Acrylic Elastomer Research Articles

A Quasi-experimental Study to Explore the Effect of Barrier Cream on the Peristomal Skin of Patients With a Tracheostomy

Peristomal skin problems represent one of the most common complications of a tracheostomy. A quasi-experimental study was conducted among patients ages 18 to 65 years hospitalized in a Turkish university hospital ear-nose-throat clinic between August 15, 2013, and December 15, 2013, to compare the effect of using or not using a barrier cream on the peristomal skin with regard to pH, moisture, temperature, color, odor, turgor, infections, and lesions after tracheostomy surgery. Patients were selected using a purposeful sampling method and included if they had not undergone another operation for a complication (eg, pneumothorax, tube misplacement, hemorrhage) within 24 hours following the tracheostomy operation. In phase 1 of the study, 9 registered nurses were observed 3 times each by the researcher, who completed an observation form. From these observations and related nursing textbooks, the researcher developed a protocol entitled "Nursing Care Steps for Patients with a Tracheostomy." This protocol was followed during phase 2 of the study during which participants were alternately assigned to either the intervention (a barrier cream containing dimethicone, acrylate terpolymer, oils, paraffin, water, dicapryladipate, isopropyl palmitate, and PPG-15 stearyl ether followed by gauze) or control (gauze only) group (n = 30 each) and observed for 7 days. Demographic characteristics were gathered for each patient upon admission to the study. Peristomal skin was assessed in terms of pH, temperature, and moisture (relative humidity [RH]) using a surface pH meter, surface thermometer, and digital skin moisture tester, as well as for lesions, infection, and maceration. Findings were documented on a skin condition assessment form. Twenty-four (24) hours post surgery, the barrier cream plus gauze was applied over peristomal area in the study group and gauze dressing only in the control group. Peristomal skin pH, moisture, and temperature were within the normal range for both groups during all observations throughout the study but closer to normal ranges in the intervention group. Mean peristomal skin pH in the intervention group was significantly higher (5.452 ± 0.043) than in the control group (5.123 ± 0.057; P &.001), mean peristomal skin moisture in the control group (46.90 ± 0.132 RH) was significantly greater than in the intervention group (41.71 ± 0.774 RH; P &.001), and mean peristomal skin temperature in the control group (33.59 ± 1.3˚ C) was significantly higher than in the intervention group (31.64 ± 0.607˚ C; P &.001). In both groups, Staphylococcus epidermidis was the most commonly cultured microorganism, and S aureus was the most cultured pathological microorganism in addition to the normal skin flora. Peristomal skin condition was maintained for both the intervention and control groups. Use of a barrier cream to protect tracheostomy peristomal skin beneath absorbent dressings (eg, gauze) is recommended, but additional short-term and long-term studies are needed.

An approach to developing enhanced dielectric property nanocomposites based on acrylate elastomer

High dielectric constant (high-k) polymeric materials suitable for electromechanical transducers should meet the requirements of low dielectric loss. This work introduced a ternary nanocomposite with acrylate elastomer (AE) as matrix, and chemically reduced graphene oxides (G) and poly(ionic liquid)s (PILs) as co-filler, of which AE was synthesized by solution polymerization. A unique hybrid (H) was fabricated by the ionic liquid monomers polymerized on the surface of graphene. Afterwards, hybrid of different filler contents was added into AE to prepare nanocomposites with solution casting method. The favorable π-π interaction between PILs and graphene made the co-filler a better dispersion in the matrix, which contributed to the enhanced dielectric property of the resultant nanocomposites. Dielectric constant of H/AE nanocomposite at 102Hz was as high as 680 and the dielectric loss was only 0.34 when the filler content (1.69vol%) approached to the percolation threshold (fc), which was attributed to PILs anchored on the surface of graphene acting as spacers and PILs cut the leakage currents induced by the direct connection of graphene. Moreover, the composite was still flexible that could engender larger strain in area.

