Commercial Thermoplastic Elastomers Research Articles

Supersoft Norbornene-Based Thermoplastic Elastomers with High Strength and Upper Service Temperature.

With over 6 million tons produced annually, thermoplastic elastomers (TPEs) have become ubiquitous in modern society, due to their unique combination of elasticity, toughness, and reprocessability. Nevertheless, industrial TPEs display a tradeoff between softness and strength, along with low upper service temperatures, typically ≤100°C. This limits their utility, such as in bio-interfacial applications where supersoft deformation is required in tandem with strength, in addition to applications that require thermal stability (e.g., encapsulation of electronics, seals/joints for aeronautics, protective clothing for firefighting, and biomedical devices that can be subjected to steam sterilization). Thus, combining softness, strength, and high thermal resistance into a single versatile TPE has remained an unmet opportunity. Through de novo design and synthesis of novel norbornene-based ABA triblock copolymers, this gap is filled. Ring-opening metathesis polymerization is employed to prepare TPEs with an unprecedented combination of properties, including skin-like moduli (<100kPa), strength competitive with commercial TPEs (>5MPa), and upper service temperatures akin to high-performance plastics (≈260°C). Furthermore, the materials are elastic, tough, reprocessable, and shelf stable (≥2 months) without incorporation of plasticizer. Structure-property relationships identified herein inform development of next-generation TPEs that are both biologically soft yet thermomechanically durable.

Investigating the Effects of Waste Cr-Pp Combinations on the Properties of Asphalt Binder and Mixture in Comparison to a Commercial Thermoplastic Elastomer, as Well as a Moisture Susceptibility Prediction Model Based on Radial Bias Function Neural Network

Investigating the Effects of Waste Cr-Pp Combinations on the Properties of Asphalt Binder and Mixture in Comparison to a Commercial Thermoplastic Elastomer, as Well as a Moisture Susceptibility Prediction Model Based on Radial Bias Function Neural Network

Thermoplastic Elastomer Tunes Phase Structure and Promotes Stretchability of High-Efficiency Organic Solar Cells.

Top-performance organic solar cells (OSCs) consisting of conjugated polymer donors and nonfullerene small molecule acceptors (NF-SMAs) deliver rapid increases in efficiencies. Nevertheless, many of the polymer donors exhibit high stiffness and small molecule acceptors are very brittle, which limit their applications in wearable devices. Here, a simple and effective strategy is reported to improve the stretchability and reduce the stiffness of high-efficiency polymer:NF-SMA blends and simultaneously maintain the high efficiency by incorporating a low-cost commercial thermoplastic elastomer, polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS). The microstructure, mechanical properties, and photovoltaic performance of PM6:N3 with varied SEBS contents and the molecular weight dependence of SEBS on microstructure and mechanical properties are thoroughly characterized. This strategy for mechanical performance improvement exhibits excellent applicability in some other OSC blend systems, e.g., PBQx-TF:eC9-2Cl and PBDB-T:ITIC. More crucially, the elastic modulus of such complex ternary blends can be nicely predicted by a mechanical model. Therefore, incorporating thermoplastic elastomers is a widely applicable and cost-effective strategy to improve mechanical properties of nonfullerene OSCs and beyond.

Form-stable phase-change elastomer gels derived from thermoplastic elastomer copolyesters swollen with fatty acids

Phase-change materials (PCMs) are of considerable scientific and technological interest in applications related to energy management and storage, especially as they pertain to residential or commercial construction and packaging. Most PCMs developed for these purposes consist of a crystallizable species encapsulated within an impermeable polymeric shell. Such encapsulants can then be strategically embedded throughout a construct to promote thermal stability in close proximity to the normal melting point of the encapsulated species. In this study, we introduce form-stable PCMs, which avoid the need for costly and inconvenient encapsulation and consist of commercial thermoplastic elastomer copolyesters selectively swollen with crystallizable fatty acids. Since the copolyester matrices endow the PCMs with solid-like characteristics even when swollen with liquid, we refer to this particular class of materials as phase-change elastomer gels (PCEGs). In this study, we explore the thermal characteristics of PCEG films wherein the copolyester grade, gel composition and fatty acid are all varied. Our results indicate that these PCEGs exhibit non-hysteretic thermal cycling, unaffected transition temperatures, and competitive latent transition heats. Relative to model and commercially available encapsulated PCMs, the form-stable PCEGs examined here afford an alternative capable of superior thermal performance and versatility.

