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As part of a continuous effort to develop high performance isotactic polypropylene (iPP) based on β-form crystalline and morphological change induced by rare earth nucleator (WBG), various WBG contents (from 0.025 to 1.0 wt%) were adopted to prepare β-nucleated iPP at a fixed final molten temperature (240°C) in this study. The crystallinity, polymorphic composition, and crystalline morphology were inspected in detail by a series of crystallographic characterizations, including calorimeter, X-ray diffraction, polarized light microscopy (PLM), and electron microscopy. Furthermore, the self-organization and re-crystallization behavior of β-nucleating agent occurred during cooling was characterized by rheometry. Finally, the dependence of mechanical properties, including tensile strength, elongation at break, and impact strength, on WBG content was discussed based on the variations in β-form content and crystalline morphology. Interestingly, it is found that while the WBG content is below 0.1 wt%, the toughness of β-nucleated iPP increases with increase in WBG content due to additional β-form content; as the WBG content is in range of 0.1-0.5 wt%, the toughness increases at a lower rate with increase in WBG content due to β-crystalline morphological change. However, a decrease in toughness is observed while nucleator content is above 0.5 wt% as WBG remains undissolved in iPP upon the adopted processing conditions. The result of this study provides valuable information for potential industrial applications. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: In this work, in order to investigate the combined effect of whiskers nucleation ability and shearing function on the interfacial crystal morphology of HDPE/raw whiskers composites, two different types of raw whiskers (SMCW and BW) with different diameter distribution and HDPE composites were firstly prepared by melt blending and then subjected to both traditional and dynamic injection molding. The results indicated that the nucleation ability of SMCW on HDPE crystallization is much better than BW. Furthermore, the small diameter whisker shows the better nucleation ability than the large diameter whisker. For samples prepared by traditional injection molding, the better the nucleation ability of the whisker, the more dense the HDPE crystal lamellae can epitaxially grow on its surface. However, after introducing shearing function, even for large diameter BW whisker with weak nucleation ability, a large number of HDPE crystal lamellae could be epitaxially grown on the surface of the whisker. As a consequence, the interfacial adhesion and mechanical properties of the composites are significantly improved by introducing shear function. [Copyright &y& Elsevier]

Abstract: The polymer matrix structure and the interface are strongly influenced by filler in semi-crystalline polymer composites because the fillers have the potential to nucleate the polymer crystallization. The structure of the nucleated crystalline polymer on filler is of particular interest and is a key to the interfacial enhancement. In this work, whiskers, with a large length/diameter ratio and with a diameter (0.2–2μm) much larger than that of carbon nanotubes but much smaller than that of common fibers, were used to nucleate crystal morphology in polypropylene (PP)/whisker composites. The crystal morphology, interfacial adhesion and tensile properties of the composites were carefully investigated. A kind of peculiar shish–calabash crystallization morphology, with whisker serves as shish and PP spherulites serves as calabash, was observed for the first time in the thin film via PLM and in the injection molded bars by SEM. The formation mechanism of this shish–calabash structure was attributed to be that only a few nuclei could be induced on the whisker surface, which develop into large PP spherulites without hindrance, and finally stringed by the whisker, forming the shish–calabash structure. As a result, a significant improvement of interfacial interaction and tensile properties has been achieved. [Copyright &y& Elsevier]

The dielectric elastomer (DE) generator (DEG), which can convert mechanical energy to electrical energy, has attracted considerable attention in the last decade. Currently, the energy-harvesting performances of the DEG still require improvement. One major reason is that the mechanical and electrical properties of DE materials are not well coordinated. To provide guidance for producing high-performance DE materials for the DEG, the relationship between the intrinsic properties of DE materials and the energy-harvesting performances of the DEG must be revealed. In this study, a simplified but validated electromechanical model based on an actual circuit is developed to study the relationship between the intrinsic properties of DE materials and the energy-harvesting performance. Experimental verification of the model is performed, and the results indicate the validity of the proposed model, which can well predict the energy-harvesting performances. The influences of six intrinsic properties of DE materials on energy-harvesting performances is systematically studied. The results indicate that a high breakdown field strength, low conductivity and high elasticity of DE materials are the prerequisites for obtaining high energy density and conversion efficiency. DE materials with high elongation at break, high permittivity and moderate modulus can further improve the energy density and conversion efficiency of the DEG. The ratio of permittivity and the modulus of the DE should be tailored to be moderate to optimize conversion efficiency (η) of the DEG because using DE with high permittivity but extremely low modulus may lead to a reduction in η due to the occurrence of premature "loss of tension". [ABSTRACT FROM AUTHOR]

Dielectric Elastomer Generator (DEG) has been used to harvest energy from reciprocating mechanical motion due to its variable capacitance under tension, and thus it has attracted widespread attention in the last decade. In this study, a cone DEG based on VHB elastomer was developed and its energy harvesting performance was optimized by combining equibiaxial prestretching to cone stretching mode and then tailoring the variables such as the equibiaxial prestretch ratio, input bias voltage and cone displacement. The coupling relationship among these variables and their combined influences on generated energy, energy density and conversion efficiency were systematically studied for the first time. The results indicate that prestretching plays an important role in achieving the target energy harvesting performance at shorter displacement and lower bias voltage, which means lighter weight and portability of the device. More importantly, an up-to-date highest energy density of 130 mJ/g or a maximum electromechanical conversion efficiency of 40% could be obtained by optimizing the variables. In addition, the concept of "displacement threshold" in DEG was firstly proposed and discussed based on leakage and viscoelastic. This work provides ideas for future applications of DEG on portable power and array power generators with high energy harvesting performance. Image 1 • The energy harvesting performance of a cone DEG was optimized. • The key variables on energy harvesting performance of cone DEG were studied. • An up-to-date highest energy density of cone DEG (130 mJ/g) was obtained. • An up-to-date maximum electromechanical conversion efficiency of 40% was obtained. • "Displacement threshold" in DEG was firstly proposed and discussed. [ABSTRACT FROM AUTHOR]

Using the all-atom molecular dynamics simulations integrated with the time−temperature superposition principle, we have probed the dielectric modification of poly (butyl acrylate), for example, to understand the effect of added polar groups on the dielectric and viscoelastic properties of poly (butyl acrylate-co-glycidyl methacrylate). We have verified that, after addition of 22% glycidyl methacrylate to formulate the copolymer, its dielectric permittivity can be improved about 50%, whereas the corresponding dielectric loss has been not significantly raised at low frequency. On the other hand, according to the hysteresis losses of tension–recovery and compression–recovery processes, the permanent deformation of poly (butyl acrylate) has also been diminished. Due to the significant increase of modulus, the actuated strain drops about 20%. As a consequence, the effective simulation method is capable of quantitatively evaluating the contribution of polar groups to the electro-mechanical coupling of dielectric elastomers. Image 1 • Electro-mechanical coupling of PBA was quantitatively evaluated by MD simulation. • The dielectric strength of PBA can be enhanced 50% by adding polar epoxy groups. • The enhancement mechanism was interpreted by orientation polarization of dipoles. • The corresponding dielectric loss was not significantly improved at low frequency. • The deformation of PBA can be diminished by adding a certain amount of GMA. [ABSTRACT FROM AUTHOR]

• An all-polymeric stretchable conductive fiber is fabricated by using microfluidic spinning technology. • The fiber presents wide application potential in the smart wearable textile. • The strain sensor based on the fiber exhibits a super-high sensitivity and large sensing range. It remains a great challenge to fabricate all-polymer stretchable conductive fibers simultaneously presenting high mechanical robustness, high stretchability, and high conductivity through convenient and fast process, even though they exhibit great application potential in the intelligent wearable fields in replacement of the traditional metal wires or the liquid metal-based conductive fibers. In this paper, an all-polymeric fiber with core–shell structure is continuously produced through co-axial microfluidic spinning strategy. The composition of the fluids and the processing parameters of MST are regulated to adjust the size of the obtained PU@PEDOT:PSS fiber, and then optimizing its electric properties and the mechanical performances. The polyurethane (PU) elastic shell layer and the H 2 SO 4 -doped PEDOT:PSS conductive core provide the obtained composite fiber with a high conductivity exceeding 220 S m−1, as well as an impressive stretchability up to above 400 % strain, thus endowing it with versatile intelligent wearable applications, including the super-sensitive strain sensor for human motions monitoring, textile-based triboelectric nanogenerator for self-powered impact sensing, and the electro-thermal conversion fabric for keep warming. [ABSTRACT FROM AUTHOR]

