High-performance Elastomers Research Articles

Oriented molybdenum disulfide-silica/hydrogenated nitrile butadiene rubber composites: Effects of nanosheets on mechanical and dielectric properties

A series of non-covalently functionalized molybdenum disulfide-silica (f-MoS2-SiO2) nanocomposites was prepared by an in-situ assembled method and used to fabricate the oriented molybdenum disulfide-SiO2/Hydrogenated Nitrile Butadiene Rubber (f-MoS2-SiO2/HNBR) composites. The characterization results show the synergistic dispersion between the functionalized molybdenum disulfide (f-MoS2) nanosheets and SiO2 nanoparticles. The addition of f-MoS2 nanosheets can improve the dispersion of fillers in the rubber matrix and weaken the filler network. The non-covalently functionalization improves the interface interaction between f-MoS2 nanosheets and the rubber matrix. Furthermore, the tensile strength of f-MoS2-SiO2/HNBR is 65.9% higher than that of SiO2/HNBR by adding 1.0wt% of f-MoS2. At the same time, the dielectric constant of f-MoS2-SiO2/HNBR is increased by 23.7% compared to SiO2/HNBR due to the micro-capacitor structure of parallel f-MoS2 nanosheets in the rubber matrix. Our work provides new ideas for the development of high-performance elastomer materials.

Synthesis and evaluation of biodegradable copolyimide elastomer with tunable mechanical and thermal properties

The copolymerization of biodegradable segments is one of the directions for preparing biodegradable elastomers. However, the introduction of biodegradable components usually leads to a sharp decline in the mechanical property and thermostability of materials, which hampers their further development and translation applications. Herein, we report a copolyimide elastomer with both rigid aliphatic/aromatic hard segments and elastic soft segment facilely synthesized via the straightforward melt-polycondensation based on a rationally designed aromatic bisimide diol, 1,4-butanediol, PEG1000, and 1,4-succinic acid. Such copolyimide elastomer shows advantages in both mechanical and biological properties compared with the traditional PBS-based elastomer. Moreover, the properties of such copolyimide elastomer can be facilely tuned via increasing or decreasing the mass ratio of hard segment to soft segment, and the mass ratio of the aromatic hard segment containing bisimide moieties to aliphatic hard segment, in which the higher content of hard segments and bisimide moieties are beneficial to improve the thermostability and mechanical properties of the elastomeric copolymer. Importantly, these elastomers can be biodegraded and are non-toxic to cells, showing sufficiently good biodegradability and cytocompatibility. Such elastomer is possibly considered to be a promising potential candidate for high-performance elastomers with biodegradability and cytocompatibility used in biomedicine materials and environmentally friendly materials.

Multinetwork Elastomer Using Covalent Bond, Hydrogen Bond, and Clay Plane Bond.

A high-performance elastomer was obtained by a multinetworking system of a covalent bond, hydrogen bond, and clay plane bond. By taking advantage of the characteristics of each cross-linking, the thermoplastic elastomer shows excellent compression set resistance, good flowability, and high tensile properties. The hydrogen bond gives flowability due to the bond cleavage under heating. The covalent bond contributes to the low compression set by prevention of polymer chain flow. Moreover, the clay plane bond affects the tensile properties by de-localization of the entire cross-link and increase of hysteresis energy between the clay plane surface and other cross-linking points. Furthermore, the self-healing properties and high heat resistance and recyclability were also observed.

High-Performance Elastomer from Trans-1,4 Copolymerization of Ethylene and Butadiene

High-Performance Elastomer from Trans-1,4 Copolymerization of Ethylene and Butadiene

Xanthate-modified nanoTiO2 as a novel vulcanization accelerator enhancing mechanical and antibacterial properties of natural rubber

