Thermoplastic Elastomers Research Articles

Functional Thermoplastic Polyurethane Elastomers with α, ω-Hydroxyl End-Functionalized Polyacrylates.

Thermoplastic polyurethane (TPU) is an essential class of materials for demanding applications, from soft robotics and electronics to medical devices and batteries. However, traditional TPU development is primarily relied on specific soft segments, such as polyether, polyester, and polycarbonate polyols. Here, a novel method is introduced for developing TPU elastomers with enhanced performance and superior functionalities compared to conventional TPUs, achieved through the use of α,ω-hydroxyl end-functionalized polyacrylates. This approach involves a defect-free synthesis of α,ω-hydroxyl end-functionalized polyacrylates through visible-light-driven photoiniferter polymerization. By strategically blending these functionalized polyacrylates with conventional polyols, TPUs that exhibit exceptional toughness and notable self-healing capabilities, traits rarely found in existing TPUs are engineered. Furthermore, incorporating photo-crosslinkable acrylic monomers has enabled the creation of the first TPU with superior elastomeric properties and photopatterning capabilities. This approach paves the way for a new direction in polyurethane engineering, introducing a novel class of soft segments and unlocking the potential for a wide range of advanced applications.

Lithium Plating Using a Thermoplastic Vulcanizate Electrolyte

Lithium metal anodes have generated significant interest due to their high theoretical capacity. However, issues such as dendrite growth or cell failure caused by lithium loss with either liquid electrolytes or solid polymer electrolytes (SPEs) have hindered its widespread commercialization. In this work, we report on the electrochemical characterization of symmetric Li-SPE-Li cells made with a thermoplastic vulcanizate electrolyte, PCl:HNBR LiTFSI. Full plating of the lithium metal (LiM) electrode was achieved at 100 μA.cm−2 in pressurized pouch cells. This was confirmed ex situ using scanning electron microscopy which showed the absence of dendrites. The Sand equation was employed at higher current densities to determine that the lithium diffusion coefficient at 60 °C is 1.7 × 10−8 cm2.s−1. The calculated threshold current density j* was approximately 200 μA.cm−2. The determination of the theoretical current density limit may provide critical information for the understanding of the behavior of cathode materials during cycling with lithium metal. Cell failure at high polarization or from short circuiting was experimentally confirmed in symmetric Li-Li cells where 100 cycles were performed at a current density below j* with 0.1 mAh.cm−2 of charge per cycle, while 0.5 mAh.cm−2 of charge rapidly induced cell failure.

The influence of myrcene on anionic copolymerization of 1,3-pentadiene and styrene

C5-dienes including 1,3-pentadiene (PD) and isoprene (IP) as by-products of naphtha cracking are important industrial raw materials for the production of thermoplastic elastomers, synthetic rubber and resins. The research on living anionic polymerization (LAP) of myrcene (MY) is also of great significance for the development of new bio-based materials and products. Focusing on the optimal utilization of C5 resources and the high-value utilization of biomass resources and the realization of green chemical production, this article reports the synthesizing of a novel terpolymer by LAP of PD, styrene (ST) and the biomass monomer MY. The discovery of the alternating sequence structure of ST and PD inspires us to further explore the development of copolymers containing this unique sequence structure. The special long branched side chain of MY and its low glass transition temperature are also conducive to the synthesis of new integrated rubbers. The 1H NMR tracking analysis indicates that the polymerization pattern changes from alternating sequence to gradient block sequence with the increase of MY content. Combined with FTIR analysis, the PD monomeric units are mainly trans-1,4 structure and MY monomeric units are predominant cis-1,4 structure. Considering the extremely high polymerization activity of MY compared to ST and PD, the copolymerization rate is significantly dependent on the concentration of the PD monomer. Despite this, due to the interactions between ST and PD ([ST¦PD] intermediate), ST still tends to form alternating segments with PD. The ternary copolymerization can be viewed as a “binary gradient copolymerization” of [ST¦PD] and MY (rMY > r[ST¦PD]).

