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HYPOTHESIS: MXenes (two-dimensional early transition metal carbides and carbonitrides) possess both excellent conductivity and surface hydrophilicity, enabling more diverse potential applications. However, in flexible strain sensors, the flexible substrates are usually composed of hydrophobic elastomers such as thermoplastic polyurethane (TPU). To enhance the interactions between MXenes and hydrophobic. substrates, it is wiser to change the composition of the flexible substrate than to modify the surface of MXenes, so as to improve the interactions between the flexible substrate and MXenes without losing the excellent conductivity of MXene. EXPERIMENTS: We introduce polyacrylonitrile (PAN) into TPU, and then fabricate a flexible TPU/PAN mat through electrospinning. A highly conductive and stretchable Ti3C2 MXene/TPU/PAN mat was then prepared by a simple dip-coating process. The interaction mechanism between Ti3C2 MXene nanosheets and TPU/PAN mat was investigated by XPS and FT-IR. Finally, we build the MXene/TPU/PAN mat into a flexible strain sensor with excellent properties. FINDINGS: By introducing PAN into flexible substrate, the interaction between Ti3C2 MXene and the flexible substrate was effectively improved without compromising Ti3C2 MXene's excellent conductivity. The MXene/TPU/PAN strain sensor possesses a wide sensing range (0-80%), a fast response (<140.6 ms), a low limit of detection (<0.1%), splendid coating adhesion and excellent durability (>1750 cycles). All of these properties are demanded in wearable electronics.
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Antioxidants are normally utilized to extend the service life of polymers due to the strong reducibility of the phenolic hydroxyl group of the hindered phenol structure. Inspired by this characteristic, we have introduced green tea polyphenol (TP) supported on a silica surface containing considerable phenolic hydroxyl groups to obtain a novel biomass anti-aging filler (BAF, denoted as silica-s-TP) to reinforce and improve the anti-aging property of rubber composites. The applying of silica-s-TP to enhance the thermal-oxidative stability and ultraviolet light (UV) aging resistance of styrene-butadiene rubber (SBR) was evaluated. The hybrid biomass anti-aging filler could not only uniformly disperse in the rubber matrix, giving rise to the excellent mechanical properties, but also enhance the properties of thermal-oxidative stability and UV aging resistance with the increasing silica-s-TP content of SBR distinctly. This study provides a mild and environmentally friendly strategy to prepare the functional biomass filler, which could be applied as not only a reinforcement filler but also an anti-aging additive in "green rubber".
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To avoid the negative effects of chemical herbicides and prepare herbicide with long-term efficacy, the active ingredients of eupatorium adenophorum spreng (AIEAS, negatively charged) were used as a botanical herbicide, and based on electrostatic attraction, the self-assembled hydroxyl isopropyl chitosan (HPCTS, positively charged) and carboxymethyl chitosan (CMC, with good water solubility) were successfully employed as degradable and water-soluble carrier for AIEAS to realize its controlled release. The release of AIEAS from the chitosan carrier in water could be divided into two stages. In the first stage, a fast release of AIEAS was detected and the total amount of the released AIEAS reached 41.5 %, while the release rate effectively slowed down in the second stage, indicating that good balance between fast control of weeds and long-term efficacy was achieved through this controlled delivery system. The release kinetics of AIEAS during the whole release process showed good fit to the Ritger-Peppas model with Fickian diffusion as the dominant release mechanism. Moreover, it found that the released AIEAS from chitosan carrier showed fine herbicidal effect on barnyard grass.
