Elastomers For Applications Research Articles

Arbitrarily Patterned Active Wrinkles in Highly Stretched Substrate-Free Dielectric Elastic Membrane

Abstract Dynamic wrinkle patterns provide an effective approach for on-demand tuning of membrane optical and mechanical properties to realize a smart membrane. Related applications depend on forming and controlling of a sophisticated wrinkling region. Herein, by using strip-structured electrode couples, we enable regular and ordered wrinkling patterns in an arbitrarily shaped region in a pre-stretched substrate-free dielectric elastic membrane. By considering the electromechanical coupling in a substrate-free hyperelastic membrane, the winkling condition and wavelength are predicated theoretically. Supported by the theoretical results, a series of experimental and numerical demonstrations are realized. The method proposed in this work provides a general framework for forming controllable highly ordered wrinkling patterns in a complex/large area of a substrate-free membrane, which could provide useful guidance for the application of dielectric elastomers in intelligent materials and structures.

Magnetorheological Elastomers: Fabrication, Characteristics, and Applications.

Magnetorheological (MR) elastomers become one of the most powerful smart and advanced materials that can be tuned reversibly, finely, and quickly in terms of their mechanical and viscoelastic properties by an input magnetic field. They are composite materials in which magnetizable particles are dispersed in solid base elastomers. Their distinctive behaviors are relying on the type and size of dispersed magnetic particles, the type of elastomer matrix, and the type of non-magnetic fillers such as plasticizer, carbon black, and crosslink agent. With these controllable characteristics, they can be applied to various applications such as vibration absorber, isolator, magnetoresistor, and electromagnetic wave absorption. This review provides a summary of the fabrication, properties, and applications of MR elastomers made of various elastomeric materials.

Ultra-small SiO2 nanoparticles highly dispersed on non-covalent functionalized reduced graphene oxide nanoplatelets for high-performance elastomer applications

Encouraged by results of theoretical simulations, we used non-covalently functionalized reduced graphene oxide (NFRGO) nanoplatelets as a substance to grow in situ SiO2 nanoparticles. A series of hierarchical-structured NFRGO-SiO2 nanocomposites were prepared and applied to reinforce hydrogenated nitrile butadiene rubber (HNBR). Ultra-small SiO2 nanoparticles were obtained and highly dispersed on the NFRGO due to the non-covalent functionalization of cetyltrimethylammonium bromide (CTAB). A small amount (1 wt%) of NFRGO incorporated into the SiO2 improves both the static and the dynamic mechanical properties as well as the viscoelastic behavior of NFRGO-SiO2/HNBR composites due to the weak hybrid filler network and the strong filler-rubber interfacial interaction. Significantly, the reinforcement index (RI) of 1%-NFRGO-SiO2/HNBR is 150.7% and 53.9% higher than those of SiO2/HNBR and the HNBR composites filled by a mixture of 1 wt% of RGO and SiO2 (1%-RGO-SiO2/HNBR), respectively. Our work highlights the rational design of hierarchical nanocomposites for reinforcing high-performing HNBR composites.

A dielectric elastomer membrane integrated with protective passive layers under explicit and implicit prestretch

Dielectric elastomers (DEs) are a category of soft electro-active materials that can be used as sensors, actuators and generators. In order to provide protection, insulation layers are essential and thicker layers can lead to stronger protecion. However, the presence of the additional layers can certainly constrain the deformation of DEs. Thus a balance between protection and performance is needed. Prestretch is widely used for the enhancement of actuation performance. Thus the DE membrane integrated with protective passive layers is studied here, focusing on the effect of the coexistence of the prestretch and passive layers. We identify two approaches of prestretches, where the DE membrane and protective passive layers can be explicitly prestretched by external loads, or the DE membrane can be implicitly prestretched by solely protective passive layers. For the latter approach, it does not require additional components such as rigid clamps or dead weights. We then establish a coupled model for the DE membrane and passive layers. The effects of the prestretches and passive layers on the electromechanical behavior and voltage-induced deformation of the DE membrane are then revealed numerically. Furthermore, we theoretically study the detailed effects of specific mechanical properties of passive layers such as the thickness and shear modulus, which are useful for the design of the system. This theoretical research thus sheds insights for the design of dielectric elastomer applications where both safety and performance are required.

