Search

• An SH surface was created on elastomeric substrate by thiol-ene click chemistry. • The SH surface shows ultrahigh adhesive force and good anti-scratching property. • The silanized nano-silica formed the micro-nano structure on the substrate. • The polymerized fluorinated monomer decreased the surface energy of the substrate. • The SH coating was covalently bonded with the elastomer substrate. In this study, a Superhydrophobic (SH) surface with ultrahigh adhesive force and good anti-scratching property was created on elastomeric substrate by thiol-ene click chemistry. The elastomer substrate was prepared by solution mixing of styrene butadiene rubber (SBR), polar fluorinated monomer, multi-functional thiol, and photoinitiator. Then the silanized nano-silica was simply sprayed on the elastomer substrate to prepare the SH coating. Through UV irradiation, thiol-ene click reaction between multi-functional thiol and double bonds of SBR, fluorinated monomer and silanized nano-silica simultaneously occurs, leading to the crosslinking of SBR, the polymerization of fluorinated monomer, the graft of fluorinated monomer on silanized nano-silica, and the covalently bonding of fluorinated monomer with SBR substrate. As a result, the polymerized fluorinated monomer bonded silanized nano-silica is covalently bonded with the SBR substrate. Meanwhile, the silanized nano-silica forms the micro-nano structure on the substrate and the polymerized fluorinated monomer decreases the surface energy of the substrate. A stabilized SH coating with ultrahigh adhesive force (123 μN) to water was achieved. In addition, the SH surface shows strong interfacial bonding and a good anti-scratching property because of the covalent bonding of SH coating with the SBR substrate. This is a facile, simple and efficient method to fabricate SH coating on the elastomeric substrate, which may open a door to fabricate SH coating on other surfaces and provide more potential applications. [ABSTRACT FROM AUTHOR]

Despite many investigations, phase inversion in rubber/plastic blends and its origin are far from being understood. Here we focus on the heterogeneous phase inversion in partially miscible blend of polyolefin elastomer (POE) and polypropylene (PP) using the classical density functional approach. We have shown that the blend decomposes into the POE-rich and PP-rich phases on the surfaces of POE or PP domains. For example, the free energy barriers and critical sizes of the POE-rich droplets on the two surfaces obviously decrease compared to the analogous values in the homogeneous nucleation. These values can be further reduced after introduction of nanoparticles, which act as the compatibilizer, improving morphology and final properties of the blend. These results indicate different phase inversion mechanisms in the blend, and can explain why different sizes of nanoparticles can observed in experiments. [ABSTRACT FROM AUTHOR]

The interface between nanofillers and elastomers is one of the most important factors to determine the performance of elastomer nanocomposites. In this study, for the first time, we developed a method to quantitatively characterize the interfacial layer thickness of carbon nanotubes (CNTs)/Natural rubber (NR) composites by using peak force quantitative nanomechanical mapping (PF-QNM) technique of atomic force microscopy (AFM). We obtained the modulus and adhesion distribution of the composites, and selected those CNTs close to the sample surface, where the CNTs show lower adhesion for the accurate characterization of the interfacial thickness. Then, we characterized the thickness of interfacial layer according to the gradient change in Young’s modulus. The results show that the average interfacial thickness of CNTs/NR composites is about 9 nm, similar with that in carbon black (CB)/elastomer composite (10 nm) reported in previous study, indicating the good interfacial interaction between CNTs and NR matrix. The average interfacial thickness of the modified CNTs/NR composites is about 17.4 nm, indicating the stronger interfacial interaction. The “Payne effect” and mechanical properties of these nanocomposites were also examined, and the results were consistent well with the AFM PF-QNM results. This study provides a new method to quantitative characterize the interface between filler and elastomer matrix at nanoscale resolution. [ABSTRACT FROM AUTHOR]

It is common practice to blend polymers to obtain high-performance polymer materials for new applications. Thermoplastic vulcanizates (TPVs), consisting of a high content of crosslinked rubber as a dispersed phase and a low content of thermoplastic as a continuous phase, are usually prepared by pre-blending rubber and plastic phases followed by dynamic vulcanization. They are a special class of high performance thermoplastic elastomers (TPEs) as they combine both the excellent elasticity and mechanical properties of crosslinked rubbers and good processability and recyclability of thermoplastics. As such, in the recent decades they have attracted much attention and have become the fastest growing elastomers to replace unrecyclable thermoset rubbers. This review focuses on recent progresses in TPVs, and more specifically on the following issues: (1) preparation methods of TPVs, (2) mechanisms of formation of the microstructure of TPVs; (3) relationships between the microstructure and properties, (4) review of various types of TPVs, including general TPVs, special TPVs, bio-based TPVs, and TPVs-based nanocomposites, (5) future challenges on TPVs. [ABSTRACT FROM AUTHOR]