In the present study, carboxylated nitrile rubber (XNBR) with high dielectric constant (ε r) and low elastic modulus (Y) was introduced into thermoplastic polyurethane (TPU) with good mechanical properties to prepare macroscopic homogeneous high performance dielectric elastomer (DE) blends. The results show that the XNBR macromolecules can disrupt the N-H/C=O hydrogen bonds of TPU, leading to the increase in dipole polarizability of TPU matrix. On the other hand, the formation of hydrogen bonds between XNBR and TPU increases the interfacial interaction and thus the interfacial polarizability of XNBR/TPU blends. The improvement of both the dipole polarizability and the interfacial polarizability result in the significant improvement of ε r of TPU with increasing the content of XNBR. Meanwhile, the Y of TPU is decreased due to the disruption of hydrogen bonds of TPU and the softening effect of XNBR. The simultaneous increase in ε r and decrease in Y of TPU results in the large increase in electromechanical sensitivity (β) and actuated strain at low electric field of XNBR/TPU blends. Interestingly, the ε r at 103 Hz, the β and the actuated strain at certain electrical field of the blend with XNBR/TPU blending ratio of 80/20 is even higher than that of pure XNBR, which is attributed to the co-continuous structure of this blend as well as the synergetic effect of the increase in dipole polarizability of both TPU and XNBR and the increase in interfacial polarizability. Comparing with our previous study on TPU DE blend by adding low molecular weight plasticizer, XNBR/TPU macromolecular DE blend show better overall performance such as higher mechanical strength, higher breakdown strength and better stability, thus are more likely to be applied in biological and medical fields, where a low electric field is required. Image 1 • Macroscopic homogeneous high performance XNBR/TPU DE blends were prepared. • XNBR disrupts the hydrogen bonds of TPU, increasing the dipole polarizability of TPU. • The formation of XNBR/TPU Hydrogen bonds increases the interfacial polarizability. • The elastic modulus of TPU is decreased by blending with XNBR. • The ε r and actuated strain of XNBR/TPU 80/20 blend is higher than that of pure XNBR. [ABSTRACT FROM AUTHOR]

Metal materials play an important role in electromagnetic interference (EMI) shielding due to their ultra‐high electrical conductivity, but they are rigid and inflexible, as well as of high density, which limits their application in some areas. In this study, a novel and simple method to fabricate the composites of metal foil and polymer is reported. A copper foil (Cuf) with micropores on the surface is used as a shielding matrix, then interpenetrating and interlocking nanostructure as well as reactive groups are introduced on its surface, and then silicone rubber (SiR) is coated on both surfaces to form a sandwich structure, and the obtained Cuf/SiR composites possesses high EMI shielding efficiency (SE), strong interface adhesion, and low density. The average EMI shielding efficiency of the obtained Cuf/SiR composites in the range of 1.13–18 GHz is 111.5 dB, with a high interface adhesion strength of 5.2 N cm−1 and low density of 1.3 g cm−3, and it also possesses bending and splicing properties, which exhibits broad potential application in the field of EMI shielding tents and shielding rooms. This preparation method of the composites is simple and efficient, and provides a guideline for the design and fabrication of metal foil/polymer composites in molding method. [ABSTRACT FROM AUTHOR]

Intelligent fluorescent coatings have received widespread attention in the encryption technique field such as anti‐counterfeit, while the traditional fluorescent coatings are easy to be damaged by external force. In this study, the fluorescent and self‐healing anti‐counterfeit coatings are prepared after rational molecular design. Two polymers containing fluorescent groups, including polyurethane containing the anthracene (AN) side group and polyimide containing the naphthalenediimide (NDI) structure are synthesized to realize multiple color changes with fluorescence through simply blending. Due to the overlapping fluorescence spectra of the groups, enabling the fluorescence resonance energy transfer effect (FRET), the coating with different group ratios exhibits tunable fluorescence under the same excitation light, providing diverse patterns. Moreover, due to the reversible photo‐crosslinking and thermal de‐dimerization properties of anthracene, the recording, erasure, and rewriting of the surface pattern can be realized, and the fluorescent anti‐counterfeit coatings exhibit excellent self‐healing properties after cross‐linking due to the FRET effect, which solves the problem of poor healing and ensures the stability and integrity. The fluorescent coating with cross‐linked structure and self‐healing behavior based on the FRET effect greatly expands the functional applications of traditional polyurethane materials. [ABSTRACT FROM AUTHOR]

Carbon black (CB) is widely used as a good reinforcing filler in rubber industry. Due to the complex cluster structure of CB aggregate, it is difficult to clearly visualize its topological morphology and interfacial properties at nanoscale of CB/rubber composites. Thus, the good reinforcing mechanism of CB on rubber is still not fully understood. In this study, the surface topography structure of CB with different specific surface area (SSA) were characterized and their surface roughness were quantified using atomic force microscope (AFM). By using low content of CB and applying strong shear force to minimize the size of CB aggregate, the clear visualization of the bound rubber around CB aggregate was obtained using Quantitative Nanomechanical Mapping (QNM) technique of AFM (AFM-QNM). For the first time, the quantitative characterization of interfacial thickness and nano-mechanical modulus of CB/rubber composites were realized by AFM-QNM. Results show that the higher SSA of CB is mainly attributed to the higher surface roughness caused by the more complex topological structure of CB. And the higher surface roughness results in the higher interfacial thickness and Young's modulus at the nanoscale. Why CB with slightly smaller diameter shows largely increased reinforcing effect on rubber matrix is well explained. [Display omitted] [ABSTRACT FROM AUTHOR]

Comfort fitting shape memory elastomer exhibits various potential application in flexible wearable and biomedical devices, which can be developed by mixing the comfort fitting elastomer with the materials of reversible transition. However, it's very difficult to obtain the soft touching feeling, high elongation, and excellent shape memory property at the same time, and the key point mainly depends on improving interface stability and adjusting the morphology by the compatibilizer. In the work, silicone elastomer with excellent shape memory property was obtained by developing an amphiphilic PCL-JP-PDMS hybrid Janus particles compatibilizer for methyl vinyl silicone elastomer/polycaprolactone (MVQ/PCL) blend. Only through increasing the PDMS grafting ratio on the PCL-JP-PDMS particles compatibilizer, the morphology of PCL dispersed phase changed from short fibrous to similar spherical, which ensured the comfort feeling (E = 5.9 MPa), high fixity (R f = 95%) and recovery ratio (R r = 99%) of shape memory MVQ/PCL blends. Furthermore, the shape memory silicone elastomer exhibited impressive elasticity in temporary shape at T = 25 °C, which is quite suitable for designing wearable device. Silicone elastomer with excellent shape memory property was obtained by developing an amphiphilic PCL-JP-PDMS hybrid Janus particles compatibilizer for MVQ/PCL blend, the amphiphilic PCL-JP-PDMS Janus particles were anchored at the interface of MVQ/PCL blends by the similar molecular chain entanglement and the stable conformation of asymmetric SiO 2 @PDVB particles. Much more importantly, the PCL-JP-PDMS particles with different PDMS grafting ratio were prepared as the compatibilizer, which made the interface adhesion and the property of MVQ/PCL blend be regulated by PDMS grafting ratio, which ensured the comfort feeling (E = 5.9 MPa), high fixity (R f = 95%) and recovery ratio (R r = 99%) of shape memory MVQ/PCL blends under the content of 3 wt % particles and 30 wt % PCL. Furthermore, the shape memory silicone elastomer exhibited impressive elasticity in temporary shape at T = 25 °C, which is quite suitable for designing wearable device. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, an elastomeric FeO nano-particles (NPs)/polybutadiene rubber (BR) composite membrane was prepared by using the combined technique of electrospinning and in-situ crosslinking. The results showed that the saturation magnetization (M) and the coercive force (H) of the electrospun composite membrane with 5 wt.% FeO NPs was increased by 21 % and 69 %, respectively, comparing with the membrane prepared by solution casting. This was ascribed to the fine nano-dispersion of FeO NPs in BR matrix by using the electrospinning and in-situ crosslinking technique because the re-aggregation of FeO NPs was largely restrained by the fast evaporation of solvent, the confined space of nano/micro-sized fibers and the rapid crosslinking during electrospinning. Our work demonstrated that electrospinning and in-situ crosslinking is a simple and efficient method to improve the dispersion of nanoparticles in an elastomer matrix, and thus prepare high performance elastomeric nanocomposite. [ABSTRACT FROM AUTHOR]