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Quitosana/análogos & derivados , Preparações de Ação Retardada , Eupatorium/química , Herbicidas/química , Herbicidas/metabolismo , Eletricidade Estática , Quitosana/químicaRESUMO
In this study, a nitrogen-phosphorus intumescent flame-retardant 3-(N-diphenyl phosphate) amino propyl triethoxy silane (DPES), the ionic liquid (IL) of 1-butyl-3-methyl-imidazole phosphate, and a phosphorous-containing ionic liquid-modified expandable graphite (IL-EG), were synthesized, and their molecular structures were characterized. The flame-retardant rigid polyurethane foams (RPUFs) were compounded with synergistic flame-retardant IL-EG/DPES to study the effects of the combination IL-EG and DPES on the pore structure, mechanical properties, thermal decomposition behavior and thermal decomposition mechanism of RPUF. The results showed that IL-EG/DPES had good thermal stability, and an excellent expansibility and char yield. The flame-retardant RPUF, modified with IL-EG and DPES at the ratio of 1:1, had a relatively uniform pore size, the highest compressive strength, and an excellent flame-retardant performance due to the form interwoven hydrogen bonds between IL-EG and DPES, as well as the new synergistic flame-retardant coating on the RPUF surface to restrict the transfer of gas or heat into the PU matrix.
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Functionalized super-repellent polymeric materials play important roles in academic and industrial fields. In this work, a versatile continuous super-repellent polymeric film (CSPF) integrating reversible wettability with design manipulation was synthesized. On the basis of the optimal combination of a polyurethane acrylate (PUA)/precipitated silica particle (PSP)/ethanol suspension, covalently cross-linking networks and hierarchical topography were constructed in a polymer skeleton, endowing the CSPF with solid mechanical strength (B hardness). Taking advantage of the continuous superhydrophobicity established by the silica particle across the film bulk, the CSPF was found to be repetitively exposed via the shedding of the surface layer to achieve reversible wettability and repair its nonwetting performance (>50 cycles). Accordingly, the continuous superhydrophobicity and regenerative feature enabled the CSPF to realize design manipulation successively and underwater display rapidly, which may broaden the application fields of super-repellent materials in marine transportation and undersea exploration. Furthermore, the CSPF also displayed enticing damage-resistance (>200 cycles), environmental stability (>5 days), and self-cleaning behavior. Our findings convincingly propose a feasible approach to fabricate versatile super-repellent polymeric materials as candidates for advanced and smart materials.
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Ti3C2 MXene with a layered 2D structure was applied as a novel functional filler in rubber for the first time. A facile and green method was proposed to fabricate rubber/Ti3C2 nanocomposites via a freeze-drying & mechanical mixing process. It was found that Ti3C2 with â¼1 nm thickness fabricated by etching Al from Ti3AlC2 phases can be dispersed in styrene-butadiene rubber (SBR) evenly in a single-layered state. Mechanical strength and electrical and thermal conductivities of the rubber nanocomposites were remarkably enhanced by the incorporation of Ti3C2, showing dramatic improvement compared with reduced graphene oxide (rGO) reinforced rubber composites. For example, the thermal conductivity of SBR nanocomposites with 3 wt% rGO was 0.265 W m-1 k-1, while that of SBR nanocomposites with only 1.96 wt% Ti3C2 reached 0.477 W m-1 k-1. Meanwhile, the resistance of rubber/Ti3C2 nanocomposites was stable under complex deformation and their sensitivity was well recovered during stretching/shrinking cycles under large strain. Moreover, it was discovered that incorporating Ti3C2 in rubber nanocomposites dramatically improved the wet skid resistance and thermal stability without increasing the rolling resistance. Ti3C2 MXene with a distinctive structure and properties as well as uniform dispersion will have more potential for the preparation of high-performance rubber nanocomposites, especially for green tires and flexible sensors.
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It is still a challenge to achieve simultaneous improvements in aging resistance, mechanical strength, thermal conductivity and dielectric constant of rubber composites via incorporation of graphene obtained by conventional methods. Herein, an effective and green method was proposed to simultaneously reduce and functionalize graphene oxide (GO) with 2-mercaptobenzimidazole (antioxidant MB) via a one-pot method. GO was successfully reduced by MB which was also chemically grafted on the reduced GO (G-MB). G-MB sheets were uniformly dispersed in rubber with strong interfacial interaction, and graphene-graphene conductive paths were formed through intermolecular H-bonding between the grafted antioxidant molecules. Consequently, rubber composites with G-MB showed higher thermal conductivity, mechanical strength and dielectric constant than rubber composites with hydrazine hydrate reduced GO (rGO). Moreover, the thermo-oxidative aging resistance of rubber composites with G-MB was also superior to that of rubber composites with rGO because of the elimination of blooming effect of the grafted MB molecules. Thus, this work may open a new way for the eco-friendly functionalization and reduction of GO and may boost the development of high-performance, functional graphene-elastomer composites.