Abstract Understanding the glass transition of water is still a major scientific challenge. Here we propose a dynamic density functional renormalization group approach to analyze the liquid–liquid phase transitions and diffusion dynamics of water molecules under supercooling condition. We find that, as the temperature approaches the glass transition point, the metastable phase transition displays the confined critical scaling behavior, and the dynamic correlation length actually diverges simultaneously. The predicted glass temperature is 142.5 K, close to the experimental value of 136 K. These results suggest a deep coupling feature of the thermodynamic and dynamical heterogeneities during the glass transition of supercooled water. Highlights • Glass transition of water shows thermodynamic and dynamical heterogeneities. • The RG theory is integrated into DDFT to deal with such transition. • Evolution of liquid-liquid transition on ice surface leads to glassy water. • Glass transition shares similar attributes of critical transition under confinement. [ABSTRACT FROM AUTHOR]

In this study, moderate content of polyethylene glycol (PEG) with ionic conductivity and low content of graphene oxide (GO) were simultaneously introduced into thermoplastic polyurethane (TPU) followed by in-situ chemical reduction of GO (rGO) to prepare TPU/PEG/rGO dielectric elastomer (DE) composites with largely improved electromechanical performance. The results showed that PEG remarkably disrupted the hydrogen bonds between TPU chains in TPU/PEG/rGO composites and formed new hydrogen bonds with TPU. In addition, PEG molecules can also form hydrogen bonds with rGO, leading to the coating of PEG on GO and thus the separation of rGO from TPU. Interestingly, PEG and rGO showed significant synergistic effect on the dielectric constant ( ε′ ) of the composites, resulting in the large increase in ε′ at 10 3 Hz from 7 for pristine TPU to 71 for TPU/PEG/rGO composite. This was attributed to the increase in dipole polarizability of TPU chains caused by the disruption of hydrogen bonds and the increase in interfacial polarizability caused by the favorable electron transfer from partially reduced GO coated by PEG to TPU. The elastic modulus ( Y ) of the TPU/PEG/rGO composites largely decreased because of the plasticizing effect of PEG and the separation of GO from TPU. Owing to the simultaneous increase in ε′ and decrease in Y , the composite showed 49 times increase in electromechanical sensitivity ( β ) and 6.5 times increase in actuated strain at a certain electric field over that of pristine TPU. [ABSTRACT FROM AUTHOR]

We studied the effect of the microstructure of multiwalled carbon nanotubes (MWCNTs) on interfacial interaction in seven kinds of MWCNT/natural rubber (NR) composites. Unexpectedly, the degree of defects (I D /I G ) of MWCNTs was found to play a key role in the interfacial interaction of MWCNT/NR composites. The content of bound rubber (BR) of the composites almost linearly increased with the increase in the I D /I G of MWCNTs. Then we studied the interfacial interaction between MWCNTs with high degree of defects and NR. Interestingly, the BR of the composites consisted of loosely adsorbed BR (LBR) and tight BR (TBR). TBR occupied about half of the total BR, and cannot be removed by extraction in hot toluene for 48 h. Meanwhile, the mobilities of macromolecules in TBR were more restricted than those in LBR. We discussed in depth the molecular origin of the interfacial interaction between defected MWCNTs and NR, and then proposed that LBR was topologically confined by the steps-like structure of defected MWCNTs whereas TBR was principally chemically bonded to MWCNTs. This study provided new insight on the interfacial interaction between MWCNTs and NR and thus provides guidance for the preparation of high-performance elastomer composites with strong interfacial interaction. [ABSTRACT FROM AUTHOR]