Experimental study on vibration energy harvesting based on E-ACE

According to the power generation mechanism and power generation characteristics of an electroactive acrylic elastomer (E-ACE), a new idea of vibration energy harvesting with the use of E-ACE was proposed, which is based on the analysis of vibration energy harvesting technology research status and development trend. The prototype of the vibration energy generator was constructed by using the E-ACE material, and its mechanism characteristic of vibration energy harvesting was analyzed and studied in the experiments. Experimental results show that the generated voltage of the E-ACE material increases with the increasing vibration amplitude and vibration frequency. The generated voltage of the E-ACE material exhibited nonlinearity with the increase in the strain area, and there existed an inflection point. It is not true that the bigger the prestretching, the better it is. There is a suitable prestretching condition. The results provide the basis for further research in the field of vibration energy harvesting for E-ACE.

Morphological and rheological footprints corroborating optimum foam processability of PP/ethylene acrylic elastomer blend

ABSTRACTThe focus of the present work is optimization of microcellular foam processing of Polypropylene (PP)/ethylene acrylic elastomer blends, through design of experiment approach using Taguchi technique and establishing correlation among foamability, morphological, and rheological parameters of blends. PP and elastomer are melt blended in a twin screw extruder and thereafter foaming parameter optimization is carried out using Taguchi method followed by analysis of variance (ANOVA) for batch foaming setup. Scanning electron microscope reveals development of submicron elastomer domains, which increase with the elastomer content. Further, complex viscosity and van Grup–Palmen plots are found to have a vital role in attaining cellular morphology development in blends. From Taguchi and ANOVA analysis it is established that foaming temperature has a great influence and major contribution on foamability. Blends with low elastomer content are optimized for better foamability using statistical approach and proved to be consistent with the morphological and rheological outcomes. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46322.

Applying VHB acrylic elastomer as a cell culture and stretchable substrate

ABSTRACTElastomers are flexible polymers with low young’s modulus and high failure strain. VHB, considered as an acrylic elastomer, is widely used in smart materials due to its dielectric and electromechanical actuating properties. To the best of our knowledge, this polymer has not been applied as cell culture and stretching substrate and this role has played by PDMS. Herein, we present the structural properties of VHB vs. PDMS and then prove the safety of using this polymer as cell culture substrate by different viability assays. Moreover, we analyzed the effect of stretching of VHB substrate on the cultured cells.

The Use of Dielectric Elastomer Actuators for Prosthetic, Orthotic and Bio-Robotic Applications

To characterize dielectric elastomer (DE) mechanically & electrically, several standard experimental tests like uniaxial tensile test, uniaxial compression test, and electrically actuated strain test on a commercially available acrylic dielectric elastomer film have been conducted. To characterize this visco-elastic material electro-mechanically, the uniaxial tensile (different stretch rates) test, and uniaxial compression test were performed on the Universal Testing Machine (UTM), whereas electrical actuation test has been conducted through a DC to high voltage DC convertor used to scaled-up the input voltage from 0-5 V to output of 0-10 kV. It is noticed that the ability of DE film to sustain the maximum load increases thereby increases the induced stresses also from their individual peak values from 0.16 N/mm2 to 0.35 N/mm2 by increasing the strain rate from 100 mm/min to 400 mm/min respectively. Results of tests have been discussed and compared with observations of various researches on skeletal muscles and suggested some recommendations on material selection for futuristic approach for mimicking skeletal muscle behaviour for bio-robotic applications made of this material.

Dielectric elastomer generator with diaphragm configuration

The dielectric elastomer generator (VHB 4905, 3M) with diaphragm configuration was investigated with the constant-voltage harvesting scheme in order to investigate its energy harvesting ability. The maximum energy density and energy conversion efficiency is measured to be 65 J/kg and 5.7%, respectively. The relatively low efficiency indicates that higher energy conversion efficiency is impeded by the viscosity of the acrylic elastomer, suggesting that higher conversion efficiency with new low-viscosity elastomer should be available.

Effect of zinc oxide induced metal-ligand crosslink on the mechanical properties in the ethylene acrylic elastomer (AEM)

The metal-ligand complex (sacrificial bonds) that exist in the mussels, bone and silk can dissipate energy and reinforce mechanical strength. Inspired by the high performance of metal-ligand complex, we introduced a kind of metal-ligand crosslink into the rubber network. In this work, ethylene acrylic elastomer (AEM) was filled with ZnO, and was cured by the amine cure system. The metal-ligand crosslink structure was verified by FTIR and XPS, and the tensile strength and dynamic properties were examined with a universal testing machine and rubber process analyzer (RPA). The results showed that coordination crosslink formed in the AEM matrix and exhibited outstanding tensile strength and unexpected dynamic properties due to the coordination bonds between Zn2+ and amine group.

