Thermoplastic Elastomers Research Articles

Stability of ischial pressure with 3D thermoplastic elastomer cushion and the characteristics of four types of cushions in pressure redistribution.

Wheelchair cushions are recommended to be used with wheelchair and can protect the buttocks from pain and injury by relieving interface pressure for wheelchair users. However, further investigations are required for proper use in response to the development of new types of wheelchair cushions. The objective of this study was to evaluate physical characteristics of wheelchair cushions by comparing pressure redistributing effects of four types of cushions. The participants were 16 healthy adults who consented to participate in this study. A pressure mapping system (CONFORMat, Nitta Corp.) was used for the measurements. Pressure at ischium was measured immediately after the stabilization of the sitting posture and 10 minutes after. The pressure at ischium significantly decreased with any wheelchair cushions (P < 0.01). A significant negative correlation between body mass index and pressure at ischium was observed without a wheelchair cushion (r = - 0.70), however, the correlation disappeared upon use of a wheelchair cushion. The pressure at ischium increased over time with cushions of urethane, air, and urethane-air hybrid while that with the 3D thermoplastic elastomer cushion did not, and the change in the pressure was statistically less than that in other cushions (P < 0.01). Use of wheelchair cushions was effective in redistribution of the pressure at ischium, and the overtime change in the pressure depends on the type of used cushions.

Investigation of electrospinning parameters and fiber collection methods on morphology of thermoplastic polyester elastomer fibers

Electrospinning is an easy and simple process for the preparation of ultrafine fibers with tunable morphology. Thermoplastic Elastomers (TPEs) are engineering polymers with an elastomeric nature that can be processed as thermoplastics. They can be classified based on their chemical structure and polyester-based TPEs are counted as high-performance materials due to their mechanical properties and can be used for various applications from automotive, construction, furniture, and consumer goods. In this study, electrospun polyester-based thermoplastic elastomer fibers were prepared and characterized. Thermoplastic polyester elastomer, Hytrel 4056 was used as the polymer, and chloroform was used as a solvent. The effects of polymer: solvent weight ratio, feed rate, applied voltage, and collector type were investigated in terms of fiber formation and morphology. For this aim, the polymer: solvent weight ratio was varied as 1:7, 1:11, and 1:15; the feed rate was set to 1 and 3 ml h-1. To collect the fibers metal plate and water bath collectors were used at a constant needle-to-collector distance under 10, 15, and 20 kV. The viscosity of the polymer solutions was measured as a function of the polymer: solvent ratio to observe the effects of viscosity on fiber morphology.

Polymer dispersity modulation by statistical copolymerization of (α-alkyl)acrylate monomers with disparate reactivity: Enhanced monomer conversion and tailored dispersity for dielectric elastomer application

Polymer dispersity (Ð) is an important parameter in determining polymer properties. We report a new strategy for Ð modulation by statistically copolymerizing steric-hindered itaconates with methacrylate and acrylate monomers via organocatalyzed controlled radical polymerization. Due to the disparate monomer reactivity, Ð values can be tunable in a broad range (1.1–1.6) in a batch system. This strategy has demonstrated the sequential and topological generality for Ɖ modulations, serving as a model tool for Ð modulation in any segment of A-B diblock, B-A-B and A-B-A triblock, and 3-arm star A-B diblock copolymers. The unique aspects of this method are that the segment after Ð modulation can initiate polymerization of various types of monomers (e.g., methacrylate, acrylate) by the labile tertiary carbon-iodide chain-end without any external assistance or special initiator and monomer selection, the metal-free nature and the renewable substitution of petroleum-based methacrylate and acrylate monomers with bio-based itaconates without sacrificing inherent properties. This work broadens the application scope of Ð modulation to many other emerging technologies, such as antifreezing thermoplastic dielectric elastomers used as film capacitors in the field of energy storage.

A nonequilibrium constitutive equation for tensile behavior of polyolefinic thermoplastic vulcanizates

Polyolefinic thermoplastic vulcanizates (TPVs) composed of iPP (isotactic polypropylene) and crosslinked EPDM (ethylene-propylene-diene rubber) prepared by dynamic vulcanization process exhibit rubber domains dispersed in the iPP matrix, even though the EPDM component is the major component. Here we proposed a kinetic nonequilibrium constitutive equation that considers the transition of the mechanical nature from plasto-rigid deformation to rubbery deformation during uniaxial extension to explore the origin of the thermoplastic elastomer behavior of TPV (thermoplastic vulcanizate) materials. Fitting of the constitutive equation to the experimental stress‒strain curves quantitatively revealed the critical transition point of the mechanical properties. The transition shifted to higher strains with decreasing EPDM content. In situ wide-angle X-ray diffraction profiles monitored during the uniaxial extension confirmed the mechanical transition process.

