High-performance Elastomers Research Articles

Syncretic of soft, hard, and rigid segments cultivate high-performance elastomer

In materials science, achieving polymers that possess both high strength and high toughness—traditionally seen as contradictory properties—remains a significant challenge. In this study, a poly (urethane-imide-urea) (PUIU) was synthesized, featuring soft, hard, and rigid segment groups alternately distributed along the main chain. By integrating a polyurethane (PU) prepolymer, urea, and imide, with the PU prepolymer acting as the soft segment to confer malleability, urea-formed hydrogen bonds serving as the hard segment to provide toughness, and imide acting as the rigid segment to enhance material strength. The synergistic effects of these elements result in an elastomer with outstanding strength (70.1 ± 2.6 MPa), high elongation at break (1813.9 ± 76.0 %), and high toughness (420.4 ± 22.3 MJ/m3). Furthermore, it demonstrates superior fatigue, tear, and wear resistance. Through a blend of simulation and experimentation, we uncover the reasons behind its high performance. This study demonstrates the feasibility of preparing an elastomer that combines softness, hardness, and rigidity, meanwhile, achieving a balance between strength and toughness, thereby offering valuable theoretical guidance for the integration of high strength and high toughness.

Upcycling of Carbon Fiber/Thermoset Composites into High-Performance Elastomers and Repurposed Carbon Fibers.

Recycling of carbon fiber-reinforced polymer composites (CFRCs) based on thermosetting plastics is difficult. In the present study, high-performance CFRCs are fabricated through complexation of aromatic pinacol-cross-linked polyurethane (PU-AP) thermosets with carbon fiber (CF) cloths. PU-AP thermosets exhibit a breaking strength of 95.5 MPa and toughness of 473.6 MJ m-3 and contain abundant hydrogen-bonding groups, which can have strong adhesion with CFs. Because of the high interfacial adhesion between CF cloths and PU-AP thermosets and high toughness of PU-AP thermosets, CF/PU-AP composites possess a high tensile strength of >870 MPa. Upon heating in N,N-dimethylacetamide (DMAc) at 100 °C, the aromatic pinacols in the CF/PU-AP composites can be cleaved, generating non-destructive CF cloths and linear polymers that can be converted to high-performance elastomers. The elastomers are mechanically robust, healable, reprocessable, and damage-resistant with an extremely high tensile strength of 74.2 MPa and fracture energy of 149.6 kJ m-2. As a result, dissociation of CF/PU-AP composites enables the recovery of reusable CF cloths and high-performance elastomers, thus realizing the upcycling of CF/PU-AP composites.

A fluorine-based strong and healable elastomer with unprecedented puncture resistance for high performance flexible electronics

There is usually a trade-off between high mechanical strength and dynamic self-healing because the mechanisms of these properties are mutually exclusive. Herein, we design and fabricate a fluorinated phenolic polyurethane (FPPU) elastomer based on octafluoro-4,4′-biphenol to overcome this challenge. This fluorine-based motif not only tunes interchain interactions through π−π stacking between aromatic rings and free-volume among polymer chains but also improves the reversibility of phenol-carbamate bonds via electron-withdrawing effect of fluorine atoms. The developed FPPU elastomer shows the highest recorded puncture energy (648.0 mJ), high tensile strength (27.0 MPa), as well as excellent self-healing efficiency (92.3%), along with low surface energy (50.9 MJ m−2), notch-insensitivity, and reprocessability compared with non-fluorinated counterpart biphenolic polyurethane (BPPU) elastomer. Taking advantage of the above-mentioned merits of FPPU elastomer, we prepare an anti-fouling triboelectric nanogenerator (TENG) with a self-healable, and reprocessable elastic substrate. Benefiting from stronger electron affinity of fluorine atoms than hydrogen atoms, this electronic device exhibits ultrahigh peak open-circuit voltage of 302.3 V compared to the TENG fabricated from BPPU elastomer. Furthermore, a healable and stretchable conductive composite is prepared. This research provides a distinct and general pathway toward constructing high-performance elastomers and will enable a series of new applications.