Rubber nanoparticles in thermoplastic vulcanizate (TPV) may agglomerate during processing, leading to the deterioration of mechanical properties of TPV. This work shows how important an interfacial agent (Polyolefin Elastomer, POE) can be for stabilizing rubber particles in Ethylene-Propylene-Diene Monomer (EPDM)/polypropylene (PP) TPV during processing. The optimal type and dosage of POE was theoretically calculated. The time at which the POE interfacial agent is added is optimized based on the fragmentation kinetics of the EPDM rubber particles. The experimental results show that POE is indeed encapsulated on EPDM rubber particles in TPV, resulting in the large decrease in average size of EPDM rubber particles from 1.2 μm for TPV without encapsulation to 0.7 μm for TPV encapsulated with optimal dosage of POE. As a result, at an optimal dosage of POE, the elastic modulus, tensile strength, and elongation at break of TPV simultaneously increases by 70 %, 44 %, and 37 %, respectively. [Display omitted] • A good method was proposed to improve property of TPV by interfacial encapsulation. • Rubber domains in TPV are stabilized by an interfacial agent POE during processing. • AFM results verify that POE is encapsulated on EPDM rubber particles in TPV. • A fine rubber phase and good properties of TPV are obtained at suitable POE dosage. [ABSTRACT FROM AUTHOR]

Fiber-reinforced rubber composites (FRRC) are widely used in tires, hoses, conveyor belts and other fields. Currently, the industry heavily relies on the resorcinol-formaldehyde-latex (RFL) system to enhance interfacial adhesion performance of FRRC; however, both resorcinol (R) and formaldehyde (F) pose significant risks to human health and the environment. Thus, some two-step RF-free dipping systems have been developed to replace RFL system. Nevertheless, these complex two-step systems face challenges during industrialization. In this study, we proposed a novel one-step eco-friendly dipping system (PCGL) for polyamide66 (PA66)fibers. By using the new system, a solid transition bridge between PA66 fiber and rubber matrix can be formed, due to the bonding between PA66 and isocyanate, the interaction among polyacrylic acid resin, isocyanate and epoxy, the catalytic effect of triethanolamine, as well as the co-crosslinking of styrene-butadiene-vinyl-pyridine latex and rubber. The interfacial adhesion performance of PA66 fiber/rubber composites treated by PCGL with optimized ratio of epoxy groups/isocyanate groups can reach more than 90% of RFL level, meeting industry requirements for high interfacial bonding performance, while maintaining strength and safety of composites. The mechanism of largely enhanced interfacial adhesion was revealed through the analysis of modulus transition and co-crosslinking at the composite interface. [Display omitted] • A novel one-step eco-friendly dipping system was developed for PA66 fibers. • The adhesion of this new dipping system reaches 90% of traditional RFL system. • It overcomes complex process and high cost of current two-step RF-free systems. • It shows equal interfacial adhesion with current two-step RF-free systems. • The mechanism of its high interfacial adhesion performance was revealed. [ABSTRACT FROM AUTHOR]

Abstract: Crystalline structures especially the interfacial crystalline layers of semi-crystalline polymer/filler composites are markedly affected by the extensional force and keep an important role in macroscopic properties. In this study, we prepared the polypropylene and SiO2–MgO–CaO whisker (SMCW) composite fibers by melt-spun technology. The structure–property relationship of the PP/SMCW composite fibers was investigated by scanning electron microscopy, polarizing light microscopy, differential scanning calorimeter, the polarized Fourier transform infrared spectroscopy and tensile test. Two different interfacial crystalline structures were observed by adopting two drawn ratios – shish-calabash structure obtained at the low drawn ratio and transcrystalline (TC) structure obtained at the high drawn ratio. Remarkable reinforcement of the fibers was realized for the composite fibers prepared at high drawn ratio, compared with that obtained at the low drawn ratio. It was deduced that the formation of transcrystalline structure could result in a better interfacial interaction than shish-calabash structure, and could be one of the most important reasons for the large improvement of tensile properties of composite fibers fabricated at high drawn ratio. [Copyright &y& Elsevier]

Abstract: In this article, a quantitative measurement of orientation functions for both the polymer matrix and the filler has been carried out, for the first time, in high-density polyethylene (HDPE)/inorganic whisker (SMCW) composite fibers, with aid of polarized Fourier transform infrared (FTIR) spectroscopy. A highly oriented structure was observed in the as-spun fibers, and the orientation functions of both polyethylene and the whisker decreased with the increase of whisker content. During tensile deformation of the fibers, the orientation functions were continuously enhanced as increasing of the strain for the matrix and the filler. However, a fast increase of orientation was found for pure polyethylene fiber and composite fibers with less whisker content, and a slow increase for composite fibers with higher whisker content. Very interestingly, a formation of hybrid shish-kebab structure with whisker acting as shish and polyethylene lamellae as kebab was observed in the as-spun fiber with low loading of whisker (less than 10wt.%), resulting in a strong interfacial interaction between polyethylene and whisker. As a result, the highest tensile strength was observed in this sample even it had a lower orientation compared with that of pure HDPE. For the composite fiber with 10 and 20wt.% whisker, no obvious formation of hybrid shish-kebab was observed, resulting in a poor interfacial interaction and subsequently, lower tensile strength. That result indicates that the tensile strength of the fibers depends not only on the orientations of the polyethylene and the whisker, more importantly, on the interfacial interaction between matrix and the filler. The change of orientations of the composite fibers by adding whisker and the formation of hybrid shish-kebab structure were discussed based on rheological measurement. [Copyright &y& Elsevier]

With the current decreasing fossil resources and increasing carbon dioxide emissions, researchers are increasingly concerned about the development and utilization of biomass resources. The development of bio-based waterborne polyurethanes (BWPU) provides a new direction for the utilization of biomass resources and the protection of the environment. BWPU has attracted much attention from academia and industry due to their good physical and chemical properties, no volatile organic compounds (VOCs) emissions, exploitation of renewable substances, and structural design-ability. BWPU typically includes the polymerization of bio-based monomers, such as animal and vegetable oils, the addition of bio-based nanofillers, such as cellulose, lignin, and chitosan, and antimicrobial modifications, such silver nanoparticles and carvacrol, which can effectively replace traditional petroleum-based resources. At present, there are few reviews on the synthesis and applications of BWPU. Therefore, this paper reviews the recent progress in the synthesis of BWPU, and focuses on its applications in coatings, adhesives and antimicrobials, which is expected to provide reference and summarize research priorities and issues. [Display omitted] • Summarize bio-based waterborne polyurethanes (BWPU) recently produced from bio-based raw materials. • Summarize the current applications of BWPU, including coatings, adhesives and antimicrobials. • Suggestions are provided for further future research by BWPU in other areas. [ABSTRACT FROM AUTHOR]

Methyl vinyl silicone rubber (MVQ)/thermoplastic polyurethane (TPU) blending is an efficient way to develop biomedical elastomer with high strength and chemical stability. However, the MVQ and TPU phases are immiscible with each other and the interfacial adhesion is very weak. In this research, the amphiphilic hybrid particles (PU–SiO 2 @PDVB-PDMS) are synthesized by grafting polydimethylsiloxane (PDMS) and polyurethane (PU) molecular chains respectively onto two sides of SiO 2 @PDVB particles, which formed Janus particle compatibilizer with amphiphilic brush which can improve the interfacial adhesion via the similar molecular chain entanglement at the interface. Compared with traditional polydimethylsiloxane-polybutadiene-polyurethanes (PU-PB-PDMS) triblock copolymer compatibilizer, the MVQ/TPU blending compatibilized with this Janus particle is very stable even after annealing at 180 °C, with the average size of dispersed phase (D n) decreasing sharply about 3.5 times under the addition of only 1 wt% content addition through solution mixing. In our opinion, this amphiphilic hybrid Janus particle will pave a new possibility to realize blending MVQ with other immiscible polymers. The asymmetry and amphiphilic PU-SiO 2 @PDVB-PDMS particles were developed successfully, which were stably anchored at the interface of MVQ/TPU blends and the thickness of interfacial layer increased 200 nm than SiO 2 @PDVB particles at 5 wt% content. The size of dispersed phase was still stable after annealing at 180 °C and the elongation at break of MVQ/TPU blends with PU-SiO 2 @PDVB-PDMS was significantly increased, which reflected excellent interface stability and adhesion. Image 1 • The PU-SiO 2 @PDVB-PDMS particles with amphiphilic brush were developed, which were used as the compatibilizer for MVQ/TPU. • The PU–SiO 2 @PDVB-PDMS avoided micelles formation, which obviously optimized phase size and interface stability. • PU-SiO 2 @PDVB-PDMS were stably located at the interface, the thickness of interface layer was increased obviously. • The elongation of MVQ/TPU with PU-SiO 2 @PDVB-PDMS was significantly increased from 487% to 644%, compared to MVQ/TPU blends. [ABSTRACT FROM AUTHOR]