Supergiant Barocaloric Effects in Acetoxy Silicone Rubber over a Wide Temperature Range: Great Potential for Solid-state Cooling

Solid-state cooling based on caloric effects is considered a viable alternative to replace the conventional vapor-compression refrigeration systems. Regarding barocaloric materials, recent results show that elastomers are promising candidates for cooling applications around room-temperature. In the present paper, we report supergiant barocaloric effects observed in acetoxy silicone rubber - a very popular, low-cost and environmentally friendly elastomer. Huge values of adiabatic temperature change and reversible isothermal entropy change were obtained upon moderate applied pressures and relatively low strains. These huge barocaloric changes are associated both to the polymer chains rearrangements induced by confined compression and to the first-order structural transition. The results are comparable to the best barocaloric materials reported so far, opening encouraging prospects for the application of elastomers in near future solid-state cooling devices.

Terpene Based Elastomers: Synthesis, Properties, and Applications

The limited source of fossil-fuel and the predominance of petroleum-based chemistry in the manufacturing of commodity polymers has generated tremendous interest in replacing the fossil source-based polymers with renewable counterparts. The field of sustainable elastomers has grown in the past three decades, from a few examples to a plethora of reports in modern polymer science and technology. Applications of elastomers are huge and vital for everyday living. The present review aims to portray a birds-eye view of various sustainable elastomers obtained from the wide family of acyclic terpenes (renewable feedstocks from different plant oils) via various polymerization techniques and their properties, as well as plausible developments in the future applications of sustainable polymers. Not only the homopolymers, but also their copolymers with both green and commercial fossil based comonomers, are reviewed.

Preparation of hydroxyethyl cellulose/halloysite nanotubes graft polylactic acid-based polyurethane bionanocomposites

2-Hydroxyethyl cellulose graft polylactic acid copolymer (HLAC) was prepared by graft copolymerization of lactic acid (LA) and 2-hydroxyethyl cellulose (2-HEC), initiated by dibutyltin dilaurate (DBTDL) catalyst in aqueous media. Halloysite nanotubes (HNTs)/polyurethane (PU) bionanocomposites were prepared using the HLAC as chain extender in the step-growth polymerization. HNTs were dispersed in HLAC based PU matrix at different weight ratios of 0.30, 0.50, 1.00, and 3.00. Chemical structure and morphology of the graft copolymer and bionanocomposite elastomers were characterized using solid state 1H NMR, ATR-FTIR, XRD, and SEM-EDX, while thermal degradation behavior was studied by TGA and DSC techniques. Surface morphology of the HNTs reinforced HLAC/PU bio-nanocomposites demonstrated the homogeneous dispersion of HNTs with little wavy rough surface at low contents which turned to be brittle at higher contents due to agglomerated HNTs. It is observed that the lower contents of HNTs were completely exfoliated in the HLAC/PU matrix. Crystalline pattern of the elastomers improved at lower contents of HNTs that enhanced the thermal stability of the bionanocomposites. The mechanical testing suggested that HNTs/HLAC/PU bionanocomposites have higher values of tensile strength and % elongation with only 0.3–0.5 wt% contents of HNTs that suggested the potential applications of elastomers at economic cost.

The study of enhancement of magnetorheological effect based on natural rubber/thermoplastic elastomer SEBS hybrid matrix

Magnetorheological elastomers are one kind of smart materials which consist of matrix materials and magnetic particles. The mechanical properties of magnetorheological elastomers were controllable under an external magnetic field. Applications of magnetorheological elastomers are limited as a result of their poor magnetorheological effect and mechanical performance, so enhancing the magnetorheological effect of them is critical for their application. Styrene-ethylene-butylene-styrene based thermoplastic elastomer was added to natural rubber to fabricate hybrid matrix–based magnetorheological elastomers. Zero modulus of magnetorheological elastomers increased from 0.50 to 0.64 MPa and magnetorheological effect increased from 28.00% to 43.75% with the addition of styrene-ethylene-butylene-styrene based thermoplastic elastomer. The contact angle of carbonyl iron particles with the matrix showed that styrene-ethylene-butylene-styrene based thermoplastic elastomer can improve the compatibility of carbonyl iron particles with the matrix. Fourier-transform infrared spectroscopy analysis has been carried out to investigate the internal structure of hybrid matrix–based magnetorheological elastomers.