In Vivo Release of Zafirlukast from Electrospun Polyisobutylene-Based Fiber Mats to Reduce Capsular Contracture of Silicone Breast Prostheses.

Silicone rubber tissue expanders and breast implants are associated with chronic inflammation, leading to the formation of fibrous capsules. If the inflammation is left untreated, the fibrous capsules can become hard and brittle and lead to formation of capsular contracture. When capsular contracture occurs, implant failure and reoperation is unavoidable. Fibrous capsule formation to medical grade silicone rubber breast implants and polyisobutylene-based electrospun fiber mats attached to silicone rubber with and without an anti-inflammatory therapeutic were compared. A linear polyisobutylene (PIB)-based thermoplastic elastomer is currently applied as a polymer coating for drug release on coronary stents to reduce restenosis. Recent work has created a drug releasing electrospun fiber mat from PIB-based materials. Important to this study, poly(alloocimene-b-isobutylene-b-alloocimene) (AIBA) was electrospun with zafirlukast (ZAF). ZAF is an anti-inflammatory drug that is able to reduce capsule formation and complications to silicone breast implants. Fiber mats are advantageous for local drug delivery because of their high porosity and surface area for drug release. The chief hypothesis was that local release of ZAF from AIBA would lower inflammatory signaling and resulting capsular formation after 90 days in vivo. Electrospun AIBA mats locally released ZAF, lowering inflammation and fibrous capsule development compared to medical grade silicone rubber. Locally and orally released ZAF led to similar results, but the former had much lower concentration that highlights local delivery's therapeutic potential. Released ZAF from AIBA fiber mats mitigated inflammation and serves as an alternative to existing clinical approaches.

2-Cyanopropan-2-yl versus 1-Cyanocyclohex-1-yl Leaving Group: Comparing Reactivities of Symmetrical Trithiocarbonates in RAFT Polymerization.

This study introduces bis(1-cyanocyclohex-1-yl)trithiocarbonate (TTC-bCCH) as a novel trithiocarbonate chain transfer agent and compares its reactivity with the previously described bis(2-cyanopropan-2-yl)trithiocarbonate (TTC-bCP) for the reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene (St), n-butyl acrylate (nBA), and methyl methacrylate (MMA). Significant findings include the effective control of Mn and low dispersities from the onset of polymerization of St and nBA showing swift addition-fragmentation kinetics, leading to similar behaviors between the two RAFT agents. In contrast, a fourfold decrease of the chain transfer constant to MMA is established for TTC-bCCH over TTC-bCP. This trend is confirmed through density functional theory (DFT) calculations. Finally, the study compares thermoplastic elastomer properties of all-(meth)acrylic ABA block copolymers produced with both RAFT agents. The impact of dispersity of PMMA blocks on thermomechanical properties evaluated via rheological analysis reveals a more pronounced temperature dependence of the storage modulus (G') for the triblock copolymer synthesized with TTC-bCCH, indicating potential alteration of the phase separation.

One-step Synthesis of Fully Biobased Two-Sided Tapered ABA-type Thermoplastic Elastomers

One-step Synthesis of Fully Biobased Two-Sided Tapered ABA-type Thermoplastic Elastomers

Life cycle environmental evaluation of medical oxygen masks in the UK

In a clinical setting, medical oxygen masks (MOMs) are made using lightweight and transparent materials with Polyvinyl Chloride (PVC) being a popular choice. Environmental concerns around the use of PVC have arisen due to the toxicity of plasticisers required; in particular the use of increasingly regulated phthalate (Pht) based plasticisers. Non-Pht plasticisers and alternative materials to PVC are being sought as potential replacements in order to keep MOMs in line with current and expected regulations. This study explores the environmental impacts of three (low-flow) MOMs using a life cycle assessment approach from cradle to grave with a functional unit defined as ‘one single-use low-flow medical oxygen mask for adult use in the UK’. The results account for all 11 impact categories as provided by the CML-IA baseline v3.03 methodology. PVC is the main component of two MOMs: mask A using a non-Pht based plasticiser and mask C (a hypothetical mask) using Pht-based plasticiser DEHP. For Mask B, styrene-ethylene-butadiene-styrene based thermoplastic elastomer (TPE-S) and polypropylene is used instead of PVC. Mask B shows the lowest environmental impact across all impact categories. For six out of 11 impact categories (including global warming potential and ozone depletion), mask C scores highest, whereas mask A is highest for the other five categories (with large impacts in human toxicity and ecotoxicities). Two scenario analyses show the importance of supply chain logistics (i.e., the location of the manufacturing site and location of end user) on overall environmental impact. The results of this study intend to provide evidence to policy makers, healthcare professionals, and manufacturers of MOMs to improve the overall environmental impacts of these products, as they contribute around 4437 tonnes of CO2 eq. yearly in the UK alone. The results show that switching from plasticised PVC to TPE-S would reduce the impacts of the use of MOMS within the UK by 2755 tonnes of CO2 eq. per year.