In this study, we introduced silver-coated glass particles (SG) into methyl vinyl silicone rubber (PMVS) matrix to prepare conductive elastomeric composites (CECs) with high electrical conductivity. The effect of the content of SG, the tensile strain and the stretch-recovery cycle times on the conductivity of CECs were studied. Interestingly, the conductivity of all the composites obviously increases with the increase in the applied tensile strain or the stretch-recovery cycle times to certain degree, different from that reported in many previous studies. The reason is that the dispersion of SG in PMVS matrix becomes more nonuniform with the increase in tensile strain, and the redistribution of SG in matrix results in the formation of much more new conductive network. On the other hand, the change in conductivity of the composites with the content of SG just exceeding the percolation threshold is much more significant than that with the content of SG far exceeding the percolation threshold. This is attributed to the more perfect conductive network in the composites with higher content of SG. The relationship between the conductivity and conductive filler network of SG/PMVS composites were clarified. This study provides guidance for the preparation and application of high performance CECs with excellent conductivity and stability of conductivity. [ABSTRACT FROM AUTHOR]

Herein, graphene oxide (GO)-encapsulated silica (SiO2) hybrids (GO@SiO2) were prepared via electrostatic self-assembly of the 3-aminopropyltriethoxysilane (APS)-modified SiO2and GO. The as-prepared GO@SiO2was introduced into polydimethylsiloxane (PDMS) elastomer to simultaneously increase the dielectric constant (k) and mechanical properties of PDMS. Then, the in situ thermal reduction of GO@SiO2/PDMS composites was conducted at 180°C for 2 h to increase the interfacial polarizability of GO@SiO2. As a result, the values ofkat 1000 Hz are largely improved from 3.2 for PDMS to 13.3 for the reduced GO@SiO2(RGO@SiO2)/PDMS elastomer. Meanwhile, the dielectric loss of the composites remains low (<0.2 at 1000 Hz). More importantly, the actuated strain at low electric field (5 kV/mm) obviously increases from 0.3% for pure PDMS to 2.59% for the composites with 60 phr of RGO@SiO2, an eightfold increase in the actuated strain. In addition, both the tensile strength and elastic modulus are obviously improved by adding 60 phr of RGO@SiO2, indicating a good reinforcing effect of RGO@SiO2on PDMS. Our goal is to develop a simple and effective way to improve the actuated performance and mechanical strength of the PDMS dielectric elastomer for its wider application. [ABSTRACT FROM AUTHOR]

Previous studies using molecular simulation indicated that carbon nanotubes (CNTs) can act as nanosprings to adjust the viscoelasticity of elastomer composites. In this study, we prepared elastomer composites with both high elasticity and conductivity for the first time using carbon nanotubes array (CNTA) as nanosprings. A special CNTA bundle prepared by electrostatic self-assembly was directly blended with the polymethylvinylsiloxane (PMVS) matrix. The results indicated that these CNTAs were well dissociated into many single CNTs with almost no change in length in the PMVS matrix with low viscosity during mechanical shearing, and exhibited a nanospring effect. The CNTA composites exhibited not only higher conductivity and electromagnetic shielding effectiveness but also higher elasticity than the commonly used conductive carbon black composites at the same filler content. This study indicated that high performance conductive elastomer composites can be obtained by using special CNTAs as nanosprings. [ABSTRACT FROM AUTHOR]

To meet the growing demand of environmental protection and resource saving, it is imperative to explore bio-based elastomers as next-generation dielectric elastomers (DEs). In this study, we used a bio-based gelatin/glycerin (GG) elastomer as the DE matrix because GG exhibits high dielectric constant ( ɛ r ). Cellulose nanocrystals (CNCs), extracted from natural cellulose fibers, were used to improve the mechanical strength of GG elastomer. The results showed that CNCs with a large number of hydroxyl groups disrupted the hydrogen bonds between gelatin molecules and formed new stronger hydrogen bonds with gelatin molecules. A good interfacial adhesion between CNCs and GG was formed, and thus a good dispersion of CNCs in GG matrix was obtained, leading to the improved mechanical strength of GG. More interestingly, the ɛ r of GG elastomer was obviously increased by adding 5 wt% of CNCs, ascribed to the increase in the polarizability of gelatin chains caused by the disruption of hydrogen bonds of gelatin. As a result, a 230% increase in the actuated strain at low electric field of GG was obtained by adding 5 wt% of CNCs. Since CNCs, gelatin and glycerol are all bio-based, this study offers a new method to prepare high performance DE for its application in biological and medical fields. [ABSTRACT FROM AUTHOR]