Influence of selective distribution of SiO2 nanoparticles on shape memory behavior of co-continuous PLA/NR/SiO2 TPVs

As a kind of commercial thermoplastic elastomers, thermoplastic vulcanizates (TPVs) have been widely used in many fields. In this work, a shape memory polymer (SMP) was fabricated based on co-continuous polylactide (PLA)/natural rubber (NR)/silica (SiO2) TPVs. Selective distribution of SiO2 nanoparticles was achieved with the impact of thermodynamic factor and different processing methods, and the influence on shape memory behavior was investigated as well. The results demonstrated that the co-continuous structure functioned actively in both shape fixity and recovery. The PLA phase played the role of “switch” to control the shape memory behavior, while the deformation of continuous rubber network stored sufficient resilience and successfully drove the shape recovery process. Excellent shape fixing ratio (~100%) and shape recovery ratio (>90%) were obtained when SiO2 nanoparticles were distributed in NR phase. The addition of SiO2 nanoparticles reinforced the rubber phase and the recovery ratio was effectively improved.

Access to polyethylene elastomers via ethylene homo-polymerization using N,N′-nickel(II) catalysts appended with electron withdrawing difluorobenzhydryl group

A library of five hither-to-unknown unsymmetrical N,N′-diiminoacenaphthylenes, 1-[2,4,6-{(4-FC6H4)2CH}3C6H4N]-2-(ArN)C2C10H6 (Ar = 2,6-Me2Ph L1, 2,6-Et2Ph L2, 2,6-i-Pr2Ph L3, 2,4,6-Me3Ph L4 and 2,6-Et2-4-Me-Ph L5), have been synthesized and used to prepare their corresponding nickel(II) halide complexes of the type LNiBr2 (Ni1–Ni5) and LNiCl2 (Ni6–Ni10). Single-crystal structures of Ni1 and Ni2 reveal the nickel center and coordination atoms formed distorted tetrahedral geometry. Upon activation with either methylaluminoxane (MAO) or diethylaluminum chloride (Et2AlCl), Ni1–Ni10 displayed high activities towards ethylene polymerization with the optimal performance being observed using Ni5 in combination with MAO (1.29 × 107 g of PE (mol of Ni)−1 h−1 at 30 °C), which produced high molecular weight elastomeric polyethylene (Mw = 4.6 × 105 g mol−1, Tm = 47.13 °C) with narrow polydispersity (Mw/Mn = 2.6). Dynamic mechanical analysis (DMA) and monotonic stress–strain test has been employed on the obtained polymeric materials and reveal high tensile strength, good elastomeric recovery (up to 93.6%) and high elongational break (up to 1037.1%), which indicates a promising equivalent material to currently commercial thermoplastic elastomers (TPEs).

Influence of temperature upon properties of tailor-made PEBAX® MH 1657 nanocomposite membranes for post-combustion CO2 capture

Tailor-made block copolymer nanocomposite membranes are prepared by incorporation of 40wt% methoxy poly(ethylene glycol) (PEG) functionalized polyoctahedral oligomeric silsesquioxanes (POSS) nanoparticles in commercial thermoplastic elastomer multiblock copolymer PEBAX® MH 1657. Atomic force microscopy was used to find out the location of the nanoparticles in the block copolymer matrix. Separation of CO2 from N2 and H2 is studied by measurements of single gas transport properties of nanocomposite materials using the time-lag method in the temperature range 30–70°C. PEG functionalized POSS nanoparticles increase the CO2 permeability of the nanocomposite membranes without loss of CO2/N2 and CO2/H2 selectivity. Thermal properties of the nanocomposite membranes are studied by differential scanning calorimetry (DSC) to assess the stability of the nanocomposite membranes upon melting of polyether and polyamide blocks.

Prototyping of microfluidic systems using a commercial thermoplastic elastomer

This article describes the fabrication of microfluidic networks (μFNs) from a commercially available (styrene)–(ethylene/butylene)–(styrene) (SEBS) block copolymer (BCP). The unique combination of hard and elastomeric properties provided by this material promotes high-throughput replication of fluidic structures using thermoforming technologies, while retaining the advantage of quick and easy assembly via conformal contact, as commonly achieved for devices fabricated from poly(dimethylsiloxane (PDMS). We employ Versaflex CL30, which is optically transparent, available at low cost (e.g., $2.50/Lbs), and likely to be compatible with a broad range of biological species. We demonstrate excellent fidelity in replication of fluidic structures using hot embossing lithography in conjunction with a photolithographically prepared Si/SU-8 master mold. Moreover, we introduce rapid prototyping of high-quality structures using an approach that we call soft thermoplastic lithography (STPL). Thanks to the rheological characteristics of the SEBS copolymer, STPL enables thermoforming on a heated master at temperatures around 170°C. Using this approach, replication can be completed within a very short period of time (e.g., less than 3 min) without the need of resorting to pressure- or vacuum-assisted instrumentation. Serving as a proof-of-concept, we devise a μFN that is suitable for the formation of miniaturized arrays comprising fluorescently labeled oligonucleotides and proteins on hard plastic substrates. Resultant spots are characterized by high fluorescent contrast, excellent edge definition, and uniform distribution of probes within the modified areas.

