Properties Of Elastomers Research Articles

Molecular-scale free volume and dynamic properties of a model ionomeric elastomer: Effect of curative systems

Cross-links significantly influence the chain packing efficiency and free volume in elastomeric materials, affecting their segmental dynamics. In this context, ionomeric elastomers serve as model systems that can undergo vulcanization through covalent and ionic cross-linking, enabling tuning their macroscopic properties. In this study, we investigate the effects of sulfur (covalent) and zinc oxide (ionic) cross-linking (with and without stearic acid) on the cross-link density, molecular-scale free volume, segmental relaxation and mechanical properties of carboxylated nitrile butadiene rubber (XNBR) networks by using a combination of analytical techniques including swelling studies, positron annihilation lifetime spectroscopy (PALS), dynamic mechanical analysis (DMA) and tensile testing. PALS measurements revealed a distinctive bimodal distribution of free-volume elements in the ionomeric networks, observed for the first time. This feature provided evidence of ionic aggregation-induced immobilization of polymer chains, which resulted in smaller free volume elements (1.5–2 Å) than in the bulk ionomeric matrix (3.0–3.5 Å). DMA studies revealed two segmental relaxations (α and α′) in the cross-linked elastomers, which could be tailored based on the cross-link density of the networks. The frequency-dependent DMA master curves, derived through time-temperature superposition, showed broad tan δ (loss factor) vs. frequency profiles for the networks with tan δ values exceeding 0.50, indicating their potential suitability for passive vibration damping applications. The ionically cross-linked networks exhibited superior mechanical properties compared to the networks prepared by covalent and mixed modes of curing.

Thermal and radiation effects on the cross-linking and mechanical properties of HNBR elastomers

This study investigates the enhancement of the properties of mixtures based on hydrogenated butadiene nitrile rubber (HNBR) under thermal, radiation and thermo-radiation effects by introducing into them the composition of chlorine-containing triazine and peroxide compounds (HCPX and ABTST) into the composition. It has been shown that radiation-chemical cross-linking and the formation of effective chemical cross-links in HNBR depend both on the absorbed dose of radiation and on the addition of vulcanizing agents. It has been established that the activity of hexachloroparaxylene (HCPX), dicumyl peroxide (DP) and triazine (ABTST) is not the same; the content of the gel increases markedly with increasing absorbed dose. A higher crosslinking density is observed for images subjected to thermo-radiation crosslinking. The change in the molecular structure of HNBR, observed both during heating and irradiation, has the same nature. It has been shown that the physical and mechanical properties of saturated radiation and thermal vulcanizates are practically inferior to thermo-radiation ones in strength.

Electromagnetic Slime Sentinels: Transforming Drug Delivery, Object Extraction, and Healing Innovations

Magnetic small soft-bodied robots are perfect for targeted medication administration, micromanipulation, and minimally invasive surgery because they provide non-invasive access to confined locations. Presently available magnetically operated small soft robots are based on elastomers (silicone) and fluids, such as ferrofluid or liquid metal; however, they have certain drawbacks. Robots built on elastomers have trouble deforming, which makes it challenging for them to maneuver in extremely constrained spaces. Although they may deform more easily, fluidbased robots have unstable forms and limited environmental adaptation. The non-Newtonian fluid- based magnetically actuated slime robots shown in this work combine the notable deformation capabilities of fluid-based robots with the flexibility of elastomer-based robots. These slime robots can move on different surfaces in intricate surroundings and navigate via tiny channels as little as 1.5 mm in diameter. They can carry out various tasks, including transporting, ingesting, and gripping solid items, and also adapt to various surfaces. Magnetic slime robots, combining the properties of non-Newtonian fluids and elastomers, offer promising solutions for targeted drug delivery and minimally invasive surgeries. This review discusses the design, preparation, and applications of magnetic slime robots, highlighting their potential to revolutionize biomedical operations. It also highlights their stability among different atmospheric conditions, marking a new age of targeted drug delivery systems and predicting various innovations and concepts related to magnetic slime robots.

