Thermoplastic Elastomer Material Research Articles

Tracking the evolution of the morphology and stress distribution of SIS thermoplastic elastomers under tension using atomic force microscopy

ABSTRACT Styrene-based ABA-type triblock copolymers and their blends are widely investigated thermoplastic elastomers (TPEs). The design of tough TPE materials with high strength and resilience requires further clarification of the relationship between microstructure and macroscopic properties of stretched samples. Here, we applied atomic force microscopy (AFM)-based quantitative nanomechanical mapping to study the deformation behavior of poly(styrene-b-isoprene-b-styrene) blends under tension. The results indicated that the glassy polystyrene (PS) domains deformed and inhomogeneous stress distributions developed in the initial stretching stage. At 200% strain, the glassy PS domains started to crack. The change in the peak value in the JKR Young’s modulus diagram during stretching was consistent with the stress – strain curve. Analysis of the particles before and after stretching suggested that the glassy domains separated and reorganized during stretching.

Preparation and performance characteristics study of thermoplastic polyurethane elastomer (TPU) for basketball shoe soles

Thermoplastic Polyurethane Elastomer (TPU) materials have found extensive applications in the preparation of basketball shoe soles, owing to their excellent elasticity, lightweight properties, and durability. However, TPU materials still face challenges related to breathability, temperature sensitivity, and weather resistance, necessitating further research and improvement. This paper primarily investigates the advancements in E-TPU materials with high rebound foam particles tailored for basketball shoe sole applications. It emphasizes the factors influencing their performance and presents performance control methods from the perspectives of synthesis, molding, and usage. This research provides innovative approaches and methodologies for basketball shoe sole design.

3d printing of thermoplastic elastomers with electrical conductivity

On April 03, 2024, Kraiburg TPE published this blogpost from Johanna Schmid, Market Manager Industry at Kraiburg TPE, discussing the challenges and advancements in using thermoplastic elastomers (TPE) in 3D printing with electrically conductive materials. In her blogpost, she also highlights the limitations of traditional 3D printing processes with TPE materials due to issues like conversion difficulties and uniform extrusion. She outlines the solution of using pellet extrusion technology for TPE, emphasizing its versatility, cost-effectiveness, and suitability for functional prototyping and serial production. Additionally, she underscores the growing demand for electrically conductive materials in various applications.

Reversible Sensing Technologies Using Upcycled TPEE: Crafting pH and Light Responsive Materials towards Sustainable Monitoring.

Multiresponsive materials with reversible and durable characteristics are indispensable because of their promising applications in environmental change detections. To fabricate multiresponsive materials in mass production, however, complex reactions and impractical situations are often involved. Herein, a dual responsive (light and pH) spiropyran-based smart sensor fabricated by a simple layer-by-layer (LbL) assembly process from upcycled thermoplastic polyester elastomer (TPEE) materials derived from recycled polyethylene terephthalate (r-PET) is proposed. Positively charged chitosan solutions and negatively charged merocyanine-COOH (MC-COOH) solutions are employed in the LbL assembly technique, forming the chitosan-spiropyran deposited TPEE (TPEE-CH-SP) film. Upon UV irradiation, the spiropyran-COOH (SP-COOH)molecules on the TPEE-CH-SP film undergo the ring-opening isomerization, along with an apparent color change from colorless to purple, to transform into the MC-COOH molecules. By further exposing the TPEE-CH-MC film to hydrogen chloride (HCl) and nitric acid (HNO3) vapors, the MC-COOH molecules can be transformed into protonated merocyanine-COOH (MCH-COOH) with the simultaneous color change from purple to yellow.

Reversible bonding in thermoplastic elastomer microfluidic platforms for harvestable 3D microvessel networks.

