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Temperature-resistivity behaviors of carbon black/polyamide 6/high-density polyethylene conductive polymer composites containing electrospun polyamide 6 fibrous network were studied systematically. The positive temperature coefficient intensity of the conductive polymer composites increased firstly and then reduced gradually with increasing heating rate, showing a heating rate-dependent positive temperature coefficient intensity. The fascinating phenomenon was ascribed to the microstructure change of conductive network induced by the volume expansion and the thermal residual stress generated in the composites. During the heating-cooling runs at different top testing temperature of 140, 150 and 180℃, the room-temperature resistivity of sample was observed to be 30, 2.3 and 1.6 orders of magnitude higher than the initial value after one heating-cooling run, respectively. The thermal treatment time above the melting temperature of high-density polyethylene and the viscosity variation of the conductive polymer composites were responsible for the increased resistivity. This study provides a guideline for fabricating conductive polymer composites with tuning positive temperature coefficient property. [ABSTRACT FROM AUTHOR]

Electrically conductive carbon black (CB)/polypropylene (PP) nanocomposites with a segregated structure are fabricated by localizing CB particles at the interfaces among the PP granules. Interesting double-peak positive temperature coefficient (PTC) effect when exposed to temperature field is observed and ascribed to the breakage of unique segregated conductive network due to the volume expansion stemming from the crystal melting of interfacial PP and the bulk PP matrix. With extending thermal treatment time, the PTC intensity first increases and then decreases obviously. Long treatment time is required for the composites with high CB loadings to reach the PTC intensity maximum value. This phenomenon is attributed to the evolution of segregated microstructure during the thermal treatment, which is traced visually in situ through an optical microscope (OM). The diffusion due to the concentration gradient and the subsequent aggregation of CB particles lead to this behavior. A model based on the OM observation is proposed to reveal the origin of this novel resistivity-temperature behavior. [ABSTRACT FROM AUTHOR]

Liquid-sensing behaviors of carbon black (CB)/polyamide 6 (PA6)/high-density polyethylene (HDPE) composite containing conductive electrospun fibrous network were investigated by detecting electrical resistance variations toward different solvents. The material exhibited a good sensing selectivity, which could be predicted by Flory-Huggins interaction parameter χ . In immersion-drying runs (IDRs), the composite showed a large liquid-sensing responsivity but poor reproducibility toward 'good solvent' xylene. After long-term immersion treatment in xylene, the metastable conductive pathways became stabilized, and a better reproducibility was finally achieved. Absorption/desorption equilibrium state of the composite in 'moderate' or 'poor' solvents was reached more easily than that in good solvent. Additionally, more rapid response, higher sensing responsivity, and better reproducibility of the composite in 'moderate solvent' cyclohexane were observed at a higher environment temperature. These results indicated that liquid-sensing behaviors of conductive polymer composites could be tailored by tuning the microstructure or utilizing the pretreatment. [ABSTRACT FROM AUTHOR]

Liquid-sensing behaviors of carbon black (CB)/polypropylene (PP) and carbon nanotubes (CNTs)/PP-conductive polymer composites (CPCs) were studied in detail. It was found that the CB/PP showed a higher liquid-sensing intensity but a poorer reproducibility toward the 'good solvent' xylene. The main origin is that the conductive works formed by CB, the zero-dimensional filler, are vulnerable to the swelling effect of PP during the immersion-drying runs (IDRs), whereas CNTs in the CNTs/PP with a large aspect ratio have better capacity in maintaining the conductive networks. To investigate the influence of the remaining solvent on the evolution of conductive networks, liquid-sensing tests of the two composites after long-term immersion in xylene were investigated. Results showed that the liquid-sensing behaviors of CNTs/PP changed less weakly compared with that of the CB/PP. Liquid-sensing behaviors of the two composites, cyclohexane and tetrachloromethane, to the 'poor solvents' were also studied. The results of this article indicate that liquid-sensing behaviors of the CPCs were affected by the microstructure of the conductive filler, the solubility parameter, and the molar volume of the solvent significantly. POLYM. COMPOS., 36:205-213, 2015. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