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Vulcanization and reinforcement are critical factors in governing the ultimate practical applications of elastomer composites. Here we achieved a simultaneous improvement of curing and mechanical properties of elastomer composites by the incorporation of a functionalized halloysite nanotubes-silica hybrid (HS-s-M). Typically, HS-s-M was synthesized by 2-mercapto benzothiazole (M) immobilized on the surface of halloysite nanotubes-silica hybrid (HS). It was found that the HS-s-M uniformly dispersed in the styrene-butadiene rubber (SBR) matrix, offering more opportunity for M molecules to communicate with rubber. In addition, the physical loss of accelerator M from migration and volatilization was efficiently suspended. Therefore, SBR/HS-s-M composites showed a lower curing activation energy and a higher crosslinking density than SBR/HS composites. Moreover, a stronger interfacial interaction between HS-s-M and SBR was formed by the cross-linking reaction, giving a positive contribution to the eventual mechanical properties. The possible vulcanization and reinforcement mechanisms of SBR/HS-s-M composites were also analyzed in detail.
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In this paper, rigid polyurethane foams that were filled with expandable graphite (RPUF/EG) composites were prepared by the liquid blending method, and then the structure and flame retardancy performance of materials were investigated through optical microscope, scanning electron microscope, limit oxygen index, cone calorimeter, thermogravimetric analysis coupled to fourier transform infrared spectrum, and X-ray photoelectron spectroscopy. The results showed that a large number of EG could be good to the exhibition of flame retardancy of RPUF, where the optimal material was found at loading 15 phr EG that showed an increased limit oxygen index value and a decreased calorific or fuming value. TGA coupled FTIR and XPS revealed that EG could disassembled before RPUF under heating treatment, and it could form a pyknotic and enahnced residual carbon layer on RPUF surface after the fire, which restricted the transfer of gas, like oxygen or heat into PU matrix, finally resulting in the promotion of flame retardancy of RPUF.
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Improving the interfacial interaction between rubber and silica nanoparticles, and simultaneously reducing free sulfur and preventing migration and volatilization of a rubber vulcanizing agent, commercial sulfur compound aliphatic ether polysulfide (VA-7) was chemically attached to the silica surface to obtain a functionalized nanoparticle (silica-s-VA7). Functional nanoparticles can not only effectively crosslink rubber without sulfur as a novel vulcanizator, but are also evenly dispersed in the rubber matrix and improve the dispersion of the remaining pristine silica as an interfacial compatibilizer. In addition, the thicker immobilized polymer layer and prominent crosslinking density of SBR nanocomposites simultaneously demonstrate that the novel vulcanizing agent silica-s-VA7 gives rise to significant improvement on the rubberâ»filler interfacial adhesion on account of the covalent linkages of organic and inorganic interfaces between elastomer and nanofillers. We envisage that this strategy may provide a new avenue to implement high-efficiency design for a multifunctional rubber-vulcanizing agent through an organic and inorganic hybridization mechanism.
