Search

To get strong and anti-freezing hydrogel with multiple contact and non-contact sensing performance, a facial method is proposed in this work using multiple physical bonding crosslinking and glycerol (GL) immersing strategy. The obtained hydrogels show a tensile stress at break of 5.4 MPa, an elongation at break of 1420 %, and a compression strength of 12.2 MPa at 80 % strain. Additionally, benefiting from the GL immersing the hydrogel shows superior anti-freezing (no ice formation at −60 °C) and water retention ability (water loss less than 17 % after storing at 50 °C for 7 h). Furthermore, the volume resistance of hydrogels exhibits excellent responses against humidity, temperature, strain, and stress. The variation of the resistance against temperature can be well described by the Arrhenius equation with an activation energy of 501.3 meV, verifying a band-gap dominated diffusion hopping conductive mechanism of the hydrogel. The sufficient humidity and temperature responses make the hydrogel applicable as a non-contact sensor, and the wide temperature strain sensing (−40 to 50 °C) and stress sensing capability ensures that the hydrogel can be used as a contact sensor, ensuring that the hydrogel can be used as perfect flexible sensor for monitoring human motion and physiological signals. [Display omitted] • Strong and anti-freezing hydrogel with multiple sensing performance is obtained. • The hydrogel is prepared using multiple physical bonding crosslinking and glycerol immersing strategy. • The resistance variation against temperature is described by the Arrhenius equation with an activation energy of 501.3 meV. [ABSTRACT FROM AUTHOR]

Addressing water pollution issues is directly related to green sustainable development. In this work, a heterostructure polyurethane-based (PU) sponge was prepared by a facile "dip-adhere" strategy to achieve simultaneous and efficient removal of oils and dyes from water. This innovatively designed sponge comprises two functional layers. The hydrophobic/lipophilic octadecylamine-molybdenum disulfide coated PU sponge (ODA-MoS 2 @PU) layer exhibits excellent sorption capacity, ranging from 37.35 to 63.52 times its own weight, for eight organic solvents (DMSO, isopropanol, n-hexane, petroleum ether, n-butanol, glycol, acetone, xylene) and five oils (soybean oil, olive oil, gasoline, diesel, and lubrication). Furthermore, it exhibits robust stability in extreme environments and maintains a high separation efficiency (99 % after 50 separations). The photocatalytic/superhydrophilic polydopamine-molybdenum disulfide coated PU sponge (PDA-MoS 2 @PU) layer demonstrates great photocatalytic degradation efficiency for dyes (96.80 % for methylene blue and 97.39 % for methyl orange). Consequently, the heterostructure PU sponge holds application potential in environment remediation. [Display omitted] • A dual-functional heterostructure sponge was prepared. • Continuous oil-water separation was realized with the oil-gathering device. • The simultaneous treatment of removing oils and dyes was achieved. [ABSTRACT FROM AUTHOR]

Being as lightweight and thin as possible is highly desirable for electromagnetic interference (EMI) shielding materials in electronic devices as the high requirement in miniaturization and weight reduction. Constructing three-dimensional (3D) porous conductive architecture into two-dimensional (2D) film provides one of the feasible strategies. Herein, pyrolytic carbon aerogel films from aramid nanofiber (ANF) with novel skin-core structure containing compact film skin and 3D porous nanofiber network core were fabricated by a facile method. The abundant conjugate aromatic structure in backbone endows ANF-derived carbon aerogel film with a high conductivity of 1029.5 S/m. Remarkably, the high electrical conductivity, as well as the 3D porous skin-core structure, which not only constructs the interconnected electron transmission paths but also significantly extends the propagation path of EM waves, enables the carbon aerogel film a high EMI shielding effectiveness (SE) of 41.4 dB at low density (54.4 mg/cm3) and thin thickness (162 μm) with high specific shielding effectiveness (SSE/t) of up to 47122.6 dB cm2/g. Besides, ANF-derived carbon aerogel film exhibits an excellent photothermal conversion ability, which greatly broadens the application environment. More interestingly, the easy and flexible preparation method with adjustable film thickness, density and area makes large-scale production of carbon aerogel film possible. [Display omitted] • ANF-derived carbon aerogel film prepared by a facile and scalable method. • The film reveals skin-core structure with compact skin and nanofiber network core. • The carbon aerogel film exhibits high EMI SE at low density and thin thickness. • The carbon aerogel film shows an excellent photothermal conversion capacity. [ABSTRACT FROM AUTHOR]

The chemical conversion of the surface termination of 2D transition metal carbides/nitrides (MXenes) has opened up a design space that previously had not been extensively explored for this functional material. Herein, via a simple sealed thermal method, the amino terminated groups were successfully introduced on Ti 3 C 2 MXene surface. The substitution reaction of amino group to hydroxyl group was proposed to elucidate this aminated process. As the amination would reduce the carrier density on the surface of MXene, the electrical conductivity of MXene-NH 2 film decreased, while it still reached a high conductivity of 2.11 × 104 S m−1. This film also possessed an excellent electromagnetic interference shielding effectiveness of 16160 dB cm2 g−1. Importantly, although the introduction of amino termination altered Zeta potential value, Zeta potential sign remained negative and the MXene-NH 2 exhibited excellent dispersity in water similar to that of traditional MXenes. Furthermore, the existence of covalent bonds endowed MXene-NH 2 polymer composite film with improved mechanical properties. Compared with that of traditional CMC/MXene film, the tensile strength and fracture energy of CMC/MXene-NH 2 increased by 65.5% and 132.7%, respectively. These results demonstrated that the introduction of amino terminated group on MXene surface would be an effective strategy to obtain higher performance MXene-based films. [Display omitted] [ABSTRACT FROM AUTHOR]

For smart devices, there is a growing demand for multi-functional soft actuators, nevertheless, well-developed actuators always respond to single stimulus, and it is still challenging to achieve the application diversity standards. Herein, a bidirectional multi-stimuli responsive soft actuator based on Ti 3 C 2 T X MXene-cellulose nanowhiskers (CNWs)-polyvinyl alcohol (PVA)/polydimethylsiloxane (PDMS) multilayer membranes is proposed (MXCP-P). By grafting CNWs onto MXene nanosheets, a freestanding composite film with gradient layered structure was prepared. Due to the hygroscopicity among MXene nanosheets, increased interlayer space is in favor of adsorption/desorption of water molecules, causing invertible shape change and humidity-driven deformation with a rapid response. Based on high photothermal conversion capacity of MXene and large difference of coefficient of thermal expansion between PDMS and MXene, the MXCP-P achieves an ultra-large amplitude and fast response driven by natural light. A Venus flytrap soft robot is constructed with good actuation behaviors. The MXCP-P film was employed as actuators in the opera of The Male Phoenix Pursui from Han Dynasty and in shadow puppetry "Monkey King Subdus the White-Bone Demon" of China, both exhibiting excellent performances towards humidity and light stimuli synchronously. This paper inspires a new strategy for multi-stimuli responsive soft bionic robots and intelligent traditional shadow play. MXCP-P based multi-stimuli responsive flexible actuator was fabricated, showing improved mechanical properties and bidirectional bending characteristics. In addition to its application in traditional fly traps and rolling robots, the MXCP-P actuator is also employed to develop traditional Chinese opera culture, such as "The Male Phoenix Pursui" and "Shadow puppetry". [Display omitted] [ABSTRACT FROM AUTHOR]