Effect of temperature on the rupture behavior of highly stretchable acrylic elastomer

Dielectric elastomer has been recently explored extensively to make diverse soft actuators and energy harvesting devices. The lack of study on the rupture behavior under the influence of temperature hinders further applications where heat generation and accumulation are unavoidable. In this paper, an experimental study has been carried out to investigate the effect of temperature on the rupture behavior of acrylic dielectric elastomer. By using VHB 4910 films with and without an initial crack, the fracture energy at different temperature and stretch rate is measured by pure shear test. The storage modulus and phase angle have been investigated by dynamic mechanical analysis (DMA). The images of defects and rupture surface are provided by scanning electron microscope (SEM). It is found that the stretch at rupture is insensitive to the temperature for both pristine and precut samples. In addition, the maximum nominal stress and fracture energy linearly decrease with environmental temperature, especially at high stretch rate. Furthermore, we measure the stretch at rupture for rectangular strips with a single edge-notch under uniaxial tension and compare them with the theoretical prediction using nonlinear fracture mechanics based on the measured fracture energy. The results obtained in this paper will give a reference to the engineering design and applications of dielectric elastomer, especially for those working at different temperatures.

Influence of stretch and temperature on the energy density of dielectric elastomer generators

Application of dielectric elastomers (DE) has remarkably increased in mechatronics because they are suitable candidates for energy harvesting due to their low cost, light weight, and high energy density. The dielectric elastomer generators (DEGs) exhibit high performance regardless of the applications scale. However, functioning as a generator, a DE may lose its efficiency due to several failure modes including material rupture, loss of tension (LT), electrical breakdown (EB), and electromechanical instability (EMI). The failure modes confine the area of allowable states for generation process. Dielectric constant and dielectric strength of such elastomers depend on the amount of applied deformation and also working temperature, which are often ignored in theoretical simulations. In this paper, variations of the above-mentioned parameters are considered in mechanical and electrical modellings to investigate their effects on energy density and efficiency of generators. Obtained results show that, ignoring the variations of material dielectric constant and dielectric strength leads to overestimation of the specific energy. Furthermore, it is shown that, for an acrylic-based generator, the specific energy sharply decreases with temperature rise.

Hierarchical Machine Learning Model for Mechanical Property Predictions of Polyurethane Elastomers From Small Datasets

Polyurethanes are a broad class of material that finds application in coatings, foams, and solid elastomers. The urethane chemistry allows a diversity of monomers to be used, and prediction of mechanical properties, which are determined by complex interplay between monomer chemistry and chain architecture, is an unresolved challenge. Urethanes are based on aromatic or cyclic isocyanates and linear or branched polyols, and polymerization results in linear chains for bifunctional monomers or branched chains for multifunctional monomers. Strong intermolecular interactions between aromatic groups result in the formation of hard-segment domains that generate physical crosslinks between disorganized rubbery domains and anchor the material microstructure, contributing to resistance to deformation. Here, a general hierarchical machine learning (HML) model for predicting the stress-at-break, strain-at-break, and Tan δ for thermoplastic and thermoset polyurethanes is presented. The algorithm was trained on a library of 18 polymers with different diisocyanates, bifunctional or trifunctional polyols, and NCO:OH index. HML reduces data requirements through robust embedding of domain knowledge and surrogate data in a middle layer that bridges input variables (composition) and output responses (mechanical properties). In this work, the middle layer included information on overall polymer composition, predictions of chain architecture derived from Monte Carlo simulations of polymerization, information on interchain interactions from empirically derived molecular potentials and shifts in infrared (IR) spectroscopy absorbances. The HML predictions are shown to be more accurate than those from a Random Forest model directly relating composition and properties, suggesting that embedding domain knowledge provides significant advantages in predicting the properties of complex material systems based on small datasets.

Physical and Chemical Properties of Composites Produced on the Basis of Disperse-Filled Blends of Polymers

The present paper contains data on experimental studies of regularities in the influence rendered by the nature of polymers and the addition of disperse fillers and various elastomeric compatibilizers, as well as the temperature conditions of extrusion processing, compaction, and die casting molding on the physical and chemical properties of composites. The paper features experimental data on dependencies of burning speed and obscuring power in various compositions on many-component disperse-filled composites. It also covers structural peculiarities and phase transformations of composites on the basis of chlorinated paraffin waxes that are used today as the basis for pyrotechnic products, as well as the prospects of application of powder elastomers in new high energy materials.

