Publications

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.

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

Although hydroxy is an easily-available group for polymer functionalization and can serve as a ligand to coordinate with metal ions, the hydroxy-ion cluster coordination remains unexploited as sacrificial bond to reinforce elastomers. This work reports a very strong rubber by introducing iron ion cluster-OH coordination into a covalently-crosslinked rubber. With the introduction of 4.2 wt% Fe3+, the rubber exhibits a 6-fold increase in tensile strength and an 8-fold increase in modulus when compared with neat rubber. The achieved tensile strength (~20.9 MPa) and modulus (~12.7 MPa) are competitive to the highly-filled engineering rubbers. Overall, this work presents a new method to prepare high performance elastomers based on a hydroxylated polymer. As hydroxylated polymers can be readily prepared with commercially available polymers, the present study should promote comprehensive research and industrial applications of sacrificial bond strategy.

The development of efficient electrocatalyst is one of the effective ways to speed up the efficiency of water electrolysis. In this work, we prepared a nested-like Ce-doped CoP nanowires catalytic material on carbon cloth by simple hydrothermal and phosphating methods. After adjusting the doping ratio of Ce, the doping ratio (Ce/W = 6 %) with the best performance is obtained and named as Ce-CoP NWs/CC. The Ce-CoP NWs/CC exhibits preeminent electrocatalytic activity with low overpotentials with 80 and 290 mV at 10 mA cm−2 for HER and OER, respectively. Moreover, the Ce-CoP NWs/CC electrocatalyst also exhibits excellent electrochemical performance in overall water splitting with a low voltage of 1.506 V at 10 mA cm−2, outperforming many reported electrocatalysts. This work provides a feasible electrocatalytic material for the introduction of rare earth elements into water electrolysis.

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.

The effects of secondary particle size distribution on the electromagnetic properties of the carbonyl iron powder cores have been investigated in this work. For preparing the cores, the iron powders were firstly undergone insulation treatments including phosphorization and organic coating. After granulation, the secondary particles with different size distributions were molded into the final shape and cured at 200 °C. The results show that for the secondary particles with unimodal size distribution, the real part of the complex magnetic permeability of the powder core is in inverse proportion to the particle size. For the cores prepared from the secondary particles with bimodal size distribution, the effects of the size ratio and volume ratio of the coarse particle/fine particle on the magnetic properties are discussed. It is found that the permeability increases with the increasing volume of fine secondary particles. The minimum magnetic loss factor value is obtained at the coarse/fine secondary particles volume ratio of 7:3. The density and magnetic properties including complex permeability and magnetic loss of the cores prepared with coarse/fine particles size ratio of ~3 and ~7 are both in inverse proportional to the volume fraction of coarse secondary particles. The present work indicates that a reasonable size distribution of the secondary particles is required to improve the magnetic properties of the soft magnetic powder cores.

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.

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.

Sustainable, recyclable and robust elastomers are prepared <italic>via</italic> the construction of exchangeable ester linkages between natural rubber and carbon black.

Natural rubber/carbon black (NR/CB) composites have found indispensable application in aircraft tires. Interfacial modification of NR/CB composites for acquiring uniform CB dispersion and strong interfacial adhesion is a persistent and challenging theme, as it is a prerequisite to improve comprehensive mechanical properties and decrease energy loss of the composites under dynamic deformations. In this work, we reported the use of an amino-functionalized polysulfide (PDAS) synthesized by inverse vulcanization of sulfur and m-phenylenediamine as a novel interfacial modifier in NR/CB composites. Specifically, the amino of PDAS can react with the carboxyl groups on the CB surface, meanwhile the polysulfide chains of PDAS can react with rubber chains, enabling the crosslinking of NR and establishment of a molecular bridge between NR and CB. The influences of PDAS dosages on CB dispersion and interfacial adhesion are revealed, and their correlations with composite properties are discussed. Compared with the unmodified counterpart, CB dispersion is greatly improved and interfacial adhesion is significantly enhanced in the PDAS-modified composite having an identical crosslink density, leading to remarkably decreased hysteresis loss. In addition, PDAS can significantly resist thermal-oxidative aging of the composites due to its radical scavenging activity.

The silanization reaction between boehmite (BM) nanoplatelets and bis-[3-(triethoxysilyl)-propyl]-tetrasulfide (TESPT) was characterized in detail. Via such modification process, the grafted sulfide moieties on the BM endow reactivity toward rubber and substantially improved hydrophobicity for BM. Accordingly, TESPT was employed as in situ modifier for the nitrile rubber (NBR)/BM compounds to improve the mechanical properties of the reinforced vulcanizates. The effects of BM content and in situ modification on the mechanical properties, curing characteristics and morphology were investigated. BM was found to be effective in improving the mechanical performance of NBR vulcanizates. The NBR/BM composites could be further strengthened by the incorporation of TESPT. The interfacial adhesion of NBR/BM composites was obviously improved by the addition of TESPT. The substantially improved mechanical performance was correlated to the interfacial reaction and the improved dispersion of BM in rubber matrix.

Inverse vulcanization provides a facile but effective methodology to create sulfur-based polymers with diverse applications by utilization of element sulfur, a massive waste product from petroleum industry. An integration of functional groups into sulfur-based polymers may inject new vitality for the traditional discipline of rubber composites, though the examples remain limited. Herein, we reported the synthesis of polysulfur copolymers (STs) via one- or two-step methods by inverse vulcanization of sulfur and triethoxyvinylsilane (TEVS) and their function mechanism in silica-filled diene rubber composites. Owing to the presence of polysulfide and multiple alkoxysilyl moieties, STs could provide two functions of vulcanizator and interfacial modifier through the reaction with the rubber chains and silica, enabling the crosslinking of rubber and uniform dispersion of silica. Importantly, ST-modified composites exhibited more uniform silica dispersion and stronger interfacial interaction than sulfur cross-linked BR/silica composites modified with conventional coupling agents, thus leading to more enhancements of the mechanical properties. Moreover, the mechanism of ST copolymers in the silica filled diene rubber composites was proposed.