Publications

The filler dispersion and network in rubber composites are critical factors in determining the properties of the composites. In this study, we incorporate a graphene-like layered material, molybdenum disulfide (MoS2), to partly substitute carbon black (CB) in styrene butadiene rubber/CB composites, and primarily focus on the filler dispersion and network as well as their effects on the mechanical properties of the composites. With the addition of MoS2, the dispersion of CB is greatly improved and the CB agglomerates are suppressed. When MoS2 substitution content is less than 1 phr, the modulus and strength of the composites are slightly decreased due to the release of trapped rubber from CB agglomerates, while the dynamic mechanical properties are significantly improved. At higher MoS2 substitution loading, MoS2 and CB form a denser and continuous hybrid filler network, which shows remarkable synergistic effects in improving the both static and dynamic mechanical properties of the composites. For example, the addition of 3 phr MoS2 leads to a 50% increase in the tensile modulus and 10 °C decrease in the heat build-up of the composite.

A natural clay halloysite, which is a kind of aluminosilicate with a predominantly nanosized hollow tubular structure, was modified by polymers achieving polymer‐halloysite composite nanotubes. Polymer chains can grow from both interior and exterior surfaces of the halloysite nanotubes by atom transfer radial polymerization (ATRP). Eventually, the composite nanotubes were evolved to a core‐shell coaxial structure after the interior cavity was fully covered by the polymer. After dissolution of the halloysite template, polymeric nanotubes and nanowires were derived. The composition could be controlled from polymer to carbon after being treated at high temperature. The idea can be extended to a cast halloysite fabric resulting nonwoven composites, which had some interesting wettability. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Pt-based catalysts suffered from the wastage of active sites, resulting in unsatisfactory actual catalytic performance and poor durability as non-self-supporting catalysts for alkaline hydrogen evolution reaction (HER). In this work, we designed a self-supporting electrode material with multi-level structure that utilized carbon nanofibers anchored with cobalt to load and stabilize Pt nanoparticles (Pt@Co/CNFs) for achieving high activity and stability in alkaline HER. The carbon nanofibers served as a framework, with cobalt nanoparticles as an electron donor that can transfer electrons to the metal Pt to accelerating water splitting. In addition, the morphology of the multi-level structure surface was controlled by the content of the reducing agent to giving the material excellent superhydrophilic/underwater superaerophobic properties with ultra-low Pt load (0.29 mg cm−2), which was beneficial for HER. HER test results showed that Pt@Co/CNFs exhibited great catalytic activity, with η10 = 15 mV and η100 = 101 mV. Besides, the stable mechanical structure and the stability of the designed catalytic surface and electron donor in the multi-level structure gave the material exceptional stability. During the 100-hour stability test at 100 mA cm−2, the voltage change was only 50 mV. Besides, utilizing the Pt@Co/CNFs self-supporting electrode directly in the AEM water electrolysis system, a cell voltage as low as 2.18 V was achieved at 500 mA cm−2. Impressively, it demonstrated operational stability for over 200 h without noticeable decay. This work provides a promising approach for the development of advanced self-supporting electrode catalysts.

The development of biobased polymers from renewable resources offers a solution to the growing environmental concerns and scarcity of fossil feedstock. The synthesized biobased polymers, especially for biobased elastomers, are mechanically weak, which greatly restricts their applications. In the present work, we demonstrate that the integration of transient and sacrificial quadruple H-bonding motifs into as-synthesized biobased elastomer can enhance the mechanical properties and bestow it with adaptive performance. Specially, the biobased elastomer was synthesized through melting poly-condensation using biobased di-acids and diols as the starting materials. The biobased elastomer is covalently crosslinked and grafted with ureido-pyrimidinone (UPy) containing acrylate through thiol-ene click reaction by using pentaerythritol tetra(3-mercaptopropionate) as the linkers. Under external load, UPy aggregations based on H-bonding can function as sacrificial units through reversible rupture and re-formation events, leading to significant improvements on the modulus and strength of the biobased elastomer while maintaining the extensibility. In addition, the dissociation and re-formation of H-bonding under thermal stimuli impart the elastomer with thermo-activated shape memory behavior.