A carbon black (CB)/polypropylene (PP)/ultrahigh-molecular-weight polyethylene (UHMWPE) composite with a segregated structure was fabricated by using binary polymer granules as matrices. In preparation, an ethanol-assisted dispersion method was employed to disperse CB particles on the surface of the two polymer granules. The segregated conductive network was then constructed by hot compaction based on the volume exclusion effect of the polymer matrices. The conductive composite shows an ultralow percolation threshold of 0.34 vol.%. In temperature-resistivity test, a double positive temperature coefficient (PTC) effect was observed. In addition, the negative temperature coefficient (NTC) effect was eliminated significantly. These interesting temperature-resistivity behaviors were ascribed to the introduction of the binary polymer matrices and the mobility limitation of CB particles located at the PP/UHMWPE interface. These characteristics were probed by in situ morphology observation in heating process. The present paper provides a novel route for preparing conductive composites with an ultralow percolation threshold, a wider PTC region, and a zero NTC effect. [ABSTRACT FROM AUTHOR]

Abstract: Electrically conductive carbon black (CB)/polyamide 6 (PA6)/high density polyethylene (HDPE) composite with a low percolation threshold was fabricated by embedding conductive CB/PA6 membrane into the HDPE matrix. The CB/PA6 membrane was prepared by localizing CB particles on the surfaces of the electrospun PA6 fibrous membrane by a dip-coating method. Percolation threshold of this CB/PA6/HDPE composite was only ca. 4.3vol%, showing a considerable reduction compared to that of the common CB/HDPE (8.5vol%). Through the present method, a conductive polymer composite with enhanced processability and lowered cost has been achieved with extremely low loading of PA6 (1.5vol%). [Copyright &y& Elsevier]

Carbon black (CB)/poly (lactic acid) (PLA) conductive biopolymer composite were fabricated by casting. A low percolation value (1.25 vol%) is achieved due to the formation of a two-dimensional conductive network in the composite. Vapor sensing behaviors of the CB/PLA conductive composite were studied. A high chemical selectivity with respect to different organic vapors and a good reproducibility to two typical solvents, ethyl acetate and ethanol, during exposure-drying runs have been demonstrated. The variations of the sensing behaviors during exposure-drying processes were associated with the evolvement of CB conductive networks. The results indicate that the Flory-Huggins interactions parameter x12, related to the solubility parameter (thermodynamic factor), molar volume (kinetic factor) and the measurement temperature, affects the vapor sensing behaviors of CB/PLA composite significantly. These results suggest CB/PLA conductive biopolymer composite can be applied as a nice vapor sensor candidate. [ABSTRACT FROM AUTHOR]

The conductive polymer composite (CPC) based on carbon black (CB), polyethylene (PE), and poly(ethylene terephthalate) (PET) was fabricated, in which the majority of CB particles were selectively localized in the surface of in situ deformed, highly oriented PET microfibrils. The on-line measurement of the electrical resistivity of the CPC materials indicated that the critical time for conductive network formation decreased with the increase of the annealing temperature and the filler loading. The activation energy for conductive network formation was about 96 kJ/mol, which was much higher than that for common CB/PE composite due to the large size of the conductive microfibrils. By a thermodynamic percolation model, the percolation threshold at equilibrium state was 1.735 vol.%, below which the effective conductive network was never formed. The reorganization velocity of the conductive microfibrils was a function of annealing temperature. This study extended insight into the dynamic process of the conductive network formation during annealing. [ABSTRACT FROM AUTHOR]

The resistivity response of anisotropically conductive polymer composite (ACPC) with carbon black (CB) particles selectively localizing at the surfaces of aligned polyethylene terephthalate (PET) microfibrils was investigated during cooling from 180°C in the parallel and perpendicular directions. The ACPC exhibited a cooling positive temperature coefficient (PTC) around the crystallization temperature of polyethylene (PE) matrix. With the increase of CB loading, the cooling PTC effect decreased gradually. When the ACPC experienced isothermal annealing, the aligned microfibrils disordered to form more conductive pathways. The increase of annealing time caused the gradual attenuation of the cooling PTC effect in both directions. [ABSTRACT FROM AUTHOR]