Hydrogenation of olefinic bonds in nitrile butadiene rubber on single-atom Pd1/CeO2−x catalysts with ultrahigh mass activity and stability

As pivotal high-performance elastomers, hydrogenated nitrile butadiene rubber (HNBR) was commonly manufactured by selective hydrogenation of nitrile butadiene rubber (NBR). Nevertheless, the high cost and poor stability of current noble metal-based catalysts seriously limit their large-scale applications. Herein, we report single-atom Pd supported by oxygen vacancies-rich CeO2−x nanorods (Pd1/CeO2−x) as a novel catalyst for selectively hydrogenating the NBR. As a result of strong interaction between single-atom Pd and CeO2−x support, the electrophilicity of Pd sites, and the nucleophilicity of olefinic bonds in NBR, the Pd1/CeO2−x show a very high hydrogenated degree of 97.6 %, an unprecedentedly high Pd mass activity of 93.9 gNBR gPd−1h−1, and outstanding cycling stability, which considerably outperform those for previously reported catalysts. Therefore, this work will promote the low-cost manufacture of HNBR and the exploration of single-atom catalysts for selective hydrogenation.

Filler effects inspired high performance polyurethane elastomer design: segment arrangement control.

Elastomers with high strength and toughness are in great demand. Previous research on elastomers focused mainly on the design of new chemical structures, but their complicated synthesis process and expensive monomers have restricted the practical application of these materials. Inspired by general filler effects, a strategy is proposed to remarkably enhance the mechanical properties of thermoplastic polyurethane (TPU) elastomers by designing the arrangement of hard/soft segments using traditional chemical compositions. By utilizing the synergetic effect of weak hard segments, normal TPU elastomers are upgraded into advanced elastomers. Combining experiments and simulations, it is demonstrated that a suitable sequence length can achieve considerably enhanced strength and toughness by maximizing the relative surface area of hard domains. Mixing the obtained elastomer with an ionic liquid can result in a durable ionogel sensor with balanced mechanical strength and ionic conductivity. This easy-to-implement strategy offers a new dimension for the development of high-performance elastomers.

Bio-inspired self-healing and anti-corrosion waterborne polyurethane coatings based on highly oriented graphene oxide

In the face of ubiquitous corrosion threats, the development of high-performance elastomer protective materials with active self-healing functions is extremely challenging and significant. We propose an approach by combining WPU elastomer with GO to create the multifunctional pearl layer structured polymers with interface hydrogen bonds. By crosslinking the polycaprolactone diol (PCL) chain with a hydrogen bond array, the elastomer with high mechanical strength, extensibility, elasticity, excellent damage resistance, and healing properties was successfully synthesized. The elastomer exhibits remarkable mechanical properties, including a tensile strength of 39.89 MPa, toughness value of 300.3 MJ m−3, and fracture energy of 146.57 kJ m−2. The enhanced damage resistance of the elastomer can be attributed to the decomposable hydrogen bond array as well as the strain-induced crystallization of PCL fragments, which effectively dissipate energy. Importantly, due to the reversibility of the hydrogen bonding array, the fractured WPU can easily heal and restore its original mechanical properties when subjected to heating at 50 °C. Moreover, the photothermal properties of GO enable the biomimetic polymer coating to achieve damage recovery after being irradiated with NIR for 30 s. The obtained biomimetic coating exhibits a highly oriented lamellar structure, thereby greatly enhancing physical barrier performance and anti-corrosion performance. Electrochemical impedance spectroscopy (EIS) shows that the impedance modulus is one order of magnitude higher than that of the blank coating. Additionally, scanning vibrating electrode (SVET) confirmed that the self-healing performance and protection effect of the biomimetic coating in 3.5 wt% NaCl solution were also reliable. This highly reliable biomimetic coating presents a revolutionary solution for creating multi-functional, high-performance smart material in harsh environments.