Graphene Nanoplatelet Induced Microphase Separation in Poly(ether-block-amide)s

The inclusion of graphene nanoplatelets (GNP) in segmented block copolymers offers a route to manipulate microphase separation for tailoring the mechanical properties of thermoplastic elastomers. GNP loading, lateral size, surface chemistry, interactions with the copolymer hard (HS) and soft (SS) segments and the relative ratio of HS:SS determine the mechanical properties achievable. To test this hypothesis, two different GNPs with similar surface chemistry but which differed in lateral dimensions by one order of magnitude (GNP1, ∼2μm and GNP2, ∼20μm) were melt mixed with three different poly(ether-block-amide)s (PE-b-A)s with variable HS and SS content from high to low. The inclusion of the larger lateral sized GNP2 had a more pronounced effect on PE-b-A morphology as it was more effective at hindering SS chain mobility resulting in microphase separation and suppression of the glass transition temperature (Tg) of the PE-b-A with the largest SS content. At low loadings GNP2 preferentially locates to the HS region, inducing reorganisation of this phase resulting in increased microphase separation. Strain induced crystallisation (SIC) phenomena were also observed for the lowest HS content PE-b-A, behaviour not evident for the PE-b-A with the largest HS content as the SS are not long enough to allow SIC. Inclusion of GNP2 to the PE-b-A with the largest HS content resulted in the largest increase in Young’s modulus (E) of 46%, tensile strength (σ) of 37% and elongation at break (ε) of 53% relative to the unfilled polymer.

Micromechanical insights for enhancing the rebound resilience of sealing materials based on TPV

Thermoplastic vulcanizate (TPV) with fascinating high elasticity has been received the ongoing research attention in the application of sealing system for the engineering machine. However, there still exists one factor, the plastic strain of plastic matrix adjacent to rubber particles in equatorial direction, which has greatly inhibited the resilience improvement of TPV. Traditional in-situ online experiments could not accurately obtain and quantify the stress-strain evolution behavior of heterogeneous rubber-plastic materials, crucial for resilience. Herein, one kind of TPV based on polyamide thermoplastic elastomer (TPAE) and ethylene-propylene-diene monomer (EPDM) with outstanding rebound resilience has been fabricated via introducing the interfacial compatibilization reaction and reinforcing particles during the melt-reactive blending. One three-dimensional representative volume element (3D-RVE) model has been established to analyze the deformation mechanism of such designed TPV in this work compared with that for TPV based on polypropylene (PP) and EPDM. By analyzing the forces on the RVE mesh units, it could reveal that the TPAE matrix exhibited more uniform stress transfer behavior at the thin ligament, and the recovery behavior of TPV matrix mainly occurred at the thin ligament. This work would provide important value for the preparation of new high elastic TPV materials from a microscopic level.

Cellulose nanofibers enabled strong and flexible plant-derived thermoplastic polyester elastomer foams for high-performance thermally insulating applications

Flexible thermal insulation materials have garnered significant attention owing to the proliferation of flexible electronic devices and their diverse application environments. Plant-derived thermoplastic polyester elastomer (TPEE) foams emerge as promising candidates in the field of flexible thermal insulation. However, inevitable shrinkage behavior of TPEE foams would result in reduced porosity and inferior thermal insulation performance. Hence, a pioneering approach is proposed wherein cellulose nanofibers (CNF) are integrated into TPEE matrixes, complemented by microcellular foaming, aimed at mitigating shrinkage process and enhancing thermal insulation properties. In this work, the relaxation behavior of nanocomposite, corresponding to shrinkage process, has been elucidated through dynamic mechanical analysis. It's found that entanglement of CNF could heighten the internal friction with TPEE molecular chains, coupled with establishment of hydrogen bonds, thereby curbing relaxation phenomena and facilitating the attainment of foams with enhanced and stable porosity. The shrinkage ratio of TPEE/CNF composite foam could be reduced by 20 % without compromising the final porosity. The thermal conductivity would decrease to 37.9 mW/m·K for the TPEE/CNF composite foam with the higher porosity of 0.947. Moreover, the utilization of CNF presents a novel avenue for fabricating TPEE/CNF nanocomposite foams endowed with flexibility, lightweightness, increased porosity, and reduced thermal conductivity.