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Commercial herbicide atrazine (AT) was first loaded into the lumen of halloysite nanotubes (HNTs) in the amount of 9 wt %, and then the AT-loaded HNTs (HNTs-AT) were further incorporated into poly(vinyl alcohol)/starch composites (PVA/ST, with the weight ratio of 80/20) to construct a dual drug delivery system. AT loaded in nanotubes displayed much slower release from PVA/ST film in water than free AT; for example, the total release amount of AT from PVA/ST film with loaded AT was only 61% after 96 h, while this value reached 97% in PVA/ST film with free AT. The release behavior of AT from PVA/ST film with HNTs-AT was first dominated by the mechanism of matrix erosion and then by the mechanism of Fickian diffusion. In addition, combining HNTs and PVA/ST blends together in the controlled release of herbicide also reduced its leaching through the soil layer, which would be useful for diminishing the environmental pollution caused by pesticide.
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Preparações de Ação Retardada/química , Portadores de Fármacos/química , Sistemas de Liberação de Medicamentos/métodos , Herbicidas/química , Nanoestruturas/química , Álcool de Polivinil/química , Amido/química , Sistemas de Liberação de Medicamentos/instrumentação , CinéticaRESUMO
Novel hybrid elastomer/regenerated chitin (R-chitin) composites were developed, for the first time, by introducing chitin solution (dissolved in alkaline/urea aqueous solution at low temperature) into rubber latex, and then cocoagulating using ethanol as the cocoagulant. During the rapid coprecipitation process, the chitin solution showed rapid coagulant-induced gelation and a porous chitin phase was generated, and the rubber latex particles were synchronously demulsificated to form the rubbery phase. The two phases interlaced and interpenetrated simultaneously to form an interpenetrating polymer network (IPN) structure, which was evidenced by SEM observation. The ensuing compound was also characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), and swelling experiments. The unique porous structure of R-chitin could result in strong physical entanglements and interlocks between filler and matrix, thus a highly efficient load transfer between the filler and the matrix was achieved. Accordingly, R-chitin endows the elastomer with a remarkable reinforcement. We envisage that this work may contribute new insights on novel design of chitin-based elastomer hybrids with IPN structure.
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The research advances in rubber/halloysite nanotubes (rubber/HNTs) nanocomposites are reviewed. HNTs are environmentally-friendly natural nanomaterials, which could be used to prepare the rubber-based nanocomposites with high performance and low cost. Unmodified HNTs could be adopted to prepare the rubber/HNTs composites with improved mechanical properties, however, the rubber/HNTs nanocomposites with fine morphology and excellent properties were chiefly prepared with various modifiers by in situ mixing method. A series of rubber/HNTs nanocomposites containing several rubbers (SBR, NR, xSBR, NBR, PU) and different modifiers (ENR, RH, Si69, SA, MAA, ILs) have been investigated. The results showed that all the rubber/HNTs nanocomposites achieved strong interfacial interaction via interfacial covalent bonds, hydrogen bonds or multiple interactions, realized significantly improved dispersion of HNTs at nanoscale and exhibited excellent mechanical performances and other properties.
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Silicatos de Alumínio/química , Cristalização/métodos , Nanotubos/química , Nanotubos/ultraestrutura , Borracha/química , Argila , Módulo de Elasticidade , Dureza , Substâncias Macromoleculares/química , Teste de Materiais , Conformação Molecular , Tamanho da Partícula , Propriedades de SuperfícieRESUMO
In this work, a novel silicone rubber/nano-copper nanocomposite for use in intrauterine devices (IUDs) was developed. Moreover, the release rate of Cu2+ ions and the water absorption of the prepared nanocomposite were investigated in detail. The results indicate that the release rate of Cu2+ ions and water absorption capability of the silicone rubber/nanocopper nanocomposite increase as the nano-copper content increases. SEM analysis suggested there is a uniform dispersion of nano-copper in the silicone matrix. Further, systematic analysis indicated that the release rate of Cu2+ ions in the prepared nanocomposite-based IUD can be stabilized for months, which is not possible in the case of traditional IUDs.