Unveiling the Influence of Natural Weathering on the Nanomechanical Properties of Magnetorheological Elastomers

Examining the physical aging of materials is essential for assessing their long-term performance and determining their suitability for specific applications. Material aging involves changes from their initial state, including deterioration or degradation. A key example of such a progressive, continuous process is the aging of materials in response to natural weathering conditions. While extensive research has focused on macro- and micro-scale aging, further investigation at the nanoscale could provide a more detailed understanding of material deterioration. This study explores the nanomechanical properties of magnetorheological elastomers (MREs) after nine months of natural weathering, focusing on stiffness, elasticity, surface roughness, and adhesion at the nanometer scale. Atomic Force Microscopy (AFM) with a sharp tip affixed to a cantilever was employed to characterize these properties. After nine months of exposure to natural weathering, MREs exhibited unique nanomechanical changes compared to their bulk properties, highlighting the significance of nanoscale analysis. At the nanoscale, the nanomechanical properties of MREs, including stiffness and elasticity, exhibited noticeable alterations within the first month of exposure, followed by a gradual reduction, and slight increments observed up to the nine-month mark. Surface roughness steadily increased over the nine months, while adhesion energy initially rose during the first month before gradually decreasing by the end of the study. These findings provide valuable insights into the material's mechanical behavior and offer a deeper understanding of its structural and functional properties at the nanoscale.

Benzosuberyl-congested asymmetrical α-diiminonickel halides for achieving methyl-branched polyethylenes with tunable plastic to elastomeric properties

Benzosuberyl-congested asymmetrical α-diiminonickel halides for achieving methyl-branched polyethylenes with tunable plastic to elastomeric properties

Property Prediction of Bio-Derived Block Copolymer Thermoplastic Elastomers Using Graph Kernel Methods.

Increasing the diversity of bio-based polymers is needed to address the combined problems of plastic pollution and greenhouse gas emissions. The magnitude of the problems necessitates rapid discovery of new materials; however, identification of appropriate chemistries maybe slow using current iterative methods. Machine learning (ML) methods could significantly expedite new material discovery and property identification. Here, PolyAGM, a ML algorithm using graph kernel methods, is introduced and used to predict the properties of block copolymers and identify the responsible structural 'motifs'. It applies a "fingerprinting" method to convert Graph representations of polymers into numerical vectors. The Graphs explicitly encode the entire copolymer of atoms and bonds such that the sequencing of chemical features and polymer chain length are included, alongside relevant stereochemical information. PolyAGM gives predictions for both thermal and mechanical properties that are in good agreement with experimental measurements. This work focuses on predicting the properties of bio-derived ABA-block polymer thermoplastic elastomers, but the general fingerprinting technique of PolyAGM should be relevant to other application fields.

Elastic properties of a magnetic elastomer

Magnetoactive (aka magnetorheological) elastomer is a composite material consisting of an elastic matrix and magnetic filling substance. A study dedicated to the relationship between its viscoelastic parameters and the strength of the external magnetic field has been done. Under the influence of a field, the material can demonstrate elasticity and viscosity increased by ten folds. The elastic properties of the composite remaining under those conditions heavily depend on the degree of deformation of the sample. Thus, this type of magnetic composite is a prospective material for being used as the working body in controllable dampers.

Prediction and Explanation of Properties in Multicomponent Polyurethane Elastomers: Integrating Molecular Dynamics and Machine Learning

Prediction and Explanation of Properties in Multicomponent Polyurethane Elastomers: Integrating Molecular Dynamics and Machine Learning

Molecular dynamics simulations of the mechanical properties of dissociative dynamic bond elastomers with different binding-site sequences

Molecular dynamics simulations of the mechanical properties of dissociative dynamic bond elastomers with different binding-site sequences

A systematic review of methodologies and solutions for recycling polyurethane foams to safeguard the environment

Today, plastic plays a pervasive role in everyday life. Their improper disposal can create ongoing environmental challenges. Polyurethane (PU) is a polymer with elastomeric properties that exhibits significant adhesion and durability. PU has various colors and resistance to acid and alkali substances. The widespread use of PU has caused a significant presence of these compounds in landfills. Therefore, it can cause significant plastic pollution globally. This increased environmental concern has prompted researchers and innovators to explore sustainable methods for recycling PU foam. Therefore, the recycling of PU waste is recognized as an essential requirement due to its economic and environmental benefits. Although the latest reviews focused on physical, chemical, and biological methods of PU recycling, a comprehensive review of other PU recycling methods is needed. Therefore, the present study is a systematic review of recent initiatives and innovations in the field of recycling and modification of PU foam production methods to recognize and reduce environmental impacts. In the present study, major global databases such as Web of Science, PubMed, Scopus, Google Scholar, and Iranian databases (up to January 2024) were searched with relative keywords to identify studies published in authoritative journals. Data were collected from qualified articles on different PU recycling methods and innovative processes. From a total of 1088 articles found, finally, 46 studies met the objectives and inclusion criteria. Based on the results, today various methods are used to recycle PU compounds, but more attention has been paid to efficient methods such as energy production and high-consumption products such as rubber and adhesive from these compounds. In addition, it highlights some approaches, such as the production of absorbents from PU foams, which not only improve the current technology but also show promise in reducing the environmental impact of this ubiquitous material.