The effect of organophosphorus (OP) content on the flame retardancy and the flame retardancy mode of thermoplastic polyurethane (TPU) are reported. The limiting oxygen index (LOI) value for TPU increased from 23.1% to 24.6% and 33.5% by adding 20 wt% and 40 wt% of OP, respectively. UL-94 test showed V-2 rating for pure TPU, and V-1 rating and V-0 rating for the blends with 20 wt% and 40 wt% of OP, respectively. Potential reasons for the improved flame retardancy of TPU blends with increasing OP content were discussed based on the morphology of the char layers resulting from the combustion of TPU blends. The gas phase flame retardancy mode dominated in the composite with 20 wt% of OP by forming a loose, thin, and breakable porous char layer. The condensed phase charring mode dominated for the composite with 40 wt% of OP by forming a continuous, thicker, and denser char layer during combustion, which acted as a more effective barrier to reduce heat feedback to the polymer surface and thus resulted in the better flame retardancy. This study indicated for the first time that the content of flame retardant plays an important role in the flame retardancy mode of OP for TPU. [ABSTRACT FROM AUTHOR]

Abstract: The effects of aluminium phosphinate (AlPi) on the flame retardancy of three different polymers, namely, poly(2, 6-dimethyl-1, 4-phenylene oxide) (PPO), thermoplastic polyurethane (TPU) and polypropylene (PP), were investigated through cone calorimeter tests (CONE), vertical burning tests (UL-94), limiting oxygen index (LOI), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) observation. The results showed that the amounts of AlPi needed to reach V-0 UL-94 rating in the PPO, TPU and PP matrices were 0 wt%, 30 wt% and 50 wt%, respectively. Moreover, the addition of AlPi significantly increased the LOI values of PPO and PP, but had almost no effect on that of TPU. With the addition of AlPi, the peak of heat release rate (PHRR) of PPO and TPU decreased whereas that of PP increased. The total heat evolved (THE) of all polymers decreased by adding AlPi into the polymers. With the addition of AlPi, PPO composite formed a dense char layer and showed the best flame retardancy, TPU composite formed a thinner char layer and PP composite did not form char layer during combustion. Based on the thermal degradation behaviour and the char residue of these composites, the flame retardancy mechanisms of the three systems were discussed. For AlPi/PPO composites, the flame retardancy mechanism was condensed phase charring mechanism because of the formation of continuous char layer during combustion. For AlPi/TPU composites, AlPi acted mainly in gas phase, and a synergistic reaction of phosphorus and nitrogen compounds occurred and diethylphosphic acid providing flame inhibition was released during the burning process. As a result, the addition of AlPi successfully reduced the melt-dripping and enhanced flame retardancy of TPU matrix. For AlPi/PP composites, AlPi acted as a flame inhibitor in gas phase, decreasing the effective heat of combustion of the volatiles (THE/TML) and increasing the amount of CO. [Copyright &y& Elsevier]

Abstract: We demonstrate that comprehensive electrical network and mechanical property of polymer nanocomposite (PNC) are coherently related to the specific dispersion of nanoparticles, which can be controlled by grafting like and unlike polymer chains. For PNC where the graft chain has the same chemistry as matrix, if the graft chains are relatively short, the grafted nanoparticle containing 0.4 chains in unit area can result in a loose and continuous percolating cluster, at which the optimized electrical and mechanical utilities can be achieved. At low grafting density (0.08 chains in unit area), the optimized characteristics can be fulfilled through extending the graft chain length to the ratio of 0.4 (graft chain length to matrix chain length). If the graft chain has different chemical structure, the optimum performance of PNC emerges at the low grafting density, where the matrix–graft interaction is 1.5 times the matrix–matrix interaction, and the ratio is 0.5. [Copyright &y& Elsevier]