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Cobre/química , Dispositivos Intrauterinos , Nanocompostos/química , Elastômeros de Silicone/química , Absorção , Materiais Biocompatíveis/química , Cobre/administração & dosagem , Desenho de Equipamento , Feminino , Humanos , Íons , Teste de Materiais , Nanopartículas Metálicas/química , Microscopia Eletrônica de Varredura , Fatores de Tempo , Útero/patologia , Água/químicaRESUMO
In this work, a novel tri-methacrylate oligomer, GPTEMA, with three long-branched chain structures was synthesized through the reaction of glycerol propoxylate triglycidyl ether (GPTE) and methacrylic acid. The structure of GPTEMA was confirmed by FT-IR, (1)H-NMR, gel-permeation chromatography (GPC) and element analysis. The GPTEMA was used to partially or completely replace TEGDMA as reactive diluent and applied in a root canal sealant system containing Bis-GMA. The effects of GPTEMA on the polymerization behavior of Bis-GMA/TEGDMA/GPTEMA co-polymer and properties of its polymerizing product were investigated. Polymerization shrinkage, double bond conversion, glass transition temperature, flexural strength, flexural modulus, water sorption and diffusion coefficient of the Bis-GMA/TEGDMA/GPTEMA co-polymer were measured. The results illustrated that the Bis-GMA/TEGDMA/GPTEMA co-polymer attained lower polymerization shrinkage and higher double bond conversion. However, its T g, flexural strength and flexural modulus decreased with increasing content of GPTEMA, water sorption and diffusion coefficient increased with increasing content of GPTEMA.
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Materiais Restauradores do Canal Radicular , Bis-Fenol A-Glicidil Metacrilato/química , Cromatografia em Gel , Difusão , Vidro/química , Teste de Materiais , Metacrilatos/síntese química , Metacrilatos/química , Estrutura Molecular , Polietilenoglicóis/química , Polimerização , Ácidos Polimetacrílicos/química , Espectroscopia de Prótons por Ressonância Magnética , Materiais Restauradores do Canal Radicular/síntese química , Materiais Restauradores do Canal Radicular/química , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura de Transição , Viscosidade , Água/químicaRESUMO
High mechanical performance nitrile-butadiene rubber (NBR) with light color was fabricated by the method of in situ formation of zinc disorbate (ZDS) or magnesium disorbate (MDS). The in situ formed ZDS and its polymerization via internal mixing was confirmed by X-ray diffaraction. The mechanical properties, ageing resistance, morphology and the dynamic mechanical analysis were fully studied. It was found that with increasing loading of metallic disorbate both the curing rate and the ionic crosslink density was largely increased. The modulus, tensile strength and tear strength were largely increased. With a comparison between internal mixing and opening mixing, the mechanical performance for the former one was obviously better than the latter one. The high performance was ascribed to the finely dispersion nano domains with irregular shape and obscure interfacial structures. Except for the NBR vulcanizate with a high loading of MDS, the others' ageing resistance with incorporation of these two metallic disorbate was found to be good. Dynamic mechanical analysis (DMA) showed that, with increasing loading of metallic disorbate, the highly increased storage modulus above -20 degrees C, the up-shifted glass transition temperature (Tg) and the reduced mechanical loss were ascribed to strengthened interfacial interactions.
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The reinforcement effects of halloysite nanotubes on styrene-butadiene rubber and the modification effect of epoxidized natural rubber on styrene-butadiene rubber/halloysite nanotubes composites were studied. The structure, morphology and properties of styrene-butadiene rubber/halloysite nanotubes composites before and after the incorporation of epoxidized natural rubber were investigated. The results indicated that epoxidized natural rubber can promote the dispersion and orientation of halloysite nanotubes in styrene-butadiene rubber matrix at nanoscale and strengthen interfacial combination between halloysite nanotubes and styrene-butadiene rubber by the formation of covalent bonds and hydrogen bonds between epoxidized natural rubber and halloysite nanotubes. Consequently epoxidized natural rubber can improve the mechanical properties of the vulcanizates of styrene-butadiene rubber/halloysite nanotubes composites. Besides epoxidized natural rubber can decrease the rolling resistance of the vulcanizates and increase the wet grip property of the vulcanizates.