Transplantable ready-made microvessels have therapeutic potential for tissue regeneration and cell replacement therapy. Inspired by the natural rapid angiogenic sprouting of microvessels in vivo, engineered injectable 3D microvessel networks are created using thermoplastic elastomer (TPE) microfluidic devices. The TPE material used here is flexible, optically transparent, and can be robustly yet reversibly bonded to a variety of plastic substrates, making it a versatile choice for microfluidic device fabrication because it overcomes the weak self-adhesion properties and limited manufacturing options of poly(dimethylsiloxane) (PDMS). By leveraging the reversible bonding characteristics of TPE material templates, we present their utility as an organ-on-a-chip platform for forming and handling microvessel networks, and demonstrate their potential for animal-free tissue generation and transplantation in clinical applications. We first show that TPE-based devices have nearly 6-fold higher bonding strength during the cell culture step compared to PDMS-based devices while simultaneously maintaining a full reversible bond to (PS) culture plates, which are widely used for biological cell studies. We also demonstrate the successful generation of perfusable and interconnected 3D microvessel networks using TPE-PS microfluidic devices on both single and multi-vessel loading platforms. Importantly, after removing the TPE slab, microvessel networks remain intact on the PS substrate without any structural damage and can be effectively harvested following gel digestion. The TPE-based organ-on-a-chip platform offers substantial advantages by facilitating the harvesting procedure and maintaining the integrity of microfluidic-engineered microvessels for transplant. To the best of our knowledge, our TPE-based reversible bonding approach marks the first confirmation of successful retrieval of organ-specific vessel segments from the reversibly-bonded TPE microfluidic platform. We anticipate that the method will find applications in organ-on-a-chip and microphysiological system research, particularly in tissue analysis and vessel engraftment, where flexible and reversible bonding can be utilized.

Development and functional validation of tarsometatarsal prosthesis

Assistive Technology (AT) plays a crucial role in providing aid products, including prostheses to persons with disabilities. Tarsometatarsal (TMT) disarticulation, a type of partial foot amputation, is associated with complex gait disorders. However, there is limited research on the functional impact of TMT prostheses on gait. This study aims to develop and functionally validate a 3D-printed TMT prosthesis using finite element analysis and human motion laboratory studies. A 65-year-old patient with TMT amputation participated. Digital models of the amputated and healthy feet were obtained through 3D scanning. The prosthesis design was created using Fusion 360 software. Finite element analysis validated the prosthesis design. The prosthesis was manufactured using thermofusion printing with a biocompatible thermoplastic elastomer material. Functional validation included walking, running, and the Timed Up and Go test using motion analysis technologies. Finite element analysis demonstrated the structural integrity and safety of the TMT prosthesis during propulsion. The manufacturing process resulted in an adjustable and cost-effective prosthesis. Functional validation revealed improvements in gait quality, symmetry, and spatiotemporal parameters with the prosthesis. Vertical ground reaction forces during walking resembled the normal range, and running performance showed increased symmetry and propulsion velocity. The Timed Up and Go test showed that prostheses reduce time and improve efficiency. The development and functional validation of the 3D-printed TMT prosthesis offer a promising solution for individuals with TMT disarticulation. This approach addresses the need for assistive technologies in low-income countries with limited access to prostheses. Advanced technologies and a patient-centred approach contribute to improving mobility, gait patterns, and overall quality of life for individuals with partial foot amputations. Future research will focus on exploring additional parameters and developing new prostheses to further enhance gait improvements.

Design of Guided Bending Bellows Actuators for Soft Hand Function Rehabilitation Gloves

This study developed a soft pneumatic glove actuated by elliptical cross-sectional guided bending bellows to augment finger-knuckle rehabilitation for patients with hand dysfunction. The guided bending bellows actuators (GBBAs) are made of thermoplastic elastomer (TPE) materials, demonstrating the necessary air tightness as a pneumatic actuator. The GBBAs could produce different moments of inertia when increasing internal air pressure drives the GBBAs bending along distinct symmetry planes and exhibits anisotropic kinematic bending performance. Actuated by GBBAs, wearable soft rehabilitation gloves can be used for daily rehabilitation training of hand dysfunction to enhance the range of motion of the finger joint. To control each finger of the gloves independently to achieve the function of manipulating gestures, a multi-channel pneumatic control system is designed, and each air circuit is equipped with an air-pressure sensor to make adjustments based on feedback. Compared with general soft robotic exoskeleton gloves currently used for hand dysfunction, the GBBAs actuated soft gloves have the advantage of enhancing the rehabilitation strength, finger movement range, and multi-action coordination applied with guided bending bellows actuators.

