Elastomer Composites Research Articles

Fluorographene and carbon nanotubes fillers reinforced nitrile butadiene rubber with enhanced mechanical, wear and oil resistant properties

AbstractIn this work, we prepared nitrile butadiene rubber (NBR) composites with fluorographene (FG) and carbon nanotubes (CNTs) as hybrid fillers by a solution‐blending method. The resulting composites xFG/yCNTs‐NBR, where x and y represent the loading of FG and CNTs respectively, show significantly improved physical and mechanical properties. The hybrid fillers can form a filler network in the rubber matrix, leading to efficient energy dissipation. As a result, when the mass ratio of FG to CNTs is 1:1 and the total filler loading is 20 phr, the tensile strength of 10FG/10CNTs‐NBR is as high as 12.1 MPa. Furthermore, due to inherent lubricating and oil‐repelling effects of FG, 10FG/10CNTs‐NBR shows an abrasion resistance index (ARI) of 187% and a volume change of 2.38% after 72 h of soaking in aviation oil, which are 24% higher and 48% lower than the corresponding values of unfilled NBR composites, respectively. These results indicate that the hybrid fillers can effectively enhance the mechanical, wear and oil resistant properties of the elastomer composites, which is conductive for application of the NBR‐based composites.

Simultaneous Visualization of Microscopic Conductivity and Deformation in Conductive Elastomers.

Conductive elastomers are promising for a wide range of applications in many fields due to their unique mechanical and electrical properties, and an understanding of the conductive mechanisms of such materials under deformation is crucial. However, revealing the microscopic conduction mechanism of conductive elastomers is a challenge. In this study, we developed a method that combines in situ deformation nanomechanical atomic force microscopy (AFM) and conductive AFM to successfully and simultaneously characterize the microscopic deformation and microscopic electrical conductivity of nanofiller composite conductive elastomers. With this approach, we visualized the conductive network structure of carbon black and carbon nanotube composite conductive elastomers at the nanoscale, tracked their microscopic response under different compressive strains, and revealed the correlation between microscopic and macroscopic electrical properties. This technique is important for understanding the conductive mechanism of conductive elastomers and improving the design of conductive elastomers.

Nonlinear electromechanical responses in multi-layered fiber-reinforced dielectric elastomer composites

The capabilities of dielectric elastomer actuators (DEAs) across various applications of soft smart materials constantly expands. However, the electromechanical behavior of multi-layer anisotropic dielectric elastomer composites (DECs), has not been studied accurately despite of its great potentials. Hence, this paper proposes a comprehensive coupled electromechanical model to address this issue and effectively capture various attributes of such an actuator including the number of layers and layers’ configuration. Using a coupled nonlinear model enables it to analyze multi-layer DECs with an unlimited number of layers, and reinforcing fiber families. A new user defined material subroutine is developed to explore the actuation performance of different multi-layer DECs such as binder, diaphragm, and tubular actuators. It provides a unique insight into effects of the number and arrangement of layers on the electromechanical performance of these actuators. Experimental results have been used for validation of developed model and numerical implementation. The results propose a practical tool for designing and optimizing fiber-reinforced multi-layer DECs based on objective purposes, contributing to developing more efficient and reliable electromechanical models for these materials.

Data-driven analysis of structural instabilities in electroactive polymer bilayers based on a variational saddle-point principle

In this work, we use a data-driven approach to model the onset of wrinkling in composite dielectric elastomer (DE) bilayer structures that are subjected to combined electro-mechanical loading conditions. Specifically, the critical surface-charge density required to activate wrinkling and the resulting number of half-waves are determined as functions of the tunable geometrical and material features of the DE bilayer using supervised machine learning (ML) models. The required data for the ML surrogates is generated using a finite-element-based framework for structural stability analysis of the DE bilayer, which is rooted in a variational saddle-point formulation for non-linear electro-elastostatics. Within the considered broad design space for the DE bilayer, the data points are sampled according to a Latin-hypercube-type design, following which training and test datasets containing the values of the target variables for the sampled input-feature vectors are generated using the adopted finite-element framework. Subsequently, we implement and compare the capabilities of different ML models to capture accurately the non-linear dependence of the wrinkling characteristics on the tunable features of the DE bilayer.

Application and Properties of Polyglycolic Acid as a Degradation Agent in MPU/HNBR Degradable Elastomer Composites for Dissolvable Frac Plugs.