• A dielectric self-healing elastomer modified by TiO 2 /urea particles was prepared. • The urea on TiO 2 particles can form hydrogen bond with molecular chains. • Synthesized elastomer self-heals mechanical property after 24 h at room temperature. • The TiO 2 /urea particles effectively improve dielectric and actuated performance. • The actuator made of synthesized elastomer can operate again after first breakdown. We designed and prepared a new dielectric self-healing elastomer (TuSE) by introducing the core-shell structured TiO 2 /urea particles into self-healing supramolecular elastomer (SE) assembled by hydrogen bonds. The urea on the outer shell of TiO 2 particles forms hydrogen bonds with the amide groups in the molecular chains, so the TuSE materials exhibit higher self-healing efficiency than SE. The TuSE with 1% TiO 2 /urea particles (TuSE-1%) recovers its mechanical properties within 24 h at room temperature without any external stimulus. Moreover, the TiO 2 /urea particles effectively improve the dielectric constant (ε′) and actuated properties of the supramolecular elastomer. The TuSE-1% exhibits a much higher dielectric constant (ε′ = 16.1 at 1 kHz) and much lower elastic modulus (Y = 0.14 MPa) than those of SE (ε′ = 10.8 and Y = 3.78), resulting in a large increase in electromechanical sensitivity from 2.9 MPa−1 for pure SE to 115 MPa−1 for TuSE-1%. The dielectric elastomer actuator made of TuSE-1% shows a lateral actuation strain of 7.53% at 8.5 V μm−1, 20 times higher than that of pure SE (0.37% at 9 V μm−1). Additionally, TuSE-1% fully recovers its dielectric properties within 24 h, and the actuator can operate again after first breakdown. [ABSTRACT FROM AUTHOR]

A plasma-assisted surface modification method was introduced to enhance the interfacial adhesion of rubber composites reinforced with ultra-high molecular weight polyethylene (UHMWPE) fibers. First various reactive monomers were grafted onto the fiber surface via a plasma-assisted radical polymerization reaction. Subsequently, the grafted fibers underwent RFL (resorcinol-formaldehyde-latex) dipping process to bolster their interfacial adhesion with rubber. Compared with the original UHMWPE fibers, the modified fiber-reinforced rubber composites showed an increase in H pull-out force by 105.3 %–165.7 N and peel strength by 145.2 % to 10.3 N/mm, reaching the level of general-purpose fabric-core conveyor belt (≥4.5 N/mm). After the modification, the dynamic fatigue life and aging stability of the fiber-reinforced rubber composites were significantly improved, thereby enhancing the service life and safety of the composites. The results show that this method greatly improves the chemical activity, hydrophilicity, and surface roughness of UHMWPE fibers with minimal damage, rendering it a promising choice for industrial applications. [Display omitted] • A new strategy for UHMWPE fiber modification applicable to rubber matrix was provided. • A rubber material that can be quickly vulcanized at low temperatures for use in textile core conveyor belts was prepared. • The H pull-out force between the modified UHMWPE fiber and rubber reached 165 N, which reached the application level. • The interfacial bonding mechanism and chemical reaction processes between modified fibers and rubber are elucidated. [ABSTRACT FROM AUTHOR]

Abstract Grafting polar groups onto elastomer chains has proven to be an effective method to achieve high performance homogeneous dielectric elastomers (DE). Up to now, there still lacks an in-depth understanding of the effect of structure and content of these grafted dipoles on the electromechanical properties of the modified DE. In this study, three kinds of polar groups including carboxyl (COOH), hydroxyl (OH), and ester (COOCH 3) were grafted onto polymethylvinylsiloxane (PMVS) by using a photochemical thiol-ene reaction to prepare PMVS-COOH, PMVS-OH and PMVS-COOCH 3 DE. Three grafting degrees (15%, 50% and 95%) were prepared for each kind of modified PMVS. Interestingly, although the dipolar moment of COOH is higher than that of OH and COOCH 3 , at the same grafting degree, the dielectric constant of PMVS-OH is much higher than that of PMVS-COOCH 3 and PMVS-COOH. At high grafting degree (50% and 95%), the actuated strain at a specific electric field of PMVS-OH is significantly higher than that of PMVS-COOH and PMVS-COOCH 3. The actuated train at 15 kV/mm sharply increases from 0.2% for PMVS to 9.1% for PMVS-OH with the grafting degree of 95%, higher than that of the commercial silicone DE and the new structured silicone DE reported previously. These dielectric, mechanical and actuated properties are affected by the combined effects of moment, mobility and interactions of these dipoles, which have been deeply discussed. The present study provides guidance for the preparation of high-performance homogeneous DE by rational designing the dipolar structure and content. Graphical abstract Three different dipoles (ester, carboxyl and hydroxyl) were successfully grafted onto polymethylvinylsiloxane (PMVS) chains by using a facile one-step photochemical thiol-ene click reaction to prepare homogeneous silicone dielectric elastomer. The effects of dipole structure and content on the electromechanical and actuation performance of these silicone dielectric elastomers are deeply studied. The dielectric, mechanical and actuated properties are affected by the combined effects of moment, mobility and interactions of these dipoles. Image 1084405 Highlights • Homogeneous silicone DEs with different dipole structure and content were prepared. • The interaction and mobility of dipoles were experimentally evaluated. • The effect of dipoles structure on the electromechanical properties was studied. • The actuated properties are affected by dipole moment, mobility and interactions. [ABSTRACT FROM AUTHOR]

Abstract The interphase between nanofillers and rubber matrix, also known as "bound rubber (BR)" composed of a tightly BR (TBR) layer that strongly interacts with the filler and a loosely BR (LBR) layer that is physically adsorbed, plays an important role in the properties of rubber nanocomposites. Up to now, there is seldom direct evidence of such interfacial double layer structure and their thickness. In this study, we quantitatively identified the interphase of a representative nano silicon dioxide (SiO 2)/rubber composites by using peak force quantitative nanomechanical mapping (PFQNM) mode of Atomic Force Microscope (AFM). The thickness of interphase was quantitatively obtained, and the double layer structure of interphase was directly identified based on PFQNM images and the corresponding force-distance curves, and was further evidenced by high resolution transmission electron microscopy. We further studied the effect of molecular polarity on interphase of SiO 2 /hydrogenated nitrile butadiene rubber (HNBR) composites. Interestingly, the molecular polarity of HNBR has almost no effect on the thickness of TBR layer but has a significant effect on the LBR layer, leading to the remarkable increase in the total interfacial thickness of the composites with increasing the acrylonitrile content. The mechanism for the formation of interfacial double layer structure of BR and the effect of molecular polarity on the double layer structure was discussed. This study provides a simple method to identify and deeply understand the double layer structure of the interphase, and thus provides guidance for the design of interphase for the preparation of high performance rubber nanocomposites. [ABSTRACT FROM AUTHOR]

This work simulates the real harsh service conditions of Fiber-reinforced polymer composites (FRPC), and the dynamic adhesion and failure mechanism of nylon 66 (PA66)-reinforced natural rubber (NR) composites under large deformation and wide temperature range are deeply studied by comprehensive analysis of the interfacial adhesion evolution, microstructure and failure damage location of the composites, interfacial heating rate, and modulus ratio of PA66/NR. The failure mechanism of PA66/NR composites is interfacial debonding at −20 °C, 25 °C and 80 °C, whereas that at 120 °C is matrix cracks. Interestingly, at −20 °C, the crack expansion at the interface is slow, and the samples show two-stage damage during fatigue, resulting in the highest fatigue life. At 80 °C, the interface heating rate and modulus ratio of the PA66/NR composites is the lowest, and thus the fatigue life is higher than that at 25 °C and 120 °C. Keywords: fiber reinforced polymer composites, fatigue life, failure mechanism. [Display omitted] • The test method for fatigue life under wide temperature range was established. • They show the highest fatigue life at −20 °C and the lowest one at 120 °C. • The failure location was studied by distribution of characteristic elements. • The fatigue failure mechanisms under wide temperature range were revealed. [ABSTRACT FROM AUTHOR]

