Elastomeric Composite Materials Research Articles

The Influence of Aluminosilicate Cenospheres on the Structure and Properties of Elastomeric Composite Materials Based on Ethylene–Propylene–Diene Elastomers

The Influence of Aluminosilicate Cenospheres on the Structure and Properties of Elastomeric Composite Materials Based on Ethylene–Propylene–Diene Elastomers

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.

New recyclable and self-healing elastomer composites using waste from toner cartridges

Product recycling reintroduces what is discarded as waste and minimizes the environmental impact on our society. Among the different types of waste from electrical and electronic equipment, toner recycling often falls short, downcycling plastic components. This study introduces an innovative approach in which waste parts from toner cartridges are valorized to develop (recyclable and) self-healing elastomeric composite materials. The synergy between carboxylated nitrile rubber (XNBR) as the elastomeric phase and high-impact poly (styrene) (HIPS) as the thermoplastic phase derived from toner cartridge waste was explored and optimized. This combination resulted in the creation of a thermoplastic elastomer exhibiting robust mechanical properties and self-healing capabilities with a tensile strength of 6.6 ± 0.2 MPa and a temperature-driven mechanical recovery of 100%. Furthermore, the capacity of toner powder, an integral component of waste, to act as a reinforcing filler was confirmed, with a 50% increase in mechanical strength compared with the unfilled composite. Moreover, an increase in toner content (up to 20 phr) resulted in an optimal balance between tensile strength and self-healing capacity, surpassing the traditional antagonism between these properties. As a result, this research opens a new pathway in the field of self-healing composites and suggests a practical and environmentally friendly approach for managing electronic waste, effectively supporting the principles of Circular Economy.

Stimuli–Responsive Mechanoadaptive Elastomeric Composite Materials: Challenges, Opportunities, and New Approaches

Stimuli–responsive mechanoadaptive materials, capable of reversibly changing their mechanical properties when exposed to an external stimulus, are the next generation of smart materials with immense transformative potential for various technological applications. Although the concept of adaptive mechanical properties has been proven for some materials, it remains very challenging for soft elastomeric materials. The aim of this review is to provide new ideas and strategies for the development of mechanoadaptive elastomeric composites using commercial rubber as the matrix polymer. The fundamental question addressed here is as follows: How do the phase‐responsive functional fillers alter the mechanical properties? For a given physical network environment, what is the mechanism that gives rise to the stimuli–responsive properties of the resulting composites? Herein, the preparation, structure, and properties of recently developed mechanoadaptive elastomeric materials are summarized. Furthermore, based on their structure–property relationships, plausible applications of these smart materials in various technology‐specific applications such as soft robotics, actuators, sensors, smart tires, automotive design, aerospace, etc. are demonstrated with representative examples. Finally, the article critically discusses the existing challenges in the field of mechanoadaptive elastomers in order to provide valuable insights in this area.

Gas pyrolysis resin as a plasticizer for composite elastomer materials

The aim of the study is to study the effect of gas pyrolysis resin on the properties of elastomeric composite materials. It has been established that in the presence of it in the thiuram vulcanizing system, the relative rate of vulcanization of styrene-butadiene rubber increases, the time to reach the optimum vulcanization decreases, but the degree of vulcanization decreases, proportional to the maximum torque, and when using a sulfur vulcanizing system, it activates the vulcanization process, which is facilitated by the presence in its composition of active functional groups (-OH, -COOH, etc.). It is shown that the tensile strength and relative elongation of the vulcanizates increase, while the elasticity remains at an average level.

SELF-HEALING STRATEGIES IN RUBBER COMPOSITES

Inspired by some of the mechanisms that occur in nature, self-healing materials are characterized by the ability to recover, partially or totally, their initial properties after suffering damage. These materials constitute an efficient alternative for extending the lifecycle of products, as well as for reducing the amount of waste generated. At the same time, they reduce maintenance and repair costs. In this work, examples of recent developments in the field of elastomeric composite materials are presented, studying different matrices, natural rubber (NR), epoxidized natural rubber (ENR), styrene-butadiene rubber (SBR) and nitrile rubber (NBR), and using diverse repair strategies, hydrogen bonds, disulfide exchange reactions, Diels-Alder chemistry and ionic interactions. The effect of adding carbon-derived reinforcing fillers (graphene oxide) and sustainable alternative fillers (ground tire rubber) is also analyzed. It is studied how the presence and type of filler influences the healing capacity of elastomeric matrices, reaching repair efficiencies of up to ~80%, without detriment to their mechanical performance.