Abstract: In this work, zinc dimethacrylate (ZDMA) and 2-sulfur-benzimidazole (MB)/N-4(phenyl–phenyl)-maleimide (MC) were simultaneously used as synergistic antioxidants to improve the thermo-oxidative aging resistance of peroxide vulcanized ethylene-propylene-diene monomer (EPDM) for its application at high temperature. For comparison purpose, the control sample without antioxidants, the traditional antioxidant package, the combined antioxidant MB/MC, and pure ZDMA were also investigated. The results showed that the crosslinking density of EPDM was only slightly decreased before aging by using the combined antioxidant MB/MC/ZDMA, and the increase in crosslinking density was much less than other antioxidants at the same aging time, indicating the largely improved aging resistance of EPDM. As a result, the change in mechanical properties was the lowest for EPDM with the combined antioxidant MB/MC/ZDMA at high temperature. Meanwhile, the results from structure analysis showed that the degree of oxidation of EPDM was much lower than other systems after aging at 180 °C for 216 h by using the combined antioxidant MB/MC/ZDMA. In addition, the surfaces of EPDM samples with MB/MC/ZDMA as synergistic antioxidants or the combined antioxidant MB/MC were still smooth after aging at 180 °C for 216 h, whereas severe cracks occurred for other antioxidative systems. These results suggest the good thermo-oxidative aging resistance of the synergistic antioxidant MB/MC/ZDMA. Finally, the synergistic antioxidative mechanism of MB/MC/ZDMA was carefully discussed. [Copyright &y& Elsevier]

Ethylene-Propylene-Diene Monomer/Polypropylene thermoplastic vulcanizates (EPDM/PP TPVs) have been widely used as a kind of typical 'green' elastomer because of their excellent mechanical properties and recyclability. The industrial TPVs always contain various types of additives, which influence the viscosity ratio of EPDM and PP and the morphology of TPVs. This work studied the morphology evolution of EPDM/PP TPVs with various amounts of curing agents, fillers, and plasticizer during dynamic vulcanization in a twin-screw extruder, which provides much more complicated dynamic vulcanization process than haaker rheometer. The results show that the increased curing agents content leads to the faster morphology evolution of TPV because it enhances the cross-linking speed and the viscosity of EPDM. The increased fillers content leads to the later breakup of EPDM and the bigger size of the rubber aggregation because it enhanced the modulus of EPDM and weakens the interfacial interaction between EPDM and PP. In addition, the increase in the plasticizer content leads to the earlier breakup of EPDM and the larger size of the rubber phase in TPV. Our work firstly demonstrates the morphology evolution of industrial EPDM/PP TPV, and thus can provide a guidence for the industrial production of high-performance EPDM/PP TPVs. [ABSTRACT FROM AUTHOR]

Abstract: In this work, poly(l-lactide) (PLLA)/single-walled carbon nanotubes (SWNTs) fibers were first prepared at high drown ratio and low drown ratio, respectively. Then they subjected to tensile testing. It was found that the composite fibers obtained at low drown ratio showed no obvious enhancement of tensile strength and elongation at break, compared with the pure PLLA fibers obtained at the same low drown ratio. However, a significant property enhancement was observed for the composites fibers obtained at high drown ratio. Structure analysis of the as spun fibers before and after tensile testing suggests a possible stretching induced formation of brush-like hybrid structure in which the PLLA lamellae growing perpendicular to the SWNTs axis for fibers obtained at high drown ratio. This unique brush-like hybrid structure could largely enhance the interfacial interaction between PLLA and SWNTs, thus results in greatly improved tensile strength and elongation at break. [Copyright &y& Elsevier]

Abstract: Interfacial crystallization of polymer on the surface of filler not only offers crystallography interest but also has a potential to improve the interfacial interaction, which is a key for the preparation of high-performance polymer/filler composites. In this work, a new method is proposed to improve the interfacial crystallization between semi-crystalline polymer and glass fiber (GF) by introducing graphene oxide (GO) to the surface of amorphous GF. The coating of GO on GF surface is realized via electrostatic self-assembling of the oppositely charged GO and amino coupling agent modified GF (GF-NH2). After the thermal reduction of the coated GO (RGO), RGO coated GF (GF-RGO) is obtained. The interfacial crystallization of isotactic polypropylene (iPP) and poly(l-lactide) (PLLA) on the surface of raw GF, GF-NH2, and GF-RGO are investigated using Polarized light microscope (PLM). It is found that raw GF and GF-NH2 has almost no nucleation ability on the polymers crystallization. However, transcrystalline structure can be successfully induced at the polymers/GF-RGO interface, indicating a significantly improved nucleation ability of GF-RGO for polymer crystallization. This work could provide a new way to control interfacial crystallization, thus the interfacial adhesion of polymer/filler composites, and could also find a new application for GO as well. [Copyright &y& Elsevier]