Dielectric elastomer (DE) composites have attracted much attention owing to their potential applications such as flexible electronics, energy storage, artificial muscles and sensors. The underlying mechanism to improve the electromechanical performance of DE is believed to be the interfacial polarization between fillers and matrix. Thus, understanding the interfacial polarization mechanism is a key to design and produce high performance DE composites. Despite of extensive works on studying the effect of fillers on interfacial polarization, the role of molecular polarity of matrix is still lacking. Thus, in this study, we prepared three kinds of carbon nanotubes (CNTs)/hydrogenated nitrile butadiene rubber (HNBR) DE composites with different molecular polarity of HNBR as the matrices and a special kind of aligned CNTs as the high dielectric constant (ε′) fillers to study the role of molecular polarity of HNBR on interfacial polarization and dielectric properties of the composites. These composites exhibit the similar dispersion and filler network of CNTs in matrices, which is a precondition of this study. Interestingly, at the same content of CNTs (higher than the percolation threshold), the ε′ of these composites largely increases with the enhancement of the molecular polarity of HNBR, whereas the ε′ of these pure HNBR matrices is very close. An equivalent circuit was then established to quantitatively analyze the interfacial polarization mechanism, and it fits well with the experiment data. This study demonstrates for the first time that the higher molecular polarity of matrix leads to the stronger interfacial polarization and thus results in higher ε′ of the composites. [ABSTRACT FROM AUTHOR]

The interfacial structure and chain segment dynamics of nanofiller/polymer composites play an important role in their macroscopic properties. Nevertheless, the mechanisms on the effects of nanofiller on the chain segment dynamics and the glass transition temperature (T g) of nanocomposites are still controversial. In this study, the interfacial structure (thickness and nanomechanical properties) of silica (SiO 2)/solution polymerized butadiene styrene rubber (SSBR) composites were quantified by using quantitative nanomechanical mapping technique of atomic force microscopy. The quantitative relationship between the degree of graft of coupling agent (CA) on SiO 2 and interfacial structure was built up. The formation mechanism of interfacial structure in SiO 2 /SSBR composites with different degree of graft on SiO 2 was revealed. A new insight on the effect of interfacial interaction of polymer nanocomposites on their chain segment dynamics and T g was proposed. With the increase in degree of graft, the interfacial thinkness largely increases, the dispersion of SiO 2 is more homogeneous, and the total area of interfacial SSBR layer largely increases, resulting in the significant decrease in chain density of SSBR matrix, and thus a significant decrease in T g. This study provides guidance for the interfacial design of high performance polymer nanocomposites for their wider application in industry. [Display omitted] • The interfacial thickness and elastic modulus at nanoscale of SiO 2 /polymer composites were quantitatively identified. • The quantitative relationship between the grafting degree of coupling agent on SiO 2 and interfacial structure was built up. • The formation mechanism of interfacial structure in SiO 2 /SSBR composites with different degree of graft on SiO 2 was revealed. • The T g of SiO 2 /polymer composites decrease with the increase in the grafting degree of coupling agent on SiO 2. • A new insight on the effect of interfacial interaction on the chain segment dynamics and T g was proposed. [ABSTRACT FROM AUTHOR]

Polyolefin elastomer (POE)/polypropylene (PP) thermoplastic vulcanizates (TPVs) is considered to be a better alternative to commercial ethylene-propylene-diene monomer (EPDM)/PP TPVs owing to its better overall performance and low-cost. In this study, we deeply studied the morphology development of POE/PP blends during dynamic vulcanization (DV) and its influencing factors such as the degree of crosslinking, crosslinking rate and shear rate. The results show that POE/PP TPVs exhibits smaller rubber nanoparticles (RNPs) and their agglomerates than that of EPDM/PP TPVs because of the better compatibility between POE and PP. The morphology development during DV of POE/PP TPVs is dominated by the formation and agglomeration of POE RNPs caused by the combined effect of dynamical in-situ crosslinking and the shear-induced break-up of POE phase. Higher degree of crosslinking, higher shear rate and moderate crosslinking rate of POE phase facilitate the rapid formation of smaller RNPs and RNPs agglomerates, and accelerate the occurrence of faster phase inversion. This study provides guidance for the preparation of high performance POE/PP TPVs by controlling the microstructure. [ABSTRACT FROM AUTHOR]

Fiber-reinforced rubber composites (FRRC) are widely used in automobile, aero tires, and conveyor belts, etc. In order to obtain high performance of FRRC, strong interfacial adhesion between fibers and rubber is a key. Resorcinol-formaldehyde-rubber latex (RFL) as the widely used dipping system in industry can do harm to human health and environment because of the release of resorcinol and formaldehyde in air. In this study, a new kind of eco-friendly dipping system for PA66 fibers was designed and successfully prepared, especially to meet the harsh service environment of aero tires. Such new dipping system is composed of the first coating of tea polyphenols (TP) on fiber surface through the hydrogen bonding between TP and PA66 fibers followed by the second coating with the mixture of glycerol triglycidyl ether (GTE), 2-ethyl-4-methylimidazole (MZ) and styrene-butadiene-vinyl-pyridine (VP) latex, in which the covalent bonding between TP and GTE, the crosslinking of GTE and the co-crosslinking of VP and NR matrix result in the formation of a solid transition bridge between PA66 fibers and NR matrix. By using such eco-friendly dipping system with optimized ratio of MZ/GTE, PA66 fibers/NR composites exhibit equivalent interfacial adhesion and aging stability as that using RFL system, while maintaining the strength and safety of composites. More importantly, PA66 fibers using the eco-friendly dipping system exhibit even better fatigue stability of interfacial adhesion after 46800 times of cyclic fatigue than that using RFL system. The relationship between the dipping layer structure and the interfacial adhesion of the composites was established. [Display omitted] • A new kind of eco-friendly dipping system for PA66 fiber cords was developed. • The new dipping system shows equivalent adhesion effect as that using RFL. • The new dipping system exhibits better fatigue stability than that using RFL. • The dipping layer structure and interfacial adhesion relationship was established. [ABSTRACT FROM AUTHOR]

The reaction mechanism and the interfacial modulus gradient of the interfacial transition layer between the environmentally friendly dipping system (PAL) and the rubber have not been fully studied. In order to better understand the chemical structures and nano-mechanical properties of the interface between the dip layer and the rubber, we used advanced atomic force microscope (AFM) and nanoscale Fourier transform infrared spectroscopy (nano-FTIR) to perform detailed analysis in this article. The characterization of interfacial nano-mechanical properties and chemical structures is very significant for the illustration of interfacial adhesion mechanism. AFM can effectively characterize the detailed interfacial modulus gradient and the thickness of interface, while nano-FTIR can comprehensively measure the interfacial chemical structures and the distribution of chemical bonds. The results suggest that the thickness of the interface between the PAL dip layer and the rubber matrix is 175 nm, and the crosslinking density of the interfacial layer is high, which explains that the failure location of fiber/rubber composites after pull-out tests occurs on the side of the rubber matrix. Similarly, the microstructure of resorcinol-formaldehyde-latex (RFL) system was also characterized, and the preparation of RFL usually requires carcinogenic and toxic substances such as formaldehyde and resorcinol. [Display omitted] • The reaction mechanism and interfacial modulus gradient of the PAL and the rubber have been fully studied. • Nano-FTIR can measure the interfacial chemical structures and the distribution of chemical bonds. • The thickness of the interfacial transition layer between the PAL and the rubber is about 175 nm. [ABSTRACT FROM AUTHOR]

