Publications

In-situ decorating diene-rubber with carbamyl maleamic handles as sacrificial units toward network reinforcement

The decoration of sacrificial units (SUs) into rubber network has gained momentum as a non-filling alternative toward efficient network reinforcement. However, most established methods, including the copolymerization with SUs-containing monomers or the post-modification of rubber backbone, still suffer from the multi-step and time-consuming backbone preparation with poor designability. In this work, we proposed a facile and practical strategy to achieve efficient network reinforcement through in-situ decorating isoprene rubber (IR) network with N-carbamyl maleamic acid (NCMA) as SUs. Model compound vulcanization experiment demonstrated that during sulfur vulcanization, the poly/disulfides in active sulfurating agents or crosslinking precursors can cleave into reactive sulfur radicals, which subsequently proceeded radical addition reaction with the unsaturated NCMA. The decorated carbamyl maleamic handles can spontaneously form multiple hydrogen-bonding linkages to serve as SUs. Upon deformation, the reversible detachment/reattachment of the SUs will smooth out the local stress concentration, but also facilitate the orientation of network chains. Therefore, as the NCMA loading increases, the onset of strain-induced crystallization and the overall crystallinity of the obtained IR network are simultaneously promoted, giving rise to a gradual increase in the tensile modulus (∼80 %) of the system. By virtue of the rich variety, commercial availability and facile structural tunability of maleamic acid-derivatives, we envisage that the present study can open up a novel strategy to achieve in-situ decoration of rubber with various functional handles toward efficient network reinforcement and functionalization.

How organo-montmorillonite truly affects the structure and properties of polypropylene

Polypropylene (PP)/organo-montmorillonite (OMMT) nanocomposites were prepared by using a highly effective PP solid-phase graft as compatibilizer. As a very low amount of PP graft was used, the properties of the PP matrix were maintained. The effects of the OMMT on the structure and properties of PP were studied fully. The intercalated structure of the nanocomposites was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD and TEM results showed that a typical intercalated structure was formed in the composites. The results of mechanical properties showed that the impact strength and the modulus of the nanocomposites were improved significantly compared with those of the neat PP. The thermal stability and crystallization of the nanocomposites were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The thermal stability of the nanocomposites, characterized by the initial decomposition temperatures, was substantially improved compared with that of the neat PP. The DSC results showed that the crystallization temperature of nanocomposites was increased compared with the neat PP. The viscoelasticity of the nanocomposites was studies by dynamic mechanical thermal analysis (DMTA). The DMTA results showed that the OMMT could improve the modulus of PP substantially. The T g of PP was lowered by the incorporation of the OMMT. The changes of the properties were correlated with the formation of the PP/OMMT nanocomposites.

Styrene–butadiene rubber/halloysite nanotubes nanocomposites modified by methacrylic acid

Methacrylic acid (MAA) was used to improve the performance of styrene–butadiene rubber (SBR)/halloysite nanotubes (HNTs) nanocomposites by direct blending. The detailed interaction mechanisms of MAA and the in situ formed zinc methacrylate (ZDMA) were revealed by X-ray diffraction (XRD), surface area and porosity analysis, X-ray photoelectron spectroscopy (XPS) together with crosslink density determination. The strong interfacial bonding between HNTs and rubber matrix is resulted through ZDMA and MAA intermediated linkages. ZDMA connects SBR and HNTs via grafting/complexation mechanism. MAA bonds SBR and HNTs through grafting/hydrogen bonding mechanism. Significantly improved dispersion of HNTs in virtue of the interactions between HNTs and MAA or ZDMA was achieved. Effects of MAA content on the vulcanization behavior, morphology and mechanical properties of the nanocomposites were investigated. Promising mechanical properties of MAA modified SBR/HNTs nanocomposites were obtained. The changes in vulcanization behavior, mechanical properties and morphology were correlated with the interactions between HNTs and MAA or ZDMA and the largely improved dispersion of HNTs.