In-situ coupled mechanical/electrical investigations of EPDM/CB composite materials: The electrical signature of the mechanical Mullins effect

In-situ coupled mechanical/electrical investigations on EPDM-based composite materials prepared using CB fillers of different (low and high) structure and at different concentrations have been carried-out by cyclic and continuous loading, with simultaneous measurements of stress, strain and electrical conductivity. By investigations in dependence on the strain amplitude and unloading rate, the relationship linking the evolution of the electrical conductivity during mechanical deformation to the mechanical Mullins effect is demonstrated. A characteristic electrical signature accompanying the mechanical Mullins effect is revealed, originating from a kinetic reorganisation of the CB fillers by competing mechanisms of de-percolation and re-percolation. Notable differences between the electrical and the mechanical Mullins effect are also found, in particular, in relation to the kinetics of the stabilization of properties after the first mechanical deformation cycle. Our study brings new light into understanding the coupled evolution of mechanical and electrical properties of elastomeric composite materials, with possible applications in monitoring the material properties under mechanical deformation by in-situ electrical measurements.

Electric and magnetic properties of a composite consisting of silicone rubber and ferrofluid

Electric and magnetic properties in the frequency range (500 Hz − 2 MHz) of a composite consisting of silicone rubber and ferrofluid with magnetite particles, in a mass ratio 1/20, were investigated. Structural analysis of nanoparticles within the ferrofluid (FM sample) was performed by XRD diffraction and morphology of composite (SR-FM sample), was investigated by SEM analysis. The frequency dependence of the imaginary component, μ″, of complex magnetic permeability of composite sample exhibits two maxima. These have been associated with the Brownian relaxation process within the ferrofluid drops remained in vesicles of silicone rubber. At the same time, a dielectric relaxation process attributed to the Schwarz relaxation was also highlighted. The mechanical mobility, u, of the charge carriers, u = 1.5∙108 m/sN, from the composite sample, was computed. Based on the complex impedance measurements, the frequency dependence of the conductivity, σ(f), was determined, which respects the Jonscher universal law. The static conductivity, σdc = 2.38∙10-7 S/m, of composite sample, was determined. The results allowed the evaluation of the energy barrier of electrical conduction process, Wm = 0.353 eV and the crossover frequency, ωc = 3.39∙105 rad/s, for composite sample. The performed study is useful in manufacturing magnetic elastomeric composite materials with predetermined properties and for possible technological and biomedical applications.

Reinforcing effects in elastomeric composites, filled with particles of mineral fillers, based on silicon dioxide and carbon

When creating elastomeric composites, structures and products made from such materials, considerable attention is paid to environmental issues, as well as to improving economic efficiency and energy efficiency in its production. In this regard, the development of new types of strengthening highly dispersed fillers for elastomeric and polymer composite materials, including those of natural origin, providing an optimal balance of mechanical properties of composites and having advantages over existing solutions, is an actual task. In the course of the work, a technology was developed for producing highly dispersed fillers by ultrafine grinding of raw materials. The obtained experimental data shows a significant reinforcement effect (up to five times) with a decrease in the average particle size of the filler. It is established, that he most effective filler, in terms of reinforcement, are particles based on amorphous silicon dioxide, obtained from rice husk processing products and shungite rock. The significant influence of the surface functionality and the carbon/silicon dioxide ratio of submicron filler particles on the mechanical properties of elastomeric composites is shown. It is established that new classes of reinforcing fillers can be recommended for practical use in the future.

Characterization of the resistance to abrasive chemical agents of test specimens of thermoplastic elastomeric polyurethane composite materials produced by additive manufacturing

AbstractCurrently the development of additive manufacturing and the emerging of new materials allows to manufacturing process obtaining functional models with properties and geometries adapted to each particular case with low production times and costs. Specifically, 3D printing by fused deposition modeling (FDM) that operates with polymers, is one of the most widespread and popular techniques. Among the numerous materials available, the elastomeric polymers, whose base composition is polyurethane, are becoming increasingly important since allow to obtain flexible pieces with good mechanical and chemical resistance. The objective of this work is to study the effect of an abrasive fluid (commercial automotive petrol) on test specimens made of two different elastomeric filaments commonly used in 3D printing, thermoplastic polyurethane and thermoplastic elastomers. To do this, some of the main physical and mechanical properties – hardness, weigh variation and tensile and bending tests ‐ of these materials were analyzed after immersion of the samples in petrol for different periods of time. Specimens with different volume of material inside their structure were designed in order to determine the effect of the volume filling on the mechanical properties and the petrol effect.