The effect of calcite on the mechanical, morphological and thermal properties of virgin and recycled thermoplastic copolyester elastomer composites

The effect of calcite on the mechanical, morphological and thermal properties of virgin and recycled thermoplastic copolyester elastomer composites

Microstructured CNTs/Cellulose Aerogel for a Highly Sensitive Pressure Sensor.

Flexible sensors have been applied in human health monitoring and biomedical research, but producing high-performance piezoresistive sensors at low cost is still challenging. To address these shortcomings, we proposed a microstructured carbon nanotube (CNT)/cellulose aerogel-based pressure sensor. The sensor consists of three parts, i.e., cellulose/poly(vinyl alcohol)/CNT aerogel-based sensing layer and top and bottom thermoplastic polyurethane elastomer (TPU)/silver nanowire (Ag NW) nanofiber electrode. The aerogel is fabricated using a simple freeze-drying method and an easy electrospinning method to obtain the nanofiber-based electrode. Two TPU/Ag NW nanofiber electrodes sandwiched the aerogel with a microstructure in the middle. Benefiting from the microcone and micropore structures on the nanofiber electrode, the assembled sensors show a high sensitivity of 66.4 kPa-1, a significant detection boundary of 50 kPa, and an excellent response speed of 10 ms. The high sensing performance enables the sensor to monitor physiological signals, Morse code interactions, and gesture recognition. With the help of machine learning, the success rate of gesture recognition is as high as 98.8%. The preparation of this pressure sensor based on an aerogel shows excellent health and environmental monitoring potential as an artificial skin.

Preparation of Self-healing Thermoplastic Polysiloxane-Polyurea/Polyether-Polyurea Elastomer Blends with a Co-continuous Microphase Structure and In-Depth Research on Their Synergistic Effects.

Polymer blending has been an important method to create materials with specific properties that have synergistic effects. However, there are few reports on the mechanism of synergistic effects. It is well known that it is quite difficult to obtain ideal blends composed of nonpolar organosilicon polymers and polar polymers. In this paper, thermoplastic polyurea elastomer blends with a co-continuous microphase structure consisting of polysiloxane-polyurea (PDMS-PUA), polyether amine-polyurea (PEA-PUA), and compatibilizer PDMS-PUA-grafted PEA-PUA (PDMS-PUA-g-PEA-PUA) were prepared for the first time. For the first time, introduction of polysiloxane does not sacrifice mechanical properties of thermoplastic polyurea elastomers. For example, the tensile strength of the elastomer blend with 30 wt % PDMS-PUA content reached 25.7 MPa, which is higher than those of PEA-PUA and PDMS-PUA. The blends also show typical outstanding characters such as exceptional heat and water resistance. The mechanism of the synergistic effect on mechanical properties is revealed based on in-depth studies on mutual interphase interaction. In situ variable temperature infrared spectroscopic analysis (VTIR) shows that compatibilization facilitates the construction of a denser hydrogen bonding network at the blend interface, which is thought to play a key role in the co-continuous microphase structure. Microscopic morphological characterization shows that PDMS-PUA and PEA-PUA phases are deformed and oriented together during the stretching process, thus jointly resisting external forces. Moreover, the blends show an exceptional self-healing ability due to their strong and reversible hydrogen bonding network.