Wholly sustainable graft copolymers derived from cellulose, lignin, and hemicellulose for high-performance elastomers, adhesives, and UV-blocking materials

Sustainable elastomers derived from renewable biobased resources with excellent mechanical properties and varied functions are highly pursued to substitute traditional petroleum-based polymers yet challenging due to their limited macroscopic performance. In this work, we designed a series of wholly biobased cellulose-graft-poly(vanillin acrylate-co-tetrahydrofurfuryl acrylate) (Cell-g-P(VA-co-THFA) copolymer elastomers with cellulose as the rigid backbone, sustainable VA derived from lignin and soft THFA derived from hemicellulose as the hard and soft segments in the rubbery side chains. Moreover, the grafted side chains can be cross-linked to introduce an additional dynamic network structure via Schiff-base chemistry between the aldehyde and amino groups. The mechanical properties of Cell-g-P(VA-co-THFA) copolymer elastomers, including tensile strength, extensibility, elasticity, and toughness can be facilely manipulated by the VA/THFA feed ratio, cellulose content, and cross-linking density. These Cell-g-P(VA-co-THFA) copolymer elastomers are thermally stable and possess outstanding adhesion behavior and prominent UV-shielding performance. Besides dramatically enhanced mechanical properties, the cross-linked Cell-g-P(VA-co-THFA) counterparts exhibit remarkable shape memory behavior. This work provides a robust and convenient strategy for developing strong and versatile sustainable elastomers with different application demands by integrating different biomass feedstocks via elaborate molecular design.

Partially Biobased Block Copolymers Derived from Phenol and Butanol for High-Performance Elastomers and Pressure-Sensitive Adhesives

Partially Biobased Block Copolymers Derived from Phenol and Butanol for High-Performance Elastomers and Pressure-Sensitive Adhesives

High-Performance Branched Polymer Elastomer Based on a Topological Network Structure and Dynamic Bonding.

High performance has always been the research focus of elastomers. However, there are inherent conflicts among properties of elastomers, such as strength and toughness, strength and damping performance, strength and self-healing ability, etc. Herein, first, we synthesized a unique structure of the dangling chain containing proton donors and receptors. Then, we design and fabricate a kind of high-performance elastomer with a gradient distribution of a dangling chain and a dynamic bond structure. The dangling chains of different lengths intertwine with each other and self-assemble to form a "dense accumulation" structure driven by hydrogen bonds, and the elastomer exhibits special micro/nano scale aggregated states and microphase separation. The "dense accumulation" structure plays a vital role in the increase of mechanical properties. Meanwhile, under the joint action of a dangling chain and a dynamic bond, the damping performance and self-healing performance of the elastomer are greatly enhanced. High strength (27.5 MPa), toughness (121.9 MJ·m-3), 94.8% healing efficiency and outstanding damping performance (tan δ ≥ 0.4, high damping temperature range up to 144 °C) are simultaneously achieved beyond the current state-of-the-art. This topoarchitected polymer with a gradient distribution of dangling chains successfully solves the defects of conventional branched polymers in deteriorating their mechanical properties. This material design provides a new strategy for the development of high-performance structural and functional integrated elastomers.

Mechanically Ultra-Robust Elastomers Integrating Self-Healing and Recycling Properties Enable Information Encryption and Hierarchical Decryption.

Developing high-performance elastomers with distinctive features opens up new vistas and exciting possibilities for information encryption but remains a daunting challenge. To surmount this difficulty, an unprecedented synthetic approach, "modular molecular engineering", was proposed to develop tailor-made advanced elastomers. The customized hydrophobic poly(urea-urethane) (HPUU-R) elastomer perfectly integrated ultrahigh tensile strength (∼75.3 MPa), extraordinary toughness (∼292.5 MJ m-3), satisfactory room-temperature healing, high transparency, puncture-, scratch-, and water-resistance; and miraculously, its 0.20 g film could lift objects over 100 000 times its weight without rupture. Intriguingly, we unexpectedly discovered that the elastomers fluoresce brightly at the optimal excitation wavelength attributed to the "clusterization-triggered emission". Based on the gradient hydrophobicity and fluorescent properties of HPUU-R, a hierarchical information encryption/decryption mode was innovatively established. Using high-performance HPUU-R as a double encryption platform makes the information highly stable and persistent, thus providing a stronger guarantee for the encrypted information. More attractively, given the impressive recyclability and self-healing of HPUU-R, information encryption can be realized by using recycled elastomers, injecting new vitality into green and sustainable development.