Abstract With the emerging of sustainability, the fabrication of effective and eco-friendly agents for rubber industry has attracted extensive attention. In this study, a novel and nontoxic titanium dioxide-based vulcanization accelerator (xanthate-modified nanotitanium dioxide (TDSX)) with excellent antibacterial performance, for the first time, was synthesized under the catalyst of ceric ammonium nitrate. Notably, the thermal stability of xanthate was greatly enhanced after being grafted on titanium dioxide (TiO2) nanoparticles, in which the activation energy was increased from 6.4 to 92.5 kJ/mol, enabling the obtained TDSX with multiple functions, mainly consisting of fabulous vulcanization-promoting effects, reinforcing effects, antibacterial properties, and anti-ultraviolet aging effects for natural rubber (NR). Simultaneously, the TDSX can be effectively and uniformly dispersed in the rubber matrix along with the developed interface interaction between TDSX particles and rubber matrix. Compared to the traditional accelerators 2-mercaptobenzothiazole (M) system, the tensile strength and the tearing strength of NR/TDSX was improved by 26.3 and 40.4%, respectively. Potentially, our work for preparing green vulcanization accelerator can provide a new design strategy for multifunctional high performance elastomer materials.

Understanding the Coupling Effect between Lignin and Polybutadiene Elastomer

From an environmental and economic viewpoint, it is a win–win strategy to use materials obtained from renewable resources for the production of high-performance elastomer composites. Lignin, being a renewable biomass, was employed as a functional filler material to obtain an elastomer composite with a higher degree of mechanical performance. In the presence of a suitable coupling agent, an elevated temperature was preferred for the reactive mixing of lignin with polybutadiene rubber (BR). It is quite fascinating that the mechanical performance of this composite was comparable with carbon black-filled composites. The extraordinary reinforcing behavior of lignin in the BR matrix was understood by an available model of rubber reinforcement. In rubber composite preparation, the interfacial interaction between polybutadiene rubber and lignin in the presence of a coupling agent enabled the efficient dispersion of lignin into the rubber matrix, which is responsible for the excellent mechanical properties of the rubber composites. The rubber composites thus obtained may lead to the development of a sustainable and cost-effective end product with reliable performance. This novel approach could be implemented in other type of elastomeric materials, enabling a genuine pathway toward a sustainable globe.

Natural Rubber Latex Reinforced by Graphene Oxide/Zwitterionic Chitin Nanocrystal Hybrids for High-Performance Elastomers without Sulfur Vulcanization

Natural rubber (NR) demonstrates excellent mechanical strength and tensile elasticity after vulcanization. However, the sulfur curing system will generate many problems, including the usage of toxi...

Well-Defined Fluorinated Copolymers: Current Status and Future Perspectives

Well-defined fluoropolymers exhibit unique properties such as excellent oil and water repellency, satisfactory thermal stability, a low refractive index, and low surface energy. The origin of these properties is attributed to the presence of a strong electronegative and low polarizable fluorine atom in the backbone of such polymers, which leads to a strong C–F bond (with a high bond dissociation energy of 485 kJ mol–1). Because of these features, these polymers have found applications as functional coatings, thermoplastics, biomedical items, separators, and binders for Li ion batteries, fuel cell membranes, piezoelectric devices, high-quality wires and cables, and so forth. Usually, fluoropolymers are synthesized by the conventional radical (co)polymerization of fluoroalkenes, which leads to the production of (co)polymers with an ill-defined end group, uncontrolled molar mass, and high dispersity values. In the last two decades, significant developments of various reversible deactivation radical polymerization (RDRP) techniques have helped the design of macromolecular architectures (including block, graft, star, and dendrimers) on demand. However, for relevant new applications, well-defined fluoropolymers with controlled macromolecular architectures (e.g., block copolymers as thermoplastic elastomers and electroactive polymers or graft copolymers for fuel cell membranes) are required. Several RDRP methods, developed in the last two decades, have paved the way for the synthesis of (co)polymers with well-defined molar mass, dispersity, chain end-functionality, and macromolecular architectures. Some of these RDRP techniques have been successfully employed for the synthesis of well-defined fluorinated copolymers. These techniques include iodine-transfer polymerization (ITP), reversible addition–fragmentation chain-transfer (RAFT) polymerization, organometallic-mediated radical polymerization (OMRP), and, to a lesser extent, nitroxide-mediated polymerization (NMP). Impressive control of the molar mass parameters of the fluoropolymers synthesized via these techniques also encouraged the researchers to combine these techniques with other postpolymerization strategies, leading to innovative novel polymeric materials. Thus, synthesized well-defined fluoropolymers exhibited a unique combination of properties (such as excellent weather resistance, high thermal/chemical/aging resistance, morphological versatility, and a low dielectric constant/flammability/refractive index). These led to the application of such developed materials in various high-technology applications such as high-performance elastomers, coatings for marine antifouling applications, fluorinated surfactants, fuel cell membranes, and gel polymer electrolytes for Li ion batteries. Newer advances in the field of polymer synthesis techniques are the need of the hour in order to synthesize more advanced fluorinated materials which may change the use of such polymers in engineering and biomedical fields in the current century. However, it should be kept in mind that success in this regard shall heavily depend on a deeper understanding of the polymerization process and structure–activity relationships.