The remarkably improved filler dispersion and performance of SSBR/BR by core–shell structure SiO2@LDH nanocomposites

Core–shell structure of SiO2@MgAl-layered double hydroxide (SiO2@LDH) as a novel filler was prepared and incorporated into solution-polymerized styrene butadiene rubber/butadiene rubber (SSBR/BR) matrix to prepare SiO2@LDH–SSBR/BR composites. The results revealed the advanced structure of SiO2@LDH in the application of elastomer and the strongly interaction between SiO2 and LDH. The investigation of the fracture surface scanning and the study of ‘Payne effect’ to the SSBR/BR compounds indicated a good dispersity of filler in the rubber matrix. In addition, the SiO2@LDH–SSBR/BR composites showed an increased modulus (300% strain) and a decreased modulus (100% strain) compared with commercialized Zeosil 1165MP highly-dispersed SiO2 nanoparticles. The synergistic enhancement of SiO2 and LDH in rubber matrix was discussed. The remarkable comprehensive properties enhancement of all the SiO2@LDH–SSBR/BR was obviously observed in the dynamic mechanical analysis compared with the SiO2–SSBR/BR samples. The results in this study strongly illustrate that SiO2@LDH nanocomposites could be a good candidate as a kind of reinforcement filler for the green tires.

Worker Health and Safety in Rubber Shoe Production

The elastomers, which are called natural and synthetic rubber, have a wide usage area in the industry due to their unique properties. Rubber; they are used in many areas of industry, especially vehicles. Additive and fillers with many different properties are added during production to ensure that the products to be produced from these materials have the required properties. One of the applications of rubber-type elastomers is the footwear sector. Shoes are worn for protection against external conditions. The material that covers the bottom of the shoe from one end to the other and is in contact with the ground when it is worn is called the shoe sole. Rubber base with elastomer properties, the importance of occupational health and safety rules in manufacturing sector is increasing day by day. In this study, the occupational diseases caused by chemical substances which are used in the production of rubber shoe sole and the methods of protection from them are explained. Employers and employees have responsibilities to reduce the risk of occupational accidents and occupational diseases in the manufacture of rubber shoe sole. In this article; According to the required technical formula, the preparation of the rubber, additives and fillers in the mixture in the preparation of dough and the effects of gas, dust, smoke and steam on the environment and human health during the vulcanization of the prepared dough under high temperature with suitable chemical cookers were examined. It also covers the literature on occupational health risk groups, which employees are interested, and what occupational safety measures should be taken on a sectoral basis. Keywords : Shoe soles, Rubber shoe soles, Occupational health and safety, Production of rubber soles. DOI : 10.7176/JSTR/5-2-44

Damping in magnetorheological elastomers under compressive stress

Magnetorheological elastomers are an important area of study in non-classical engineering materials. These are smart materials, in which some of the physical properties are dependent on the applied magnetic field. This unique property allows to suggest new, innovative practical applications. It is therefore relevant to carry out studies in the possible application of magnetorheological elastomers in machine construction. The present article presents the results of study regarding the properties of the discussed materials subject to compressive stresses. Particular attention is given to the observed growth of surface area of mechanical hysteresis loops, which is evidence of the possibility to change the damping properties of magnetorheological elastomers. This property can be utilized in the construction of different types of machines and devices. These mostly applies to energy absorbers such as active vibration absorbers.

Nanocellulose-templated assembly of polyaniline in natural rubber-based hybrid elastomers toward flexible electronic conductors

The wide-ranging applications of electroconductive elastomers in next-generation soft electronics demand more renewable bio-based materials derived from natural forest crops than the non-sustainable materials currently available. However, it still remains a critical challenge to construct an effective, stable and continuous conductive network in a non-conductive elastomer matrix with enhanced mechanical properties and desired electrochemical performances especially using natural polymer. Here, we report a novel type of electroconductive hybrid elastomers based on a natural rubber (NR) matrix and nanostructured CNF-PANI (cellulose nanofibers-polyaniline) complexes that synergizes the conductive nature of PANI and the biotemplate role of CNFs. The CNF-PANI complexes with ideal dispersity and high aspect ratio are synthesized through in situ oxidative polymerization of aniline monomers on the surface of CNF templates, which are further uniformly dispersed into NR latex to synthesize CNF-PANI/NR elastomers with a hierarchical 3D network structure through a latex cocoagulation process. The incorporation of sustainable and biodegradable CNFs can not only built a reinforcing network, but also support the hierarchical 3D conductive network in NR matrix. The final bio-based elastomers with a homogeneous texture exhibited intrinsic flexibility, enhanced mechanical properties (tensile strength up to 9.7 MPa, Young’s modulus up to 10.9 MPa), decent stretchability (elongation at break up to 511%), low density (∼1.16 g cm−3) and ideal conductivity (up to 8.95 × 10-1 S m-1). The highly sensitive and repeatable strain-sensor integrated by the elastomer with 8 phr of PANI could monitor the real-time motion of human body. The specific capacitance of elastomer-based electrode with 20 phr of PANI can reach up to 110 F g-1 at a current density of 0.3 A g-1, and its capacitance degradation is less than 22% after 1200 cycles, exhibiting promising electrochemical properties. The multifunctional elastomers synthesized through a facile, scalable and green approach in this work promotes the advanced applications of bio-based materials including CNFs and NR in prospective soft electronics, such as strain sensors and flexible electrodes.