High performance elastomer blend based on maleated natural rubber and hydroxyl-terminated polydimethylsiloxane

High performance elastomer blend based on maleated natural rubber and hydroxyl-terminated polydimethylsiloxane

Dynamic Aliphatic Polyester Elastomers Crosslinked with Aliphatic Dianhydrides.

Chemically crosslinked elastomers are a class of polymeric materials with properties that render them useful as adhesives, sealants, and in other engineering applications. Poly(γ-methyl-ε-caprolactone) (PγMCL) is a hydrolytically degradable and compostable aliphatic polyester that can be biosourced and exhibits competitive mechanical properties to traditional elastomers when chemically crosslinked. A typical limitation of chemically crosslinked elastomers is that they cannot be reprocessed; however, the incorporation of dynamic covalent bonds can allow for bonds to reversibly break and reform under an external stimulus, usually heat. In this work, we study the dynamic behavior and mechanical properties of PγMCL elastomers synthesized from aliphatic dianhydride crosslinkers. The crosslinked elastomers in this work were synthesized using the commercially available crosslinkers, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, and 1,2,3,4-cyclobutanetetracarboxylic dianhydride and three-arm hydroxy-telechelic PγMCL star polymers. Stress relaxation experiments on the crosslinked networks showed an Arrhenius dependence of viscosity with temperature with an activation energy of 118 ± 8 kJ/mol, which agrees well with the activation energy of transesterification exchange chemistry obtained from small molecule model studies. Dynamic mechanical thermal analysis and rheological experiments confirmed the dynamic nature of the networks and provided insight into the mechanism of exchange (i.e., associative or dissociative). Tensile testing showed that these materials can exhibit high strains at break and low Young's moduli, characteristic of soft and strong elastomers. By controlling the exchange chemistry and understanding the effect of macromolecular structure on mechanical properties, we prepared the high-performance elastomers that can be potentially reprocessed at moderately elevated temperatures.

Engineering of Chain Rigidity and Hydrogen Bond Cross-Linking toward Ultra-Strong, Healable, Recyclable, and Water-Resistant Elastomers.

High-performance elastomers have gained significant interest because of their wide applications in industry andourdaily life. However, it remains a great challenge to fabricate elastomers simultaneously integrating ultra-high mechanical strength, toughness, and excellent healing and recycling capacities. In this study, ultra-strong, healable, and recyclable elastomers are fabricated by dynamically cross-linking copolymers composed of rigid polyimide (PI) segments and soft poly(urea-urethane) (PUU) segments with hydrogen bonds. The elastomers, which are denoted as PIPUU, have a record-high tensile strength of ≈142MPa and an extremely high toughness of ≈527MJm-3 . The structure of the PIPUU elastomer contains hydrogen-bond-cross-linked elastic matrix and homogenously dispersed rigid nanostructures. The rigid PI segments self-assemble to generate phase-separated nanostructures that serve as nanofillers to significantly strengthen the elastomers. Meanwhile, the elastic matrix is composed of soft PUU segments cross-linked with reversible hydrogen bonds, which largely enhance the strength and toughness of the elastomer. The dynamically cross-linked PIPUU elastomers can be healed and recycled to restore their original mechanical strength. Moreover, because of the excellent mechanical performance and the hydrophobic PI segments, the PIPUU elastomers are scratch-, puncture-, and water-resistant.