ТЕПЛОФИЗИЧЕСКИЕ И ДИНАМИЧЕСКИЕ СВОЙСТВА БУТАДИЕН-НИТРИЛЬНОЙ РЕЗИНЫ НАПОЛНЕННОЙ СВЕРХВЫСОКОМОЛЕКУЛЯРНЫМ ПОЛИЭТИЛЕНОМ

The results of the study of the complex of properties of an elastomeric composite material based on nitrile butadiene rubber BNKS-18 and ultrahigh molecular weight polyethylene are presented. The effect of UHMWPE on the vulcanization characteristics of rubber compounds, the physicomechanical properties of vulcanizates before and after thermal aging in a hydrocarbon environment and air, and also on the dynamic properties before and after curing are investigated.

Natural rubber‐carbon black coagulation: Following the nanostructure evolution from a colloidal suspension to a composite

AbstractMaking elastomeric composite materials via heteroaggregation of a binary colloidal suspension of Natural Rubber (NR) latex and Carbon Black (CB) filler is an interesting production method to obtain an efficient dispersion in the polymer matrix. This study successfully employs an original approach of field emission scanning electron microscopy (FESEM) to investigate for the first time the nanostructure evolution of a coagulum originated from the aggregation of NR globules with CB filler in suspension. More specifically, we exploited a chemical fixation method allowing simultaneous acquisition of backscattered electron (BSE) and secondary electron (SE) imaging modes. Additionally, the role of external physical stresses, like mechanical shear and sonication was also investigated in terms of structural effect induced on the formed coagulum at the nanoscopic scale. Our results highlight destabilization of NR globules, either induced by direct interaction with small CB aggregates or governed by solvent evaporation. Reduction in the size of CB agglomerates, obtained using sonication, highly improved filler distribution and confirmed that the size of CB aggregates is an important parameter responsible for the destabilization of NR globules.

Evaluation of a conducting elastomeric composite material for intramuscular electrode application

Electrical stimulation of the muscle has been proven efficacious in preventing atrophy and/or reanimating paralyzed muscles. Intramuscular electrodes made from metals have significantly higher Young's Moduli than the muscle tissues, which has the potential to cause chronic inflammation and decrease device performance. Here, we present an intramuscular electrode made from an elastomeric conducting polymer composite consisting of PEDOT-PEG copolymer, silicone and carbon nanotubes (CNT) with fluorosilicone insulation. The electrode wire has a Young's modulus of 804 (±99) kPa, which better mimics the muscle tissue modulus than conventional stainless steel (SS) electrodes. Additionally, the non-metallic composition enables metal-artifact free CT and MR imaging. These soft wire (SW) electrodes present comparable electrical impedance to SS electrodes of similar geometric surface area, activate muscle at a lower threshold, and maintain stable electrical properties in vivo up to 4 weeks. Histologically, the SW electrodes elicited significantly less fibrotic encapsulation and less IBA-1 positive macrophage accumulation than the SS electrodes at one and three months. Further phenotyping the macrophages with the iNOS (pro-inflammatory) and ARG-1 (pro-healing) markers revealed significantly less presence of pro-inflammatory macrophage around SW implants at one month. By three months, there was a significant increase in pro-healing macrophages (ARG-1) around the SW implants but not around the SS implants. Furthermore, a larger number of AchR clusters closer to SW implants were found at both time points compared to SS implants. These results suggest that a softer implant encourages a more intimate and healthier electrode-tissue interface. Statement of significanceIntramuscular electrodes made from metals have significantly higher Young's Moduli than the muscle tissues, which has the potential to cause chronic inflammation and decrease device performance. Here, we present an intramuscular electrode made from an elastomeric conducting polymer composite consisting of PEDOT-PEG copolymer, silicone and carbon nanotubes with fluorosilicone insulation. This elastomeric composite results in an electrode wire with a Young's modulus mimicking that of the muscle tissue, which elicits significantly less foreign body response compared to stainless steel wires. The lack of metal in this composite also enables metal-artifact free MRI and CT imaging.