Biodegradation of polyurethane‐polyhydroxybutyrate elastomeric composite investigated from morphological and structural viewpoint

ABSTRACTMorphological, structural, and tensile changes of polyurethane‐poly(3‐hydroxybutyrate) (PU‐PHB) elastomeric composites were evaluated after accelerated test in standard compost media. Size of PHB particles together with their uniform dispersion in the matrix were found to be key parameters for material's resistivity against degradation media. PU‐PHB composite films were synthesized by the “green” solvent free method, where commercially available PHB (PHB‐COM) and PHB produced by bacterium Cupriavidus necator H16 (PHB‐BUT) were both used in the amount of 1, 5, and 10 wt % in composites. Scanning electron microscopy revealed excellent dispersion of PHB‐COM microparticles in the PU matrix resulting in negligible weight losses of the material (max 0.7 wt %). On the contrary, PHB‐BUT particles were agglomerated which promoted partial degradation of the material (max 3.3 wt % loss) manifested by holes on the surface but without severe damage (e.g. fragmentation). Structural analysis confirmed lower crystallinity and less ordered crystalline phase of PHB after the degradation test, particularly in composites made of PHB‐BUT. Moreover, the materials were less stiff after the composting test, but beneficial with higher elongation at break. Such properties are favorable for the use of renewable PHB in the current industrial applications of PU elastomers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46909.

The possibility of application of agglomerate elastomers (EPP) as media for biological bed in aquaculture

The aim of the study was to determine the possibility of experimental media (agglomerate elastomers EPP) application as biological media bed, which serves the purpose of water purification in recirculating aquaculture systems (RAS). RAS enables mass-production of fish in small volume of water in a limited area. This involves the possibility of multiple usage of water during culture. However, for that purpose of maintaining proper physico-chemical parameters, water purification from products of metabolism, especially toxic nitrogen compounds, is required. One of the simplest and most effective ways to achieve it is combining application of two types of water filtration: mechanical and biological. It is needed to study new media for biological bed with proper filling is able to purify water from toxic nitrogen compounds.

Nonlinear dynamic analysis and active control of visco-hyperelastic dielectric elastomer membrane

Dynamic analysis and active control are important bases for dielectric elastomer (DE) applications. Most of the DE materials exhibit significant viscoelasticity. Although the visco-hyperelastic constitutive relations of DEs have been studied before, the dynamic analysis of the DEs with the consideration of viscoelasticity has rarely been explored. In this study, we lay out the dynamic equations for the visco-hyperelastic DE structures. The Gent hyperelastic model is applied to take into account the strain-stiffening effect of the elastomer. Based on the model, we derive an analytical solution for the dynamic DE under homogeneous in-plane deformation. We show that the model can capture the nonlinear oscillation of the DE and allows us to investigate how the viscoelasticity and strain-stiffening effect influence the resonant frequencies and oscillation amplitudes of the system. Given the nonlinear and viscoelastic nature of the material, its dynamic response could be complicated and deviate from the desired harmonic oscillation pattern. To achieve precise control over the outputs, we employ a PID controller to build a closed-loop feedback control and demonstrate its feasibility to correct most of the undesired outputs such as nonlinear oscillation, beating phenomenon, phase lag and so on.

A feasibility work on the applications of MRE to automotive components

A feasibility work on the application of magneto-rheological elastomers (MREs) to automotive components, such as engine mounts is presented. While vehicle components require the high resonance frequency in terms of ride quality and handling, it is required to have the low resonance frequency to isolate the incoming vibration. With the conventional automotive technologies, it is challenging to combine these two conflicting performance trade-offs, ride quality including handling, and NVH (noise, vibration and harshness). Over the last decades, MREs, one of the new emerging smart materials, have been widely used to resolve this technical limitation. For example, an advanced engine mount was developed by using MRE to isolate the vibration transmitting from engines. In this paper, we will focus on rear cross member bushes, which is a key component for isolating the vibration from the road, and demonstrate their improved performance by utilizing MRE. The resonance frequency shift induced by the stiffness change of MRE will be presented through the frequency response functions estimated by simulation result.