Abstract: Polymer/filler composites have been widely used in various areas. One of the keys to achieve the high performance of these composites is good interfacial interaction between polymer matrix and filler. As a relatively new approach, the possibility to enhance polymer/filler interfacial interaction via crystallization of polymer on the surface of fillers, i.e., interfacial crystallization, is summarized and discussed in this paper. Interfacial crystallization has attracted tremendous interest in the past several decades, and some unique hybrid crystalline structures have been observed, including hybrid shish–kebab and hybrid shish–calabash structures in which the filler served as the shish and crystalline polymer as the kebab/calabash. Thus, the manipulation of the interfacial crystallization architecture offers a potential highly effective route to achieve strong polymer/filler interaction. This review is based on the latest development of interfacial crystallization in polymer/filler composites and will be organized as follows. The structural/morphological features of various interfacial crystallization fashions are described first. Subsequently, various influences on the final structure/morphology of hybrid crystallization and the nucleation and/or growth mechanisms of crystallization behaviors at polymer/filler interface are reviewed. Then recent studies on interfacial crystallization induced interfacial enhancement ascertained by different research methodologies are addressed, including a comparative analysis to highlight the positive role of interfacial crystallization on the resultant mechanical reinforcement. Finally, a conclusion, including future perspectives, is presented. [Copyright &y& Elsevier]

Abstract: Periodic patterning of carbon nanotubes (CNTs) with semi-crystalline polymers, especially the novel nanohybrid shish kebab (NHSK) superstructure, in which fibrous CNTs act as shish while polymer lamellae as kebab, is of interest both scientifically and technologically. So far the reported NHSK are mostly prepared using polymers with zigzag conformation in crystal and it seems difficult to obtain NHSK using polymer with helical conformation. In this work, we report the formation of NHSK structure by using single-walled carbon nanotube (SWNT) bundles. A promoted formation of NHSK was observed even using polymer with helical conformation, and the formation mechanism of NHSK was attributed to the unique “groove structure” formed by the stacked SWNTs in parallel arrays, which could facilitate the orientation of helical polymer chains along the SWNTs axis and the lateral formation of stable nucleus. The NHSK structure in helical polymer/SWNT bundles system could widen application of this unique superstructure, offering value in both application field and crystallography aspect as well. [Copyright &y& Elsevier]

Abstract: The mechanical responses including monotonic and cyclic tensile responses have been investigated on a microphase-separated poly (styrene-isoprene-styrene) triblock copolymer (SIS). The specimens were injection-molded by using different melt temperatures to acquire different microphase structures. As a result of temperature-dependent segregation driving force, the specimens with reduced microphase separation can be obtained by increasing processing melt temperature from 180 °C to 240 °C. On the basis of stress-strain behavior, Young''s modulus was found to increase with increasing PS domain continuity in the order of disorder state to disordered spheres to body-cubic-centered (BCC) spheres to oriented cylinders morphology. Meanwhile, cyclic hysteresis decreases with reduced microphase separation and with decreasing the applied predetermined maximum tensile strain. In addition, the Mooney–Rivlin phenomenological approach was used to evaluate and explore the relationship between the polymer topological networks and the rubber elasticity of thermoplastic elastomers. [Copyright &y& Elsevier]

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]

In this work, the conductive network, probability, and percolation threshold of nanorod/polymer composites under tensile strain are investigated using the molecular dynamics simulation. The internal interactions, including polymer-polymer, polymer-nanorod, and nanorod-nanorod interactions, are taken into account in simulations. In particular, the influence of polymer induced depletion force on the orientation of nanorods is analyzed. Under a constant strain, the conductive stability firstly declines and then rises with the increasing concentration of fillers, and the minimum corresponds to the percolation threshold. As strain increases, the result exhibits a strong anisotropy in the stability of conductive property. [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-soft, highly stretchable liquid metal (LM) conductor with high electrical conductivity, excellent electrical conductivity stability under various mechanical deformations and good mechanical properties was achieved. The stretchable conductor was prepared by infiltrating Gallium-indium-tin (GIT) LM into porous polyurethane sponge (PUS) with large porosity and small pores using a vacuumizing method followed by encapsulation with Polydimethylsiloxane (PDMS) to prevent the leakage of GIT-LM and to improve the mechanical properties. The as-made PDMS/PUS/LM composite shows a high tensile strength (1.11 MPa), high elongation at break (419%), excellent electrical conductivity (104 S/cm) and electrical conductivity stability under various mechanical deformations. The normalized resistance is of highly repeatability in stretch-release and bend-release cycle experiments. Image 1 • A highly stretchable liquid metal/polyurethane sponge conductor was prepared. • A dense LM network was formed due to the large porosity and small pores of PUS. • The conductor shows high conductivity stability under mechanical deformations. • A good interfacial interaction between PUS and LM was achieved. • The conductor shows relatively high tensile strength and high elongation at break. [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]