Polyimide foams (PIFs) are usually synthesized by solution polymerization, followed by chemical foaming to prepare thermosetting foam. In this research, lightweight microcellular thermoplastic polyimide foams (TPIFs) were fabricated via a novel two-step foaming approach using supercritical carbon dioxide (scCO 2) as a blowing agent. The poly(amic acid) (PAA) and polyester ammonium salt (PEAS) precursor solutions were synthesized with pyromellitic dianhydride (PMDA) as dianhydride reagents and polyether amine Jeffamine D230 as aliphatic diamine reagent via blending and solution polymerization, respectively. The solution polymerization process demonstrated a higher molecular weight and superior formability than the blending process. The optimum thermal imidization temperature of 200 °C was optimized via the thermal and rheological property analysis. The cell morphology and mechanical properties of the TPIFs could be turned by varying the saturation time, foaming pressure, and imidization temperature. At a thermal imidization temperature of 200 °C, the TPIFs exhibited a branched structure with a small mean cell diameter (123.78 μm), and a high compressive strength (0.4 MPa) under 10 % strain at high temperature and pressure, which was more than ten times that of the TPIFs with thermal imidization temperature of 130 °C. This research provides a feasible method for producing high volume expansion ratio TPIFs with adjustable microcellular structures and outstanding mechanical properties. [Display omitted] • Poly(amic acid) and polyester ammonium salt precursor were synthesized by blending and solution polymerization, respectively. • Adding a flexible linkage provided the torsional capacity of the chain segment, and improved its flexibility. • Microcellular TPI foams were fabricated via a novel two-step foaming approach using supercritical CO 2 as a blowing agent. • The branched molecular structure was favourable for improving cell uniformity and mechanical properties. [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]

Graphene (Gr) and its derivatives (such as graphene oxide (GO), reduced graphene oxide (RGO), nanoparticles decorated graphene, etc.) reinforced metal matrix composites (MMC) with good structural mechanical properties and functional properties have wide applications in aerospace, automotive, electronics and military fields. However, some problems exist in preparing high performance MMC including poor wettability between Gr-type fillers and metal matrix, and weak interfacial bonding strength. Efficient methods for preparing Gr-related nanomaterials filling metal matrix parts with high performance, especially for complex parts still need be further developed. The engineering application field of Gr MMC needs to be further expanded. In this paper, methods to prepare high performance MMC including surface modification of Gr and its derivatives, properties and applications of these reinforced MMC were reviewed with detailed examples. The main challenges were analyzed and the development trend of Gr-type types reinforced MMC was discussed. Image 1 • Surface modification of graphene improved wettability between graphene and metal matrix. • Methods for preparing metal matrix composites were reviewed. • Properties of graphene reinforced metal matrix composites were reviewed. • Applications of the metal based graphene composites were reviewed. [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]

Excess sludge, a carbon-rich valuable by-product from wastewater treatment, is utilized as a carbon precursor for synthesizing porous activated carbon. However, improving specific surface area (S BET) is the main challenge for the sludge derived activated carbon (SAC). In this study, the carbonization process was optimized as following: carbonization temperature of 900 °C, heating rate of 10 °C/min, and dwell time of 30 min. Moreover, the residue heavy metals and bound water remaining in the sludge were demonstrated to be important in the pore formation of the SAC. The metals acted as hard template to form the pores in the SAC after the metals were removed by acid wash. The bound water was found to be soft templates for forming pores due to its evaporation during carbonization. A maximum S BET of 1018.8 m2/g was achieved for the SAC when the bound water content was controlled at 2 wt%. Image 1 [ABSTRACT FROM AUTHOR]

In this study, reduced graphene oxide-alumina (RGO-Al 2 O 3) metacomposites with tunable negative permittivity were obtained from spark plasma sintering method. Regulation of negative permittivity was realized by adjusting the sintering process conditions. The effects of sintering temperature and pressure on the dielectric properties of RGO-Al 2 O 3 metacomposites were firstly studied in details. Interestingly, the Fano-like resonance phenomenon was observed in the RGO-Al 2 O 3 metacomposites containing 8.91 and 15.01 vol% GO produced from 1000 °C at 50 MPa. This phenomenon was attributed to the interference of two kinds of resonances, which was different from general polarization dipole resonance. The sintering temperature regulated the permittivity via the micro-capacitance of RGO itself and the interfacial effect between RGO and Al 2 O 3 grains. The resonance frequency was also dependent on the sintering temperature. The sintering pressure effectively controlled the value of permittivity and the resonance frequency which were influenced by the degree of GO reduction and the mutual contact between grains. With the increase of the sintering pressure, the value of permittivity increased and the resonance frequency advanced. Overall, the permittivity and the resonance frequency of the RGO-Al 2 O 3 metacomposites were easily regulated by adjusting the sintering process conditions. [ABSTRACT FROM AUTHOR]

Frequent oil spill incidents have resulted in serious environmental pollution posing a great threat to human health and ecological system, thus developing new absorbents to efficiently remove and recycle high-viscosity crude oil is attracting more attention. We herein report an eco-friendly flexible poly(butylene adipate-co-terephthalate) (PBAT)-based monolith with MXene (Ti 3 C 2 T x) and polydimethylsiloxane (PDMS) coatings (P-MXene@PBAT monolith) by convenient and economical preparation method for self-heating driven fast crude oil cleanup. Due to unique three-dimensional interconnected pore structure and superior hydrophobicity, the P-MXene@PBAT showed high saturated absorption capacity and cyclic separation efficiency for multifarious low-viscosity oils. The P-MXene@PBAT was endowed with excellent photo/electro-thermal performance via wrapping MXene layer. The maximum surface temperature of monolith quickly reached up to 81 °C under 1.0 kW m−2 (1.0 sun) irradiation and 91 °C under 8 V voltage, respectively. Furthermore, the P-MXene@PBAT could self-heat crude oil to dramatically decrease oil viscosity and accelerate separation process. Specially, the P-MXene@PBAT was able to continuously separate crude oil from water with a simple pump-assisted absorption device (crude oil flux of 204 kg m−2 h−1), which adapted to varied working conditions by coupling solar heating and Joule heating. Such environmental-friendly all-weather absorbent design provides a sustainable strategy for efficient remediation of crude oil spill. [Display omitted] • Biodegradable porous P-MXene@PBAT monolith with all-day work mode was fabricated. • The as-prepared monolith possessed outstanding solar/electro-thermal performance. • The flexible monolith exhibited excellent recyclability for oil/water separation. • The self-heating monolith could continuously recover viscous crude oil from water. [ABSTRACT FROM AUTHOR]