Currently adopted cross-linking methods in rubber industry are suffering from variable persistent issues, including the utilization of toxic curing packages, release of volatile organic compounds (VOCs) and difficulties in the recycling of end-of-life materials. It is of great importance to explore a green cross-linking strategy in the area. Herein, we report a new “green” strategy based on hydrolyzable ester cross-links for cross-linking diene-typed elastomers. As a proof of concept, a commercial carboxylated nitrile rubber (XNBR) is efficiently cross-linked by a bio-based agent, epoxidized soybean oil (ESO), without any toxic additives. ESO exhibits an excellent plasticization effect and excellent scorch safety for XNBR. The cross-linking density and mechanical properties of the ESO-cured XNBR can be manipulated in a wide range by changing simply varying the content of ESO. In addition, zinc oxide (ZnO) performs as a catalyst to accelerate the epoxide opening reaction and improve the cross-linking efficiency, serving as reinforcement points to enhance the overall mechanical properties of the ESO-cured XNBR. Furthermore, the end-of-life elastomer materials demonstrate a closed-loop recovery by selectively cleaving the ester bonds, resulting in very high recovery of the mechanical performance of the recycled composites. This strategy provides an unprecedented green avenue to cross-link diene elastomers and a cost-effective approach to further recycle the obtained cross-linked elastomers at high efficiency.

Although carbon nanotubes (CNTs) have been produced in industrial scale, their poor dispersibility in organic solvents still imposes a huge challenge for their practical applications. In the present work, we propose a generic mechanochemical grafting strategy to prepare the organo-soluable CNTs, which is facile, efficient, and scalable. Significantly, the solvent spectrum of the CNTs suspension can be simply extended by changing the chemical composition of the grafted elastomer chains. The prospect of the organo-solubale CNTs is demonstrated by the free-standing buckypapers by direct filtration of the CNT colloids. Such buckypapers exhibit great potential as robust and ultraflexible conductors due to the combination of high toughness and stable conductivity under cyclic bending and twisting. Furthermore, this facile surface modification strategy of CNTs also enables remarkable improvement in mechanical properties of CNT-based rubber composites. We envision that the present work offers a facile yet efficient strategy for scalable production of organosoluable CNTs and other nanoparticles, which is of great scientific and technological interest.

Vitrimer-like elastomer composites with lignin as a renewable bio-filler, showing effective reinforcement, recyclability and photothermal performance, were prepared.

Recovered carbon black (rCB), a regenerative product from the thermal pyrolysis of waste tires, can be reused as a reinforcement for rubbers, with the goal of achieving high-value utilization of...

The dispersion of filler and properties of elastomer composites are always the focus in the rubber researching. In this work, RGO/SiO2 nanocomposites were obtained by self-assembling of silica nanoparticles (SiO2) and reduced graphene oxide (RGO), which were used to manufacture RGO/SiO2-SSBR/BR composites by means of compounding with solution-polymerized styrene butadiene rubber/butadiene rubber (SSBR/BR). The structure and morphology characterization showed that SiO2 nanoparticles were homogeneously distributed on RGO. With the adding of RGO, the mechanical properties were enhanced and the RGO/SiO2-SSBR/BR with 1% weight percentage of RGO possessed the optimal wet skid resistance and rolling resistance compared with commercialized Zeosil 1165 MP highly-dispersed nano-SiO2 (Zeosil 1165 MP)-SSBR/BR (tan δ is 16.8% higher at 0 °C and 50.0% lower at 60 °C). In addition, the heat build-up exhibited considerable decrease with low RGO weight percentage, and wear resistance considerably enhanced. The reinforced integrated performances provide a potential application of RGO/SiO2 for green tires.

It is a significant but challenging task to simultaneously reinforce and functionalize diene rubbers. Inspired by "sacrificial bonds", the authors engineer sacrificial hydrogen bonds formed by pendent urazole groups in crosslinked solution-polymerized styrene butadiene rubber (SSBR) via triazolinedione click chemistry. This post-crosslinking modification reveals the effects of the sacrificial bonds based on a consistent covalent network. The "cage effect" of the pre-crosslinked network facilitates the heterogeneous distribution of urazole groups, leading to the formation of hydrogen-bonded multiplets. These multiplets further aggregate into clusters with vicinal trapped polymer segments that form microphase separation from the SSBR matrix with a low content of urazole groups. The clusters based on hydrogen bonds, serving as sacrificial bonds, promote energy dissipation, significantly improving the mechanical properties of the modified SSBR, and enable an additional wide transition temperature region above room temperature, which endows the modified SSBR with promising triple-shape memory behavior.