In this article, the effects of nanorod–polymer interaction, aspect ratio of nanorods, block stiffness, and external tensile force on the microstructure and electrical properties of diblock copolymer nanocomposites have been investigated using molecular dynamics simulation. It is shown that, under suitable interactions of block-block and nanorod-block, a continuous localization of anisotropic nanorods in a continuous block with a slight uniaxial orientation can dramatically reduce the percolation threshold. Such effect is reinforced in the systems with high aspect ratio nanorods, but can be suppressed as block stiffness increases. Meanwhile, the external tensile strain breaks the continuity of the three-dimensional network but induces strong orientation along with the stretching direction, leading to a decrease of homogeneous probability and an increase of directional probability. [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]

In this study, the early stage of interfacial crystallisation behaviour of low molecular weight polyethylene (PE) and isotactic polypropylene (iPP) oligomer on the surface of carbon nanotubes (CNTs) with different diameters, chiralities and topography structures was studied using MD simulations. We started to simulate the effect of CNTs chirality and diameter on PE molecular chain orientation, and then the effect of CNTs topography structure on PE and iPP molecular chain orientation was investigated. Finally, some experiments were carried out to prove the simulated results. Our study shows that for CNTs with a diameter comparable with the radius of gyration (Rg) of a polymer chain, an easy orientation of PE chains along CNTs axis is observed for all the systems of the CNTs with different chiralities due to a geometric confinement effect. For CNTs with a much larger diameter, multiple orientation of PE chains is induced on its surface due to the lattice matching between graphite lattice and PE molecular chains. In this case, the chirality of CNTs dominates the orientation of graphite lattice, which determines the orientation of PE chains arrangement on CNTs surface. More importantly, it was found that the groove structure formed by CNT bundles is very useful for the stabilisation of polymer chain, and thus facilitates the orientation of molecular chain along the long axis of CNTs. As a result, a novel nanohybrid shish–kebab (NHSK) structure with CNTs acting as central shish while polymer lamellae as kebab can be successfully obtained for both PE with zigzag conformation and iPP with helical conformation. This simulation result was well supported by the experimental observation. Our study could provide not only a deep understanding of the origin of the polymer chain orientation on CNTs surface but also the guidance for the preparation of polymer/CNTs nanocomposites with novel NHSK structure. [ABSTRACT FROM PUBLISHER]

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]

The interfacial interactions between ultra‐high molecular weight polyethylene (UHMWPE) fiber and polymer determine the overall performance and service life of the fiber reinforced composite materials. In this article, polyaniline (PANI) layer is uniformly deposited on the surface of the UHMWPE fiber after plasma treatment to enhance the interfacial adhesion between UHMWPE fiber and rubber. At the same time, the PANI layer can also form a conductive path at the interface to monitor the damage of the composites in real time. Compared with the untreated UHMWPE fiber, the H pull‐out force of the PANI‐deposited UHMWPE fiber with rubber is increased by 67.9%, which is due to good mechanical interlocking and chemical bond between the fiber and the matrix. Moreover, the electrical resistance change during the fiber pull‐out process has a good correlation with the pull‐out force curve, which provides a new idea for in‐situ monitoring of the damage of composites. [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]

Oriented thermoplastic polyurethane (TPU) fiber and fiber network were first prepared by electrospinning. The as-prepared TPU fiber or fiber network was then pre-fixed in poly(lactic acid) (PLA)/TPU composite to improve the toughness of PLA. For comparison purpose, TPU/PLA composites with sea-island morphology were also prepared by traditional solution blending and mechanical blending. The results show that the toughness of PLA is greatly increased by the special pre-fixed oriented TPU fibers even at a low content, and the toughness is further increased by the TPU fiber network. Our results indicate for the first time that the toughening effect of special TPU fibers or fiber network is much better than that of traditional TPU with sea-island morphology. This study provides guidance to largely improve the toughness of PLA by designing the special phase morphology of TPU. [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]