Fabrication of polymer films with superb mechanical properties is far from mature compared to that of fibers, hampering the further engineering applications of lightweight polymer materials. Herein, high density polyethylene (HDPE) films reinforced with re-dispersed or refined reduced graphene oxide (rGO) are prepared via a facile melt-stretching strategy. The incorporation of only 0.2 wt% rGO is demonstrated to endow the melt-stretched film (80× stretch ratio) with ultrahigh Young's modulus of 2.9 GPa and tensile strength of 162.2 MPa, which are comparable to many engineering plastics and also significantly superior to the existing HDPE/graphene composites. More importantly, these modulus and strength values are increased by 71 and 65% compared to the neat PE (80×), respectively, far more than the theoretical prediction with the mixing rule. Experimental characterizations indicate that the high-efficient mechanical enhancement is attributed to the strong synergy of melt stretching-driven crystallization and rGO re-dispersion or refinement in constructing the compact and robust shish-kebabs crystal network. Such microstructural characteristics greatly promote the load transfer along the covalently bonded molecular chains, and also from polymer to rigid fillers under loading. Furthermore, the excellent puncture resistance and thermo-mechanical properties of PE/rGO films have been demonstrated. This work provides a feasible way towards scalable manufacturing of high-performance polymer nanocomposite films from general plastics and carbonaceous nanomaterials. [Display omitted] • HDPE/rGO nanocomposite films are fabricated by a facile melt stretching process. • Superb mechanical performance of films is achieved at very low filler content. • Melt stretching-driven rGO re-dispersion or refinement is demonstrated. • rGO re-dispersion enhances the formation of robust shish-kebabs crystal network. • Good puncture resistance and thermo-mechanical properties of films are revealed. [ABSTRACT FROM AUTHOR]

• PTFE template with micro-cavity was prepared by micromilling. • As-prepared PTFE templates have the advantages of easy demoulding and reusability. • A facile and low-cost method to fabricate microgroove-crack-based strain sensor. • Such strain sensor exhibits high sensitivity and low detection limit. • Detect body motion underwater and sound vibration with different frequencies. Strain sensor is a crucial component of high-performance wearable electronic devices. Crack-based sensor has attracted much attention due to its high sensitivity that allow an extensive application for wearable electronic devices. However, facile, efficient and cost-effective fabricating crack-based sensors is still a challenge. Herein, a facile, highly efficient, and low-cost approach was proposed to fabricate stretchable microgroove-crack-based strain sensor whose highest sensitivity is 27818.5 and low detection limit is 0.01%. Moreover, it can be pasted on human body to detect motion both in air and underwater conditions. Furthermore, it can recognize the recorded vibration spectrum of different musical scores. This study offers a facile and efficient approach for fabricating stretchable microgroove-crack-based strain sensor, showing tremendous potential in future wearable electronic devices production. [ABSTRACT FROM AUTHOR]

In this work, the β-nucleating agent (β-NA) filled isotactic polypropylene (iPP) parts were prepared via an overflow microinjection molding (OMM). All OMM parts show an obvious skin-core structure. With increasing the β-NA content, the shear layers with highly oriented shish-kebab structure are progressively thickened, resulting in an effective improvement in tensile strength. Specifically, a maximum tensile strength of 69.8 MPa is observed in the OMM sample with 0.2 wt% of β-NA. Moreover, the elongation at break gradually increases with increasing β-NA content, which is ascribed to the increase of β-crystal content. This study gives more insights into the microstructures of β-nucleated iPP microparts processed under intense shear flow, which could open a promising door to optimize the properties of microparts. Image 1 [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 Improving the burning progressivity is an effective approach to improve the muzzle velocities of projectile of a gun. Composite multi-layered flaky gun propellant is a combination of a fast-burning inner layer and a slow-burning outer layer. It has an obvious burning progressivity which decreases the pressure in bore and increases the muzzle velocity, thus this characteristic is widely concerned by the research of gun propellant. The thermal expansion coefficient of composite multi-layered gun propellant has a significant influence on the combustion performance. Therefore, understanding the thermal expansion properties of the composite multi-layered gun propellant is important. In this study, the thermal expansion coefficients were measured by thermal mechanical analyzer (TMA) for a three-layered flaky gun propellant, and the influence of laminating and coating flaky gun propellant on thermal expansion coefficient was investigated. The results showed that the slow-burning layers had a higher thermal expansion coefficient than the faster-burning layers, the thermal expansion coefficient of slow-burning layers was 4–5 times bigger than that of fast-burning layers, and the order of magnitudes was 1 × 10−5 K−1. The laminating and coating had a great influence on the thermal expansion coefficient of flaky gun propellant, the thermal expansion coefficient of laminate sample was 10 times greater than that of the original sample, and the order of magnitudes for two layers and three layers propellant reached 1 × 10−4 K−1. Furthermore, the theoretical relations between the thermal expansion coefficient of axial and the thermal expansion coefficient of the fast and slow burning layer were derived. Graphical abstract Preparation and different test conditions for composite multi-layered flaky gun propellant. Image 1 Highlights • A method to improve the loading density of double-based gun propellant was presented. • A thermal expansion model for the flaky gun propellant was proposed. • The expansion coefficient is only related to the ratio of the fast-burning and slow-burning layers. [ABSTRACT FROM AUTHOR]

In this work, a unique high negative permittivity is observed in the carbon nanosphere (CNS) supported nanosilver-polydopamine (PDA) metacomposites (called CNS-PDA/Ag). The CNS possesses a uniform spherical structure (average diameter of about 200 nm) with a bridge to link CNS together. The Ag nanoparticles are observed to be uniformly deposited on the surface of CNS-PDA core-shell structures with an average diameter of around 10–20 nm. Both impedance and optical band gap results confirm that the CNS-PDA/Ag metacomposites can form a conductive network pathway for further improving their electrical conductivity (about 1 and 2 magnitudes higher than that of CNS and CNS-PDA, respectively). With the support of CNS, the enhanced high negative permittivity observed in the CNS-PDA/Ag metacomposites (about −6.1 × 105) compared with CNS (around −1.2 × 105), CNS-PDA (around 2.5 × 104), and PDA/Ag (around 2.0) is ascribed to uniform decoration of PDA and Ag nanoparticles, induced electric dipole polarization, excellent electrical conductivity as well as anisotropy in dielectric and electrical properties of CNS, PDA, and Ag. The negative permittivity and positive reactance demonstrate an inductance character of the CNS-PDA/Ag metacomposites. This work opens up a new strategy for design and development of metacomposites. Image 1 [ABSTRACT FROM AUTHOR]