Because of the fuel diversification, the harsher use environment and the requirements of environmental protection, the automotive fuel pipeline system requires not only good mechanical properties and high elasticity but also high temperature and oil resistance, high gas barrier property, easy processibility, and recyclability. Nevertheless, the traditional materials cannot simultaneously meet the requirements of these properties. In this study, fluororubber (FKM)/fluoro-thermoplastic (EFEP) TPV (FTPV) with fine dispersion of FKM rubber phase in EFEP matrix was successfully produced through the design and optimization of crosslinking systems of FKM and the processing technology. The as prepared FTPV not only shows good mechanical properties, elasticity, rheological property and recyclability, but also excellent oil resistance and gas barrier properties, outperforms the other TPVs. The mechanism on morphological development of the FKM/EFEP TPV are revealed. Interestingly, a large number of single rubber sub-micron particles (RPs) are formed in the blend during the dynamic vulcanization, which is mainly attributed to an improvement in compatibility and an increase in crosslinking degree of FKM. The combined effect of shearing stress and the improvement of compatibility results in a decrease in the size of rubber sub-micron particles agglomerates and an increase in the content of single rubber sub-micron particles. [Display omitted] • A new kind of FKM/EFEP TPV(FTPV) was developed. • It exhibits good mechanical properties, elasticity, rheological property recyclability, and excellent oil resistance and gas barrier property. • A large number of single rubber sub-microparticles (RPs) of 350–400 nm in diameter are formed during the dynamic vulcanization. • The relationship between microstructure and properties of the FTPV was revealed to provide guidance on controlling the phase morphology to produce high performance of FTPVs. [ABSTRACT FROM AUTHOR]

We prepared hydrogenated butadiene-acrylonitrile (HNBR) elastomer composites with random orientations of carbon nanotubes (CNTs) and aligned CNTs, denoted by random composites and aligned composites, respectively, by means of a simple mechanical blending method. The CNTs were dispersed uniformly in the HNBR matrix in both types of composites. Interestingly, at CNT contents of 1-2.5 vol%, the dielectric loss (tan δ) of the aligned composites increases slightly, and the dielectric constant ( ε′) of aligned composites increases largely with the increasing content of CNTs, whereas both the tan δ and the ε′ of the random composites increase largely with the increasing content of CNTs. As a result, a high ε′ (5000 at 1000 Hz) and a low tan δ (0.42 at 1000 Hz) were obtained in the aligned composite with a CNT content of 2.5 vol%, whereas a high ε′ and a high tan δ were obtained in the random composites. The relationship between the microstructure and dielectric properties was qualitatively analyzed by means of the percolation theory and intercluster polarization model. The mechanism for the achievement of high ε′ and low tan δ for dielectric composites was discussed. This study provides a guide to design microstructure that yields composites with improved dielectric properties. [ABSTRACT FROM AUTHOR]

Dielectric elastomer generators (DEGs) can harvest energy by converting mechanical energy from natural movement into electrical energy. Despite of many studies on improving the energy harvesting performances of DEG by the design of dielectric elastomer (DE) materials, how do the electromechanical properties such as dielectric constant (ε) and elastic modulus (Y) of DE materials affect their energy harvesting performances is still unclear. In this study, we purposefully designed and prepared two sets of brominated isobutylene isoprene rubber (BIIR) based DE materials, one set with almost the same ε but different Y and the other set with almost the same Y but different ε. And the effect of the single electromechanical property (ε or Y) on the energy harvesting performances of DEG under the cone stretching mode was revealed for the first time. In a single energy generating cycle, the generated energy and energy density are basically independent of Y, but interestingly, they sharply increase as the ε increases. Under the premise of high cone stretch displacement, DE with higher ε and lower Y has a higher electromechanical conversion efficiency. The "amplification effect" of actual generated energy with the increase in ε is quantitatively analyzed by considering the existence of charge leakage, the introduction of transfer capacitor, and the non-uniform stretching of DE film. This study provides a guidance for designing and optimizing DE materials with high energy harvesting performances. The electromechanical properties of DE materials (dielectric constant and elastic modulus) on energy harvesting performance and the tremendous "amplification effect" of actual generated energy were studied, which provide guidance for DEG with high harvesting performance. [Display omitted] • Two sets of samples with ε and Y as variables have been designed and prepared. • The effect of ε or Y of DE on the energy harvesting performance were revealed. • The energy density is independent of Y but sharply increase with increasing ε. • DE with higher ε and lower Y has a higher electromechanical conversion efficiency. • The amplification effect of actual generated energy with increasing ε is analyzed. [ABSTRACT FROM AUTHOR]

Dielectric elastomer generator (DEG) based on SiO 2 /PMVS composite with high efficiency/generating energy density and long fatigue life has been obtained by introducing a kind of SiO 2 with strong interfacial polarization ability into PMVS matrix and tailoring interfacial interaction. In addition, the mechanism on that enhanced interfacial interaction can more effectively diffuse both stress and charges, thus improve fatigue life, dielectric properties and energy harvesting performances of SiO 2 /PMVS based DEG is revealed. [Display omitted] • Adding SiO 2 into SiR shows 5 times increase in ε r than traditional ceramic fillers. • The grafting of CA on SiO 2 improves both E b and fatigue life of the composites. • High energy density (47.9 mJ/g) and conversion efficiency (32.3%) were achieved. • The full-life generating energy density reaches over 2,000 J/g, 290 times higher than VHB material. • The influences of the interfacial interaction on fatigue life and dielectric properties are revealed. Dielectric elastomer generator (DEG) can easily realize the energy harvesting from nature motion sources such as waves and human movements. Up to now, the bottleneck of the development of DEG is the lack of dielectric elastomer (DE) material with excellent dielectric properties and long fatigue life, restricting the practical application of DEG. In this study, a kind of nano-silica (SiO 2) with strong interfacial polarizability was introduced into polydimethyl(methylvinyl)siloxane (PMVS) matrix to enhance its permittivity. The results show that the increase of permittivity of PMVS by adding SiO 2 is five times that by adding traditional ceramic filler, and all these composites maintain high insulation. After the grafting of a coupling agent (CA) on SiO 2 (CA@SiO 2), the co-crosslinking reaction between CA@SiO 2 and PMVS can occur, leading to the large enhancement of the interfacial interaction and thus the improvement of both breakdown strength and fatigue life of the CA@SiO 2 /PMVS composites. The as-prepared unprestretched DE composite was then used as DE substrate for cone DEG, and an up-to-date highest generating energy density (47.9 mJ/g) and conversion efficiency (32.3%) were achieved. More importantly, the as-prepared DEG exhibits long fatigue life of over 50,000 cycles and its full-life generating energy density reaches over 2,000 J/g, approximately 290 times higher than that using the most widely used VHB material based DEG. By combining atomic force microscopy, the finite element analysis and experimental results, the mechanism why enhancing the interface interaction can improve the energy harvesting performance and fatigue life of DEG is revealed. [ABSTRACT FROM AUTHOR]

Thermally reduced graphene oxide (TRG)/thermoplastic polyurethanes (TPU) dielectric elastomer with high dielectric constant ( k ), low dielectric loss and greatly improved actuated strain at low electric field was prepared by solution blending followed by in situ thermal reduction. The results showed that a good dispersion and alignment of TRG in the TPU matrix was obtained. The k at 10 3 Hz was sharply increased from 7 for pure TPU to 1875 for the composite with 2 vol. % of TRG because of the partial restoration of graphite structure and the great increase in dipole polarizability of TPU caused by the disruption of hydrogen bonds of TPU chains. The dielectric loss at 10 3 Hz of the composite with 2 vol. % of TRG remained low (0.43). Despite of the increase in elastic modulus with the increase in the content of TRG, the great increase in k lead to the great increase in electromechanical sensitivity ( β ). As a result, a 106 times increase in β at 10 3 Hz and 17 times increase in actuated strain at low electric field (250 V/mm) were achieved by adding 2.0 vol% of TRG. This study provides a simple and effective method for the improvement of actuated strain at low electric fields through partial reduction of graphene oxide and the disruption of hydrogen bonds in TPU, facilitating the applications of dielectric elastomers in the biological and medical fields, where a low electric field is required. [ABSTRACT FROM AUTHOR]