Improved resistance stability for tactile sensor fabrication and investigation of the dispensing parameters of a nanocomposite material

Flexible electronics are showing a promising potential as the next technology revolution in electronics. Flexible tactile sensors, in particular, are getting a lot of attention and have been rapidly developing in the last few years. This is due, inter alia, to the large expansion of the wearable electronic market, flexible displays and the robotic applications where robots are developed to better interact with the external environment through physical contact via the use of tactile sensors. 3D printing technology is being more applied to develop electronic devices giving its numerous advantages. In this regard, the present work reports an improved strain sensor in terms of low and stable electrical resistance over a considerable period of time. The structure of the sensor consists of an elastomeric composite material composed of polydimethylsiloxane (PDMS) and a multi-walled carbon nanotubes (MWCNTs) conductive line deposited using the Direct-Write technique in between two elastomer substrates (PDMS). The developed sensor was able to display significant stability and relatively low resistance. The stability of the resistance throughout a period of 10 days, allowed the study of the dispensing parameters (such as the feed rate and the dispensing pressure of the conductive nanocomposite) influencing the dimensional characteristics (such as the dispensed line width and height). A numerical representation of the relation between the dispensing parameters and the obtained characteristics of the conductive line is presented.

Synthesis and characterization of electrospun nanofibrous tissue engineering scaffolds generated from in situ polymerization of ionomeric polyurethane composites

Tissue scaffolds need to be engineered to be cell compatible, have timely biodegradable character, be functional with respect to providing niche cell support for tissue repair and regeneration, readily accommodate multiple cell types, and have mechanical properties that enable the simulation of the native tissue. In this study, electrospun degradable polar hydrophobic ionic polyurethane (D-PHI) scaffolds were generated in order to yield an extracellular matrix-like structure for tissue engineering applications. D-PHI oligomers were synthesized, blended with a degradable linear polycarbonate polyurethane (PCNU), and electrospun with simultaneous in situ UV cross-linking in order to generate aligned nanofibrous scaffolds in the form of elastomeric composite materials. The D-PHI/PCNU scaffold fibre morphology, cross-linking efficiency, surface nature, mechanical properties, in vivo degradation and integration, as well as in vitro cell compatibility were characterized. The results showed that D-PHI/PCNU scaffolds had a high cross-linking efficiency, stronger polar nature, and lower stiffness relative to PCNU scaffolds. In vivo, the D-PHI/PCNU scaffold degraded relatively slowly, thereby enabling new tissue time to form and yielding very good integration with the latter tissue. Based on a study with A10 vascular smooth muscle cells, the D-PHI/PCNU scaffold was able to support high cell viability, adhesion, and expression of typical smooth muscle cell markers after a 7-day culture period, which was comparable to PCNU scaffolds. These characterization results demonstrate that the unique properties of a D-PHI/PCNU scaffold, combined with the benefits of electrospinning, could allow for the generation of a tissue engineered scaffold that mimics important aspects of the native extracellular matrix and could be used for functional tissue regeneration. Statement of SignificanceTissue engineered scaffolds should recapitulate native extracellular matrix features. This study investigates the processing of a classical polycarbonate polyurethane (PCNU) with a cross-linked and degradable ionomeric polyurethane (D-PHI), polymerized via in situ rapid light curing to yield a 3-dimensional co-electrospun nanofibre matrix with chemical diversity and low modulus character. This research advances the use of D-PHI for tissue engineering applications by providing a facile means of changing physical and chemical properties in classical PCNUs without the need to adjust spinning viscosities of the base polymer. Further, the in vivo and cell culture findings set the stage for introducing unique elastic materials which inherently support wound healing, repair, and regeneration in tissues, for applications that require the recapitulation of native extracellular matrix physical features.

Synthesis and Characterization of Electrospun Nanofibrous Tissue Engineering Scaffolds Generated from in Situ Polymerization of Ionomeric Polyurethane Composites

Tissue scaffolds need to be engineered to be cell compatible, have timely biodegradable character, be functional with respect to providing niche cell support for tissue repair and regeneration, readily accommodate multiple cell types, and have mechanical properties that enable the simulation of the native tissue. In this study, electrospun degradable polar hydrophobic ionic polyurethane (D-PHI) scaffolds were generated in order to yield an extracellular matrix-like structure for tissue engineering applications. D-PHI oligomers were synthesized, blended with a degradable linear polycarbonate polyurethane (PCNU), and electrospun with simultaneous in situ UV cross-linking in order to generate aligned nanofibrous scaffolds in the form of elastomeric composite materials. The D-PHI/PCNU scaffold fibre morphology, cross-linking efficiency, surface nature, mechanical properties, in vivo degradation and integration, as well as in vitro cell compatibility were characterized. The results showed that D-PHI/PCNU scaffolds had a high cross-linking efficiency, stronger polar nature, and lower stiffness relative to PCNU scaffolds. In vivo, the D-PHI/PCNU scaffold degraded relatively slowly, thereby enabling new tissue time to form and yielding very good integration with the latter tissue. Based on a study with A10 vascular smooth muscle cells, the D-PHI/PCNU scaffold was able to support high cell viability, adhesion, and expression of typical smooth muscle cell markers after a 7-day culture period, which was comparable to PCNU scaffolds. These characterization results demonstrate that the unique properties of a D-PHI/PCNU scaffold, combined with the benefits of electrospinning, could allow for the generation of a tissue engineered scaffold that mimics important aspects of the native extracellular matrix and could be used for functional tissue regeneration.