Role of lysine amino acid in zinc‐based ionic thermoplastic elastomer: Dosage‐properties correlation study

AbstractIonic thermoplastic elastomer (TPE) materials have substantial scientific and commercial value due to their recyclable nature and wide adaptive applications. This article presents experimental results and analysis on the effects of the addition of “zwitterionic component” on various properties of maleic anhydride–grafted ethylene–propylene (M‐EPM)–based ionic TPEs. For this purpose, L‐lysine amino acid has been used, which contains a zwitterionic group and a primary amine group. The present work aims to understand how zwitterionic compounds can influence the behavior of the typical ionic TPEs. In this work, a reference ionic TPE sample and different test batches were prepared by varying the dosage of lysine amino acid in the rubber compound. Samples were easily prepared by using conventional rubber processing equipment, such as an internal mixer, two‐roll mill, and hydraulic press. Mechanical and other physical properties were investigated to examine the ionic cluster formation assisted by lysine amino acid. Adverse and favorable aspects of using lysine amino acid in zinc‐based M‐EPM ionic TPE have been discussed comprehensively.

Smart TPE Materials Based on Recycled Rubber Shred.

Thermo-responsive shape memory materials were developed based on recycled ethylene-propylene-diene (EPDM) rubber shred and thermoplastic elastomers (TPE). Ethylene-1-octene TPEs (Engage 8180, 8411, 8452) with varying degrees of crystallinity and Mooney viscosity were used to prepare the composite materials. To avoid the deterioration of static mechanical properties after mixing recycled EPDM rubber shred (RS) with thermoplastic elastomers, they were partially cured using dicumyl peroxide. The peroxide curing was the most effective for a rubber shred/Engage 8180 blend, where the highest cure rate index (CRI), 1.88 dNm⋅min−1, was observed. The curing caused an approximately 4-fold increase of tensile strength (TS) values for EPDM rubber shred/thermoplastic elastomer blend to the level acceptable for the rubber industry compared with an uncured blend. The incorporation of EPDM rubber shred changed thermoplastic elastomers’ viscoelastic behavior, increasing the values of storage (G′) and loss (G″) modulus. The lowest viscosity of molten Engage 8411 during mixing led to higher compatibility of rubber shred RS/8411 blend, as confirmed by analysis of Cole-Cole plots and the blend morphology. All rubber shred RS/TPE blends showed the shape memory behavior. For the RS/Engage 8452 blend, the highest shape fixity (F) value (94%) was observed, while the shape recovery (RR) was 87%. Studies confirmed that the intelligent materials with shape memory effect could be obtained via selectively chosen thermoplastic elastomers; ethylene-1-octene as a binder for recycled EPDM. Prepared recycled TPE/rubber shred blends can be successfully reused due to their viscoelastic and mechanical properties. Therefore, such a concept can be potentially interesting for the rubber industry.

Thermoplastic Polyamide Elastomers: Synthesis, Structures/Properties, and Applications

AbstractThermoplastic polyamide elastomers (TPAEs) have emerged as important thermoplastic elastomer materials with significant potentials owing to their excellent low‐temperature flexibility, easy processability, lightweight, good thermal stability and mechanical properties, etc. Over the last few decades, TPAEs have rapidly developed into a large variety of kinds of TPAEs. Striking advancements have been achieved in this research field. Unfortunately, there is not yet a review to summarize the progress. The present paper summarizes the major advancements dealing with TPAEs, in which synthesis, structures/properties as well as applications are introduced in detail. Moreover, current challenges and main developmental directions dealing with TPAEs are also presented. This review may motivate more interest in TPAEs, further facilitating their all‐side research and more large‐scale applications.