In-situ interfacial engineering towards highly fatigue resistant rubber composites enabled by aniline-functionalized oligomers

Topological network design toward high‐performance vegetable oil–based elastomers

As a kind of bio‐derived feedstock, vegetable oil (VO) shows great potential to replace petroleum‐based monomers to develop sustainable polymer materials because of its easy availability, low cost, bio‐renewable, and environmentally friendly nature. However, due to the high cross‐linking density and amorphous nature, directly cured VOs generally tend to be brittle and weak. To date, it is still difficult to adopt VOs and their derivatives as structural materials to prepare high‐performance elastomers. To address this important issue, a multi‐scale topology design strategy was proposed in this work. First, topology regulation and functionalization of VO‐based networks were realized by managing functional groups proportion during the bulk polymerization of epoxidized soybean oil with dimer fatty acids. Furthermore, a second polymer (SN) network was introduced into the VO‐based network as a protective layer via interfacial cross‐links. The generated VO‐based elastomers (VOEs) exhibit unprecedented comprehensive properties (VO content ≥70 wt.%, T g as low as −24.4°C, toughness up to 6.8 MJ/m 3 ). Besides, the VOEs also exhibit excellent reprocessability and self‐healing capability. Overall, this work developed a novel kind of VOEs with significant comprehensive advantages and provided important inspiration for the preparation of high‐performance elastomers through multi‐scale topology regulation.

<scp>PVA</scp>@tea tree oil‐emulsion core–shell microfiber membranes for extending the shelf life of fruits

In this work, a temperature‐regulating and antimicrobial–antioxidant fiber membrane was fabricated using coaxial electrospinning technology. The tea tree oil (TTO) emulsion used as the core solution, polyvinyl alcohol (PVA) as the shell solution for coaxial electrospinning, has been demonstrated. Compared with the original PVA fibers, the average diameter of the fibers is increased after coaxial electrospinning, and the diameter increases with the core flow rate. The diameters corresponding to core flow rates of 0.05, 0.1, and 0.15 mL/h are 561, 597, and 849 nm, respectively. Via in vitro release experiment demonstrated that the quantity of TTO released from the composite membrane increased with the elevation of temperature. The inclusions TTO and polyethylene glycol give the film excellent antibacterial–antioxidant properties and a delayed thermal response. More intriguingly, core–shell fiber membranes containing TTO in the core part are effective in slowing down the formation of oxidation spots on the surface of banana compared with pure PVA membranes. Seven days after wrapping bananas with different membranes, the surface of banana in pure PVA film was full of oxidized spots, whereas banana in PVA core–shell fibers showed only one obvious spot.

Crystallization behavior of polyamide 6/halloysite nanotubes nanocomposites

Non-isothermal crystallization and the polymorphism of the PA6 and the polyamide 6/halloysite nanotubes (PA6/HNTs) nanocomposites are studied by adopting differential scanning calorimetry (DSC) analysis, X-ray diffraction (XRD) analysis and polarized optical microscopy (POM) observations. HNTs act as nucleating agent and accelerate the crystallization. The kinetics analysis indicates that the fold-surface free energy of PA6/HNTs nanocomposites is larger than that of neat PA6. The increasing tendency of the fold-surface free energy of PA6/HNTs nanocomposites is restricted at higher HNTs loading. Interestingly, the crystallinity of the PA6/HNTs nanocomposites increases with cooling rate. HNTs content is found to have a significant effect upon the crystallinity of the PA6/HNTs nanocomposites, and the crystallinity reaches its maximum with 5phr of HNTs content. Moreover, the higher HNTs content is, the larger percentage γ-phase crystals take up. The crystallization behavior of the PA6/HNTs nanocomposites is correlated with the multiple roles of HNTs in the crystallization of PA6.