Investigation on γ-irradiated PP/ethylene acrylic elastomer TPVs by rheological and thermal approaches

Polypropylene (PP) was melt blended with varying concentration of ethylene acrylic elastomer (AEM) in a twin screw extruder and then γ-irradiated at several radiation doses to achieve a series of thermoplastic vulcanizates (TPV). The effect of AEM concentration and γ-irradiation on flow characteristics, crystallization and thermal degradation of blends were explained using melt dynamic rheology, differential scanning calorimetry and thermogravimetric analysis. Gel content values and dynamic rheological data of PP and AEM at different radiation doses confirmed the incessant scissioning of PP chains with radiation doses except for highest radiation dose, where crosslinking of PP chains took place and the incessant crosslinking of AEM chains irrespective of radiation doses. Oxidative degradation of PP was confirmed by FTIR spectroscopy, which also exhibited absence of any chemical interaction between two constituent polymers. Normalized crystallinity and melting point of compositions, obtained from DSC, decreased with the radiation doses. Furthermore, with the radiation doses clear shifts of maxima of the melting peak towards the lower temperature were observed for neat PP and blends. Thermal stability of PP and blends, as observed by TGA, reduced significantly with irradiation; whereas for AEM, no discernable change was observed. Enhanced chain scissioning of PP in presence of AEM reduced the thermal stability of blends, especially at lower irradiation. This reduction of thermal stability was established by “rule of mixture”, applied to the activation energy of thermal degradation. Thus, optimization of radiation doses to prepare TPVs was established.

Influence of fiber characteristics on directed electroactuation of anisotropic dielectric electroactive polymers with tunability

Dielectric elastomers constitute a technologically important class of stimuli-responsive polymers due primarily to their unique ability to achieve large strains (>300 area%) upon exposure to an external electric field. In most reported cases, actuation strains are measured as dielectric elastomers constrained to a circular test configuration essentially waste energy by undergoing isotropic, rather than directional, electroactuation. Recent independent studies have demonstrated, however, that the addition of relatively stiff fibers to a soft dielectric elastomer matrix promotes more energy-efficient anisotropic mechanical behavior and electroactuation response. In this work, we investigate the effects of fiber strain and mechanical properties on electroactuation in anisotropic dielectric electroactive polymers with tunability (ADEPT) fabricated from an acrylic dielectric elastomer. Increases in fiber loading level and stiffness are observed to enhance both mechanical and electroactuation properties to different extents, and we introduce an electroactuation anisotropic enhancement factor to quantify the ratio of electroactuation to mechanical anisotropy. This factor is determined to vary linearly with fiber concentration for nearly all the different ADEPT composites examined in this study.

Highly Transparent and Integrable Surface Texture Change Device for Localized Tactile Feedback.

Human-machine haptic interaction is typically detected by variations in friction, roughness, hardness, and temperature, which combines to create sensation of surface texture change. Most of the current technologies work to simulate changes in tactile perception (via electrostatic, lateral force fields, vibration motors, etc.) without creating actual topographical transformations. This makes it challenging to provide localized feedback. Here, a new concept for on-demand surface texture augmentation that is capable of physically forming local topographic features in any predesigned pattern is demonstrated. The transparent, flexible, integrable device comprises of a hybrid electrode system with conductive hydrogel, silver nanowires, and conductive polymers with acrylic elastomer as the dielectric layer. Desired surface textures can be controlled by a predesigned pattern of electrodes, which operates as independent or interconnected actuators. Surface features with up to a height of 0.155 mm can be achieved with a transformation time of less than a second for a device area of 18 cm2 . High transparency levels of 76% are achieved due to the judicious choice of the electrode and the active elastomer layer. The capability of localized and controlled deformations makes this system highly useful for applications such as display touchscreens, touchpads, braille displays, on-demand buttons, and microfluidic devices.