Screw extrusion additive manufacturing of thermoplastic polyolefin elastomer

Screw extrusion additive manufacturing of thermoplastic polyolefin elastomer

A Review of Road Bitumen Modification Methods. Part 1 – Physical Modification

The information in this study is based on a thorough review of recent articles related to the production of binders for road construction and the improvement of their performance properties. The main attention is paid to the physical modification of road bitumen with polymer modifiers. The influence of the three main types of polymers (thermoplastics, elastomers, and thermoplastic elastomers) on the main physical and mechanical properties of bitumen-polymer compositions is shown. The main technological parameters and features of the physical modification of bitumen by different types of polymer modifiers have been determined.

Chain Shuttling Polymerization for Cycloolefin Block Copolymers: From Engineering Plastics to Thermoplastic Elastomers

Chain Shuttling Polymerization for Cycloolefin Block Copolymers: From Engineering Plastics to Thermoplastic Elastomers

Design and synthesis of poly(styrene-b-(ethylene-co-butadiene)-b-styrene) anion exchange membranes with high ion conductivity

Poly(styrene-b-(ethylene-co-butadiene)-b-styrene) copolymers (SEBS) have garnered significant attention to develop anion exchange membranes (AEMs) for fuel cells. However, SEBS commodities encounter a formidable obstacle of fabricating high-performance AEMs as thermoplastic elastomer. Herein, a series of poly(styrene-b-butadiene-b-styrene) copolymers (SBS) with high content of 1,4-butadiene units (>90 % of middle block) and variable content of polystyrene (PS, 51.3, 61.6 and 70.7 wt%) has been designed to develop SEBS AEMs with high-strength polyethylene phase via hydrogenation, chloromethylation, quaternization and alkalization. The results demonstrate that high PS content broadens the ion transport channel, improves the ion exchange capacity (IEC) and alkali resistance stability, and substantially boosts the ion conductivity, water uptake and swelling ratio of AEMs. Besides, the high proportion of polyethylene phase from 1,4-butadiene unit of SBS copolymers provides good dimensional stability to the AEMs. Remarkably, the AEMs with 70.7 wt% PS and an IEC value of 3.37 mmol g−1 significantly upgrades the ionic conductivity to ∼190 mS cm−1 at 80 °C. It attains a peak power density of ∼1000 mW cm−2 at 2.09 A cm−2 in a H2/O2 single cell operating at 80 °C. This outstanding performance underscores the promising potential of such SEBS copolymers in the development of high-performance SEBS AEMs for fuel cells.

Thermoplastic Elastomers with High Service Temperature and Thermal Stability through Hydrogenation of Polybenzofulvene-Based Triblock Copolymers Synthesized by Living Anionic Polymerization

Thermoplastic Elastomers with High Service Temperature and Thermal Stability through Hydrogenation of Polybenzofulvene-Based Triblock Copolymers Synthesized by Living Anionic Polymerization

Self-Amputating and Interfusing Machines.

Biological organisms exhibit phenomenal adaptation through morphology-shifting mechanisms including self-amputation, regeneration, and collective behavior. For example, reptiles, crustaceans, and insects amputate their own appendages in response to threats. Temporary fusion between individuals enables collective behaviors, such as in ants that temporarily fuse to build bridges. The concept of morphological editing often involves the addition and subtraction of mass and can be linked to modular robotics, wherein synthetic body morphology may be revised by rearranging parts. This work describes a reversible cohesive interface made of thermoplastic elastomer that allows for strong attachment and easy detachment of distributed soft robot modules without direct human handling. The reversible joint boasts a modulus similar to materials commonly used in soft robotics, and can thus be distributed throughout soft robot bodies without introducing mechanical incongruities. To demonstrate utility, the reversible joint is implemented in two embodiments: a soft quadruped robot that self-amputates a limb when stuck, and a cluster of three soft-crawling robots that fuse to cross a land gap. This work points toward future robots capable of radical shape-shifting via changes in mass through autotomy and interfusion, as well as highlights the crucial role that interfacial stiffness change plays in autotomizable biological and artificial systems.

