Publications

Effects of substitution for carbon black with graphene oxide or graphene on the morphology and performance of natural rubber/carbon black composites

In this study, nanosheets including graphene oxide (GO) and reduced graphene oxide (rGO), were incorporated into natural rubber (NR), to study the effects of substituting GO or rGO for carbon black (CB) on the structure and performance of NR/CB composites. The morphological observations revealed the dispersion of CB was improved by partially substituting nanosheets for CB. The improvements in static and dynamic mechanical properties were achieved at small substitution content of GO or rGO nanosheets. With substitution of rGO nanosheets, significant improvement in flex cracking resistance was achieved. NR/CB/rGO (NRG) composites has a much lower heat build‐up value compared with NR/CB/GO (NG) composites at a high load of nanosheets. However, both GO and rGO tended to aggregate at a high concentration, which led to the poor efficiency on enhancing the dynamic properties, or even deteriorate the performance of rubber composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132 , 41832.

Wrapping of polyrhodanine onto tubular clay and its prominent effects on the reinforcement of the clay for rubber

Polyrhodanine (PRd) was wrapped onto the surface of halloysite nanotubes (HNTs) through the oxidative polymerization of rhodanine on Fe3+-impregnated-HNTs. The wrapping mechanisms were disclosed. The PRd-HNTs exhibited a prominent reinforcing effect for rubber. With the incorporation of 30phr of PRd-HNTs, the tensile strength was increased by almost 8-fold, and the modulus (at 300% strain) was increased by 257% compared to neat SBR. More strikingly, with only 2.9wt.% of PRd (relative to HNTs), the tensile strength and modulus of the composite were enhanced by 117% and 87%, respectively, suggesting the high efficiency of the modification. Such profound changes in the reinforcement were attributed to the formation of covalent linkages between PRd-HNTs and rubber through the participation of PRd-HNTs in curing process. In view of the versatility of PRd-wrapping procedure, this method offers significant insight into the interfacial design of rubber nanocomposites consisting of nonpolar matrices and inorganic reinforcements.

Engineering Cobalt-Doped Nickel Oxide/Gadolinium-Doped Cerium Dioxide Heterojunction Nanofibers for Highly Selective and Sensitive Dopamine Detection

Developing accurate and effective methods of dopamine (DA) detection is vital for the rapid diagnosis of diseases related to abnormal DA levels. Herein, we developed a high-performance, nonenzymatic dopamine electrochemical sensor for DA detection. The sensor was fabricated by synthesizing metal-oxide heterojunction porous nanofibers (PNFs), specifically cobalt-doped nickel oxide and gadolinium-doped cerium dioxide (Co-NiO/GDC), on a carbon nanofiber template using electrospinning and high-temperature annealing. The doping of Co²⁺ and Gd³⁺ was shown to induce lattice distortions in NiO and CeO₂, which in turn generated microstrains and surface defects at the phase interface. These structural enhancements played a key role in significantly boosting the material's catalytic activity for DA detection. The Co-NiO/GDC PNFs sensor demonstrated remarkable performance metrics, including a wide linear dynamic range (0.1 to 1100 μM), a high sensitivity (508.7 μA·mM^-1·cm^-2) and an exceptionally low detection limit (LOD = 0.018 μM, S/N = 3). The sensor also exhibited superior anti-interference properties, repeatability, reproducibility, and long-term stability. The sensor's practical utility was further validated by its ability to accurately detect DA levels in complex biological matrices such as animal serum and artificial urine, showcasing its potential for practical clinical applications.

Properties of halloysite nanotube–epoxy resin hybrids and the interfacial reactions in the systems

A naturally occurred microtubullar silicate, halloysite nanotubes (HNTs), was co-cured with epoxy/cyanate ester resin to form organic–inorganic hybrids. The coefficient of thermal expansion (CTE) of the hybrids with low HNT concentration was found to be substantially lower than that of the plain cured resin. The moduli of the hybrids in the glassy state and rubbery state were significantly higher than those for the plain cured resin. The dispersion of HNTs in the resin matrix was very uniform as revealed by the transmission electron microscopy (TEM) results. The interfacial reactions between the HNTs and cyanate ester (CE) were revealed by the results of Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS). The substantially increased properties of the hybrids were attributed to the covalent bonding between the nanotubes and the matrix.