Rational design for enhancing mechanical and conductive properties of Ti3C2 MXene based elastomer composites

Herein, we propose a novel Ti3C2 grafted SiO2 (Ti3C2-g-SiO2, 21.2% loading weight content of SiO2) multifunctional filler with an average thickness of 10 ± 2 nm, which is skillfully prepared via an in-situ growing approach, to blend with styrene-butadiene rubber (SBR) and create high-performance elastomer composites. Thanks to the incorporation of SiO2, the Ti3C2-g-SiO2 not only disperses better (a uniform state) than Ti3C2 in the rubber matrix but also obtains innumerous nano protuberances on its surface to constrain more rubber chains than Ti3C2, significantly improving the interfacial interaction. Therefore, by comparison of the unfilled SBR sample, the mechanical strengths of the prepared Ti3C2-g-SiO2 filled SBR sample are dramatically enhanced, including tensile strength (enhanced by 244%, from 4.09 to 14.1 MPa) and elongation at break (enhanced by 93%, from 271 to 522%). More importantly, the Ti3C2-g-SiO2 filled SBR sample featuring excellent electrical (8.96 × 10−4 S m−1) and thermal conductivities (0.449 W m−1 k−1), which could exceed the reduced graphene oxide filled SBR sample.

Rational design of a novel NDI-based thermoplastic polyurethane elastomer with superior heat resistance

Thermoplastic polyurethanes (TPUs) hold immense developing potential in engineering products. However, the poor heat-resistance property restricts its large-scale application. 1,5-Naphthalene diisocyanate (NDI) is a rigid aromatic diisocyanate with highly symmetric structure, and the synthesized NDI-based polyurethane has been proved to perform excellent thermal dynamic mechanical properties. In view of this, the development of a new TPU based on NDI and poly(tetramethylene ether) glycol (PTMG) proves to be important. To our best knowledge, it is the first investigation to focus on NDI-based TPU with high heat resistance for 3D printing materials. Moreover, the structure-property behavior of variations in the molecular weight of soft segment (SS) and the content of hard segment (HS) is investigated. It is found that, as the concentration of HS becomes higher or SS becomes shorter, the hydrogen bonding interaction becomes stronger, together with the glass transition temperature, storage modulus, softening temperature and hardness becoming higher. Meanwhile, the peak value of tan δ becomes lower with a higher HS content or longer SS. The results of WAXD indicate the NDI-based TPU exhibit strain-induced crystallization and orientation after deformation, which reinforces the TPU. The results of SAXS and AFM show HS are well-dispersed in the matrix and in nanoscale. This NDI-based TPU is superior to recently reported high-performance TPU materials in terms of heat resistance and can be used as 3D printing materials. The exceptional comprehensive properties, especially high temperature resistance of the proposed NDI-based TPU, provide a new horizon in the development of high-performance elastomer and will contribute to better design of NDI-based TPU.

Exploiting Synergistic Experimental and Computational Approaches to Design and Fabricate High-Performance Elastomer

Silicone elastomers (SRs) are of great scientific and technological importance due to their resistance to low temperatures. However, the glass transition temperature (Tg) of existing SRs is not low...