Robust and Highly Stretchable Ionic Conductive Thermoplastic Elastomers Prepared via Easily Scalable Melt Transesterification and Melt Blending for Flexible Triboelectric Nanogenerators

In recent years, the rapid advancement of self‐powered wearable electronic devices has propelled the research focus toward flexible electrodes for single electrode triboelectric nanogenerators (STENG). However, there is currently a lack of reported methods for large‐scale preparation and high‐efficiency molding of these flexible electrodes. In this study, PBAT‐co‐PEG/NaSCN blends‐based ionic conductive thermoplastic elastomer (ICTE) are successfully prepared by initially conducting melt transesterification, followed by melt blending. The STENG, featuring an ICTE electrode, exhibited a remarkable open‐circuit voltage of 50 V, short‐circuit current of 460 nA and charge transfer of 16 nC. With the aid of Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC), the conduction mechanism of ICTE is elucidated. Due to good fluidity and processing performance, bars of ICTE suitable for mechanical properties test could be conveniently prepared via injection molding, which demonstrates the tensile strength and elongation, 13 MPa and 2500%, respectively. A 4 × 4 cm2 STENG fabricated with ICTE electrode could not only have good energy‐harvesting performance but also could be used in a sensor to sense the motion detection. The ICTE, with its simple and environmentally friendly preparation process and high‐efficiency molding, exhibits a promising prospect in the large‐scale preparation and application of flexible STENG.

A new strategy applying ternary blends of modified natural rubber with fluoroplastic and fluorocarbon elastomer for high-performance thermoplastic vulcanizate

High-performance thermoplastic vulcanizates (TPVs) are a class of specialty polymers with exceptional mechanical properties, rubber-like elasticity, excellent processability and recyclability, and an excellent price-performance ratio that make them ideal for a variety of industrial applications. In this work, a successful method of creating high-performance TPV using a ternary blend of poly(methyl methacrylate) modified natural rubber (MGNR), poly(vinylidene fluoride) (PVDF), and fluorocarbon elastomer (FKM) was employed. Combining NR known for its exceptional rubber elasticity and resilience, with fluoropolymers, known for their exceptional chemical resistance and thermal stability, resulted in materials with a synergistic blend of properties. The developed PVDF/FKM/MGNR blend showed higher elasticity, tensile strength, and elongation at break than PVDF/FKM and PVDF/MGNR blends because the ternary blend had greatly improved phase morphology and compatibility between the three phases. The domain size in the ternary blend was smaller than 150 nm. The ternary blends also exhibited excellent thermal properties, where melting and crystallization temperatures were reduced significantly with MGNR due to possible dipole-dipole interactions. At the same time, the oil resistance and shape memory behavior of PVDF/FKM/MGNR were improved at an appropriate blend ratio. The ternary TPVs demonstrated good shape fixities (90–100 %) and shape recoveries (70–80 %). This research offers valuable insights into the design of high-performance thermoplastic elastomers based on natural rubber, which have excellent mechanical properties, solvent resistance, and potential for intelligent and lightweight application.

Statistical modeling and optimization of process parameters for additive manufacturing of styrene–ethylene–butylene–styrene block copolymer parts using solvent cast 3D printing technique

AbstractAdditive manufacturing of thermoplastic elastomers is challenging using fused deposition modeling due to their high melt viscosity, low column strength, and poor fusion among layers. Solvent‐cast 3D printing (SC‐3DP) is an efficient alternative to successfully 3D print such materials. However, selection of suitable 3D printing parameters is crucial to realize parts with optimum physicomechanical properties. In this work, statistical modeling and SC‐3DP parameter optimization for styrene–ethylene–butylene–styrene (SEBS) block copolymer were performed. The effect of 3D printing process parameters on shrinkage, relative density, and tensile strength was analyzed using response surface methodology. Experiments were planned as per central composite design and analysis of variance was performed to evaluate the significant parameters. SEBS content in the polymer solution significantly affected the shrinkage of SC‐3DP samples. Moreover, relative density and tensile strength were significantly affected by print speed and layer height. A significant interaction between print speed and layer height was also noticed for tensile strength and relative density of printed samples. Multi‐objective optimization using genetic algorithm was also performed to minimize shrinkage and maximize relative density and tensile strength. Finally, a case study was conducted comparing the physicomechanical properties of SC‐3DP samples printed at optimized process parameters and compression molded samples.Highlights Statistical models were developed using response surface methodology. Genetic algorithm based multi‐objective optimization was performed. Optimum solvent‐cast 3D printing (SC‐3DP) process parameters were determined.

