Constructing conductive titanium carbide nanosheet (MXene) network on polyurethane/polyacrylonitrile fibre framework for flexible strain sensor.

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.

Novel Hybrid Biomass Anti-Aging Filler for Styrene-Butadiene Rubber Composites with Antioxidative and Reinforcing Properties.

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".

The Synergistic Effect of Ionic Liquid-Modified Expandable Graphite and Intumescent Flame-Retardant on Flame-Retardant Rigid Polyurethane Foams.

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.

A-kinase interacting protein 1, a potential biomarker associated with advanced tumor features and CXCL1/2 in prostate cancer.

OBJECTIVE: This study aimed to investigate the correlation of A-kinase interacting protein 1 (AKIP1) with chemokine (C-X-C motif) ligand 1 (CXCL1) and CXCL2, as well as their associations with clinical characteristics and prognosis in prostate cancer patients. METHODS: A total of 248 eligible prostate cancer patients who underwent surgery were consecutively recruited, and tumor tissues were collected during the surgery. AKIP1, CXCL1, and CXCL2 expression in tumor tissues were assessed by immunohistochemistry. Disease-free survival and overall survival were recorded, and the median follow-up time was 27 months. RESULTS: The proportion of patients with AKIP1, CXCL1, and CXCL2 high expression was 56.5%, 63.7%, and 56.9%, respectively. Additionally, AKIP1 expression positively correlated with CXCL1 expression (P<0.001) and CXCL2 expression (P<0.001), and CXCL1 expression was positively associated with CXCL2 expression (P<0.001). Furthermore, AKIP1 expression positively correlated with pathological T stage (P<0.001) and pathological N stage (P=0.003). CXCL1 expression was positively associated with pathological T stage (P<0.001) and pathological N stage (P<0.001) as well. However, the CXCL2 expression only positively correlated with pathological T stage (P=0.002). Also, AKIP1 high expression correlated with worse disease-free survival (P=0.049) and OS (P=0.013), and CXCL1 high expression was associated with unfavorable disease-free survival (P=0.023) but not overall survival (P=0.052). CXCL2 expression was not correlated with disease-free survival (P=0.083) or overall survival (P=0.065). Multivariate Cox's regression disclosed that AKIP1 high expression independently predicted worse overall survival (P=0.009). CONCLUSION: AKIP1 positively associates with CXCL1/2 and is a potential biomarker for disease monitoring as well as prognosis in prostate cancer.

A Robust and Versatile Continuous Super-Repellent Polymeric Film for Easy Repair and Underwater Display.

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.

Immobilization of rubber additive on graphene for high-performance rubber composites.

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.

Functionalized Halloysite Nanotubes⁻Silica Hybrid for Enhanced Curing and Mechanical Properties of Elastomers.

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.

Structure and Flame-Retardant Actions of Rigid Polyurethane Foams with Expandable Graphite.

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.

A Comprehensive Study on The Accelerated Weathering Properties of Polypropylene-Wood Composites with Non-Metallic Materials of Waste-Printed Circuit Board Powders.

In this study, non-metallic materials of waste-printed circuit board powders (WPCBP) were successfully used as reinforcing filler to produce polypropylene (PP)⁻wood composites, and their effect on the weathering properties of PP composites were fully evaluated via oxidation induction time (OIT), attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry, vicat softening point (VST), scanning electron microscopy, and mechanical properties analysis. The OIT analysis confirmed that the anti-thermal oxidative aging properties of PP⁻wood composites were decreased with the loading of WPCBP. Apart from that, the PP composite, reinforced with 30 wt.% of WPCBP, exhibited the highest value of active energy, which suggests that it is more sensitive to temperature and oxygen when compared with other PP composites. The mechanical properties analysis revealed that neat PP exhibited the poorest weathering properties after being subjected to UV exposure, and its retention rate of tensile strength and notched impact strength were only 70.6% and 59.6%, respectively, while WPCBP and wood flour (WF) could efficiently improve the retention rates of the mechanical properties of the PP composites when subjected to UV exposure. The visual appearance of the PP composites after being subjected to UV exposure showed more and smaller cracks with the loading of WPCBP and WF. The ATR-FTIR results revealed that the carbonyl index increased for all the weathered samples, and the more WPCBP was added into the PP composites led to a higher carbonyl index value, which might be due to the multivalent transition metals in WPCBP, which accelerate the photo-oxidation of the PP composites. The VST results show that both WPCBP and WF can effectively enhance the heat deformation resistance of the PP composites that have been subjected to UV exposure.