Enhancing the Properties of Liquid Crystal Polymers and Elastomers with Nano Magnetic Particles.

Side-chain liquid crystal polymers have been mixed with ferromagnetic particles, and the formation of a monodomain in magnetic fields studied. At relatively low concentrations, the presence of ferroparticles substantially speeds up the rate of formation of a monodomain within the magnetic field, and, at a given concentration of ferroparticles, that rate is independent of the magnetic field's strength. In this way, the rapid formation of a monodomain is possible at magnetic field strengths far lower those required for the liquid crystal polymer alone. This is anticipated to be very helpful in the fabrication of devices based on monodomain liquid crystal elastomers. Wide-angle x-ray scattering has been used to monitor the formation of the monodomain and small-angle x-ray scattering gives some indication of the ferroparticles' behaviour. A model is developed to explain their behaviour. The alignment properties of the ferroparticles are related to their ability to form chains under the influence of very low magnetic fields; these chains are of relatively low stability and may become disrupted after long periods of time, high magnetic fields, or high concentrations. In general, the best results for alignment were at volume fractions below 1%, and under these conditions there is the potential for producing monodomain samples with improved properties; in particular, shape changes with temperature are significantly larger as a result of improved backbone orientation. Experiments involving monodomain formation and director realignment suggest that the presence of ferroparticles results in a modification of the mechanism for alignment development, driven by the organization of the polymer backbone, as a consequence of the constraints offered by the morphology of the chains of the ferroparticles.

Recent Advances of PDMS In Vitro Biomodels for Flow Visualizations and Measurements: From Macro to Nanoscale Applications.

Polydimethylsiloxane (PDMS) has become a popular material in microfluidic and macroscale in vitro models due to its elastomeric properties and versatility. PDMS-based biomodels are widely used in blood flow studies, offering a platform for improving flow models and validating numerical simulations. This review highlights recent advances in bioflow studies conducted using both PDMS microfluidic devices and macroscale biomodels, particularly in replicating physiological environments. PDMS microchannels are used in studies of blood cell deformation under confined conditions, demonstrating the potential to distinguish between healthy and diseased cells. PDMS also plays a critical role in fabricating arterial models from real medical images, including pathological conditions such as aneurysms. Cutting-edge applications, such as nanofluid hemodynamic studies and nanoparticle drug delivery in organ-on-a-chip platforms, represent the latest developments in PDMS research. In addition to these applications, this review critically discusses PDMS properties, fabrication methods, and its expanding role in micro- and nanoscale flow studies.

Preparation and properties of polyamide elastomers by a new synthesis route of Michael addition reaction

At present, the mainstream industrial synthesis method of polyamide is still bulk fusion polymerization, which is not in line with the concept of green synthesis because of the high threshold of reaction conditions and large energy consumption. Based on this, a new synthesis route of polyamide elastomer was studied in this paper. By synthesizing the end-functionalized long carbon chain diacrylamide (DDA) containing amide bonds, the synthesis mechanism was made by the thiol double bond Michael addition reaction. A series of polyamide elastomers with different ratios of hard and soft segments were synthesized by using dimercaptan chain extenders with different molecular weights. The results showed that the new synthesis route successfully prepared DDA and polyamide elastomers. The mechanical properties of the products were excellent, and the strain rate could reach 383 %. Tensile strength up to 23.08 MPa. The synthesis route has the characteristics of simple reaction process, mild reaction conditions and high reaction conversion rate. It provides theoretical guidance for the new synthesis route of polyamide elastomer.