Scalable Microwires through Thermal Drawing of Co-Extruded Liquid Metal and Thermoplastic Elastomer.

This article demonstrates scalable production of liquid metal (LM)-based microwires through the thermal drawing of extrudates. These extrudates were first co-extruded using a eutectic alloy of gallium and indium (EGaIn) as a core element and a thermoplastic elastomer, styrene-ethylene/butylene-styrene (SEBS), as a shell material. By varying the feed speed of the co-extruded materials and the drawing speed of the extrudate, it was possible to control the dimensions of the microwires, such as core diameter and shell thickness. How the extrusion temperature affects the dimensions of the microwire was also analyzed. The smallest microwire (core diameter: 52 ± 14 μm and shell thickness: 46 ± 10 μm) was produced from a drawing speed of 300.1 mm s-1 (the maximum attainable speed of the apparatus used), SEBS extrusion speed of 1.50 mm3 s-1, and LM injection rate of 5 × 105 μL s-1 at 190 °C extrusion temperature. The same extrusion condition without thermal drawing generated significantly large extrudates with a core diameter of 278 ± 26 μm and shell thickness of 430 ± 51 μm. The electrical properties of the microwires were also characterized under different degrees of stretching and wire kinking deformation which proved that these LM-based microwires change electrical resistance as they are deformed and fully self-heal once the load is removed. Finally, the sewability of these microwires was qualitatively tested by using a manual sewing machine to pattern microwires on a traditional cotton fabric.

Bead Size and Rheological Properties of SEBS-Based Elastic Beads

Abstract Styrene-ethylene-butylene-styrene, (SEBS), is a thermoplastic elastomer that has applications in robotics and shock absorption. While SEBS as a bulk material as well as an additive to solid composites has been extensively studied, this work focuses on developing SEBS-based beads to enhance material, particularly fluid, elasticity; the first time this has been seen in literature. SEBS bead mixtures were developed by mixing SEBS elastomer, water, and surfactant (Triton X-100) at high temperature. Stability, rheology, and microscopy of SEBS bead mixtures were studied as a function of neat SEBS concentration in SEBS elastomer, SEBS elastomer concentration, and surfactant concentration. Resulting bead mixtures were classified as creamed, homogenous and stable, or aggregated bead mixtures based on the mixture's tendency to separate into layers and ability to disperse in excess water. Microscopic studies suggest that while bead mixtures exhibit size polydispersity, the average bead size is a strong function of neat SEBS, SEBS elastomer, and surfactant concentrations. Rheological studies suggest that all the bead mixtures exhibit shear thinning behavior, and the overall viscosity of a given bead mixture is a function of both SEBS elastomer and surfactant concentration. The developed SEBS elastic beads can be used as additives to enhance the viscoelastic properties of fluid-based systems like magnetorheological and damping fluids.

Antibacterial activity of 3D printed thermoplastic elastomers doped with carbon quantum dots for biomedical applications

3D printing provides a lot of varieties for the manufacturing of personalized biomedical devices. Incorporation of the nanoparticles with potential antibacterial activity to the printed materials is another added value. One example of such nanoparticles are hydrophobic carbon quantum dots (hCQDs), which are zero-dimensional redox-active materials with high chemical stability and low production costs. They produce singlet oxygen only when activated by a specific wavelength of visible blue light which allows for controlled antibacterial action and minimizes the chances of bacterial resistance emergence. We prepared and characterized polymer composites based on thermoplastic elastomers (TPE) doped with hCQDs (TPE/hCQDs). The composites were 3D printed using fused deposition modeling method. In the first set of samples, a filament of pure TPE was immersed in a solution of hCQDs (0.5 mg/mL), then 3D printed, and compared with unmodified TPE filament. The mechanical properties, swelling behavior, hardness, and thermal stability of TPE/hCQDs were compared with the pure TPE printed samples. The production of singlet oxygen was confirmed by the electron paramagnetic resonance method. The antibacterial activity of the samples was tested according to ISO 22196 against Staphylococcus aureus and Escherichia coli after one hour of exposure to blue light, which completely inhibited bacterial growth. Besides, the cytotoxicity of samples was evaluated by MTT assay, and no significant effect of the materials on cell viability was observed. 3D printed materials with antibacterial activity represent a perspective for the future, especially in the field of personalized medicine, as well as in products for other industries.