Abstract In this work, the rheological and electrical behavior of carbon black (CB) filled poly(methyl methacrylate) (PMMA) nanocomposites in the molten state as a function of CB concentration were investigated by simultaneous electrical and rheological measurements. Shear deformations applied during a stress amplitude sweep caused both changes in the linear viscoelastic behavior and electrical conductivity. The storage modulus increased with measuring time for all PMMA nanocomposites. However, the changes in the time-dependent behavior of storage modulus decreased above the percolated CB concentrations for all investigated nanocomposites, which was in good agreement with the changes in the time-dependent electrical conductivity. The different behaviors can be explained by the agglomeration of CB particles and the decrease of averaged force on a single CB particle. Highlights • Shear deformation applied during stress amplitude sweep caused both changes in the linear viscoelastic and conductivity • Time-dependent behavior of storage modulus was agreed with the conductivity at above the percolated CB content. • Different behaviors were attributed to the CB agglomeration and the decrease of averaged force on a single CB particle. [ABSTRACT FROM AUTHOR]

The use of reduced graphene oxide (rGO) in high-temperature oxidization (HTO) environment, is limited by its poor thermal oxidation and fire resistance. In this study phosphorus and nitrogen co-doped reduced graphene oxide (PN-rGO) with high oxidation and fire resistance was prepared by hydrothermal and microwave treatment and its thermal oxidation decomposition kinetics and mechanisms were analyzed. Concisely, PN-rGO presents an increment of 162 °C in the decomposition temperature relative to undoped rGO (WrGO), and excellent fire resistance with only a ∼20% mass loss after burning. Thermal oxidation degradation kinetics reveals that WrGO shows continuously increasing activation energy (E) within a range of 119.7–182.9 kJ/mol, while PN-rGO exhibits almost constant E of ∼171.8 kJ/mol during main degradation stage. Moreover, the improved E at initial stage by phosphorus/nitrogen doping, combining with the char analysis, suggested that the introduction of strong chemical bonds replacing the reactive oxygen-containing groups was the key to preventing the oxidation of rGO. As one of the main properties, the electrical conductivity of PN-rGO is well kept after HTO treatment. This work demonstrates that a doping strategy can effectively expand the application of graphene-based devices in HTO environment. Image 1 [ABSTRACT FROM AUTHOR]

• Cylindrite of Poly(lactic acid) with inner and outer layers was first observed. • The critical shear conditions of hierarchical cylindrite formation were given. • Formation mechanism of shear induced crystallization, especially the hierarchical cylindrite was described. • The relationships between inner layer thickness and shear affected region were quantified. The shear-induced interfacial crystallization structure and morphology of poly(lactic acid) (PLA) was investigated by pulling a single glass fiber (GF) at different velocities and over different durations at 120 °C. The hierarchical cylindrites with two layers were found when the GF pulling speed or pulling time arrived at a critical value according to the polarized optical microscopy (POM) results. Beyond the critical value, the cylindrite thickness of the inner layer sharply increased and finally reached saturation at 18.5 μm along the radial direction. The POM results were consistent with the value of the shear affected range assessed by the thermomechanical model (Monasse, 1992). The relative degree of crystallinity (A 922 / A 956), based on polarized Fourier transform infrared spectroscopy (FTIR), increased with fiber pulling speed, and then reached a plateau at 1.68, corresponding to the critical speed. The spatial competitiveness at the fiber surface is the main factor responsible for the formation mechanism of the cylindrite, especially the hierarchical cylindrite. [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]

Abstract The self-assembly behavior of N,N′,N ″-tricyclohexyl-1,3,5-benzenetricarboxylamide (BTCA) and its nucleating effect on poly(lactic acid) (PLA) crystallization were studied by differential scanning calorimetry and polarized optical microscopy. The effect of melting temperatures (T f) from 190 to 240 °C, BTCA concentrations from 0 to 0.5 wt%, and cooling rates from 2.5 to 20 °C/min was investigated. It was found that, when T f was 240 °C, BTCA could dissolve completely in PLA matrix, and then self-assemble into supermolecular frameworks upon decreasing temperature. The core findings are as follows: (1) for the two-step crystallization, the half-crystallization time of PLA showed a bell shaped dependence on the pre-crystallization temperatures of BTCA, which was higher than that without pre-treatment; (2) for nonisothermal crystallization, the crystallization peak temperature of PLA presented a bell shaped dependence on the concentration of BTCA at each rate. Meanwhile, the BTCA concentration, which corresponded to the maximum crystallization rate of PLA, shifted to higher value with the increase of cooling rate. The observations were discussed in term of the effective nucleating surface area of BTCA. Graphical abstract Image 1 Highlights • We examined the nucleating effect of BTCA on PLA crystallization. • PLA crystallization presents a bell-shaped dependence on BTCA concentration. • Optimized BTCA concentration for PLA crystallization depends on cooling rate. [ABSTRACT FROM AUTHOR]

Abstract Isolation of earth abundant biopolymer, Lignin, from Dendrocalamus sinicus and their structural properties were investigated to achieve its large-scale practical applications in value-added products. Two lignin fractions (MWL, DSL) were isolated with successive treatments of dioxane and dimethylsulfoxide (DMSO) from dewaxed and ball milled bamboo (D. sinicus) sample. The two-step treatments yielded 52.1% lignin based on the total lignin content in the dewaxed bamboo sample. Spectroscopy analyses indicated that the isolated bamboo lignin was a typical grass lignin, consisting of p -hydroxyphenyl, guaiacyl, and syringyl units. The major interunit linkages presented in the obtained bamboo lignin were β - O -4′ aryl ether linkages, together with lower amounts of β - β ', β -5′, and β -1′ linkages. The tricin was detected to be linked to lignin polymer through the β - O -4′ linkage in the bamboo. In addition, phenyl glycoside and benzyl ether lignin-carbohydrate complexes (LCC) linkages were clearly detected in bamboo (D. sinicus), whereas the γ -ester LCC linkages were ambiguous due to the overlapping NMR signals with other substructures. The detailed structural properties of the obtained lignin fraction together with the light-weight will benefit efficient utilization of natural polymers as a possibly large-scale bio-based precursor for making polymeric materials, biochemicals, functional carbon and biofuels, and multifunctional polymer nanocomposites. [ABSTRACT FROM AUTHOR]