Preparing Exfoliated MMT/Polymer Nanocomposites by Combined Latex Compounding and Spray‐Drying

A facile and easily industrialized approach for preparing highly dispersed MMT/polymer nanocomposites is developed by combining the latex compounding method and a spray‐drying process. Clay particles are successfully delaminated into layers, and layer re‐stacking is effectively prevented. HR‐TEM and XRD results confirm that MMT layers achieve exfoliated or nearly exfoliated dispersion in both MMT/styrene‐butadiene rubber and MMT/PS nanocomposites. Compared with melt‐blended MMT/SBR composites, MMT/SBR nanocomposites prepared by this new strategy exhibit extremely high dynamic modulus. magnified image

High-performance rubber/boehmite nanoplatelets composites by judicious in situ interfacial design

Interfacial interaction plays a vital role in the final properties of polymer composites as it affects the filler dispersion and stress transfer in the composites. In this study, we utilized two types of phosphate ester, hydroxyethyl methylacrylate phosphate (PH) and butyl phosphate (PB), as modifiers in boehmite (BM)-filled styrene-butadiene rubber (SBR) to tailor the interfacial structures in the composites. The modification mechanism of phosphate ester on BM and the interfacial structure in the composites are characterized. In PH-modified BM/SBR composites, a covalently bonding interface is obtained because PH can act as molecular bridge that can form covalent linkage with both BM and SBR chains. Consequently, the resulting composites show significantly improvements in the physical and mechanical properties of the composites. While in PB-modified BM/SBR composites, the properties of the composites are slightly improved due to the lack of covalent linkage in the interface.

Naphthylhydrazone-based imines as a multifunctional regulator for rubber composites with superior dynamic performance and thermo-oxidative resistance

Carbon black (CB), as one of the most widely used reinforcements for rubbers, can integrally improves the processability and static/dynamic mechanical properties of rubber. Nevertheless, the dispersion state of CB and the interfacial adhesion in the composites are generally subject to the significant difference in surface energy between these two components, which leads to external hysteresis loss and hence compromises the lifetime of the products. In this study, naphthylhydrazone-based imine (HZO) was used as a feasible interfacial regulator for rubber/CB composites, since the naphthylhydrazone moiety can efficiently capture and stabilize the macroradicals generated by the rupture of rubber chains during the mixing process and then transferred to the surface energy trap of CB through the charge-sharing effect. Accordingly, the interfacial adhesion and dispersion state of the CB particles in the composites can be remarkably enhanced. Incorporating only 1 phr (parts per hundred of rubber) HZO can enable substantial decreases of approximately 11 °C in heat generation and 22 % in energy loss to the composites under dynamic loading. Besides, due to its excellent radical-trapping capacity, HZO can effectively scavenge the reactive radicals generated during the thermo-oxidation process, which considerably enhances the aging resistance of the resulting samples. We envisage that the as-prepared HZO with radical-trapping capacity can open up a practical methodology to achieve efficient interfacial regulation of rubber/CB composites, which has significant potential in the preparation of energy-saving and aging-resistant tire products.

Malleable, Mechanically Strong, and Adaptive Elastomers Enabled by Interfacial Exchangeable Bonds

Reinforcement, recycling, and functional applications are three important issues in elastomer science and engineering. It is of great importance, but rarely achievable, to integrate these properties into elastomers. Herein, we report a simple way to prepare covalently cross-linked yet recyclable, robust, and macroscopically responsive elastomer vitrimers by engineering exchangeable bonds into rubber–carbon nanodot (CD) interphase using CD as high-functionality cross-linker. The cross-linked rubbers can rearrange the network topology through transesterification reactions in the interphase, conferring the materials the ability to be recycled, reshaped, and welded. The relatively short chains bridging adjacent CD are highly stretched and preferentially rupture to dissipate energy under external force, resulting in remarkable improvements on the mechanical properties. Moreover, the malleable and welding properties allow the samples to access reconfigurable/multiple shape memory effects.

Catalyzed silanization by supporting ceria on silica towards rubber composites with improved mechanical properties

The silane modification in silica-filled rubber composites is essential to fulfil the potentials of silica. However, the silanization efficiency of silica generally remains unsatisfactory. Promoting silica silanization contributes to not only the improvements on composite properties, but also the reduction in volatile organic compound emissions during processing. In this work, we present a novel way to promote silica silanization in rubber composites by supporting ceria nanocrystals on silica surface. Specifically, silica supported with varied ceria nanocrystal loading is synthesized and used as a novel reinforcement for styrene-butadiene rubber. Model compound experiments demonstrate that the ceria on silica surface can effectively promote the silanization reaction based on its unique acid-base property. Due to the promoted silica silanization, silica dispersion is greatly improved and interfacial interaction is remarkably enhanced in the composites. Accordingly, the resulting composites filled with ceria-anchored silica exhibit desirable improvements on the tensile modulus and dynamic mechanical properties, which is conductive to tire application.