Enhanced dielectric properties of all-organic acrylic resin elastomer-based composite with doped polyaniline

Polyaniline (PANI) doped with p-toluene sulfonic acid (PTSA) was synthesized by chemical oxidation method under the condition of conventional magnetic stirring (PTSA–PANI) and ultrasonic vibration (uPTSA–PANI) separately. Acrylic resin elastomer (ArE) was synthesized via radical polymerization. Novel all-organic dielectric elastomer composites (refer to the resultant composites herein as ArE/PTSA–PANI and ArE/uPTSA–PANI) were obtained by solution casting method. Chemical and microstructure characterization of the two kinds of resultant composites suggested that uPTSA–PANI possessed larger crystalline domain than that of PTSA–PANI and a unique branched structure. The dielectric properties of composites were measured in a wide frequency range, and the results demonstrated that both ArE/2.0% PTSA–PANI and ArE/2.0% uPTSA–PANI owned a high dielectric constant of more than 30 at 100 Hz, representing ten times increase with respect to neat ArE matrix (≈ 3). Moreover, it was found that ArE/2.0%uPTSA–PANI held better comprehensive dielectric properties at high frequency than that of ArE/2.0% PTSA–PANI composite; that was to say, ArE/2.0% uPTSA–PANI composite possessed not only high dielectric constant but also low dielectric loss. In addition, the thermogravimetric analysis indicated that the composite possessed better thermal stability than that of neat ArE. In addition, the elastic modulus of ArE/2.0% uPTSA–PANI composite was lower than 5 MPa.

Evaluation of thermochromic elastomeric roof coatings for low-slope roofs

Thermochromic elastomeric roof coatings for low-slope roofs were prepared by incorporating a commercial thermochromic dye (with transition temperature, Tc∼32°C) into a white acrylic elastomer matrix. Freshly applied coatings showed an initial temperature-dependent solar reflectance change of 22–25%, with a maximum solar reflectance of 70% in the colorless state (T>Tc). Weathering studies revealed that these thermochromic coatings undergo irreversible photodegradation in as little as 96h of accelerated aging. Attempts to protect thermochromic dyes with inorganic (nano-ZnO) or organic (Lowilite® 20S) UV absorbers were partially successful but need significant improvements to achieve the required lifetime of at least 10 years. Cost calculations in three different geographies showed that even if the durability of these coatings is greatly improved, the energy savings relative to the incumbent static cool roofs are small and do not currently justify the additional cost of thermochromic pigments and UV absorbers.

The effect of clamping conditions on tearing energy estimation for highly stretchable materials

A typical measure for the toughness of highly stretchable materials is the energy for tearing, determined in mode I fracture tests on wide specimens with a lateral cut. In the present paper we show that, when slippage occurs in the grips that hold the specimens, the classical analysis of this test leads to an overestimation of the tearing energy, if sample stretches are determined from the grip displacements. Unlike for elastic properties, the use of local strain data retrieved by an optical measurement system does not remedy this issue but, vice versa, underpredicts the tearing energy. Here we propose a simple post hoc correction of the measured tearing energy, and an improved clamp design to prevent slippage. Applied to a commercial acrylic elastomer, the corrected tearing energy was independent of the occurrence of slippage and consistent with the result obtained with the new clamping system as well as values reported in literature.

Fracture Behavior of Dielectric Elastomer under Pure Shear Loading

Dielectric elastomer has become a very important material for many emerging applications areas like optics, micro fluidics, sensors, actuators and energy harvesting. However, these elastomer components are prone to fracture or catastrophic failure because of defects likes notches, flaws, and fatigue crack, impurities which occur during production or during service. To make better use of this material, it is important to investigate fracture characteristics under different operating conditions. This study experimentally investigated the effects of notch length and strain rate on the fracture toughness, failure stretch and failure stress of acrylic elastomer under pure shear deformation mode. It is observed that failure stretch depends on notch length and independent of strain rate, but failure stress decreases with increasing notch length and increases with increasing strain rate. It is also found that fracture toughness is independent of notch lengths. However, fracture toughness is found to increase with strain rate.