Effects of epoxy content on dynamic mechanical behaviour of PEI-toughened dicyanate–novolac epoxy blends

By varying the cyanate/epoxy ratio, three polyetherimide(PEI)‐modified bisphenol A dicyanate–novolac epoxy resin blends with different epoxy contents were prepared. The effects of epoxy content on the dynamic mechanical behaviour of those blends were investigated by dynamic mechanical thermal analysis. The results showed that the glass transition temperature of the cyanate–epoxy network ( T g1 ) in the modified blend decreases with epoxy content. When the epoxy content increases, both the width of the glass transition of the cyanate–epoxy network and its peak density are depressed substantially. Although the tangent delta peak value of PEI is basically independent of epoxy content, the T g of PEI ( T g2 ) decreases with epoxy content. T g1 is independent of the PEI loading. When T g1 is lower than T g2 , however, the T g1 in the blend with revised phase structure is substantially lower than other blends. Copyright © 2004 Society of Chemical Industry

Significantly enhancing the coercivity of NdFeB magnets by ternary Pr-Al-Cu alloys diffusion and understanding the elements diffusion behavior

Low melting point Pr-Al-Cu alloys were employed in grain boundary diffusion for sintered NdFeB magnets. The coercivity of the 7 × 7 × 2 mm magnet was enhanced from 1000 kA/m to 1360, 1615, and 1714 kA/m by diffusing Pr70Al10Cu20, Pr70Al15Cu15 and Pr70Al20Cu10 alloys, respectively, at 800 °C for 2 h followed by 500 °C for 3 h. The optimized microstructure with strip-like grain boundary phase was evident in diffused magnets, which helps to reduce the magnetic exchange interaction between the hard magnetic grains and improve the coercivity. Under the same diffusion process, the coercivity of the diffused magnets decreased with increasing sample thickness, but 27% coercivity enhancement can still be obtained in the magnet with 6 mm in height. A Φ10×10 mm block magnet was diffused by Pr70Al20Cu10 alloy at 800 °C for 2–10 h. Up to 49% enhancement in coercivity was achieved, which confirms the diffusion ability of Pr-Al-Cu alloy. The diffusion behavior of Pr, Al and Cu elements has been analyzed by Fick’s law. Based on the diffusion coefficients obtained at 800 and 900 °C, Pr diffuses faster than Cu and Al along the grain boundary. The current results demonstrated that Pr-Al-Cu alloys can effectively optimize the grain boundary structure and improve the coercivity of NdFeB magnets.

Carbothermal shock synthesis of FeCoNiPtRu high-entropy alloy for dual-function water splitting in alkaline media

The development of dual-function catalysts with high activity and durability is essential in overall water splitting applications. In this work, FeCoNiPtRu HEA was rapidly synthesized on carbon support by carbothermal shock process. The synergistic interaction among metal elements enhanced the catalytic activity. The catalyst demonstrated overpotentials of 104 mV for HER and 331 mV for OER at 10 mA cm−2. In addition, FeCoNiPtRu HEA was aimed on carbon paper and the nanoparticles were encapsulated by a carbon layer with a stability of up to 100 h. Finally, as a dual-function catalyst, when applied as both the cathode and anode in overall water splitting (OWS), FeCoNiPtRu demonstrated a voltage of 1.69 V at 10 mA cm−2. This work demonstrates the significant potential of high-entropy alloy catalysts in hydrogen production through overall water splitting.

LOW TEMPERATURE SEALING BEHAVIOR EVALUATION OF ELASTOMERS IN AIRCRAFT HYDRAULIC SYSTEMS

The low temperature sealing behaviors of five elastomer components used in aircraft hydraulic sealing systems were evaluated through a series of tests subsequent to exposure at 135 °C for a maximum of 28 days in air or hydraulic oil. These assessments encompassed standard material tests such as glass transition temperature (Tg), temperature retraction at 10% shrinkage, mechanical test, and compression set and a customized test to measure sealing force of a certain temperature. In addition, a low temperature gas leakage test was conducted. NBR stiffened upon aging with degradation of properties in an elongation loss, and Tg increased because chain mobility decreased due to increased crosslink density, and restoring force sharply decreased in cooling and in extracting plasticizer. In contrast, in the gas leakage test for both fluorocarbon rubber (FKM) and blends of epichlorohydrin with NBR (ECO), the Tg values showed good accordance, with minimal sealing temperature (Tseal), whether FKM or ECO were aged or not. However, the value of Tseal is significantly higher than that of Tg after NBR aging, indicating a complicated sealing mechanism. Thus, relying solely on standard material tests may not suffice for accurately forecasting the low temperature sealing performance in aircraft hydraulic sealing systems.