Abstract: A carbon black (CB) based anisotropically conductive polymer composite (ACPC) was fabricated using an easy method comprising an extrusion-hot stretch-quenching process. The resultant ACPC exhibited a very low percolation and a strong anisotropy in conductivity due to its unique structure in which the dispersed polymer phase was deformed in situ into oriented conductive microfibrils, whose surface region holds the majority of CB particles. The oriented conductive microfibrils constructed different conductive networks in the parallel and perpendicular directions of ACPC, thus leading to a strong electrical anisotropy. The conductive mechanism underlying this material took effect in a complex manner including contact conduction and tunneling conduction. [Copyright &y& Elsevier]

Polypropylene conductive composites with carbon black selectively distributed at the interfaces between polypropylene matrixes are described by Kun Dai, Zhanhu Guo, and co‐workers in article number 1700265. This segregated conductive network is damaged and constructed by thermal diffusion and aggregation of carbon black, leading to an increasing and then decreasing positive temperature coefficient (PTC) effect. [ABSTRACT FROM AUTHOR]

• CB particles were decorated on PDMS foam to fabricate a flexible porous piezoresistive sensor. • The sensor possesses a very high linear working range (up to 91%). • A fast response time (45 ms) and superior durability (>15000 cycles) have both been achieved. • The sensor possess an excellent hydrophobic property (water contact angle up to 149°). • The CB/PDMS foam can also be used for oil/water separation. The achievement of favorable pressure sensor integrated with large linear working range, high sensitivity and excellent response durability is still a great challenge for flexible and wearable piezoresistive materials. In this paper, a facile and scalable strategy is proposed to fabricate a porous foam sensor based on carbon black/polydimethylsiloxane (CB/PDMS). CB particles were decorated onto the surface of the cell walls and some particles were embedded into PDMS matrix after the ultrasonication treatment. The density and porosity of the foam are 0.13 g/cm3 and 76.1%, respectively. A very high linear working range (up to 91%), an excellent response stability, a fast response time (45 ms), and a superior durability (>15000 cycles) are achieved synchronously. Here, the large linear sensing range is mainly related to the nice CB conductive network on the cross-linked PDMS foam and the high modulus and elasticity of the composite material, which ensure the homogeneous deformation of the foam under compression. It is worth noting that the response behavior of CB/PDMS foam is maintained well even in water owing to its excellent hydrophobic property (water contact angle up to 149°), indicating that this material can be used as a waterproof piezoresistive sensor. Our CB/PDMS foam is then assembled as a wearable sensor, and it exhibits nice capability of monitoring human body motions, such as the bending of fingers and elbow, walking, jumping and squatting, etc. The porous foam sensor also has a good oil/water separation ability, showing a multifunctional characteristic. [ABSTRACT FROM AUTHOR]

In this paper, carbon black (CB), carbon fiber (CF), and hybrid CF/CB were introduced into polypropylene (PP) to fabricate different conductive composites by melt mixing, respectively. The combined effects of CF and CB on the electrical and liquid sensing properties of PP-based composites were investigated in detail. In virtue of the co-supporting conductive network, percolation threshold of the CF/CB/PP composite was reduced apparently upon the addition of 8 wt.% CF. For liquid sensing measurements, CF/CB/PP conductive polymer composites (CPCs) exhibited a superior liquid sensing behavior with higher responsivity, rapider response and better stability in contrast to the counterpart CB/PP. In addition, the response curves are found to be remarkably characteristic for discriminating different kinds of organic solvents. The present paper provides a new route to tailor the liquid sensing properties of CPCs. [ABSTRACT FROM AUTHOR]

Abstract: Under the assistance of carbon fibers (CFs) with a large aspect ratio, an evident reduction in the percolation threshold of a segregated carbon black (CB)/polypropylene (PP) conductive polymer composite (CPC) has been achieved. The origin of the ultra-low percolation threshold 0.94vol% is ascribed to the design of a shish–calabash-like conductive network, where the CFs function as bridges between the segregated CB particles and CB particles act as calabashs contributing to the conductive framework. This interesting microstructure causes a synergistic effect on the conductive properties. A model is proposed to evaluate the percolation behavior of the unique CF/CB/PP composite. [Copyright &y& Elsevier]