In this research, fully degradable elastomeric sealing materials were developed to enhance the environmental sustainability of oil and gas extraction. The modification of millable polyurethane rubber (MPU) with polyglycolic acid/hydrogenated nitrile butadiene rubber (PGA/HNBR) led to the synthesis of PGA@MPU/HNBR composite materials. The impact of varying monomer quantities on the mechanical properties, degradation behavior, degradation mechanisms, and thermal stability of these materials was investigated. Our findings illustrate that an increasing proportion of HNBR in the PGA@MPU/HNBR composite materials resulted in a decreased degradation rate. Simultaneously, higher HNBR content improved the thermal stability of the materials, while the inclusion of PGA reduced material hardness, rendering the composites more susceptible to swelling. At an HNBR content of 40 phr, MPU at 60 phr, and PGA at 6 phr, the composite material demonstrated the highest retention of mechanical properties at 31.3% following 168 h of hydrolysis at 100 °C. The degradation of the composite materials in 100 °C water primarily resulted from the hydrolysis of MPU's ester groups, with HNBR remaining unaffected.

Insight into the fracture energy dissipation mechanism in elastomer composites via sacrificial bonds and fillers.

Most tough elastomer composites are reinforced by introducing sacrificial structures and fillers. Understanding the contribution of fillers and sacrificial bonds in elastomer composites to the energy dissipation is critical for the design of high-toughness materials. However, the energy dissipation mechanism in elastomer composites remains elusive. In this study, using a tearing test and time-temperature superposition, we investigate the effect of fillers and sacrificial bonds on the energy dissipation of elastomer composites consisting of poly(lipoic acid)/silver-coated Al fillers. We found that the fillers and sacrificial bonds mutually enhance both the intrinsic fracture energy and the bulk energy dissipation, and moreover the sacrificial bonds play a more important role in enhancing fracture toughness than the fillers. It is unreasonable to rely solely on the loss factor for bulk energy dissipation. The addition of sacrificial bonds results in a chain segment experiencing greater binding force compared to the addition of fillers. This suggests that the chain segment consumes more energy during its movement. By calculating the length of the Kuhn chain segment and the Kuhn number, it is evident that the addition of sacrificial bonds results in a greater binding force for the chain segment than the addition of fillers, and this enhanced binding force increases the energy consumption during the motion of the chain segment.

SIMULATION OF CRACK PROPAGATION IN FILLED ELASTOMERS

The results of computer simulation of the crack growth in an elastomeric nanocomposite and its interaction with microscopic strands that can occur between adjacent closely spaced filler particles during material loading are presented. The hypothesis that elastomeric material is able to withstand significantly greater loads under uniaxial tension compared to other types of stress state (at the same intensity of deformation) is used in the simulation. A strength criterion taking into account this effect (maximum strength is achieved with uniaxial tension) is developed. Numerical studies showed that, with a fairly close approach of the crack front to the gap between filler particles, the formation of a reinforced microstrand is possible, connecting the crack "shores" and, accordingly, preventing its further progress. It is well known that the addition to elastomer of a rigid filler with good adhesion to matrix allows the resulting composite to withstand a significantly higher external load compared to unfilled material. This is due to the fact that micro-breaks in the material appear mostly on structural defects. So nothing prevents the crack growth in a material without filler. However, microstrands that form between close placed filler particles in an elastomeric composite can appreciably delay its propagation.

Tensile testing of composite elastomer specimen

Composite elastomers are polymers capable of large reversible highly elastic deformations over a wide temperature range. Production of elastomeric composite materials is one of the intensively developing areas of industry and science, the aim of which is to find materials ready to work in both domestic and extreme operating conditions. When creating new composite polymers, magnetically active elastomers, there are a number of physical and mechanical requirements for material characteristics that need to be checked on testing machines during tensile and compressive testing of specimens. These requirements include: elasticity, insignificant residual deformations under various test modes up to material rupture in tension. The specified requirements were tested on an automated testing machine in various modes. The diagrams of linear and nonlinear characteristics of tensile stresses of the specimen depending on the strain values up to the moment of its rupture were constructed and analyzed. The analysis of the constructed hysteresis loops at stretching - contraction of the specimen showed the possibility of its use as a shock-absorbing material. Establishing the relationship between the tensile forces and the resulting deformations, including the effect of a strong magnetic field on the material, is important for further work on selecting the most appropriate range of use of this material for various conditions of its application.

Mechanical properties and molecular adhesion exhibited by inorganic–organic composite elastomers

Organic–inorganic composite elastomers with reversible cross-links formed by β-cyclodextrin and adamantane (Ad) were prepared. Excess Ad units improve the mixability of polydimethylsiloxane and poly(ethyl acrylate) to increase the healing ratio.

Degradable biomedical elastomers: paving the future of tissue repair and regenerative medicine.