To solve the poor interface between aramid fiber and rubber, this paper studies a method of constructing nanostructures on the fiber surface. First, functional groups such as hydroxyl and amino groups were introduced onto aramid fiber through the Michael addition of tannic acid and polyethyleneimine. Then, the modified aramid fiber was impregnated in the aramid nanofiber/carbon nanotube aqueous dispersion to prepare a surface-coated fiber. The fibers and surface nanostructures were characterized by scanning electron microscopy, transmission electron microscope, Raman spectroscopy, X-ray photoelectron spectroscopy, thermalgravimetric analysis, and H pull-out tests in detail. The results show that the H pull-out force of the coated fiber is increased by 126.4% compared with the original aramid fiber, which is due to the good mechanical interlocking at the interface of the composites. In addition, carbon nanotubes could form a conductive path through mutual entanglement and overlap on the surface of aramid fiber, which also gives the function of real-time monitoring of deformation of the composites. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Thermally expanded graphene nanoplates (TGNPs) were introduced into polydimethylsiloxane (PDMS) matrix by using solution mixing method to obtain TGNPs/PDMS dielectric composites with high dielectric constant (k), low dielectric loss and large actuated strain. The results indicated that the k at 103 Hz was obviously increased from 3.1 for pure PDMS to 18.3 and 89.5 for the composite with 1.6wt% and 2.0wt% TGNPs, respectively. Meanwhile, the volume resistivity of all the composites was larger than 109 Ωcm, indicating a low direct current conductance. As a result, the dielectric loss at 103 Hz retained a low value for all the composites. In addition, a significant increase in actuated strain was obtained from 1.4% for pure PDMS to 3.6% with the addition of 2.0wt% TGNPs under a low electric field (15V/μm). The mechanism for the largely improved dielectric properties was carefully discussed based on the uniform dispersion of TGNPs in PDMS matrix, the gradual formation of many parallel or serial micro-capacitor structures (low direct current conductance) with the content of TGNPs increasing, and the remained oxygenic groups coated on TGNPs after high temperature thermal exfoliation. Our work provided a simple, low-cost and effective method to prepare high performance dielectric elastomer (DE), facilitating the wide application of DE composites, especially in the biological and medical fields such as biosensors, artificial muscles, and prosthetics. [Copyright &y& Elsevier]

Abstract: The effect of in-situ crosslinking of poly (ethylene-co-octene) (POE) rubber phase on the interfacial crystallization of isotactic polypropylene (iPP) in dynamically vulcanized iPP/POE blends was studied. The results showed that in situ crosslinking of POE obviously increased the interfacial crystallization of iPP in the dynamically vulcanized blends, comparing with that of pure iPP and the unvulcanized blend. The interfacial crystallization of iPP was further increased with the increase in crosslink degree. After annealing, the obvious interfacial crystallization was still obtained in the blend with high crosslink degree. Based on the fluctuation assisted nucleation mechanism in solution blended iPP/polyolefin block copolymer (OBC) blends, we proposed for the first time the interfacial crystallization mechanism in dynamically vulcanized blends: the oriented chains of iPP formed by concentration fluctuation at the interface during phase separation or shearing stress during melt mixing can be maintained because of the in situ crosslinking of POE phase, resulting in the enhancement of nucleation density at the iPP/POE interface. Our study proposes a new interfacial crystallization mechanism, and provides guidance for the preparation of high performance thermoplastic vulcanizates (TPVs) product by tailoring the interfacial crystallization of TPVs. [Copyright &y& Elsevier]

[Display omitted] • A hydrogen bond crosslinked supramolecular network of SiR-SN was prepared. • A high conductive stability and self-healing SiR-SN electrode was obtained. • The high energy density and low energy loss of DEG were obtained. • The relationship between microstructure and properties was revealed. Dielectric elastomer generator (DEG), consisting of highly deformable dielectric elastomer (DE) film sandwiched between two compliant electrodes, can convert mechanical energy into electrical energy. To achieve high energy harvesting performance and practical durability, electrode material with high stability of electrical conductivity (EC) and self-healing/recycling capability is required. In this study, we designed and prepared conductive rubber electrode with high EC, high stability of EC at high strain and high durability during cyclic stretching, self-healing and recycling ability for DEG by synthesizing a hydrogen bond crosslinked supramolecular network of silicone rubber (SiR-SN) followed by introducing a commercially available, highly conductive carbon black (CB) and carbon grease (CG) into SiR-SN matrix. The addition of CG composed of silicone oligomer (SO) and CB can induce the partial phase separation of polar SiR-SN and the formation of segregated conductive network, leading to the significantly enhanced EC and stability of EC at high strain. The presence of SO chains also increases the chain mobility, leading to the high durability, self-healing ability and recyclability of the electrode. Compared with CG electrode commonly used in laboratory, the energy loss at 3 kV and 400% strain of DEG using the 5 phr CB/60 phr CG/SiR-SN electrode is reduced by 83.5%, and the harvested energy density increases by 73.1%, which reaches 23 mJ/cm3, much higher than that reported in previous studies. Meanwhile, this electrode shows high self-healing efficiency of conductivity (92% at 60 °C for 4 h), and can be recycled for 5 times without negative effect on performance. [ABSTRACT FROM AUTHOR]

To strengthen the interfacial adhesion between aramid fiber and rubber, inspired by mussel adhesion protein and mimicking adhesive molecule, a new environmentally friendly dipping system was developed. Specifically, water-soluble pyrogallic acid and polyethyleneimine are reacted to form a network structure, which is then mixed with rubber latex to prepare the dipping solution. We use blocked isocyanate and epoxy aqueous solution to activate the fiber, and then conduct the dipping treatment. The H pull-out force between modified aramid fiber and rubber reached 147 N, achieving the level of traditional resorcinol-formaldehyde-latex dipping system (154 N), while avoiding the utilization of harmful resorcinol and formaldehyde. In addition, we employed atomic force microscope for the first time to quantitatively characterize the modulus of the transition layer between the fiber and rubber. Results from this research provide new insights into the interfacial design of aramid fiber/rubber composites and will facilitate the development of aramid fiber/rubber composites. [Display omitted] • An environmentally friendly dipping system for aramid fiber was demonstrated. • The H pull-out force between modified aramid fiber and rubber reached 147 N. • We quantitatively characterize the modulus of the transition layer. [ABSTRACT FROM AUTHOR]

Abstract: In this work, surface modification of fibrillar silicate (FS) is conducted by using supercritical CO2(sc-CO2) technique. For comparison purpose, conventional modification method is also carried out. The results showed that physical adsorption of the modifier (KH570) on FS surface dominated by using conventional method, whereas chemical adsorption dominated by using sc-CO2 technique. In addition, a more uniform adsorption of the modifier on FS surface is successfully obtained by using sc-CO2 method. This is ascribed to the special gaseous and liquid characteristics of sc-CO2, which can facilitate the diffuse and the full contact of KH570 on the whole surface of FS. The modified FS are then melt blended with ethylene–propylene ethylidene norbornene terpolymer (EPDM) to prepare rubber composites with excellent high temperature performance and good ageing resistance. The results showed that a more uniform dispersion of FS in EPDM matrix and a stronger interfacial interaction between FS and EPDM are successfully achieved by surface modification of FS in sc-CO2, which lead to the obviously enhanced mechanical properties of the composites. Our work demonstrates a better surface modification technique for FS to largely improve the interfacial interaction between FS and EPDM and to obtain a high performance FS/EPDM elastomer composites for its wide application such as transmission belts of automobile. [Copyright &y& Elsevier]

The application of silicone rubber as dielectric elastomer sensor is limited by its poor strain sensing performance because of low dielectric constant (ε′). In this study, we designed and fabricated a fluorosilicone dielectric composite with high ε′ and capacitive strain sensing performance by designing polar-nonpolar multiblock fluorosilicone copolymer and introducing poly(dopamine)-modified nanotubes (CNT-PDA). Firstly, a polar (bis(3-aminopropyl)-terminated poly(3,3,3-trifluoropropyl) methylsiloxane (H 2 N-PFMS-NH 2)) and a nonpolar (bis(3-aminopropyl)-terminated poly(dimethylsiloxane) (H 2 N-PDMS-NH 2)) silicone oligomers were synthesized by anionic ring opening polymerization. Then, a series of PFMS/PDMS multiblock copolymer were synthesized through a one-pot polycondensation reaction between isocyanate groups from methylene-bis(4-cyclohexylisocyanate) and amino groups from the as prepared H 2 N-PFMS-NH 2 and H 2 N-PDMS-NH 2. The hydrogen bonds between urea groups act as physical crosslinking points on the multiblock copolymer. The H 2 N-PFMS-NH 2 chains with polar CF 3 groups contribute to high dipole polarizability and thus a high ε'. A strong interfacial adhesion between CNT-PDA and the multiblock copolymer was obtained by hydrogen bonding between the urea groups of the multiblock copolymer and CNT-PDA, resulting in strong interfacial polarizability. The as-prepared composite exhibits a ε′ of about 86.7 at 103 Hz and a capacitance change (ΔC) of about 0.91 nF at 200% strain at only 0.3 vol% of CNT-PDA, which was increased by 23.8 and 8.1 times, respectively, compared with the CNT-PDA/commercial nonpolar reference SiR composites. The largely improved ε′ and capacitive strain sensing properties are mainly attributed to the synergistic polarization effect, which was discussed based on impedance analysis and calculating the contribution of each composition on ε' and ΔC. [Display omitted] • A new polar-nonpolar multiblock fluorosilicone was designed and prepared. • A strong interfacial polarizability between CNT-PDA and DE was obtained. • CNT-PDA/fluorosilicone composites can be used as DES. • Both dielectric constant and sensitivity of DES were largely improved. • The relationship between structure and sensitivity was revealed. [ABSTRACT FROM AUTHOR]