Tensile properties of elastomer process through FFF for biomedical applications

3D printing technology, specifically the fused filament fabrication technique (FFF), is growing in both, industrial and private sector. Due to the large number of possible applications for parts built through this technique, the need to study new materials increases. This paper aims to characterize a thermoplastic elastomer material, TPE 96A. TPE is a flexible material that, among others, can have applications in the field of biomedicine thanks to its flexibility and strength. In order to study the material, two controlled printing parameters (layer height and fill density) are related with its mechanical properties defining the responses obtained in a tensile test. A factorial design of experiments is applied to optimize the process. The specimens are manufactured according to the ASTM D638 standard. Finally, the results will be analyzed by means of an analysis of variance test (ANOVA). Results show that the highest Young’s modulus achieved experimentally is 129 MPa if a combination of 75% of fill density and a 0.2 mm layer height is used for manufacturing the samples.

Enhancing shape memory properties of multi-layered and multi-material polymer composites in 4D printing

The shape memory behavior of smart materials is widely used for stimulation or shape-shifting purposes. Shape memory polymers (SMPs) can shape and force recoveries accompanied by attractive attributes such as biocompatibility, biodegradability, and universality. In this paper, a thermoplastic elastomer (TPE) is used as a complementary material for 4D printed polylactic acid (PLA) structures to enhance their shape and force recovery properties and lower the stimulation temperature for more practical implementations. Two approaches are followed to provide SMP composites (SMPCs): multi-layered and multi-material lattices. In multi-layered lattices, specimens are comprised of separate layers and different ratios of SMP and TPE materials. For comparison, PLA-TPE filaments with the same ratios of multi-layered lattices are produced and used to fabricate multi-material lattices. Dynamic mechanical thermal analysis tests showed a reduction in the glass transition temperature of the manufactured PLA-TPE filament. X-ray diffraction test was conducted to prove that the crystallinity of the developed PLA-TPE material increases which explains the better shape memory effect in the multi-material specimens. Phase separation occurred in low ratios of TPE in PLA, discernible in field emission scanning electron microscope (FESEM) images, resultting in low quality in one of the developed PLA-TPE filaments. FESEM images also showed proper miscibility of TPE in PLA in higher ratios. Thermomechanical tests were done on printed specimens to examine and compare the shape and force recovery of the produced SMPCs. While the shape recovery of multi-material samples was not as good as multi-layered samples, both approaches have better shape recovery results than the PLA sample. Due to a lower glass transition temperature in multi-material lattices, their shape recovery process started at lower temperatures widening their potential practical applications. Force recovery of multi-material samples revealed a significant improvement which was due to more oriented crystalline polymer structures.

Modern Applications of 3D Printing: The Case of an Artificial Ear Splint Model.

Three-dimensional (3D) printing is a leading manufacturing technique in the medical field. The constantly improving quality of 3D printers has revolutionized the approach to new challenges in medicine for a wide range of applications including otoplasty, medical devices, and tissue engineering. The aim of this study is to provide a comprehensive overview of an artificial ear splint model applied to the human auricle for the treatment of stick-out protruding ears. The deformity of stick-out protruding ears remains a significant challenge, where the complex and distinctive shape preservation are key factors. To address this challenge, we have developed a protocol that involves photogrammetry techniques, reverse engineering technologies, a smart prototype design, and 3D printing processes. Specifically, we fabricated a 3D printed ear splint model via fused deposition modelling (FDM) technology by testing two materials, a thermoplastic polyester elastomer material (Z-Flex) and polycaprolactone (PCL 100). Our strategy affords a custom-made and patient-specific artificial ear aligner with mechanical properties that ensures sufficient preservation of the auricular shape by applying a force on the helix and antihelix and enables the ears to pin back to the head.