Smart and wearable strain sensors have sparked enormous research interests in various applications of flexible electronic devices. For this topic, it remains a huge challenge to acquire wide sensing range, high sensitivity, superior durability and fast response synergistically. Herein, we present an ultra-sensitive and durable strain sensor with sandwich structure to address the issues, which is mainly composed of the composite of carbon black (CB)/aligned thermoplastic polyurethane (TPU) fibrous mat and the Ecoflex. The CB/TPU/Ecoflex strain sensor (CTESS) is prepared via decorating CB nanoparticles onto the aligned electrospun TPU fibrous mats by ultrasonication, then encapsulated with Ecoflex to develop a sandwich structure. This structure provides effective protection for the conductive CB/TPU fibrous network, endowing the strain sensor with excellent sensing performances, including low detection limit (0.5% strain), wide response range (up to 225% strain), ultrahigh sensitivity (maximum gauge factor of 3186.4 at strain of 225%), fast response time (70 ms) and favorable repeatability even after 5000 stretching/releasing cycles. CTESS also shows an excellent anti-interference capability to external humidity and temperature. The CTESS is then assembled as artificial electronic skins to monitor various human motions, exhibiting great application prospects in next-generation wearable electronics. Image 1 [ABSTRACT FROM AUTHOR]

The preparation of a satisfactory strain sensor integrated with ultrahigh sensitivity, large application range and superior stability is still a huge challenge. Herein, a highly stretchable carbon black/thermoplastic polyurethane fibrous strain sensor with porous and core-sheath structure is successfully prepared via an efficient coaxial wet-spun approach. The fiber possesses a porous monolith structure owing to countercurrent diffusion of the solvent and coagulation. An ultrahigh sensitivity (maximum gauge factor of 28,084), fast response time (200 ms), favorable durability (>11,000 cycles) and large strain range (>200%) are achieved simultaneously. Intriguingly, the values of ln (R/R 0) of the fiber show a good linearity versus tensile strain, which can be used to predict changes of sensitivity in application. The tunneling theory is employed to analyze the response behaviors. The fibrous strain sensor is then utilized for detecting various human movements and tactile sensing, proving its tremendous potential as wearable electronics. Image 1 [ABSTRACT FROM AUTHOR]

• A flexible CB/TPU foam with a pinnate-veined aligned porous structure was prepared. • The foam can both serve as a flexible strain sensor and an adsorption material. • The foam sensor has excellent sensing discernibility and high sensitivity. • The sensor exhibits superior response stability in a wide sensing range. In this paper, flexible conductive carbon black (CB)/thermoplastic polyurethane (TPU) foam (CTF) with an intriguing pinnate-veined aligned porous structure was fabricated via a unidirectional freeze-drying process. The density, porosity and average pore size of the composite foam are 0.13 g cm−3, 83.7% and 24.9 μm, respectively. CB particles are uniformly dispersed in the skeleton of the as-prepared foam, resulting in a low percolation threshold of 0.48 vol%. The CTF is capable of distinguishing different compressive strain by change of the relative resistance. Its responsive behaviors towards compressive strain present an excellent linear characteristic with a high gauge factor (GF) up to 1.55. In the piezoresistive tests, the CTF shows a fast response/relaxation time (150/150 ms), fascinating recoverability, excellent response stability within a wide workable detection range up to 80% strain (corresponding pressure of 584.4 kPa) and a superior durability (>10000 cycles), which is mainly related to the pinnate-veined aligned porous structure along the orientation direction. The CTF was then assembled as a wearable sensor to monitor various human motions such as arm bending, squatting, tiptoeing, etc., showing good detection performances. The sensor can also deal with water pollution through oil/water separation, suggesting its multifunctionality and promising prospects in complicated situations. [ABSTRACT FROM AUTHOR]