Thermoplastic vulcanizate (TPV) have been widely used in industry, and injection molding is one of the most widely used technique to produce TPV products. In this study, effects of shear during injection molding on the anisotropic microstructure and properties of EPDM/PP TPV containing rubber nanoparticle agglomerates was systematically studied by using quantitative nanomechanical mapping of atomic force microscopy (AFM-QNM) for the first time. The shear of injection molding induced break-up of the EPDM nanoparticles agglomerates, and a significant decrease in the size of the latter with increasing shear rate was observed. Meanwhile, the shear orients both PP crystals and EPDM nanoparticle agglomerates, and their orientation degree along the shear direction, and the crystallinity of PP increase with increasing the shear rate. As a result, whatever the anisotropy, the Young's moduli at nanoscale of PP obtained by AFM-QNM, and the tensile strength and elastic modulus of TPV increase with increasing shear rate till the shear-induced PP chain degradation becomes important. Moreover, the tensile strength and elastic modulus of TPV parallel to the shear direction are much higher than those perpendicular to it, while the elongation at break and elasticity are the opposite. Interestingly, for TPV perpendicular to the shear direction, despite of the higher crystallinity and elastic modulus of TPV prepared under moderate shear rate than that under very low shear rate, the elasticity of the former is even much higher than the latter. The mechanisms on effects of shear on the anisotropy of microstructure, mechanical properties and elasticity of EPDM/PP TPV were revealed. This study provides guidance for optimizing process conditions in order to control the microstructure of the TPV and best balance their effects on mechanical properties and elasticity of TPV. Effects of injection shear on the anisotropic microstructure and properties of EPDM/PP TPV containing rubber nanoparticle agglomerates was systematically addressed. [Display omitted] • AFM-QNM was used to study the anisotropic microstructure and properties of TPV. • Shear in injection molding orients PP crystals and EPDM nanoparticle agglomerates. • Shear induced a decrease in the size of EPDM nanoparticles agglomerates. • A moderate shear rate in transverse direction results in a higher elasticity. • Mechanism on the anisotropy of microstructure and properties of TPV was revealed. [ABSTRACT FROM AUTHOR]

• This article reviews the surface modification methods of aramid fiber and its composite materials. • Interfacial adhesion is important for aramid fiber reinforced composites. • The interfacial stress transfer mechanism of aramid fiber reinforced composites is still unclear. Aramid fiber (AF), which has excellent comprehensive properties such as low density, high specific strength, and high specific modulus, is widely used in composites reinforcement. AF-reinforced composites (AFRPs), which are very suitable for preparing advanced engineering materials, have drawn much attention due to their excellent properties. However, the smooth and chemically inert surface of the AF severely limits its applications. Various methods have been conducted to modify the surface of AF to improve the interfacial adhesion between fiber and matrix. The purpose of surface modification of AF is to improve the surface chemical activity and increase the surface roughness, which aims to achieve an excellent chemical bonding and mechanical interlocking between fiber and matrix. The major focus of this review is the surface and interface modification of AF. In this review, we briefly summarize the recent progress of different surface modification methods of AF and its reinforcement to polymers. Finally, some existing problems of AFRPs as well as future research prospects are discussed. [ABSTRACT FROM AUTHOR]

In recent years, aramid nanofibers (ANFs) have been widely used in polymer reinforcement and toughening fields, due to their large specific surface area, high aspect ratio and retaining the excellent strength, modulus and high temperature resistance of aramid micron fibers (AMFs). It is considered that ANFs have excellent reinforcement effects for polymer composites and much attention has been focused on them. ANFs have excellent water dispersibility, which provides convenience for their reinforced polymers. ANF-reinforced polymers could also impart excellent properties such as high temperature resistance, flame retardancy, and tear resistance. Therefore, it is necessary to find a simple and efficient preparation method of ANFs. However, there is almost no literature review on the research progress of the fabrication of ANFs and ANF-reinforced polymer composites. This article reviews the recent research progress of the preparation of ANFs and the advantages and disadvantages of different preparation methods, and presents the applications in reinforcing various polymer matrices such as epoxy, rubber and composites. Finally, we proposed our own opinions on the issues of ANF-reinforced polymers. [ABSTRACT FROM AUTHOR]

• The interfacial cross-linking bonding between E-TiO 2 and PMVS-COOH was formed. • Both dipole and interfacial polarization lead to the large increase in ε′. • The mechanical strength was largely improved due to good interfacial interaction. • The actuated strain at low electrical field was largely improved. Silicone rubber (SiR) is one of the most promising dielectric elastomer (DE) materials for DE actuator, but it is still limited by low properties such as mechanical strength, dielectric constant and actuated strain at low electric fields. In this study, we report the design and preparation of SiR DE composite with simultaneously improved tensile strength, dielectric constant and actuated strain at low electric fields by introducing both polar functional group and multifunctional filler. Firstly, carboxyl groups were grafted onto polymethylvinylsiloxane (PMVS) by using a radical-mediated thiol-ene click reaction to improve the dipole polarizability. Meanwhile, epoxy group-functionalized TiO 2 (E-TiO 2) particles as multifunctional fillers were prepared and filled into carboxyl groups modified PMVS (PMVS-COOH). The esterification reactions between carboxyl groups of PMVS-COOH and epoxy groups of E-TiO 2 results in interfacial covalent cross-linking, good interfacial interaction, and strong interfacial polarizability of E-TiO 2 /PMVS-COOH dielectric composites. As a result, the tensile strength largely increases from 0.33 MPa to 0.89 MPa as the content of E-TiO 2 increases from 10 phr to 30 phr. The dielectric constant at 103 Hz of the composite with 30 phr E-TiO 2 reaches 8.98, which is 3.3 times as reference SiR due to the simultaneously improved dipole and interfacial polarizability. The actuated strain at low electrical field (15 kV·mm−1) of the composite with 30 phr E-TiO 2 reaches 3.7% without any pre-strains, which is 5.2 times than that of reference SiR. Our study provides a simple and effective strategy to simultaneously improve the mechanical, dielectric and actuated properties of SiR DE. [ABSTRACT FROM AUTHOR]

Due to the chemical inertness of the polyester (PET) fiber surface, it often needs to be immersed in a traditional resorcinol-formaldehyde-latex (RFL) dipping solution before it can be used in rubber composite. However, the RFL dipping system contains toxic components, resorcinol and formaldehyde, and is gradually banned. In this article, a novel resorcinol-formaldehyde-free environmentally friendly adhesion promoter for dipping treatment of PET fiber was synthesized. Specifically, water soluble ethylene glycol diglycidyl ether (EGDE) and diethylenetriamine (DETA) were introduced into the new dipping solution to replace the toxic ingredients of resorcinol and formaldehyde in RFL dipping system. We use polyester fabrics to study the effects of reaction conditions, chemical structures and interfacial adhesion mechanism on the treatment results to achieve the level of conventional RFL treatment. The surface chemical compositions of modified PET fabrics were characterized by attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The results showed that the fabric surface was successfully coated with the dipping layer. In addition, interfacial adhesive properties between modified PET fabrics and rubber were studied. The results showed that the peel adhesive strength between the modified PET fabric and the rubber was 17 N/mm, which was comparable to the RFL dipping system. • A novel resorcinol-formaldehyde-free environmentally friendly adhesion for dipping treatment of fibers was synthesized. • Interfacial adhesive properties between modified polyester (PET) fabrics and rubber matrix were studied. • The peel adhesive strength between the modified PET fabric and the rubber matrix was 17 N/mm. [ABSTRACT FROM AUTHOR]