Molecular Simulation and Experimental Study on the Damping and Aging Properties of 4010NA/Hydrogenated Nitrile Butadiene/Nitrile Butadiene Rubber Composites

AbstractThe effects of N‐isopropyl‐N′‐phenyl‐phenylenediamine (4010NA) content on the damping and aging properties of hydrogenated nitrile butadiene rubber (HNBR)/nitrile butadiene rubber (NBR) (abbreviated as H‐NBR) matrix are studied via molecular simulation and experiments. The effects of 4010NA addition on the damping and aging properties of H‐NBR are analyzed by molecular simulation using solubility parameters (δ), hydrogen bonds, free volume fraction (FFV), binding energy (Ebinding), hydrogen bond dissociation energy (ΔG), and mean square displacement (MSD). The damping, mechanical, and thermo‐oxygen aging properties of the 4010NA/H‐NBR composites are studied experimentally using infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The results indicate that 4010NA has good compatibility with HNBR and NBR, and the addition of 4010NA can effectively improve the damping properties of H‐NBR. When 4010NA is added at 32 phr, the composite has better damping properties, mechanical properties, and aging resistance, which provides a new insight for the construction of high performance elastomer composites.

Recyclable and self-healable elastomers with high mechanical performance enabled by hydrogen-bonded rigid structure

It is a challenge to develop high-performance elastomers while maintaining good recyclability and self-healable ability. Here, we synthesis the recyclable and self-healable elastomers with excellent overall mechanical properties by introducing rigid structures (benzoic acid groups and imidazole groups) into the side chains of the acrylate polymer. By virtue of the rigid structures, the mechanical performance of the elastomers is greatly improved. Further, reversible hydrogen bonds can be formed between the rigid structures, endowing the network structures with good dynamics and providing elastomers with superior capability of recycling and self-healing. As a result, the elastomers reach the strength of 20.4 MPa, Young's modulus of 79 MPa, toughness of 72 MJ/m3 and self-healing efficiency up to 98%. Besides, the samples after three times of recycling can still keep great mechanical properties.

Reversible Ratiometric Mechanochromic Fluorescence Switching in Highly Stretchable Polyurethane Elastomers with Ultratoughness Enhanced by Polyrotaxane

Multistimuli-responsive polymers containing mechanophoric motifs are highlighted as promising mechano-luminescent materials upon stretching via optical fluorescence signals. Herein, we report a distinct ratiometric force-induced fluorescence changes from green-emissive napthalimide stopper (donor) embedded in polyrotaxane (PR) cross-linkers to red-emissive rhodamine mechanophore (acceptor) incorporated in polyurethane (PU) backbones. The utilization of PR (1 wt %) can significantly enhance both toughness and stretchability in our targeted PU elastomers, where the mechanical work is largely dissipated by the ring-sliding motion and pulley effects of PR cross-linkers during stretching. Therefore, the simple soft robotic behavior with ultrafast shape memory and reversible ratiometric mechanochromic fluorescence switching by heating (60 °C) in PR-based PU films provide a distinctive strategy for the construction of molecular machines in the high-performance elastomers, which also offer pathways for practical applications of stimuli-responsive polymers in highly stretchable artificial muscles featuring both outstanding pulley effects on enhanced mechanical properties and novel signal variations of mechanochromic fluorescence simultaneously.

Dual-hard phase structures make mechanically tough and autonomous self-healable polyurethane elastomers

It is a key challenge to combine high mechanical strength and excellent autonomous self-healing properties in one elastomer to match the requirements of commercial applications. Chemical cross-linking or ordered crystalline domains can afford high mechanical strength but are often based on the cost of losing autonomous self-healing performance. To address this dilemma, a strategy involving dual hard-phase structures was developed to reinforce self-healing polyurethane elastomers, by introducing plant oil-derived aliphatic chains into the hard segments. The dangling fatty acids not only allow segmental motion of the hard domains but also suppress the crystallization within polyurethane soft segments. The tailored dual-hard phase structure and dynamic chain motion are responsible for outstanding mechanical properties (tensile strength to 21.8 MPa and toughness of 131.6 MJ m−3) and autonomous self-healing ability (∼100 % healing efficiency). Furthermore, a versatile mechanical robust flexible conductor is conveniently constructed with an auto-repair capability at ambient conditions. This work represents a molecular design paradigm of simultaneously integrating balanced mechanical strength, durability, and self-healing ability for high-performance elastomers that can find applications such as skin-inspired wearable devices.