Degradable biomedical elastomers (DBE), characterized by controlled biodegradability, excellent biocompatibility, tailored elasticity, and favorable network design and processability, have become indispensable in tissue repair. This review critically examines the recent advances of biodegradable elastomers for tissue repair, focusing mainly on degradation mechanisms and evaluation, synthesis and crosslinking methods, microstructure design, processing techniques, and tissue repair applications. The review explores the material composition and cross-linking methods of elastomers used in tissue repair, addressing chemistry-related challenges and structural design considerations. In addition, this review focuses on the processing methods of two- and three-dimensional structures of elastomers, and systematically discusses the contribution of processing methods such as solvent casting, electrostatic spinning, and three-/four-dimensional printing of DBE. Furthermore, we describe recent advances in tissue repair using DBE, and include advances achieved in regenerating different tissues, including nerves, tendons, muscle, cardiac, and bone, highlighting their efficacy and versatility. The review concludes by discussing the current challenges in material selection, biodegradation, bioactivation, and manufacturing in tissue repair, and suggests future research directions. This concise yet comprehensive analysis aims to provide valuable insights and technical guidance for advances in DBE for tissue engineering.

ВЛИЯНИЕ ГИДРОЛИЗАТА КОЛЛАГЕНА НА КИНЕТИКУ ВУЛКАНИЗАЦИИ И ПЛОТНОСТЬ СШИВАНИЯ РЕЗИН НА ОСНОВЕ БУТАДИЕН-НИТРИЛЬНОГО КАУЧУКА БНКС-18

The effect of collagen hydrolysate (CH) obtained from the swim bladder of northern fish species on the set of operational properties of elastomers based on BNKS-18 nitrile butadiene rubber with acrylonitrile content of 18 wt.% was studied. The vulcanization kinetics of elastomeric blends were determined on a D-RPA 3000 rotorlessrheometer (MonTech, Germany). Tensile strength and elastic properties of vulcanizates were determined on an Autograph AGS-JSTD testing machine (Shimadzu, Japan). Frost resistance was evaluated by the value of frost resistance coefficient according to elastic rebound after compression at -20, -30, -40, -50 °C. The density of the vulcanization network of the studied elastomers was determined according to the Flory-Rener equation by the method of equilibrium swelling of vulcanizates in chloroform. The analysis of vulcanization kinetics showed that the introduction of collagen hydrolysate obtained by us into the composition of BNKS-18 based elastomer increased the minimum torque. That is, the viscosity of the studied elastomers increased before the start of the main vulcanization process. As demonstrated in this study, CH significantly affects the crosslinking density of elastomer. Introduction of CH in the composition of elastomers leads to the formation of a sufficiently dense and strong vulcanization network. This is apparently associated with the fact that CH fragments interact with the ingredients of the vulcanizing system and the rubber macromolecules, participating in the structuring of the material. It was found that the introduction of CH increased modulus at 100% elongation and tensile strength, while elongation at break decreased. The maximum value of tensile strength corresponds to the introduction of 3phr of CH and amounts to 16.9 MPa, which is 37% higher in comparison with control elastomers without CH. It was shown that the increase of crosslink density of vulcanization network of the obtained elastomers was accompanied by increase of frost resistance coefficient at -30 and -40 °C. The field of application of the developed materials is manufacturing of rubber seals, cuffs, oil seals, gaskets designed for the Far North and the Arctic equipment.

Влияние алюмосиликатных ценосфер на структуру и свойства эластомерных композиционных материалов на основе этилен-пропилен-диеновых эластомеров

The use of industrial waste to develop new value-added materials and reduce their environmental impact is one of the most important tasks of science and industry, which can largely solve the problem of waste pollution. This work is aimed at studying the effect of different concentrations of fly ash aluminosilicate cenospheres on the structure and properties of elastomeric composites. In this work, using laboratory rollers, composite materials based on ethylene-propylene-diene rubber (EPDM-40) with different mass fractions of fly ash (10, 20 and 30 %) were obtained. Using the method of optical microscopy, the microstructure of mixtures of EPDM and aluminosilicate cenospheres was studied and it was shown that the filler content of more than 30% increases the content of larger cenosphere agglomerates in the structure, which indicates interfacial separation in mixtures, probably due to the fact that mechanical mixing on mixing equipment does not allow to achieve a uniform distribution of the filler throughout the elastomeric matrix. The IR spectra show the appearance of new absorption bands in the region. 1400 – 800 cm–1, corresponding to Si – O – Si stretching vibrations present in aluminosilicate cenospheres. According to the thermogravimetry data of the studied compositions, the introduction of aluminosilicate cenospheres contributed to a slight increase in the thermal stability of the tested composition with a cenosphere content of more than 30%. The influence of the concentration of aluminosilicate cenospheres on the resistance of composites to aggressive media was analyzed and it was found that the introduction of a cenosphere filler in an amount of 10 to 30 % in a mixture based on EPDM can increase the oil and petrol resistance of materials.