Inorganic and Organic Hybrid Nanoparticles as Multifunctional Crosslinkers for Rubber Vulcanization with High-Filler Rubber Interaction.

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 rubber⁻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.

Halloysite Tubes as Nanocontainers for Herbicide and Its Controlled Release in Biodegradable Poly(vinyl alcohol)/Starch Film.

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.

Elastomer Reinforced with Regenerated Chitin from Alkaline/Urea Aqueous System.

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.

Preparation and characterization of silicone rubber/nano-copper nanocomposites for use in intrauterine devices.

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.

Evaluation of new tri-methacrylates as a reactive diluent in root canal sealant.

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.

Styrene-butadiene rubber/halloysite nanotubes composites modified by epoxidized natural rubber.

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.

Synthesis, characterization and photopolymerization of a new dimethacrylate monomer based on (alpha-methyl-benzylidene)bisphenol used as root canal sealer.

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.

Synthesis and characterization of a new dimethacrylate monomer based on 5,50-bis(4-hydroxylphenyl)-hexahydro-4,7-methanoindan for root canal sealer application.

In this study, a new dimethacrylate monomer 5,5'-bis[4-(2'-hydroxy-3'-methacryloyloxy-propoxy)-phenyl]-hexahydro-4,7-methan-oindan (5,5'-BHMPHM) with molecular weight of 640 and large molecular volume was designed and synthesized. The structure of monomer 5,5'-BHMPHM was confirmed by FT-IR, 1H-NMR and elemental analysis. Degree of double bond conversion, volume shrinkage, contact angle, water sorption and solubility, diffusion coefficient value, flexure strength and modulus of 5,5'-BHMPHM/tri(ethylene glycol) dimethacrylate (TEGDMA) based resin were measured. 2,2-bis[4-(2'-hydroxy-3'-methacryloyloxy-propoxy)-phenyl]-propane(Bis-GMA)/TEGDMA based resin was used as reference. The result illustrated that the double bond conversion, polymerization shrinkage, and diffusion coefficient value of 5,5'-BHMPHM/TEGDMA based resin were significantly lower than that of Bis-GMA/TEGDMA based resin (P<0.05). Water sorption, solubility, flexure strength and modulus of 5,5'-BHMPHM/TEGDMA based resin were higher than that of Bis-GMA/TEGDMA based resin (P<0.05). There was no statistical difference between 5,5'-BHMPHM/TEGDMA based resin and Bis-GMA/TEGDMA based resin in contact angle (P>0.05).

Synthesis and characterization of a new trimethacrylate monomer with low polymerization shrinkage and its application in dental restoration materials.

In this study, a new trimethacrylate monomer alpha,alpha,alpha'-tri[4-(2'-hydroxy-3'-methacryloyloxy-propoxy)phenyl]-1-ethyl-4-isopropylbenzene (alpha,alpha,alpha'-THMPEIB) with a molecular weight of 850 and a large molecular volume was designed and synthesized. The structure of monomer alpha,alpha,alpha'-THMPEIB was confirmed by FT-IR, (1)H NMR, and elemental analysis. Degree of double-bond conversion, volume shrinkage, water sorption and solubility, diffusion coefficient value, and flexure strength of alpha,alpha,alpha'-THMPEIB/tri(ethylene glycol) dimethacrylate- (TEGDMA) based resin were measured. 2,2-Bis[4-(2'-hydroxy-3'-methacryloyloxy-propoxy)-phenyl]-propane (bis-GMA)/TEGDMA monomer mixture was used as reference. The result showed that the alpha,alpha,alpha'-THMPEIB/TEGDMA-based resin had the lower double-bond conversion, polymerization shrinkage, and water solubility than bis-GMA/TEGDMA-based resin. Water sorption and diffusion coefficient value of alpha,alpha,alpha'-THMPEIB/TEGDMA-based resin were nearly the same as those of bis-GMA/TEGDMA-based resin. Flexural strength of alpha,alpha,alpha'-THMPEIB/TEGDMA-based resin was higher than that of bis-GMA/ TEGDMA-based resin.