Modification of morphology of polycarbonate/thermoplastic elastomer blends by supercritical CO 2

The effect of supercritical CO 2 on the morphological features of blends of polycarbonate and a commercial thermoplastic elastomer was investigated. The as-prepared films of the blend showed phase separated domains of the elastomer. With the combination of pressure and temperature, the large domains were “burst” into smaller domains. Temperatures higher than the critical temperature are required to cause any change in the morphology. The size distribution of the elastomer domains is effectively narrowed by the supercritical CO 2 treatment. The time of exposure also plays a role. It was also seen that above 60 °C, crystallization of polycarbonate begins. Based on the previous work on this system, it is proposed that enhancement of elongation, Young’s modulus and abrasion resistance would occur due to the reduction in the domain size and distribution.

Feature Article: Experimental Design and Molecular Modeling of Novel Graft Copolymers

The tensile properties of tetra-functional multigraft copolymers have been shown to have surprising high strain at break (~2100%), about double that of commercial thermoplastic elastomers such as Kraton! Currently, multigraft copolymers can be synthesized with a variety of branches (single, bi, tri-, tetra, and with different lengths) at each branch point and there can be a large number of branch points per molecule that are regularly, randomly, or heterogeneously spaced, each of which can have effects on mechanical properties. Unfortunately experimental synthesis and characterization of these novel polymer systems is quite time consuming. This is where molecular modeling and simulation can be critical for mapping out the fundamental mechanisms responsible for the observed behavior and to optimize/focus the experimental efforts. In this article we report details of our experimental synthetic and characterization effort along with some preliminary results from molecular dynamics, molecular mechanics, Monte...

Tetrafunctional Multigraft Copolymers as Novel Thermoplastic Elastomers

Tensile properties and morphology of tetrafunctional multigraft copolymers are investigated dependent on PS volume fraction and number of branch points. It is found that tetrafunctional multigraft copolymers with 22 vol % PS and seven branch points show a surprising high strain at break of about 2100%, about double that of commercial thermoplastic elastomers (TPE's) such as Kraton. With increasing number of branch points, strain at break and tensile strength increases, and strain at break is about 2300% for a sample with 10 branch points. Investigation of morphology using transmission electron microscopy indicates that a sample with 22 vol % PS has a wormlike microphase-separated structure with much lower long range order than other TPE's s such as Kraton. The multigraft copolymers of this study have two PS arms at each branch point. This, together with a large number of branch points per molecule, allows the elastic PI backbone to couple into a large number of reinforcing PS domains, resulting in huge elasticity, combined with a high tensile strength. Two parameters for adjusting mechanical properties of multigraft copolymers are found in our investigations: (1) functionality of the graft copolymer, tri- or tetrafunctional, and (2) number of branch points per molecule.

Scanning electron microscopy studies on tensile, tear and abrasion failure of thermoplastic elastomers

The tensile strength, tear resistance and abrasion resistance of four different types of commercial thermoplastic elastomers have been studied and their fracture surfaces examined by scanning electron microscopy. Thermoplastic polyurethane (TPU) showed elastic deformation under tensile fracture, whereas in 1,2 polybutadiene (1,2 PB) the fracture was initiated by craze formation and propagated by tear failure. Styrene-isoprene-styrene block copolymer (K1107) showed ductile type failure whereas in styrene-butadiene-styrene block copolymer containing a higher proportion of styrene and silica filler (K5152), the fracture occurred by shearing action. The tear failure surfaces of the thermoplastic elastomers showed different fracture patterns which could be correlated with the tear strength of the materials. The tear fracture surface of 1,2 PB showed stick-slip tear lines and that of TPU had a broad tear path with vertical striations. The fracture surfaces of K5152 and K1107 had the characteristics of laminar tearing and uninterrupted continuous tearing processes, respectively. The abrasion resistance of the samples was in the order TPU>1,2 PB>K5152, which was manifested through the type of ridge patterns formed on the abraded surfaces. Abraded surfaces of TPU, 1,2 PB and K5152 showed closely spaced stable ridges, widely spaced ridges bridged by elongated fibrils and highly deformed ridges, respectively.