PP/POE thermoplastic elastomer prepared by dynamic vulcanization and its flame retardant modification

Flame retardant thermoplastic elastomer (TPE) with excellent mechanical properties and thermal oxidative aging resistance was prepared by dynamic vulcanization technology with ethylene-octene copolymer (POE) and polypropylene (PP) as raw materials. The paper first discussed the effect of the amount of vulcanizing agent on the properties of PP/POE TPE. Based on the study of tensile strength, elongation at break, cross-section morphology, processability and aging properties of TPE, it was found that the TPE prepared with 0.6 phr of bis(1-(tert-butylperoxy)-1-methylethyl)-benzene (BIPB) and 40/60 of PP/POE had the best properties. Then silicone powder (GM) is added to the traditional low-halogen bromine-phosphorus flame retardant system for flame retardant modification. The results show that the addition of GM can effectively enhance the stability of the carbon layer, prevent the material from dripping during combustion, and increase the residual carbon content of TPE at 800°C. When 3 phr of GM is combined with a bromine-phosphorus system. The comprehensive performance is the best, the limiting oxygen index (LOI) of TPE increased to 29.8%, reaching the V-0 level. At the same time, the processing fluidity and aging resistance of TPE materials have also been improved.

Preparation and properties of styrene ethylene butylene styrene / polypropylene thermoplastic elastomer powder for selective laser sintering 3D printing

AbstractAs one of the most important thermoplastic elastomer materials, the application of styrene ethylene butylene styrene (SEBS) in selective laser sintering (SLS) has not been reported. In this study, SEBS and polypropylene (PP) are blended and then pulverized at low temperatures. We find that SEBS with high molecular weight and styrene segment content is difficult to melt and flow under laser irradiation, which is not suitable for SLS 3D printing. SEBS with low molecular weight can be printed, and its tensile properties can reach 2.1Mpa and 134% elongation at break. We test the enhanced absorption effect of two different infrared absorbers and find that graphene (GE) can enhance absorption mainly rely on its special structure to increase the optical path of the laser. The absorption enhancement effect of each enhancer rises first and then decreases. 0.4‰ addition of GE can bring 22.5% enhancement. With the enhancement of GE, we get a product of 2.8 MPa tensile strength and 176% elongation at break.

Development and Print of Clothing through Digitalized Designs of Natural Patterns with Flexible Filaments in 3D Printers

This study proposes clothing development by digitalizing natural patterns with flexible filaments in 3D printers. The motivation to carry out this research was the similarity and evenness features of fractals. For this purpose, three natural exemplars have been selected and subsequently digitized: Snowflake, Honeycomb, and Flower of Life, with line variants and infill density at 12%. The garment was printed with Thermoplastic polyurethane (TPU) and Thermoplastic Elastomer (TPE) in two 3D printers: Anet A8 and M3D Crane Quad. Lastly, the combination of filaments, printers, line variant, and infill density resulted in forty-eight (48) samples. Two tests were carried out on the printed patterns for the research: The elongation and tensile strength test. The elongation test consists of applying a variable force to each exemplar in order to obtain the percentage of its elastic limit before reaching its fracture point. The tensile test applies a variable vertical power to each design to determine how it will behave under particular pressure. Results show that the snowflake pattern with line variant obtained the best performance in the elongation test compared to the tensile test. Subsequently, four clothing samples were printed with TPU and TPE materials on the two printers mentioned above. The garments are composed of twenty-nine (29) pieces respectively which were connected with a 3D pen. Finally, the item of clothing was worn by five volunteers of different sizes, as shown in the following pages.

Design of a flexible neck orthosis on Fused Deposition Modeling printer for rehabilitation on regular usage

Abstract The usage area of Additive Manufacturing (AM) already spread into the medicine and rehabilitation sphere. The advantages of AM become a driving force for fabricating prostheses, human organs, and implants. The recent studies in AM indicate excellent manufacture of limbs that possesses characteristics of market versions and, at the same time, outperform them in comfortability. Although there is a vast amount of investigation on orthosis development, only a few applications connected with neck orthosis. This paper proposes customized cervical orthosis designed through 3d scanner device and produced by Fused Deposition modeling. TPE (thermoplastic elastomer) FLEX filament used to provide the model with flexible features on par with the lightweight. FEA analysis assessment confirmed the durability of the prototype. Furthermore, the specific construction of orthosis allows patients to comfortably dress and utilize it in daily life, whereas the hole pattern of frame addresses ventilation problems. Obtained results indicate the capability of using TPE (flex) material and show that the FDM printed model able to compete with market analogs.