Sustainable Carbon Nanodots with Tunable Radical Scavenging Activity for Elastomers

The application of polymers as an essential class of material was greatly inhibited due to the aging failure of these versatile materials during normal use. Hence, it is generally recognized that stabilization against thermo-oxidative aging is indispensable to extend the service life of polymers for long-term applications. However, toxicity and pollution of the state-of-the-art antiaging technologies have long been puzzles in the polymer industry. Herein, sustainable carbon nanodots (CDs), synthesized by facile and cost-effective microwave-assisted pyrolysis, are used for first time as radical scavengers to resist the thermo-oxidative aging of elastomers. We have demonstrated that incorporation of the resultant CDs could be green and generic radical scavengers toward highly aging-resistant elastomers. Furthermore, by controlling the photoluminescent quantum yield of the CDs with various passivated agents, tunable radical scavenging activity was achieved. We established for the first time that the aging resistance originates from the prominent reactive radical scavenging activity of the CDs, which was rationally controlled by their photoluminescent quantum yield.

Alcoholysis of Silicone Rubber Waste: A Method for Efficiently Recycling Silicone Rubber Waste and Preparing Multifunctional Rubber Additive

ABSTRACT Silicone rubber waste was effectively degraded into liquid siloxane derivatives by using a green solvothermal alcoholysis method under mild conditions. The resulting products primarily comporised linear oligomers (P 1 , P 2 ) and cyclic species (D 3 , D 9 ), with composition significantly influenced by alcoholysis parameters. Systemmatic invesitgation revealed alcoholysis agents as critical determinants of product profiles, demonstrating marked differences indegradation outcomes across reagent types. Given their structural similarity to traditional coupling agents, liquid siloxane derivatives were employed as addtives in nirtile butadiene rubber/silica composites to enhance interfacial bonding and mechanical properties. The results showed the obtained liquid siloxane derivatives can not only act as a silane coupling agent, increasing tensile strength and elongation at break but also function as a plasticizer, obviously enhancing the processing properties and cold resistance of the rubber/silica composites. This study develops an efficient stragety for synthesizing multifunctional rubber addtives and enabling complete silicone rubber waste degradation through solvothermal alcoholysis under mild conditions.

A green method for preparing conductive elastomer composites with interconnected graphene network via Pickering emulsion templating

The exploitation of generic strategy for preparation of conductive elastomer composites with interconnected filler network is of significant scientific and technical interests. Herein, we report a novel, green and effective strategy to prepare conductive natural rubber (NR) composites with interconnected graphene network structure. It is found that the Pickering emulsion template is effective in constructing 3D interconnected graphene oxide (GO) networks while the thermal treatment during hot pressing step is able to convert GO to conductive thermal reduced graphene (TRG). This strategy does not rely on the toxic and corrosive reducing agents and the adopted solvents in Pickering emulsions can be recycled and reused, which makes the process environmentally friendly. As a result, interconnected graphene network is well constructed within NR matrix, which significantly enhances the electrical conductivity, mechanical properties and lowers the percolation threshold of the resulted composites. Specifically, with the incorporation of 1.90 vol% TRG, the electrical conductivity of NR composites with interconnected graphene network structure is more than 7 orders of magnitude higher than that of NR composites with uniform graphene dispersion. More intriguingly, this GO stabilized Pickering emulsion template strategy can also be used to realized the selective distribution of carbon nanotubes and assemble them into interconnected network structure, further facilitating the conductivity improvement of the resulted composites. Overall, we envision that the present work offers new insights into the design of conductive elastomer composites.

Catalyst-Free Metathesis of Cyclic Acetals and Spirocyclic Acetal Covalent Adaptable Networks

Due to the exchangeability of dynamic covalent bonds in the covalent adaptable networks (CANs) at elevated temperature, they possess recyclability while still maintaining many of the superior properties of thermosets. The exploration of dynamic covalent chemistry is of great significance to the expansion of CANs library and hence the sustainable development of thermosets. In this work, we discovered that, in absence of catalyst, the direct metathesis of the cyclic acetals proceeds while the acyclic acetals cannot. The metathesis kinetics of the cyclic acetals were fully revealed with model compounds. For the CANs demonstration, a series of cross-linked spirocyclic acetal polymers with excellent reprocessability, high thermal stability, and high refractivity were prepared via thiol-ene click polymerization. We envisage that the uncovering of the catalyst-free metathesis of cyclic acetals will enrich the dynamic chemistry of acetals and greatly promote the development of acetal-based CANs and their potential applications in optical devices.