One-step facile pathway synthesis of PAPXD/1214-PEA thermoplastic elastomer: Structure and properties

In this study, a novel and facile one-step synthesis route was conducted to prepare semi-aromatic polyamide elastomer (PAPXD/1214-PEA) with p-phenylenediamine, dodecane diamine, dodecanedioic acid and polyether amine (PEA) as monomers. A systematic investigation has been conducted into the effect of hard segment content on the thermal, mechanical and solvent resistance of polymers when semi-aromatic polyamides are used as hard segments. It was found that the melting point of the copolymers gradually increased from 191.2 °C to 231.5 °C with the hard segment content increased from 39 % to 76 %, while the Vicat softening temperature (VST) enhanced from 103.2 °C to 192.2 °C. Compared with the commercial polyamide elastomer Pebax@ (produced by Arkema Inc) with similar hard segment contents, the VST of PAPXD14/1214-PEA were 17.4–66.2 °C higher. The mechanical performance of these elastomers was also largely improved with tensile strength increasing from 15.1 to 40.6 MPa, Young's modulus from 28.2 to 168.7 MPa, toughness from 91.1 to 170.7 MJ/m3. In addition, the solvent resistance properties of PAPXD14/1214-PEA was compared with the commercial polyamide elastomer Pebax@. After soaking in hydrochloric acid for 24 h, the tensile strength of PAPXD/1214-PEA with the hard segment content increased from 50 % to 63 % decreased down to 9.4 and 14.4 MPa, respectively. While the commercial polyamide elastomer Pebax@ (with similar hard segment content) decreased down to 1.5 and 4.3 MPa, indicating the commercial polyamide elastomer products were deteriorated. This suggests the corrosion resistance of the synthesized PAPXD/1214-PEA is much better than that of commercial product, and these semi-aromatic polyamide elastomers can be potentially applied in some harsh service environment especially for high temperature and corrosion sealing.

The Effect of Aluminosilicate Cenospheres on the Structure and Thermal Properties of Butadiene–Styrene Thermoplastic Elastomer

The Effect of Aluminosilicate Cenospheres on the Structure and Thermal Properties of Butadiene–Styrene Thermoplastic Elastomer

Experimental and theoretical investigation of the effect of physical and chemical compatibilization on the properties of thermoplastic elastomers derived from natural rubber and polypropylene blends

The objective of this research was to improve the compatibility between Natural Rubber/Polypropylene NR/PP blends through physical and chemical compatibilization methods. The physical compatibilization involved the use of epoxidized natural rubber/maleic anhydride-grafted polypropylene (ENR50/PP-g-MA) as a dual compatibilizing agent (CA50), while the process of reactive compatibilization entailed chemically modifying NR and PP phases through the grafting maleic anhydride (MA). Several formulations were prepared by melt mixing using a Brabender plasti-corder. The effects of physical and chemical compatibilization on the technical properties were investigated. FTIR analysis revealed the emergence of two distinctive peaks corresponding to the CO group of MA grafted onto PP and NR chains. FTIR analysis has also confirmed the taking place of reactions between the polar functional groups of PP-g-MA and ENR50. The rheological properties indicated that the viscosity of the NR-g-MA/PP-g-MA is lower than those of the control blend and CA50-based NR/PP system. The mechanical and dynamic mechanical findings corroborated the improvement of interfacial adhesion between NR/PP phases, especially for the NR/PP/CA50 system. SEM examination demonstrated a more uniform dispersion of the PP phase in the CA50-based NR/PP, compared to the control blend and NR-g-MA/PP-MA. NR-g-MA/PP-g-MA exhibits greater miscibility and interaction potential compared to the control NR/PP, and less than NR/(ENR50/PP-g-MA)/PP system. DFT calculations further validate the effect of compatibilization methods on TPE blends. Specifically, Quantum molecular descriptors revealed the role of ENR50/PP-g-MA as an intermediary in facilitating compatibility between NR/PP. These findings indicate that the physical compatibilization method approach using ENR50/PP-g-MA as a dual compatibilizer is a potential compatibilizer for NR/PP.