A generic solvent exchange method to disperse MoS2 in organic solvents to ease the solution process

A simple solvent exchange method is presented to suspend monolayers of MoS2 in various organic solvents, which facilitates the phase transformation of MoS2 and preparation of MoS2-filled polymer composites straightforwardly in organic solvents.

A bio-based, robust and recyclable thermoset polyester elastomer by using an inverse vulcanised polysulfide as a crosslinker

We report the synthesis of a bio-based, robust and recyclable thermoset polyester elastomer by using an inverse vulcanised sulfur-polymer (SP) as a crosslinker for the bio-based polyester elastomer (BPE).

Progress in bio-inspired sacrificial bonds in artificial polymeric materials

This review focuses on the mechanisms, designs, and applications of bio-inspired sacrificial bonds in artificial polymeric materials.

Interface Engineering toward Promoting Silanization by Ionic Liquid for High-Performance Rubber/Silica Composites

In silica-filled rubber composites, the silanization modification of silica plays a vital role in enhancing the compatibility between silica and a rubber matrix and hence the properties of the composites. In the present study, with the goal of promoting silanization reactivity and extent, we utilize a phosphonium ionic liquid (PIL) as a novel catalyst for the silanization reaction between silica and bis(3-triethoxysilylpropyl)-tetrasulfide (TESPT), a commonly used silane in the tire industry, in the styrene–butadiene rubber (SBR) matrix. Dynamic rheological measurement, bound rubber measurement, freezing point depression, and heat capacity increment together show that the addition of a small amount of PIL into a TESPT-modified SBR/silica composite gives rise to significant improvement in the interfacial adhesion between silica and the rubber matrix, which is on account of the promoted silanization extent of silica with the catalyst of PIL. Consequently, the resulting composite prepared at room temperature with fewer parts of TESPT exhibits superior overall performance in comparison with the composites prepared by adding excessive TESPT and compounding at an elevated temperature. In particular, the energy loss during rolling of the rubber wheel is drastically decreased as a result of the improved interfacial silanization, which shows great potential in energy-saving green tires.

CORRELATION OF FILLER NETWORKING WITH REINFORCEMENT AND DYNAMIC PROPERTIES OF SSBR/CARBON BLACK/SILICA COMPOSITES

The use of silica to partially replace carbon black is a common practice in the fabrication of “green tires.” Although some degree of consensus has been approached concerning the improved performance conferred by silica substitution, such as the improved dispersion of carbon black, a quantitative understanding of the relationship between filler networking and the performance of rubber composites has not been established. Thus, an investigation focusing on filler network structure and the correlation between the network structure and the reinforcement of rubber composites was conducted. We prepared solution-polymerized styrene–butadiene rubber (SSBR) reinforced by carbon black and carbon black/silica in different ratios. To exclude as much of the effect from changed crosslinking, and figure out how filler blending influences filler dispersion and filler network structure, the silane generally used in the tire industry was not adopted. The quantitative predictor, the mass fractal dimension df, was derived from the Kraus model and the Huber–Vilgis model. We found that when the amount of substituted silica increases, the filler cluster branching decreases, accompanied by increased reinforcement efficiency. The depressed filler networking induced by silica substitution at an appropriate proportion leads to improved dynamic properties, including lower rolling resistance and better wet skid. When the silica proportion in the filler is too high, severe filler networking is observed, resulting in decreased reinforcing efficiency and impaired dynamic properties.

Tubular Clay Composites with High Strength and Transparency

Optically transparent composites containing nanotubular clay up to 65 wt%, prepared by a facile “one-pot” process, exhibited high mechanical strength and heat resistance. The attractive characteristics of the composites, in addition to their transparency, include use of low-cost and nontoxic raw materials, easy scaling-up, and possible petroleum independence. The properties of the composites were ascribed to the strong interfacial interactions and the excellent dispersion of nanotubular clay.