Polyrhodanine mediated interface in natural rubber/carbon black composites toward ultralow energy loss

Carbon black (CB) is a principal filler in rubber industry due to its excellent reinforcing effect and low-cost. It is of significant importance but challenging to modify the inert CB for addressing the dilemma of increased energy loss raised by the addition of CB. In this work, we reported the functionalization of CB through redox polymerization of rhodanine on its surface, and utilized the modified CB as a novel reinforcement for natural rubber (NR). Polyrhodanine coated on CB can covalently couple with NR chains by capturing macroradicals and serve as an intelligent interfacial bridge between CB and NR, which greatly improves CB dispersion and strengthens interfacial adhesion in the composites. As a consequence, the energy loss of the resultant composites is remarkably decreased, showing great advantages in reducing the rolling resistance and heat build-up for tire applications.

Malleable organic/inorganic thermosetting hybrids enabled by exchangeable silyl ether interfaces

Interfacial silyl ether networks can reshuffle the topological structure upon trans-oxyalkylation reactions, enabling malleability and recyclability to organic/inorganic hybrid vitrimers.

Biomimetic design of elastomeric vitrimers with unparalleled mechanical properties, improved creep resistance and retained malleability by metal–ligand coordination

Elastomeric vitrimers with an integration of unparalleled mechanical properties, improved creep resistance and retained malleability by engineering dynamic and sacrificial Zn²⁺−imidazole complex into the network.

Directed modulation of Pt-rich shell high-entropy alloy electrocatalysts toward efficient alkaline water splitting

Structure and Properties of Natural Rubber-Organoclay Nanocomposites Prepared by Grafting and Intercalating Method in Latex

The nanocomposites of natural rubber (NR) and organoclay with unsaturated carbon-carbon double bonds (C 1 /4C) on interlayer surfaces (USMMT) are prepared by the grafting and intercalating method in latex in the presence of butyl acrylate (BA) monomer. The conversion, grafting efficiency, and grafting percentage of BA onto NR and USMMT are determined. The structure and morphology of the nanocomposites are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmitted electron microscopy (TEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and swelling experiments. The mechanical properties of the nanocomposites are measured. The results show that graft copolymerization of BA monomer onto NR molecular chains can take place with high conversion, grafting percentage, and grafting efficiency. At the same time, BA can intercalate into the interlayer galleries of USMMT and polymerize in situ together with C 1 /4C bonds on the interlayer surfaces. As a result, the interlayer spacing of organoclay is increased and the interfacial combination between the silicate layers and rubber is strengthened. The results of XRD and TEM demonstrate the formation of the nanocomposites of NR-M-USMMT. The glass transition temperatures of the nanocomposites are higher than that of the NR vulcanizate. The mechanical properties of the nanocomposites are remarkably improved compared with those of the NR and NR-USMMT vulcanizate.

Heterogeneous network design strategy toward mechanically robust and recyclable elastomers

It is well-accepted that thermoplastic vulcanizates (TPVs) integrate the fascinating recyclability of thermoplastics and the mechanical robustness comparable to nano-filled elastomers, deriving from the particular heterogeneous network structure. However, the elasticity of TPVs is inferior to covalently cross-linked elastomers, since the irreversible deformation or even collapse of plastic phases of TPVs will certainly give rise to considerable hysteresis loss and therefore deteriorate the elasticity. Herein, we proposed a facile network design strategy toward covalently cross-linked elastomer with mechanical robustness and recyclability by engineering heterogeneous blend networks into diene-rubber system. Specifically, two conventional diene-rubbers, ethylene propylene diene terpolymer (EPDM) and styrene-butadiene rubber (SBR), were adopted as thermodynamic incompatible pair and then directly admixed. Due to the significant difference in the cross-linking reactivity between the pair, the resulting system assembled into a microphase-separated structure with strong interfacial adhesion upon in situ co-cross-linking. Upon deformation, the overall chain orientation of the networks is promoted by the efficient interfacial stress transfer and a striking reinforcement of the networks is achieved accordingly. More importantly, by virtue of the slightly cross-linking attribute of EPDM component, the resulting system featured with desirable recyclability and high elasticity in comparison with conventional TPVs. We envisage that this work will provide important inspiration for the non-filling reinforcement of elastomers and the development of a new generation of thermoplastic vulcanizates with considerably low hysteresis through manipulating the covalent network heterogeneity.