Ultra-small SiO2 nanoparticles highly dispersed on non-covalent functionalized reduced graphene oxide nanoplatelets for high-performance elastomer applications

Encouraged by results of theoretical simulations, we used non-covalently functionalized reduced graphene oxide (NFRGO) nanoplatelets as a substance to grow in situ SiO2 nanoparticles. A series of hierarchical-structured NFRGO-SiO2 nanocomposites were prepared and applied to reinforce hydrogenated nitrile butadiene rubber (HNBR). Ultra-small SiO2 nanoparticles were obtained and highly dispersed on the NFRGO due to the non-covalent functionalization of cetyltrimethylammonium bromide (CTAB). A small amount (1 wt%) of NFRGO incorporated into the SiO2 improves both the static and the dynamic mechanical properties as well as the viscoelastic behavior of NFRGO-SiO2/HNBR composites due to the weak hybrid filler network and the strong filler-rubber interfacial interaction. Significantly, the reinforcement index (RI) of 1%-NFRGO-SiO2/HNBR is 150.7% and 53.9% higher than those of SiO2/HNBR and the HNBR composites filled by a mixture of 1 wt% of RGO and SiO2 (1%-RGO-SiO2/HNBR), respectively. Our work highlights the rational design of hierarchical nanocomposites for reinforcing high-performing HNBR composites.

An Ultrastrong and Highly Stretchable Polyurethane Elastomer Enabled by a Zipper-Like Ring-Sliding Effect.

Elastomers with excellent mechanical properties are in substantial demand for various applications, but there is always a tradeoff between their mechanical strength and stretchability. For example, partially replacing strong covalent crosslinking by weak sacrificial bonds can enhance the stretchability but also usually decreases the mechanical strength. To surmount this inherent tradeoff, a supramolecular strategy of introducing a zipper-like sliding-ring mechanism in a hydrogen-bond-crosslinked polyurethane network is proposed. A very small amount (0.5 mol%) of an external additive (pseudo[2]rotaxane crosslinker) can dramatically increase both the mechanical strength and elongation of this polyurethane network by nearly one order of magnitude. Based on the investigation of the relationship between molecular structure and mechanical properties, this enhancement is attributable to a unique molecular-level zipper-like ring-sliding motion, which efficiently dissipates mechanical work in the solvent-free network. This research not only provides a distinct and general strategy for the construction of high-performance elastomers but also paves the way for the practical application of artificial molecular machines toward solvent-free polyurethane networks.

Toughening natural rubber by the innate sacrificial network

Although natural rubber (NR) is widely used in rubber industry, the reason why NR owns superior mechanical properties still remains as an open question. Previous studies mainly focus on the molecular chain structure investigation of NR (for example, highly cis stereoregularity) and neglect the importance of non-rubber components (NRC) to strength and toughness. Herein, we use transmission electron microscopy to clearly observe the network constructed by NRC in the NR matrix. Such network is considered as an innate sacrificial network. Upon deformation, the innate sacrificial network preferentially ruptures to dissipate energy, leading to improvement in toughness of NR. Moreover, some NRC can act as the crosslinking points in the NR matrix, which further improve the strength and toughness. Therefore, our group ascribes the excellent strength and toughness of NR to the contribution of sacrificial network constructed by NRC. This work provides another understanding for the relationship among structure, components, and properties of NR, which can further act as a design strategy for high performance elastomer materials.

The Promising Future of Fluoropolymers

AbstractThis article aims at showing the usefulness of fluoropolymers (FPs), supplying an overview of their synthesis, applications, and recycling. FPs are currently prepared by conventional radical polymerization of fluoromonomers. These specialty polymers, produced in low tonnage compared to that of commodity ones, display outstanding properties, such as chemical, oxidative, and thermal resistances, low refractive index, dissipation factor, permittivity, and water absorptivity, and excellent weatherability and durability. More recent routes for their preparations are suggested, controlled or not, leading to random, alternated, block, graft, dendrimers, or multiarm copolymers, as well as their applications ranging from coatings to high performance (thermoplastic) elastomers, energy related‐materials (e.g., fuel cell membranes, components for lithium‐ion batteries, electroactive devices, and photovoltaics) to original and surfactants, optical devices, organic electronics, composites, and shape memory polymers.