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In this contribution, halloysite nanotubes (HNTs), a kind of natural hydrophilic nanoclay, are incorporated into polypropylene (PP) for tailoring the surface microstructures of the composites prepared by solution casting. HNTs act as heterogeneous nuclei for PP, which leads to the change of phase separation process during drying of the composites and consequently the microstructures of composite surfaces. Micro-papilla like hybrid spherulites with nanostructures are formed on the PP/HNTs composite surfaces. The rough surfaces demonstrate superhydrophobicity with a maximum water contact angle as nearly 170 degrees and sliding angle of about 2 degrees. The spherulites size, surface roughness, and wetting property of PP can be tuned by HNTs. HNTs can significantly improve the thermal degradation behavior of the composites which is attributed to the well-dispersed HNTs and the improved interfacial interactions by the nucleation effect. The present work provides an alternative routine for preparing polymer superhydrophobic surfaces via tailoring the surface microstructures by adding nanoparticles in a solution process.
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Methacrylate resin-based sealers have attracted wide attention because of their easy handling, superior aesthetic qualities, good mechanical properties and excellent adhesive ability with dentin. 2,2-Bis[4-(2'-hydroxy-3'-methacryloyloxypropoxy)-phenyl]-propane (Bis-GMA) is the main component of the newly developed commercial root canal sealer 'Epiphany', which is one of the methacrylate resin-based sealers. In order to further reduce the polymerization volume shrinkage of Bis-GMA, 4,4'-(alpha-methylbenzylidene)-bis(2'-hydroxy-3'-methacryloyloxy-propoxy)benzene (4,4'-AMBHMB) with higher molecular weight and larger molecular volume was synthesized to replace Bis-GMA as one of the components of the root canal sealer used in this study. The structure of monomer 4,4'-AMBHMB was confirmed by FT-IR, (1)H-NMR, mass spectrum and elemental analysis. The photopolymerization behavior of mixture of 4,4'-AMBHMB and triethylene glycol dimethacrylate (TEGDMA) was investigated by FT-IR. Degree of double bond conversion, volume shrinkage, water sorption and solubility, diffusion coefficient value, flexure strength and glass transition temperature of 4,4'-AMBHMB/TEGDMA system with a mass ratio of 50:50 were measured. A 50:50 Bis-GMA/TEGDMA formulation was used as reference. The results illustrated that 4,4'-AMBHMB/TEGDMA system had the same double bond conversion and water sorption with Bis-GMA/TEGDMA system. Polymerization shrinkage, water solubility and diffusion coefficient of 4,4'-AMBHMB/TEGDMA system were lower than that of the Bis-GMA/TEGDMA system, whereas the flexural strength and glass-transition temperature of 4,4'-AMBHMB/TEGDMA system were higher than that of the Bis-GMA/TEGDMA system.
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Compostos de Benzilideno/química , Resinas Compostas/química , Processos Fotoquímicos , Polímeros/química , Polímeros/síntese química , Materiais Restauradores do Canal Radicular/química , Materiais Restauradores do Canal Radicular/síntese química , Peso Molecular , Polietilenoglicóis/química , Ácidos Polimetacrílicos/química , Resinas Sintéticas/síntese química , Resinas Sintéticas/química , Análise EspectralRESUMO
A novel Cu-IUDs material, PU/PEG/Cu nanocomposite, was prepared by melt blending method with thermoplastic polyurethane (PU) as the matrix, with polyethylene glycol (PEG) as a hydrophilic modifier, and with nanometer particles of copper as active matter instead of copper wire or copper tube. The structure, morphology, mechanical properties, thermal stability and water absorption were investigated by using FT-IR, XRD, SEM and so on. The results indicated that the nanometer particles of copper were uniformly dispersed in the matrix in PU/PEG/ Cu nanocomposites. It can be seen that the water absorption ability of this nanocomposite was obviously improved while mechanical properties and thermal stability were at high levels. These results provided a good basis for the studies on the cupric ions release of the nanocomposites in future.