Tackling the Thermodynamic Stability of Low-Ceiling Temperature Polymers for the Preparation of Tough and Chemically Recyclable Thermoplastic Polyurethane-Urea Elastomers

Tackling the Thermodynamic Stability of Low-Ceiling Temperature Polymers for the Preparation of Tough and Chemically Recyclable Thermoplastic Polyurethane-Urea Elastomers

Grafting of nonpolar polyisoprene as midblock and polar polylactide as outer block onto cellulose to produce bio-based thermoplastic elastomers

Sustainable cellulose-graft-diblock copolymers (cellulose-graft-polyisoprene-block-polylactide, MCC-g-PI-b-PLLA, MCC was chemically-modified microcrystalline cellulose) were designed and delicately synthesized for the first time by a mild and facile procedure via combining ring-opening polymerization and reversible addition-fragmentation chain transfer polymerization techniques, which conquered the difficulties in synthesis due to the distinct chemical properties among the MCC backbone, PI and PLLA blocks. Two separate glass transition temperatures were detected for MCC-g-PI-b-PLLA copolymers by differential scanning calorimetry, indicative of microphase separation, consistent with small-angle X-ray scattering and atomic force microscopy measurements. The α-form crystals of PLLA outer blocks were revealed by wide-angle X-ray diffraction measurement. The monotonic and step-cyclic tensile tests revealed that the mechanical property could be tuned by changing the molecular mass of PI midblock. The two ends of the soft PI midblock were anchored by rigid cellulose backbone and hard PLLA outer block, respectively, which served as physical crosslinking points. The rigid cellulose backbones brought the PI rubbery domains and PLLA hard domains together to form a whole hierarchical microstructure, endowing the copolymers with distinguished mechanical property. This work provided a feasible approach to producing environmental-friendly cellulose-based copolymers with fully biomass-derived feedstocks, having a profound impact on the development of sustainable polymer-based materials.

Ultra-high volume expansion ratio branched PBT/TPEE three-dimensional reticulated foams of supercritical CO2 melt foaming for efficient oil/water separation

The development of polymer reticulated foams with high expansion ratios (VER) for selective oil-adsorption applications has been hindered by technical challenges. In this article, high VER reticulated foam with outstanding selective oil-adsorption performance was realized through the synergistic effect of molecular topological structure and blending heterostructure. Branched polybutylene terephthalate(B-PBT)/thermoplastic polyester elastomer(TPEE) was prepared by blending reaction. Then, B-PBT/TPEE blends were foamed by supercritical CO2 melting foaming, a solvent-free process. The nano-scale TPEE, acting as the weak point, induced the cell wall to rupture and form reticulated foam after the B-PBT had expanded to a high VER. The branching topological structure endowed PBT high storage modulus(G’) and complex viscosity(η*), which support the expansion of foam and keep foam from collapsing before the melt solidification. As a result, ultra-high VER three-dimensional reticulated foams possessing VER of 46.9 and open-cell content of 97.8 % were prepared, which is higher about 200 % than the previous research. The water contact angle of reticulated foams is 132° and cyclohexane droplets diffuse into reticulated foam showing the contact angle of 0°, indicating the reticulated foam have oleophilicity and hydrophobicity. The adsorption capacity of the reticulated foam for various oils is from 24 to 67 g/g. Moreover, the adsorption rate constant of reticulated foam is 8 times more than that of conventional open-cell foam. These benefits from the unique cell structure and high VER of reticulated foam. The work provides a facile and novel method for the green preparation of high-performance oil/water separation materials.