Abstract The search of multifunctional epoxy nanocomposites with both strength and toughness combined with smart features such as electrical conductivity is essential in design of advanced materials. In this work, by utilizing a binary nanofiller strategy, both strength and toughness as well as high electrical conductivity are obtained in epoxy with trace nanopolystyrene grafted with epichlorohydrin (nano g -PS) to facilitate the dispersion of multi-walled carbon nanotubes (MWCNTs). The increased tensile strength (37.6%) and flexural strength (34.4%) are acquired in nano g -PS (0.0677 vol%)/MWCNTs (0.0335 vol%)/epoxy in contrast to pure epoxy. A remarkably improved tensile toughness up to 379.2% and an increased elongation at break up to 208.3% are obtained in this epoxy nanohybrid. The synergistic interactions among nano g -PS, MWCNTs and epoxy matrix as well as the state transition of nano g -PS from glassy state to fluid state provide an improved dispersion of nanofillers which is responsible for the increased electrical conductivity and enhanced mechanical properties. The decreased surface resistivity allows these nanohybrids to sufficiently dissipate surface charges as an antistatic material. This work provides an effective way to disperse carbon nanotubes with small amount of thermoplastic PS to simultaneously strengthen and toughen the thermosetting epoxy while introducing highly conductive function. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Carbon black (CB)/thermoplastic polyurethane (TPU) nanocomposites with a range of nanoparticle loadings were prepared successfully by using a joint co-coagulation technique and hot pressing. The presence of hydrogen bonding interactions between the CB particles and TPU chains was identified from the results of Fourier transform infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC). Uniform dispersion of CB particles throughout the TPU matrix improved the overall mechanical properties of the TPU nanocomposites, as compared with the neat TPU. The thermal conductivity and thermal stability of the CB/TPU nanocomposites were also found to be enhanced with increasing the CB loading. All samples exhibited a rapid increase of erosion rate with the impact velocity between 20 and 30 m/s. The largest and smallest erosion rates (ER) were observed at 30° and 90° impact angle, respectively, for all CB/TPU nanocomposites. This shows a typical ductile erosion behavior in this material. In addition, the ER (TPU-2CB > TPU-12CB > TPU > TPU-6CB) under all test conditions showed an opposite trend to the tensile strength. These results indicate that the CB/TPU nanocomposites are suitable for protective coatings. Graphical abstract Image 1 Highlights • Thermoplastic polyurethane nanocomposites were fabricated using co-coagulation plus compression molding technique. • Uniform dispersion of CB nanoparticles effectively enhanced the tensile strength of the nanocomposites. • The solid particle erosion behavior was characterized by different impact angles, velocities and time. • The erosion rate showed an opposite trend to the tensile strength. [ABSTRACT FROM AUTHOR]

Abstract Based on the contributions of carbon nanostructures and their composited species, great advances in electromagnetic wave interference shielding have been achieved. In this article, recent progress in electromagnetic wave shielding enabled by the synergism of carbon nanostructures and their corresponding composites is discussed encompassing the factors of microstructural defects, filler concentration, filler alignment, filler inherent conductivity and the surrounding temperature. Carbon nanostructures and their composites would energize the advanced electromagnetic wave shielding because of their light weight, high corrosion resistance, excellent thermal, mechanical, and electrical properties, broad absorption frequency bandwidth and cost-effectiveness. In this context of identifying suitable carbon composites that can enhance electromagnetic wave absorption. This review provides updated electromagnetic wave shielding knowledge of carbon nanostructures and their composites as well as their prospects and challenges. Graphical abstract Image [ABSTRACT FROM AUTHOR]

Abstract The advancement of the super absorbent materials with a prominent mechanical robustness for oil-water separation is urgently needed because marine oil-spillage and industrial oily-wastewater have aroused great attention. In this work, a lightweight carbon nanotubes (CNTs)/thermoplastic polyurethane (TPU)/epoxy (EP) composite foam with a novel three-dimensional (3D) herringbone-like structure was successfully fabricated via a simple and facile ice-templating method for oil absorption and oil-water separation. The density and porosity of the sample are 0.11 g cm−3 and 63%, respectively. The durability of the as-prepared porous foams was demonstrated by repeated mechanical compressions in air and organic solvent, respectively. The influence of the varied CNTs and EP content on the water contact angle (WCA) of the composite foams were investigated. The composite foams are of sufficient oil absorption capacity and high selectivity due to their particular wettability and high porosity. Moreover, the hydrophobic foams can rapidly and selectively absorb a variety of oils and organic solvents, and the adsorbates can be collected easily by distillation methods. Interestingly, the as-prepared composite foams could also be used as a filter and showed superior filtering capabilities for separating graphene nano-fillers from ethanol. Therefore, the composite foam has remarkable prospects in the oil-water separation and cleanup application. Highlights • A novel herringbone-like structure foam was fabricated by using a facile method. • The hydrophobic foam shows excellent flexibility and high mechanical durability. • The foam exhibits high oil absorption capacity and high selectivity in testing. • The foam shows excellent recyclability by using the distillation method. • The foam has a superior filtering capability for separating graphene. [ABSTRACT FROM AUTHOR]

Abstract Macroscopic three-dimensional (3D) free-standing porous all-graphene aerogel with ultralight density and high compressibility is successfully fabricated through a mild in-situ self-assembly and thermal annealing processes. The formed interconnected 3D porous graphene network, high thermal stable all-graphene composition and large porosity of aerogels made it possible to remove heat quickly during combustion, exhibiting a conspicuous fire-retardancy. Meanwhile, excellent recoverable compressibility with high strain levels of up to 75% endowed the aerogel with high sensitive strain-responsive characteristic in volume electrical conductivity, thereby opening a new way for realizing the adjustment of internal free space and electrical conductivity of 3D architecture. Based on the results, the microwave absorption performance of the graphene aerogel was effectively self-adjusted via a simple mechanical compression. The optimal absorbing value was up to 61.09 dB with a broad qualified bandwidth of 6.30 GHz at the thickness of 4.81 mm when the compression strain ratio of the sample was controlled to be 30%. Graphical abstract Image 1 [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]

Molecular orientation and dynamic modulus of the high and low temperature drawn polycarbonate splines were investigated using wide-angle X-ray diffraction (WAXD) and dynamic mechanical analysis (DMA). For high-temperature stretched splines, the storage modulus in the glassy state and the loss modulus in the rubbery state increased with increasing the orientation. No obvious regularity was observed for the low-temperature stretched ones. These behaviors could be interpreted by a relation between relaxation modulus and average orientation angle, which was derived from the elastic dumbbell model and wormlike chain model. Through associating the molecular orientation defined by Herman's factor with the storage modulus at the end of the glassy state plateau and the loss modulus at the tan δ peak respectively, the relationship between orientation and dynamic viscoelasticity of polycarbonate was built as well. [ABSTRACT FROM AUTHOR]

The creep behavior is one of the most important properties and should be characterized to evaluate long-term durability and reliability of polymeric materials. An alteration of the crystalline structure and morphology in the semicrystalline polymer leads to a change in the creep behavior as well. In this work, in order to understand the creep behavior of different morphologies, a modified injection molding technology with twice melt filling (M2) was used to prepare isotactic polypropylene (iPP) samples with controllable skin-core structure. The different shear layer thicknesses were obtained by adjusting the time intervals of the twice melt filling. Compared with the conventional injection-molded samples (M1), M2 samples present better efficiencies in reducing the creep and recovery response, and the response was strongly influenced by the shear layer thicknesses. For example, the thickness of skin layer of M2 sample with a time interval of 9 s increased approximately 42% and its creep deformation reduced to 52% at 80 °C. It was also found that the creep and recovery strain reduced with decreased temperature or with applied stress. In addition, several theoretical models were used to describe the creep and recovery behavior of M2 samples for a better understanding of the mechanisms. [ABSTRACT FROM AUTHOR]