Co Hybrids modified piperazine pyrophosphate towards efficient flame retardancy, smoke suppression, and high mechanical properties of styrenic thermoplastic elastomer

The highly flammable nature of thermoplastic elastomers (TPE) results in poor fire safety performance. The large addition of flame retardants leads to a significant decrease in mechanical properties. To solve above challenges, we design a multilayer core-shell flame retardant, piperazine pyrophosphate@ tannic acid@ Co amorphous hybrids (PAPP@TA@Co-2-MIM) and add it to TPE to enhance the fire safety and mechanical performance simultaneously. It was found that the addition of 32 wt% PAPP@TA@Co-2-MIM achieved a UL-94 V-0 rating of TPE composites, with a limiting oxygen index of 27 %. Compared to pure TPE, the peak heat release rate, total heat release, total smoke production, and peak CO release rate of TPE/PAPP@TA@Co-2-MIM were reduced by 79.8 %, 37.1 %, 42.9 %, and 82.5 %, respectively, effectively suppressing the release of heat, smoke, and toxic gases. Besides, the flame-retardant mechanism was also explained. In terms of mechanical performance, benefiting by the bridging effect of the core-shell structure, the tensile strength of TPE/PAPP@TA@Co-2-MIM increased by 52.7 %, compared to TPE/PAPP. This study designed a TPE composite material that showed good thermal stability, high fire safety performance and enhanced mechanical properties.

Quantitative Study on Reinforcing Mechanism of Nanofiller Network in Silicone Elastomer Based on Fluorescence Labeling Technology

Although there have been many theoretical studies on the enhancement effect of nanofiller networks and their interaction with elastomer molecular chains on the mechanical properties of elastomers, its mechanism description is still not completely clear. One of the main obstacles is the lack of quantitative characterization techniques and corresponding theoretical models for the three-dimensional morphology of complex nanofiller networks. In this paper, the precipitated silica-filled silicone rubber was studied by fluorescence labeling combined with laser scanning confocal microscopy, and the real three-dimensional images of dispersion and aggregation structure of filled rubber systems were obtained. The microstructure evolution of nano-particle aggregates caused by the increase in the filler volume fraction was quantitatively described, and the reinforcement mechanism of elastomers with a distribution of aggregates and filler networks composed of nanoparticles was studied. Furthermore, a nano-composite reinforcement model based on volume fraction, particle shape, interaction, and filler dispersion has been proposed.

Effect of in-situ Incorporated Silica Particles on Properties of Polyurethane Elastomer

Effect of in-situ Incorporated Silica Particles on Properties of Polyurethane Elastomer

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.

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.

Polyglycerol Sebacate/polycaprolactone/reduced graphene oxide composite scaffold for myocardial tissue engineering

The aim of this research was to fabricate and evaluate polyglycerol sebacate/polycaprolactone/reduced graphene oxide (PGS-PCL-RGO) composite scaffolds for myocardial tissue engineering. Polyglycerol sebacate polymer was synthesized using glycerol and sebacic acid prepolymers, confirmed by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Six PGS-PCL-RGO composite scaffolds (S1-S6) with various weight ratios were prepared in chloroform (CF) and acetone (Ace) solvents at 8 CF:2Ace and 9 CF:1Ace volume ratios, using the electrospinning method at a rate of 1 ml/h and a voltage of 18 kV. The scaffolds' chemical composition and microstructure were characterized by FTIR, XRD, and scanning electron microscopy (SEM). Further investigations included tensile testing, contact angle testing, four-point probe testing for electrical conductivity, degradation testing, and cytotoxicity testing (MTT). The results showed that adding 2%wt RGO to the composite scaffold decreased fiber diameter and degradation rate, while increasing electrical conductivity and ductility. The 33%PGS-65%PCL-2%RGO (S3) composite scaffold exhibited the lowest degradation rate (23.87 % over 60 days) and the highest electrical conductivity (51E-3 S/m). Mechanical evaluations revealed an elastic modulus of 2.46 MPa and elongation of 62.43 %, aligning closely with the heart muscle's elastomeric properties. The contact angle test indicated that the scaffold was hydrophilic, with a water contact angle of 61 ± 2°. Additionally, the cell toxicity test confirmed that scaffolds containing RGO were non-toxic and supported good cell viability. In conclusion, the 33%PGS-65%PCL-2%RGO composite scaffold exhibits mechanical and structural properties similar to heart tissue, making it an ideal candidate for myocardial tissue engineering.

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.