In silico optimization of actuation performance in dielectric elastomer composites via integrated finite element modeling and deep learning

Dielectric elastomers (DEs) require balanced electric actuation performance and mechanical integrity under applied voltages. Incorporating high dielectric particles as fillers provides extensive design space to optimize concentration, morphology, and distribution for improved actuation performance and material modulus. This study presents an integrated framework combining finite element modeling (FEM) and deep learning to optimize the microstructure of DE composites. FEM first calculates actuation performance and the effective modulus across varied filler combinations, with these data used to train a convolutional neural network (CNN). Integrating the CNN into a multi-objective genetic algorithm generates designs with enhanced actuation performance and material modulus compared to the conventional optimization approach based on FEM approach within the same time. This framework harnesses artificial intelligence to navigate vast design possibilities, enabling optimized microstructures for high-performance DE composites.

Numerical Assessment of Electrical and Magnetic Characteristics of Elastomer Composites

Numerical Assessment of Electrical and Magnetic Characteristics of Elastomer Composites

Ethanol-assisted room-temperature rapid self-healing polydimethylsiloxane-polyurea/carbon composite elastomers for energy harvesters and smart sensors

Multiple H-bond networks and unique structures are designed in CCF/PDMS. This CCF/PDMS elastomer simultaneously exhibits excellent tensile, self-healing, and triboelectric properties, promising to be used in energy harvesters and motion sensors, etc.

THE FRACTAL RHEOLOGY OF MAGNETORHEOLOGICAL ELASTOMERS DESCRIBED THROUGH THE MODIFIED ZENER MODEL AND THE COLE–COLE PLOT

The main objective of this study focuses on using, for the first time, the Cole–Cole semilogarithmic fractal plot to study the fractal rheological behavior of magnetorheological elastomer materials using the fractional Zener model. Experimental data and theoretical results show that the Cole–Cole semilogarithmic fractal plot predicts the Zener mathematical model’s material parameters. This paper elucidates the benefits of using Cole–Cole semilogarithmic fractal plots to accurately predict material rheological properties of composite elastomer reinforced with nano or microiron particles observed during experimental tests.

A mechanoluminescent CdSiO3:Tb3+/PDMS composite elastomer with a deep trap

The mechanoluminescence of CdSiO3:Tb3+/PDMS composite elastomers is partly derived from the deep trap energy of phosphors under pressure.

Flexible pressure sensors based on reduced graphene oxide @ porous silicone elastomers with good resolution and wide working range

Current flexible piezoresistive pressure sensors still face challenges, such as poor stability and a limited detection range, making it difficult to accurately discern small-scale pressures in the Pa or MPa range when meeting sudden pressure events. To tackle the above issues, this study presents the development of a competent sensor composed of porous conductive elastomer and laser-induced graphene electrodes. The substrate of the composite elastomer is a porous silicone elastomer obtained by the additive reaction using template methods, and the conductive filler consisting of reduced graphene oxide is synthesized through an eco-friendly approach. We demonstrated that the sensors fabricated here have the ability to precisely resolve pressures from 542 Pa to 1.5 MPa with long-term stability, as well as the detection of subtle signals, such as pulse pulsation and throat vibrations. Above all, such sensors have great potential in the application of human-machine interaction.

Effects of Aging on Macro Performance and Multiscale Structure Change of Highly Filled Elastomer Composites for Chip Cooling Investigated by Broadband Dielectric Spectroscopy

Effects of Aging on Macro Performance and Multiscale Structure Change of Highly Filled Elastomer Composites for Chip Cooling Investigated by Broadband Dielectric Spectroscopy

Recyclable, thermally conductive, self-healing, and strong adhesive elastomer composite based on multiple hydrogen-bonded interactions

Advances in next-generation soft electronic devices, soft robotics, and biomedical devices rely on developing highly deformable, self-healable, adhesion, and thermally conductive elastomers or their composites. However, multifunctional composite elastomers that simultaneously possess these properties remain a daunting challenge. Here, we report a poly (thioctic acid)/aluminum composite elastomers to solve this problem based on multiple hydrogen-bonded interactions. The multiple hydrogen bonds provide the poly (thioctic acid)/aluminum composite elastomers with enhanced adhesion and a stretchable covalent adaptive network, leading to excellent extensibility (331 %), high adhesion energy (1327 J/m2), and excellent self-healing efficiency (93 %). The presence of aluminum fillers ensures enhanced thermal conductivity (1.73 W/(m·K)) of the composite elastomers. This work shows a promising approach to the design of functional composite elastomers for next-generation soft electronic devices.