In this work, a new method of preparing glass fiber/epoxy (GF/EP) composites with excellent solid particle erosion resistance and fracture toughness properties via thermoplastic polyurethane nonwoven fabric (TNF) was reported. TNF was prepared by virtue of the melt-blown (MB) process, and the composites were fabricated by vacuum-assisted resin transfer molding (VARTM) technique. Solid particle erosion characteristics of the composites were investigated in a confined space by impinging angular silica particles with a size about 300 μm. Compared with conventional GF/EP composites, the erosive wear resistance of TNF/glass fiber/epoxy (TNF/GF/EP) composites were improved by 99%, 108%, 205% and 493% at the impingement angles of 20°, 30°, 45° and 90°, respectively. Meanwhile, increase of 78% in G IC and 115% in G ⅡC were achieved. Microstructure characterizations, including scanning electron microscopy (SEM) and optical microscopy were performed to investigate the variations of microstructure and further to establish the relationship between epoxy matrix and glass fibers. This work suggests a promising routine to improve particle erosion resistance and fracture toughness by interleaving the laminates with lightweight thermoplastic polyurethane nonwoven fabrics. [ABSTRACT FROM AUTHOR]

Constructing surface hierarchical layer is regarded as an effective surface modification of carbon fibers (CFs) to enhance their composites mechanical properties. However, this method usually deteriorates the intrinsic properties of CF and the hierarchical layer is not fully compatible with thermal processing of the polymer. Here, a novel hierarchical layer consisting of polydopamine, polyethyleneimine and multi-walled carbon nanotubes without damages to CF was successfully decorated on CF surface (CNT@PP-CF) for simultaneously enhancing the mechanical and the electromagnetic interference (EMI) shielding properties of CF reinforced polyamide 66 (PA66) composite. The CNT@PP hierarchical layer with dynamic imine bonds enhanced the interfacial wettability and bonding between CF and PA66 during thermal processing. Compared with that of untreated-CF, the interfacial shear strength and tensile strength of CNT@PP-CF/PA66 composite were increased by 52.3% and 19.2%, respectively. Meanwhile, the EMI shielding performance was enhanced by 89.6%. This improvement would be ascribed to the dynamic imine polar groups and heterogeneous interfaces in the hierarchical layers which enhanced the conductive and dielectric losses of composites. Our research provided a novel approach based on dynamic covalent bond exchanges to achieve the functional and structural integration of CF reinforced thermoplastic resin composites. [Display omitted] • A new hierarchical layer modified method based on dynamic imine bond was proposed. • Dynamic imine bonds exchanges improved the interfacial properties of composite. • Mechanical properties and EMI shielding performance were enhanced simultaneously. • This method is suitable for CF/thermoplastic composites during thermal processing. [ABSTRACT FROM AUTHOR]

In the classical "covalent adaptive network" constructed by diglycidyl ether of bisphenol A (DGEBA) and crosslinking agent glutaric anhydride (GA), Zn-based catalyst greatly affects the curing crosslinking reaction and dynamic transesterification reaction. Herein, the crucial roles of Zn(Ac) 2 catalyst in the curing dynamics and stress relaxation were studied. The results reveal that increasing the content of Zn(Ac) 2 can significantly reduce the reaction activation energy (E α) at initial stage, thus effectively promoting the curing crosslinking reaction. The analyses of dynamic properties suggest that although stress relation time (τ) can be shortened by increasing catalyst content, the high content of catalyst would lead a fast transesterification rate at relatively low temperature, which is adverse to the mechanical stability of vitrimer resin at operating temperature. By comparison, the vitrimer resin with modest catalyst content (mole ratio of 1:0.5:0.05) shows a highest viscous flow activation energy (E τ), i.e., excellent dimensional stability and processability. Besides, the crosslinking density of resin was significantly affected by the content of catalyst. Since the competitive catalytic effects on curing cross-linking reaction and subsequent transesterification, the vitrimer resin of 1:0.5:0.05 exihits the highest crosslinking density (1855 mol/m3), so that it has highest T g (79 °C) and tensile strength (72 MPa). [Display omitted] • Increasing Zn(Ac) 2 catalyst significantly reduces E α at initial stage, thus promoting the curing crosslinking reaction. • The stress relaxation behavior relating with dynamic transesterification can be accelerated by increasing Zn(Ac) 2 catalyst. • The epoxy vitrimer with modest catalyst shows a highest E τ , thus revealing the optimal dynamic properties. • The epxoy vitrimer with modest catalyst exihits the highest crosslinking density, so that it has highest T g and tensile strength. [ABSTRACT FROM AUTHOR]

In this study, an internal electrode triboelectric nanogenerator (IE-TENG) design is proposed to enhance the stability, durability, and long-term performance of TENGs. By embedding a mesh-structured metal electrode in the friction layer, the IE-TENG becomes more flexible, lightweight, and robust than the traditional external electrode TENG (EE-TENG). When using copper mesh internal electrodes with higher grid density, the greater output can be achieved by comparing a series of polydimethylsiloxane(PDMS)-based IE-TENG. An equivalent output was obtained when using 60 copper mesh compared to EE-TENG, and the trend maintains for tribonegative low-density polyethylene (LDPE) and tribopositive polyamide (PA) polymers, which verifies the usability of the approach and the effective induction area of the internal electrode. The internal electrode design significantly enhanced the tolerance of the device to harsh environments and guaranteed excellent output stability. In addition, the IE-TENGs possess superior resistance to external interference and had about one time shorter saturation time for surface charges. As a demonstration, the IE-TENG can be used for collecting motion-sensing signals and detecting various sports activities. This study provides a novel strategy for the designing and customizing of highly integrated TENGs with enhanced durability for practical long-term applications. An embedded metal electrode design is proposed for developing highly integrated durable TENGs. The internal electrode TENGs (IE-TENGs) not only possess equvalent output performance to the traditional external electrode TENGs, but also demonstrate superior long-term stability, charge saturation velocity, flexibility, and tolerence to harsh environments. [Display omitted] • A design of embedded electrode for improving the integration of TENG is proposed. • The IE-TENG demonstrated more stable long-term signals, and high tolerance to the harsh environment. • The embedded electrode strategy enhanced the tolerance of the TENGs to interference from the external environment. • The IE-TENGs possess about one time shorter saturation time for surface charges. [ABSTRACT FROM AUTHOR]