Bis(2-hydroxyethyl) terephthalate from depolymerized waste polyester modified graphene as a novel functional crosslinker for electrical and thermal conductive polyurethane composites

Bis(2-hydroxyethyl) terephthalate (BHET) with active hydroxyl group derived from waste polyester can be applied as a polyurethane chain extender and an organic modifier for graphene oxide (GO). Herein, functionalized reduced GO (BHET-rGO) with single-layer was obtained by modifying GO with BHET, and then reduced by hydrazine hydrate. Waterborne polyurethane (WPU) nanocomposites with excellent mechanical performance, electrical and thermal conductivities were prepared via in-situ polymerization using the novel functional crosslinker BHET-rGO. Compared with the same content of rGO (7.41 wt%), WPU/BHET-rGO composites exhibit better properties containing equivalent BHET content. For example, BHET-rGO endows the WPU composites with higher tensile strength of 39.1 MPa (enhanced by 454.6%), electrical conductivity of 8×10−3 S/m (improved by 15 times), and thermal conductivity of 0.551 W m−1 K−1 (increased by 21.1%). Meanwhile, the sensitivity of WPU/BHET-rGO composite is well recovered during a large-strain stretching/shrinking cycle, and its resistance is stable under complex deformation. Besides, significant thermal stability ensures the durable of polyurethane to resist high-temperature. Hence, BHET-rGO have greater potential for fabricating high-performance elastomer composites, especially for conductive elastomer composites.

Manipulating the mechanical properties of cis-polyisoprene nanocomposites via molecular dynamics simulation

Attributed to the reinforcing effect of the NPs, filled natural rubber (NR) exhibits more excellent mechanical properties compared to pure natural rubber and has been attracting considerable scientific and technological attention. However, only a few studies have shown a systematical understanding of the structure-mechanics relation of filled natural rubber. Herein, a common strategy used to study the effects of the critical structural factors on strain-induced crystallization (SIC) and mechanical properties at the molecular level is to adopt molecular dynamic simulation (MD). Increasing the cross-linkage of the polymer matrix improves the entanglement degree, and the mechanical properties are reinforced by the high orientation of the polymer chains due to the high entanglement degree and the dissipation of energy due to the unentangling. Surprisingly, we find that the stress-strain behaviour of filled natural rubber is significantly manipulated by nanoparticle (NP) content, size and strength of interfacial interaction, evidenced by the increase of the chain orientation, SIC, and energy dissipated by NPs and polymer matrix, compared with the case of pure natural rubber. The underlying mechanism is the adsorption of the polymer by NPs, which leads to the orientation and crystallization of the polymer chains induced by NPs during the deformation process and energy dissipation through the slip of NPs and polymer chains. In general, this work demonstrates a detailed molecular-level structure-mechanics relation of filled natural rubber and provides some rational guidelines for experimentally designing and fabricating high-performance elastomer nanocomposites.

Tetramethylammonium hydroxide modified MXene as a functional nanofiller for electrical and thermal conductive rubber composites

Ti3C2 MXene with super conductivities can be used in polymer nanocomposites. However, MXene is difficult to disperse uniformly in polymer matrics due to their high surface energy, weakening the filler-rubber interfacial interaction. Herein, functional Ti3C2 (ƒ-Ti3C2) with single-layer and high surface charge loading was prepared by modifying Ti3C2 with tetramethylammonium hydroxide (TMAOH). A novel mechanical mixing and freeze-drying method was provided to fabricate styrene-butadiene rubber (SBR)/ƒ-Ti3C2 nanocomposites. Compared with the same content of Ti3C2 (3.85 wt%), SBR/ƒ-Ti3C2 exhibited better properties. For instance, ƒ-Ti3C2 endows the SBR composites with high tensile strength of 13.7 MPa (enhanced by 479%), electrical conductivity of 3.74 × 10-4 S/m (improved by 116%), and thermal conductivity of 0.659 W m-1·k-1. Besides, the wet skid resistance of SBR/ƒ-Ti3C2 nanocomposites was remarkably enhanced and the rolling resistance was decreased. Hence, ƒ-Ti3C2 has more potential for fabricating high-performance elastomer nanocomposites, especially for conductive elastomer composites.