Sulfur-containing silane coupling agents (SSCAs) are widely incorporated into silica-filled rubber composites to improve silica dispersion and enhance interfacial adhesion, maximizing the potential of silica. However, SSCA synthesis involves multistep procedures and requires organic solvents. In addition, modifying rubber composites with SSCAs has persistent issues, such as low coupling efficiency and uncontrollable structure. Herein, we report the facile synthesis of alkoxysilyl-functionalized polysulfides (SPVs) with a tunable molecular structure (sulfur rank and alkoxysilyl fraction) via inverse vulcanization of vinyltriethoxysilane (VTES) with a copolymer of sulfur and styrene. SPVs serve as interfacial modifiers in silica-filled rubber composites by separately reacting with the silica and rubber chains. In particular, the multiple alkoxysilyl sites in the SPV chain increase the probability of silanization, yielding high coupling efficiency in the rubber composite. Although the molar content of alkoxysilyl groups in SPV1 (the mass feed ratio of VTES and copolymer is 1) is half of that in the most widely used small-molecules SSCAs of bis(3-triethoxysilylpropyl)tetrasulfide, stronger interfacial adhesion and better silica dispersion are achieved in SPV1-modified composites, which consequently lead to more improvements on the composite properties. In addition, the advantages of SPV1 as an interfacial modifier in improving the "magic triangle" properties of a practical tread composite have been demonstrated. More importantly, the effects of the SPV molecular structure on silica dispersion and interfacial adhesion have been investigated, providing the fundamentals for unraveling the coupling mechanism and guiding composite property regulation.

A new curing agent based on palmitoleic acid methyl ester modified amine (PAMEA) for epoxy resin was synthesized and characterized. Diglycidyl ether of bisphenol A (DGEBA) epoxy resins cured with different content of PAMEA along with diethylenetriamine (DETA) were prepared. The mechanical properties, dynamic mechanical properties, thermal properties, and morphology were investigated. The results indicated that the PAMEA curing agent can improve the impact strength of the cured epoxy resins considerably in comparison with the DETA curing agent, while the modulus and strength of the cured resin can also be improved slightly. When the PAMEA/epoxy resin weight ratio is 30/100, the comprehensive mechanical properties of the cured epoxy resin are optimal; at the same time, the crosslinking density and glass transition temperature of the cured epoxy resin are maximal.

Covalently cross-linked elastomers with high elasticity are widely found in daily life and high-tech areas. However, the irreversibility of the crosslinked networks hinders the rubber products from reprocessing or recycling, causing a major environmental problem. Recently developed vitrimer chemistry provides fantastic avenues for cross-linked elastomers to achieve full reprocessability and recyclability. Herein, we disclose a novel CN transalkylation of pyridinium by model studies and implant this chemistry into the interfaces of an elastomeric composite. As a proof of concept, (3-bromopropyl)trimethoxysilane modified silica was used to crosslink butadiene-styrene-vinylpyridine rubber, forming pyridiniums in the interfaces. The composites were prepared by straightforward mechanical compounding and subsequent hot-pressing. Because of the covalent interfacial bridges and excellent dispersion of silica, the composites possess robust mechanical properties. Furthermore, the CN transalkylation reactions of pyridiniums at elevated temperature endows the composites with vitrimer properties, such as malleability and reprocessability. As the pyridine moieties can be easily introduced into a great variety of commercial polymers, we envision this newly demonstrated CN transalkylation of pyridinium possesses significant potential in broadening the gallery of vitrimer materials.

S-rich MoS2–NCNF hybrid nanomaterials exhibiting extraordinary HER activity, with a very low onset potential of 30 mV and a small Tafel slope of 38 mV per decade, were successfully fabricated by combining N-doped carbon nanofibers and single-layered MoS2 nanostructures with abundant edge active sites.

Covalently cross-linked rubbers are renowned for their high elasticity that play an indispensable role in various applications including tires, seals, and medical implants. Development of self-healing and malleable rubbers is highly desirable as it allows for damage repair and reprocessability to extend the lifetime and alleviate environmental pollution. Herein, we propose a facile approach to prepare permanently cross-linked yet self-healing and recyclable diene-rubber by programming dynamic boronic ester linkages into the network. The network is synthesized through one-pot thermally initiated thiol-ene "click" reaction between a novel dithiol-containing boronic ester cross-linker and commonly used styrene-butadiene rubber without modifying the macromolecular structure. The resulted samples are covalently cross-linked and possess relatively high mechanical strength which can be readily tailored by varying boronic ester content. Owing to the transesterification of boronic ester bonds, the samples can alter network topologies, endowing the materials with self-healing ability and malleability.