Thermoplastic Elastomers and Their Physical Gels Electrospun into Tunable Microfibrous Nonwoven Mats: Structure Formation and Property Enhancement

AbstractThermoplastic elastomers (TPEs) based on styrenic block copolymers constitute excellent examples of self‐networking macromolecules that are employed in a wide range of contemporary technologies as molded parts. In such applications, these TPEs exist as dense (nonporous) films or other shapes. Here, it is first demonstrated that a series of commercial TPEs possessing comparable compositions can be electrospun from solution to form microfibers that are arranged into nonwoven mats that are breathable. An important consideration for microfiber formation is the copolymer molecular weight, which regulates i) the viscosity of the parent solution prior to electrospinning, ii) the ability of these copolymers to self‐assemble during electrospinning, iii) the microfiber morphology, and iv) the mechanical properties of the resultant microfibers. The addition of a midblock‐selective aliphatic oil to these TPEs yields thermoplastic elastomer gels (TPEGs), wherein the copolymer morphology and mechanical properties become highly composition‐tunable. Electrospinning TPEGs from a binary oil+solvent solution introduces a micelle inversion mechanism that begins with an oil‐rich micellar core and ends with a styrene‐rich micellar core, required for network stabilization, as the solvent dries during microfiber solidification. This work has implications for the production of controllably low‐modulus microfibrous materials possessing modestly improved toughness but exceptional extensibility and enhanced optical transparency.

Next-Generation Structural Adhesives Composed of Epoxy Resins and Hydrogen-Bonded Styrenic Block Polymer-Based Thermoplastic Elastomers

Next-Generation Structural Adhesives Composed of Epoxy Resins and Hydrogen-Bonded Styrenic Block Polymer-Based Thermoplastic Elastomers

Regulating Vulcanization Kinetics with Deep Eutectic Solvents for Developing Greener Processing Technology of Thermoplastic Vulcanizates

Regulating Vulcanization Kinetics with Deep Eutectic Solvents for Developing Greener Processing Technology of Thermoplastic Vulcanizates

Oil Sorption Properties of Centrifugally Spun Polyisobutylene-Based Thermoplastic Elastomer Microfibers

Fiber-based sorbent materials are an essential part of containing oil spills, thus preventing ecological damage. Poly(styrene-b-isobutylene-b-styrene) thermoplastic elastomer fibers were successfully produced by centrifugal spinning. Scanning electron microscopy revealed that the fibers were bead free and smooth-surfaced, with an average fiber diameter of 5.9 ± 2.3 μm. Contact angle measurements proved the highly hydrophobic (water contact angle of 126.8 ± 6.4°) and highly oleophilic nature of the fiber mat. The sorption and retention capacities of the fiber mat were tested for various oils and benchmarked against polypropylene as the industry standard and polystyrene, which is widely used in the literature. The oil uptake of the fiber mat showed a strong correlation with the viscosity of the oil, resulting in sorption capacities of 10.1 ± 0.8 g/g for sunflower oil, 19.9 ± 2.1 g/g for motor oil, and 23.8 ± 1.8 g/g for gear oil. Oil–water separation tests were also conducted, resulting in ~100% oil removal. The thermoplastic elastomer fiber mat outperformed the industry standard; however, the polystyrene fiber mat demonstrated the best oil sorption performance.

Mechanical Properties and Thermal Decomposition Mechanism of Glycidyl Azide Polyol Energetic Thermoplastic Elastomer Binder with RDX Composite.

To improve the reinforcement effect between a binder and high solid filler in a propellant formula, grafting the bonding group into the binder to form a neutral polymeric is a practically novel approach to improving the interface properties of the propellant. In this work, a glycidyl azide polyol energetic thermoplastic elastomer binder with a -CN bonding group (GAP-ETPE) was synthesized, and the mechanical and thermal decomposition mechanism of GAP-ETPE with Hexogeon (RDX) model propellants were studied. The stress-strain results indicated that the tensile strength and strain of GAP-ETPE/RDX model propellants were 6.43 MPa and 32.1%, respectively. DMA data showed that the storage modulus (E') of the GAP-ETPE/RDX model propellants could increase the glass transition temperature (Tg) values, those were shifted to higher temperature with the increase in filler RDX percentages. TG/DTG showed the four decomposition stages of the decomposition process of the GAP-ETPE/RDX model propellants, and the thermal decomposition equation was constructed. These efforts provide a novel method to improve GAP-ETPE/RDX propellants mechanical property, and the thermal decomposition behavior of GAP-ETPE/RDX propellants also provided technical support for the study of propellant combustion characteristics.