Photonic crystals structural colors have many advantages (e.g., environmentally friendly, nonfading, etc.), showing great potential application in some emerging fields of display, detection and anti-counterfeiting. Unfortunately, they are easily damaged because of the poor mechanical robustness origined from the weak interfacial adhesion between film substrate and nanoparticles. Although some photonic crystals show good mechanical robustness, they are often suffered from complex methods. Therefore, it is still a huge challenge to prepare photonic crystals with good mechanical robustness via facile methods. Herein, an efficient and facile strategy to prepare polycarbonate (PC)/silica nanoparticles (SNPs) photonic crystals film based on microgrooves is proposed. That is, with the help of micromilling and vacuum-assisted hot-pressor, microgrooves were prepared onto PC film surface, and SNPs can be spontaneously deposited into the as-prepared microgrooves via capillary force. Such PC/SNPs photonic crystals film exhibits excellent mechanical robustness, vivid structural color, and color can change with the viewing angle. Interestingly, such films with quick response (QR) code pattern can store information and can be used as anti-counterfeiting labels. This work proposes a facile strategy to prepare microgrooves based photonic crystals film with good mechanical robustness, which can further expand its applications in anti-counterfeiting. Via micromilling and vacuum-assisted hot-pressor, PC/SNPs photonic crystals film was successfully prepared. Moreover, some complex photonic crystals patterns with vivid structural colors can also be prepared by this method. More interestingly, the as-prepared PC/SNPs photonic crystals film with QR code pattern has background-dependence and can be used as anti-counterfeiting labels. [Display omitted] • Microgrooves based PC/SNPs photonic crystals film with vivid and angle-dependent structural color was prepared. • Such PC/SNPs photonic crystals film exhibits excellent mechanical robustness thanks to the microgrooves. • Various photonic crystals patterns based on microgrooves can also be prepared and the quick response (QR) code pattern can be used as anti-counterfeiting labels. [ABSTRACT FROM AUTHOR]

In many industrial processes, polymer melt undergoes complex flow-cooling environments before being solidified into the final products. Investigating polymer crystallization under processing conditions is a necessary step to predict and customize the structures and properties of semicrystalline polymers. Herein, the crystallization behavior of high-density polyethylene (HDPE) under combined melt stretching and fast cooling fields was studied through a homemade extensional rheometer. A series of HDPE samples were prepared by cooling the stretched melt at different cooling rates (0.02–220 °C/s) immediately after flow, or after waiting for different times of isothermal crystallization at 128 °C. Microstructural characterizations confirm four different structural states related to the evolution of shish-kebabs after melt stretching, namely generation of shish precursors, shish crystal growth, kebab lamellar growth, and perfection of shish-kebabs, which diversify greatly the structures and morphologies of the final solidified samples. By prolonging the isothermal crystallization time at high temperature, the fast cooling-induced lamellae keep decreasing in thickness. This supports the occurrence of molecular segregation caused by shish-kebabs growth at high temperature, which reduces the molecular weight of the remaining un-crystallized melt. In addition, quantitative analysis of crystalline orientation manifests that the lamellar growth during isothermal process takes strictly the shish as a template and adopts a high orientation, while the fast cooling-induced lamellae are only related to the chains conformation of un-crystallized melt prior to cooling. This work would be essential to advance the in-depth understanding on the actual industrial processing of semicrystalline polymeric materials. [Display omitted] • Melt crystallization of HDPE under combined stretching and fast cooling fields was studied. • Four different structural states related to the evolution of shish-kebabs after flow were identified. • Molecular segregation caused by shish-kebabs growth at high temperature was suggested. • Isothermal and non-isothermal crystallization under flow presented different lamellar growth modes. [ABSTRACT FROM AUTHOR]

Conductive polymer composites (CPCs) based strain sensors have been studied intensively recently. For a desirable strain sensor, a high sensitivity, a nice recoverability together with a good stability are required synchronously. In this study, the design of a segregated carbon black (CB) conductive network was demonstrated to be crucial for preparing polypropylene (PP)-based strain sensors with fine recoverability and stability, but a low sensitivity. The incorporation of carbon fibers (CFs) with large aspect ratio into the segregated CB/PP was utilized to build a bridged-segregated structure, leading to a synergistic conductive network. As a result, an improved sensitivity as well as a good stability was both achieved for the CF/CB/PP composite. The origin of these results was further explained on the basis of the tunneling model proposed by Simmons and the synergetic effect. This work provides a strategy for improving the performance of strain sensor with balanced sensitivity and stability by introducing a bridged-segregated structure. [ABSTRACT FROM AUTHOR]

Polymer material exhibits a trade-off between toughness and stiffness, therefore, it remains difficult to develop a strategy that simultaneously realizes improved mechanical strength and toughness. Inspired by the bamboo-like structure, an efficient and simple melt sequential injection molding is proposed to fabricate a controllable skin-core structure of iPP samples with self-reinforcement and toughness. With increasing the melt injection number, the shear layers containing shish-kebabs are progressively thickened, resulting in an effective improvement of mechanical properties. The tensile strength increased from 35.1 to 55.3 MPa for the melt injection number from one to four, meanwhile the toughness was enhanced from 23.1 to 53.6 kJ/m 2 . A simple theoretical model was derived and utilized to describe the experimental data. Theoretically calculated tensile strength of sample with entirely shish-kebabs can even reach 222.9 MPa via this technology, which is much higher than that of most engineering plastics and polymer composites. This work not only provides an efficient way to fabricate high-performance general plastics for engineering purposes but also a new opportunity to understand the fundamental issues about the mechanism of the self-reinforced polymers. [ABSTRACT FROM AUTHOR]

Stretchable strain sensors have promising potentials in wearable electronics for human motion detection, health monitoring and so on. A reliable strain sensor with high flexibility and good stability should be designed to detect human joints motions with a large deformation. Here, a simple and facile solution mixing-casting method was adopted to fabricate a highly stretchable strain sensor based on composites mixing polydimethylsiloxane (PDMS) with hybrid carbon nanotubes (CNTs) and carbon black (CB) conductive nanofillers (CNTs-CB). Bridged and overlapped hybrid CNTs-CB nanofillers structure was achieved in the composite on the basis of the morphology observation. In monotonic stretching test, the CNTs-CB/PDMS composites strain sensors exhibited high stretchability, strain-dependent sensitivity in a wide strain sensing range ( ca. 300% strain) and an excellent linear current-voltage behavior. During stretching-releasing cycles, the strain sensors presented excellent repeatability, good stability and superior durability (2500 cycles at 200% strain). Combined with the above outstanding strain sensing performances, the fabricated stretchable strain sensors were attached onto different joints of human body to monitor the corresponding human motions, demonstrating their attractive perspective in large human motions detection. [ABSTRACT FROM AUTHOR]

Superhydrophobic and superoleophilic porous reduced graphene oxide/polycarbonate (RGO/PC) monoliths with novel micro-nanoscale binary structure were first fabricated by thermally impacted nonsolvent induced phase separation (TINIPS) method. Owing to the unique pore structure, the porous monoliths possessed high specific surface area (137.19 m 2 /g) and porosity (91.3%). The superhydrophobic RGO/PC monoliths exhibited excellent capability to selectively adsorb a wide range of oils and organic solvents from water. Furthermore, the monoliths could keep a stable repellency against corrosive mediums (e.g., acidic and alkali solutions). Based on these superior properties, porous RGO/PC monoliths will be a promising candidate for high-efficiency oil/water separation to deal with water pollution. [ABSTRACT FROM AUTHOR]

