resistance of the cast film is almost constant with strain in the elastic region and then it starts to increase with strain in the plastic region. However, for the pressed film, the normalized electrical resistance increases monotonically with strain. This unique behavior of resistance change of cast films can be applied to identify the elastic and plastic deformation in the composite. Moreover, two completely different strain sensing behaviors are presented in the cast film which undergo the cyclic tensile within the elastic regime and plastic regime. Finally, the normalized electrical resistance is simulated by using a mathematical model, taking into account the number of conductive paths and tunneling effect.

A layer-by-layer structure was constructed by alternately arranging conductive layers and insulating layers in a silicone dielectric elastomer (Ecoflex) to largely improve the actuated strain at a low electric field. In the electric field environment, the insulating layer blocks the transmission channel of electrons in the adjacent conductive layer, so the interfaces of adjacent conductive layers and insulating layers can accumulate and store a large number of charges, thereby greatly increasing the dielectric constant of the material. Meanwhile, the individual conductive layers are separated by an insulating layer to avoid causing large conductance losses. A high actuated strain (20.33%) at a relatively low electric field (12.5 kV mm−1) and good cyclic stability are obtained on the actuator without any pre-strain. These results demonstrate that our research provides a simple and effective method to significantly improve the actuated strain at a low electric field of DE and promote its practical application.

The influence of oscillatory shear on the conductivity of the isotactic polypropylene/polyethylene/carbon black composites is studied. It is found that the oscillatory shear under high strain amplitude can enhance the conductivity of the ternary composites with a HDPE/CB concentration in the percolation region. This is related to the fact that the high-strain oscillatory shear can improve the continuity of the conductive HDPE/CB phase in the composites. This finding has not been previously reported, and it may be used in industry to improve the conductivity of the ternary conductive composites with a low filler loading.

Composites of high-density polyethylene (HDPE) with different kinds of carbon black (CB) were prepared through melt blending. The influence of the CB structure on the stability and efficiency of the conductive network in HDPE/CB composites were mainly investigated. Scanning electron microscopy was used to observe the morphology of the CB primary aggregates. The relationship between the temperature-resistivity behaviors of the composites and the crystallization behaviors of the matrix were also investigated. High-structure CB built an effective conductive network at a low filler content compared to the low-structure one because of its branched morphology. Therefore, the composite containing high-structure CB revealed a lower percolation threshold. The composite containing low-structure CB obtained a stronger positive temperature coefficient (PTC) intensity because the cluster network was fragile and easily damaged during matrix melting. The reproducibility of the results of PTC effect of the composite containing high-structure CB was better than that of the composite containing a low-structure one. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

In this article, the positive temperature coefficient (PTC) effect was studied for high-density polyethylene (HDPE)/carbon fiber (CF) composites. All of the samples showed a significant PTC effect during the heating processes without a negative temperature coefficient (NTC) effect, even at a temperature much higher than the melting point of the polymer matrix. An ever-increasing PTC intensity with increasing thermal cycles was observed in our study that had never been reported in previous research. The absence of a NTC effect resulted from the increased binding force between the matrix and fillers that contributed to the very special structure of CF surface. We incorporated thermal expansion theory and quantum tunneling effects to explain PTC effect. From the SEM micrographs for the HDPE/CF composites before and after the different thermal cycles, we found that the surface of CF was covered with a layer of polymer which resulted in a change in the gap length between CF and HDPE and its distribution. We believed that the gap change induced by polymer absorption on the fiber surface had a great effect on the PTC effect.

Crystallization behavior of conductive composite has a great effect on the formation of conductive network. But very few studies have exposited, specially on the micro level, the evolution of conductive network during the crystallization of matrix. In this study, the conductive network was found to be destroyed by crystallization behavior of isotactic polypropylene (iPP) matrix, and the carbon black (CB) particles were rejected to the amorphous region or the inter-lamellar of spherulite. By comparison, the low-structure carbon black (LCB) filled system was more sensitive to the crystallization of matrix than the high-structure carbon black (HCB) filled system because of the morphology and interaction force of the CB primary aggregate. A secondary increase in volume resistivity during terminal crystallization was observed in iPP/LCB composite when it isothermally crystallized at a certain temperature. In that case, an analysis of crystallization kinetics of composites through a modified Lauritzen-Hoffman model indicated that the transition from regime I→II in the isothermal crystallization process of iPP matrix showed significant influence on the network formation of LCB particles.

Composites with multi-walled carbon nanotubes (MWNTs) involved in polyamide 11 (PA11) were prepared via a conventional melt blending method. The structure, morphology, crystallization behavior, electrical, and dielectric properties of composites were investigated. The results demonstrated that the dispersed uniformly MWNTs favored the formation of α crystal of PA11 when the composites were quenched from melt. The dielectric constant of composites was dependent on the electric field frequency and MWNTs content, and the highest value of dielectric constant was as high as 350 for the composite with 1.21 vol % MWNTs at 103 Hz, accompanied by a low dielectric loss. The enhanced dielectric properties could be interpreted by the formation of abundant nanocapacitors within the composites and the interfacial polarization effect resulting from accumulation of charge carriers at the internal interfaces between MWNTs and PA11. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42642.

Novel conductive films with a unique strain (e)-sensing behavior and based on a blend of isotactic polypropylene (iPP), high-density polyethylene (HDPE), and carbon black (CB) were fabricated by an extrusion casting method. The morphology and e-sensing behavior of the films were investigated. Scanning electron microscope images showed that the oriented lamellae with a growing direction perpendicular to the extrusion direction were obtained in the HDPE phase and were accompanied by a cocontinuous structure of the iPP phase and HDPE/CB phase. The conductive percolation threshold (mc) and resistivity–e behavior of the thin films are affected by the drawing ratio during the process of film preparation. The mc and electrical resistance of the iPP/HDPE/CB composite films increased with the drawing ratio. The gauge factor of the films within the elastic region decreased with increasing drawing ratio. Furthermore, the result of iPP/(HDPE/CB) 40/60 with a high drawing ratio shows that a reversible conductivity was obtained during the cyclic tensile testing (e = 10%), but an irreversible conductivity makes the film fail during use at the applied e values of up to 15%. This makes them good piezoresistive candidates for e-sensing materials. Moreover, a simple structural model was proposed to describe the reversible and irreversible phenomena in the electrical resistance behavior of the iPP/HDPE/CB films under tensile loading. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40686.

We report a detailed investigation on the effect of carbon black (CB) morphology on network formation and evolution in high-density polyethylene/CB composites. There were three types of networks in our study, the electrical network in the solid state and the electrical and rheological networks in the melt state. The evolution of the network in the polymer melt was traced by simultaneous electrical resistivity (R) and dynamic rheology testing. An oscillation strain sweep was used to investigate the network stability with a large strain. We found that with high-structure CB with a branched morphology, it was easier to form a filler–polymer or filler–filler network than with low-structure CB with a spherical morphology in the composite melt. The high-structure CB network was more stable with a large strain compared to the low-structure one. Meanwhile, the low-structure CB aggregates had stronger capability of movement and re-aggregation in the polymer melt. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39953.