Reversible Bonding of Thermoplastic Elastomers for Cell Patterning Applications

In this paper, we present a simple, versatile method that creates patterns for cell migration studies using thermoplastic elastomer (TPE). The TPE material used here can be robustly, but reversibly, bonded to a variety of plastic substrates, allowing patterning of cultured cells in a microenvironment. We first examine the bonding strength of TPE to glass and polystyrene substrates and com-pare it to thermoset silicone-based PDMS under various conditions and demonstrate that the TPE can be strongly and reversibly bonded on commercially available polystyrene culture plates. In cell migration studies, cell patterns are templated around TPE features cored from a thin TPE film. We show that the significance of fibroblast cell growth with fetal bovine serum (FBS)-cell culture media compared to the cells cultured without FBS, analyzed over two days of cell culture. This simple approach allows us to generate cell patterns without harsh manipulations like scratch assays and to avoid damaging the cells. We also confirm that the TPE material is non-toxic to cell growth and supports a high viability of fibroblasts and breast cancer cells. We anticipate this TPE-based patterning approach can be further utilized for many other cell patterning applications such as in cell-to-cell communication studies.

Functional Analysis Validation of Micro and Conventional Injection Molding Machines Performances Based on Process Precision and Accuracy for Micro Manufacturing

Micro polymer parts can be usually manufactured either by conventional injection moulding (IM) or by micro-injection moulding (µIM). In this paper, functional analysis was used as a tool to investigate the performances of IM and µIM used to manufacture the selected industrial component. The methodology decomposed the production cycle phases of the two processes and attributed functions to parts features of the two investigated machines. The output of the analysis was aimed to determine casual chains leading to the final outcome of the process. Experimental validation of the functional analysis was carried out moulding the same micro medical part in thermoplastic elastomer (TPE) material using the two processes by means of multi-cavity moulds. The produced batches were assessed using a precision scale and a high accuracy optical instrument. The measurement results were compared using capability indexes. The data-driven comparison identified and quantified the correlations between machine design and part quality, demonstrating that the µIM machine technology better meets the accuracy and precision requirements typical of micro manufacturing productions.

Rapid Fabrication of Membrane-Integrated Thermoplastic Elastomer Microfluidic Devices.

Leveraging the advantageous material properties of recently developed soft thermoplastic elastomer materials, this work presents the facile and rapid fabrication of composite membrane-integrated microfluidic devices consisting of FlexdymTM polymer and commercially available porous polycarbonate membranes. The three-layer devices can be fabricated in under 2.5 h, consisting of a 2-min hot embossing cycle, conformal contact between device layers and a low-temperature baking step. The strength of the FlexdymTM-polycarbonate seal was characterized using a specialized microfluidic delamination device and an automated pressure controller configuration, offering a standardized and high-throughput method of microfluidic burst testing. Given a minimum bonding distance of 200 μm, the materials showed bonding that reliably withstood pressures of 500 mbar and above, which is sufficient for most microfluidic cell culture applications. Bonding was also stable when subjected to long term pressurization (10 h) and repeated use (10,000 pressure cycles). Cell culture trials confirmed good cell adhesion and sustained culture of human dermal fibroblasts on a polycarbonate membrane inside the device channels over the course of one week. In comparison to existing porous membrane-based microfluidic platforms of this configuration, most often made of polydimethylsiloxane (PDMS), these devices offer a streamlined fabrication methodology with materials having favourable properties for cell culture applications and the potential for implementation in barrier model organ-on-chips.