In this work, non-covalently functionalized reduced graphene oxide (rGO) reinforced poly(vinyl alcohol) (PVA) nanocomposites were prepared by solution mixing. The agglomeration of graphene sheets was prevented by using surface modifying agent poly(sodium 4-styrenesulfonate) (PSS). The improved mechanical properties, including the Young's modulus and tensile strength of the PVA/rGO nanocomposites compared to neat PVA were attributed to the strong interactions between PVA and rGO such as π–π, hydrogen bonding, and CH–π. A 55% maximum increase in the modulus was obtained by adding only 0.1 wt% rGO, and an increase of 48% in tensile strength was achieved by adding 0.3 wt% rGO. In addition, the thermal properties of the nanocomposites were also improved, which was attributed to the restriction of graphene oxide (GO)/rGO sheets on the chain mobility of polymers on the GO/rGO sheets surface. [ABSTRACT FROM AUTHOR]

In this work, a novel flexible electrically resistive-type strain sensor with special three-dimensional conductive network was developed based on reduced graphene oxide (RGO)-decorated flexible thermoplastic polyurethane (TPU) electrospun fibrous mats. Scanning electron microscopy results indicated that RGO was localized on surfaces of the TPU fibers uniformly and formed conductive paths. The interaction between electrospun TPU fibers and RGO was investigated by using Fourier transform infrared spectra and X-ray diffraction. These fibers conductive paths connected with each other and constructed an excellent three-dimensional conductive network. The special hierarchical conductive network endowed our RGO/TPU strain sensors with a desirable integration of good stretchability and high sensitivity (gage factor (GF) of 11 in strain of 10% and 79 in strain of 100% in reversible strain regime), good durability and stability (stretch/release test of 6000 cycles) and a fast response speed. The mechanism of the evolution of residual resistance and residual strain of RGO/TPU strain sensors under cyclic loading were investigated in detail. RGO/TPU strain sensors were attached on skin or clothes to monitor various human motions. The results demonstrate that our flexible strain sensors have wide application prospects in smart wearable device. [ABSTRACT FROM AUTHOR]

The effect of a self-assembly nucleating agent, N , N ′, N ″-tricyclohexyl-1,3,5-benzenetricarboxylamide (BTCA), on the crystallization behavior of poly(lactic acid) (PLA) was probed by time-resolved Fourier transform infrared spectroscopy (FTIR) and wide angle X-ray diffraction (WAXD). The vibrational changes associated with inter- and intra-chain interactions during crystallization were monitored. In the initial period of crystallization, the order of intensity changes is as follows: 1458 cm −1 > 1210 cm −1 » 921 cm −1 , 1458 cm −1 ∼ 1210 cm −1 > 921 cm −1 , and 1458 cm −1 ∼ 1210 cm −1 ∼ 921 cm −1 for neat PLA, PLAs containing 0.1 wt% and 0.3 wt% BTCA, respectively. This indicates that BTCA can accelerate both the formation of skeletal conformational-ordered structure and, especially, the 10 3 helix one. The incorporation of BTCA changes the crystallization mechanism but has no impact on the crystal form of PLA. [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]

Benefiting from its superior thermal and mechanical properties, the stereocomplex crystal (SC) of PLLA/PDLA is catching increasing interest. In this work, a systematic investigation was performed to reveal the effect of solid-state stretching on the formation of SC during annealing. Results show that as the stretching temperature was close to the glass transition temperature (T s = 60 °C), the polymer chains orientation was increased gradually with draw ratio (λ). As a result, the crystallization induction time (t 0) was shortened, the growth rate (G r) of SC was enlarged, and the crystallinity of SC (X SC) was elevated as a result of orientation-induced crystallization. Whereas, the saturation of t 0 , G r , and X SC appeared quickly when λ reached 2.7, although the orientation of polymer chains continued to increase. The reason is that in addition to orientation, strong phase separation between PLLA and PDLA was also triggered therein. The phase separation prohibited greatly the crystallization of SC due to a long time would be needed for PLLA or PDLA chains to diffuse to a distance close enough to activate the hydrogen-bonding interaction, which is the prerequisite of SC crystallization. When the stretching temperature was elevated to 75 °C, the phase separation became much weaker. So X SC was higher compared to that of the blend stretched at 60 °C to the same λ. Moreover, in the annealing temperature from 180 °C–190 °C, t 0 was much smaller for the blend stretched at 75 °C since the crystallization of SC in this temperature range is a diffusion-controlled process. [Display omitted] • Strong orientation of polymer chains and phase separation are induced by solid-state stretching. • Orientation of polymer chains and phase separation exhibit a competition effect on the crystallization of SC. • The more intense phase separation at lower stretching temperature gives rise to a longer crystallization. induction time [ABSTRACT FROM AUTHOR]

In this study, a composite hydrogel with a low swelling ratio, excellent mechanical properties, and good U (VI) adsorption capacity was developed by incorporating a metal-organic framework (MOF) with a poly (acrylamide- co -acrylic acid)/chitosan (P(AM-co-AA)/CS) composite. The CS chain, which contains NH 2 , reduces the swelling ratio of the hydrogel to 4.17 after 5 h of immersion in water. The coordinate bond between the MOF and carboxyl group on the surface of P(AM-co-AA)/CS improves the mechanical properties and stability of P(AM-co-AA)/CS. The U(VI) adsorption capacity of P(AM-co-AA)/CS/MOF-808 is 159.56 mg g−1 at C 0 = 99.47 mg L−1 and pH = 8.0. The adsorption process is well fitted by the Langmuir isotherm and pseudo-second-order model. The P(AM-co-AA)/CS/MOF-808 also exhibits good repeatability and stability after five adsorption–desorption cycles. The uranium adsorption capacity of the developed adsorbent after one month in natural seawater is 6.2 mg g−1, and the rate of uranium adsorption on the hydrogel is 0.21 mg g−1 day−1. [Display omitted] [ABSTRACT FROM AUTHOR]

Conductive hydrogels (CHs) have attracted considerable attentions in the fields of wearable electronics, disease diagnosis, and artificial intelligence. However, it is still a great challenge to prepare a single CH system with integrated characteristics of high stretchability, good transparency, and multisensory function through a simple fabrication process. Herein, carboxylic cellulose nanofibers (CCNF) were used to assist the homogeneous distribution of opaque conductive poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) into the crosslinked polyacrylamide network for the fabrication of stretchable and transparent interpenetrating network CH, aiming for a high-performance multisensory system. As expected, the ready formation of hydrogen bonds between the water molecules and a great deal of hydrophilic groups in the hydrogel endow the obtained CH with excellent humidity response behavior in a wide range (0–85%), and the introduction of CCNF and PEDOT: PSS is proved to be an effective strategy to enhance the humidity sensitivity, exhibiting great potential for the noncontact sensing of human respiration and finger movement. Meanwhile, it also displays excellent strain sensing behavior with favorable sensitivity in a broad range (0–837 %), fast response and reliable stability and reproducibility. Importantly, our prepared CH can also detect and discriminate complicated human activities and physiological signals. All these demonstrate the superiority of our prepared CH for the new generation of flexible wearable electronics. [Display omitted] • Stretchable and transparent hydrogel with multiple sensing ability was prepared. • The hydrogel possesses favorable humidity response to a RH up to 85 %. • The hydrogel displays fast and reliable strain sensing capacity in a wide strain range. [ABSTRACT FROM AUTHOR]