Atomic Force Microscopic Research of Structural Features of Elastomeric Composite Materials Based on Butadiene Nitrile Rubber

The influence of hollow corundum microspheres on mechanical properties and wear resistance of nitrile butadiene rubber (NBR) with the lowest quantity of acrylonitrile (17-19%) have been studied. Results show that the abrasion resistance increased with increase in filler loadings at the two particle sizes investigated. Research of mechanical properties showed that strength at break decreased, while relative elongation at break increased with increase in microspheres loadings. Atomic force microscopy (AFM) was used to perform high-resolution imaging of surfaces of NBR composites. Microspheres exfoliation from NBR matrix at uniaxial stretching was studied with the use of special device compatible with AFM. The obtained AFM images demonstrate stretched fibrils bonded to the surface of microspheres.

Soft elastomeric composite materials with skin-inspired mechanical properties for stretchable electronic circuits.

The stretchable version of electronic circuits harnesses commercial chip scale components to achieve complex functionality and mechanical deformability, which represents an emerging technology to expand the application of conventional electronics on rigid wafers. The bottleneck lies in the lack of a robust approach for the collective integration of off-the-shelf components into a reliable system. In this study, an elastomeric composite material with skin-like mechanical responses and spatially heterogeneous rigidity is reported as an attractive platform for stretchable circuit systems. The approach utilizes a high modulus microstructure embedded in the matrix of a soft elastomer to achieve programmable mechanical properties, thereby offering selective strain isolation for fragile components and overall protection against excessive loads. A low cost procedure involving laser ablation and blade coating is established to create the composite material matching with the circuit design. In addition, ultrasonic atomization of liquid metal into microparticles allows flexible preparations of deformable conductors in the forms of interconnects and contacts. An LED matrix is demonstrated as a prototype circuit system with excellent durability to withstand repetitive stretching and external impacts. Stretchable circuit systems based on soft elastomeric composite materials may find potential uses in health monitoring, mechatronic prosthetics, and soft robotics.

Nano lead oxide and epdm composite for development of polymer based radiation shielding material: Gamma irradiation and attenuation tests

It is important to have a shielding material that is not easily breaking in order to have a robust product that guarantee the radiation protection of the patients and radiation workers especially during the medical exposure. In this study, nano sized lead oxide (PbO) particles were used, for the first time, to obtain an elastomeric composite material in which lead oxide nanoparticles, after the surface modification with silane binding agent, was used as functional material for radiation shielding. In addition, the composite material including 1%, 5%, 10%, 15% and 20% weight percent nano sized lead oxide was irradiated with doses of 81, 100 and 120kGy up to an irradiation period of 248 days in a gamma ray source with an initial dose rate of 21.1Gy/h. Mechanical, thermal properties of the irradiated materials were investigated using DSC, DMA, TGA and tensile testing and modifications in thermal and mechanical properties of the nano lead oxide containing composite material via gamma irradiation were reported. Moreover, effect of bismuth-III oxide addition on radiation attenuation of the composite material was investigated. Nano lead oxide and bismuth-III oxide particles were mixed with different weight ratios. Attenuation tests have been conducted to determine lead equivalent values for the developed composite material. Lead equivalent thickness values from 0.07 to 0.65 (2–6mm sample thickness) were obtained.

Interesting green elastomeric composites: Silk textile reinforced natural rubber

The reinforcement of natural rubber (NR) with particles and fibres enables their use in even high performance applications, such as in road-racing bicycle tire casings. Here, for the first time, we examine the potential of silk textiles as reinforcements in NR to produce a fully-green, flexible yet strengthened elastomeric composite material. Various material properties were evaluated and compared with similar nylon textile reinforced NR composites. Two types of NR were used: whole and purified natural rubbers. The composite samples were prepared by sandwiching a single layer of textile between layers of NR. NR/silk composites exhibited higher static and dynamic mechanical properties than NR/nylon composites. In addition, silk textiles in whole NR composites performed significantly better than purified NR composites, due to stronger fibre/matrix adhesion and better wettability in the former, as indicated by surface energy measurements and scanning electron microscopy micrographs. Such bio-based natural rubber/silk composites might find interesting applications in soft robotics and as flexible, inflatable tubes.