Preparation of multi-temperature responsive elastomers by generating ionic networks in 1,2-polybutadiene using an anionic melting method.

The development of reversible networks in elastomers provided unique inspiration for the design of advanced polymers with excellent properties. In this paper, we adopted an anionic melting method to introduce carboxylate groups into 1,2-polybutadiene (1,2-PB), using maleic anhydride as a modifier, and sodium hydride (NaH), calcium hydride (CaH2), and lithium aluminum hydride (LiAlH4) as metallization reagents. Na-Based, Ca-based, and Li/Al-based ionic bond networks were constructed in the covalently crosslinked 1,2-PB. The effects of the electronegativity and valence of the metal ions on the strength and reversible temperature of the ionic network were studied. Payne effect was shown by rheological tests, demonstrating the interactions between the ionic networks and rubber chains. The reforming temperature for these ionic networks was studied by stress-relaxation analysis, and shape memory experiments were performed based on these temperatures. This concept provides novel inspiration for the design of high-performance and temperature-adaptive elastomers.

Iron ion cluster-OH coordination as high-efficiency sacrificial bond for reinforcement of elastomer

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.

Novel reinforcement behavior in nanofilled natural rubber (NR) / butadiene-acrylonitrile rubber (NBR) blends: Filling-polymer network and supernanosphere

It is worthy to understand the reinforcement of nanoparticle in rubber blends in application prospect because of its dispersion and distribution. The dielectric and mechanical methods were used to study the reinforcement impact of the carbon black (CB) in NR/NBR blends, based on the percolation and reinforcement theories. Results indicated that the CB aggregates had dispersed in NBR phase and the reinforcement effect was dependent on both CB concentration and the rubber blend ratio. It has been observed that the CB particles diffused and filling in the NBR reinforcement network at 50:50 ratio of NR/NBR blend, CB particles assembled as supernanosphere at 70:30 ratio and CB particles wrapped/covered supernanosphere at 90:10 ratio. The highest elongation at break was observed in 90:10 ratio of NR/NBR.The new observations are conducive to providing guidelines for producing high mechanical performance and low conductivity percolation threshold elastomers via a maturely industrial method for a wide range of application.

Selectively catalytic hydrogenation of styrene-butadiene rubber over Pd/g-C3N4 catalyst

Hydrogenated styrene butadiene rubber (HSBR) is a high-performance elastomer with wide applications. Herein, Pd/g-C3N4 catalysts were successfully prepared via a simple chemical reduction method and applied for the selective hydrogenation of SBR. The results indicate that Pd nanoparticles are well dispersed and stably anchored on g-C3N4 due to the coordination of Pd and N, and the catalyst exhibits a superior activity with the hydrogenation degree of 95% and 100% selectivity to CC bonds of butadiene units in SBR at mild conditions. The excellent catalytic performance of Pd/g-C3N4 is attributed to: 1) the typical 2D-layered nanosheet structure can effectively eliminate the polymers diffusion effect; 2) the nitrogen-rich property of g-C3N4 itself is beneficial to anchoring Pd nanoparticles to obtain small-sized, well-dispersed and stable Pd catalyst; and 3) the π-π stacking interaction between the phenyl group in SBR and tri-s-triazine units of g-C3N4 allows SBR to be readily adsorbed on active sites.

Elastomer Reinforced with Innate Sulfur-Based Cross-Links as Ligands.

Although the incorporation of sacrificial bonds into an elastomer is an effective way to provide a combination of high strength and high fracture toughness, this method normally involves complicated chemical processes. The coordination between metal ions and polysulfides has been documented. However, the potential of polysulfide structures in vulcanizates as ligands has long been neglected. Using innate sulfur-based cross-links, we show how weak and nonpolar elastomers achieve significant reinforcement without modification of the backbone. By simply soaking vulcanizates into solutions containing metal ions, dual ions are simultaneously introduced into the vulcanizate to generate coordinations with different bond strengths, resulting in an unprecedented high modulus. Overall, this work presents a universal yet high-efficiency reinforcing strategy to prepare high-performance elastomers without additional chemical modifications, which should promote comprehensive research and industrial application of sacrificial bond strategies for elastomers.