Building a Novel Chemically Modified Polyaniline/Thermally Reduced Graphene Oxide Hybrid through π-π Interaction for Fabricating Acrylic Resin Elastomer-Based Composites with Enhanced Dielectric Property.

Sustainability urgently demands low dielectric loss and low elastic modulus as fostering high permittivity (Hi-K) conductor/polymer composites. This work introduces a ternary composite system, consisting of acrylic resin elastomer (AR), chemically modified polyaniline (HBSiPA), and the thermally reduced graphene oxides (TrGOs), for applying to actuators, of which AR was fabricated by free radical polymerization. The unique hybridized graphene (HBSiPA-TrGO) was prepared by a two-step procedure, including the doped polyaniline modified by the hyperbranched polysiloxane via a ring opening reaction, followed by the decoration of HBSiPA on the surface of TrGO, the conductivity of which is desired to be the same as that of graphene. Afterward, diverse filler contents of HBSiPA-TrGO were put into the AR matrix to fabricate composites with the solution casting method and TrGO/AR composites were fabricated as well for comparison. Unlike TrGO, HBSiPA has plenty of polyaniline chain segments that ensure better dispersion of graphene hybrids in the AR, and thus the composites inherit the excellent electrical property of graphene. The permittivity and dielectric loss of the HBSiPA-TrGO/AR composite at 100 Hz are 3.5 and 0.27 times that of the TrGO/AR composite, respectively, when the loading of fillers approaches the percolation threshold (fc), which originates from the HBSiPA anchored onto the graphene serving as spacer and thus decreases the leakage currents induced by the contact of graphene sheets. Besides, the elastic modulus of 2.83 vol % HBSiPA-TrGO/AR composite was lower than 5 MPa.

Electro-viscoelastic response of an acrylic elastomer analysed by digital image correlation

Experimental investigations are presented with respect to the electromechanically coupled and time-dependent behaviour of an acrylic elastomer, VHB 4910. For the electromechanically coupled experiments different biaxial pre-stretches have been considered and full-field measurements were made using three-dimensional surface digital image correlation. Both equi-biaxial and non equi-biaxial pre-stretches as well as both circular and non-circular electrodes are investigated. The experimental data provide new insights into the complex material behaviour of VHB 4910 and will enable enhanced calibration and development of constitutive models. Special emphasis lies on the quantification of out-of-plane deformation, i.e. the thickness change, of biaxially pre-stretched specimens based on an assumption of material incompressibility. The level of pre-stretch and thickness of the membrane plays a critical role in view of electromechanical instabilities. For completeness, cyclic uniaxial tests of the purely mechanical response are also presented and compared to similar experiments found in the literature.

Fatigue fracture of a highly stretchable acrylic elastomer

Dielectric elastomer has been extensively explored in various applications as soft active material. In most applications, dielectric elastomer is subjected to cyclic loading-unloading condition. As a result, a small initial defect in a dielectric elastomer may finally grow to a critical size to induce catastrophic rupture. In this article, we carried out an experimental study of the crack growth in an acrylic dielectric elastomer under cyclic loading-unloading. Pure-shear test specimens were used to measure the relationship between crack growth rate and energy release rate. Such relationship can be simply fit to a power-law. We further used the measured power-law to successfully predict the fatigue lifetime of the acrylic elastomer with an edge crack and subject to simple extension cyclic loading-unloading test.

DESIGNING DIELECTRIC ELASTOMERS OVER MULTIPLE LENGTH SCALES FOR 21ST CENTURY SOFT MATERIALS TECHNOLOGIES

ABSTRACTDielectric elastomers (DEs) constitute an increasingly important category of electroactive polymers. They are in a class of generally soft materials that, upon exposure to an electric stimulus, respond by changing size, shape, or both. Derived from network-forming macromolecules, DEs are lightweight, robust and scalable, and they are capable of exhibiting giant electroactuation strains, high electromechanical efficiencies, and relatively low strain-cycling hysteresis over a broad range of electric fields. Due primarily to their attractive electromechanical attributes, DEs are of growing interest in diverse biomedical, (micro)robotic, and analytical technologies. Since the seminal studies of these electroresponsive materials (initially fabricated mainly from chemically cross-linked acrylic and silicone elastomers), advances in materials design over multiple length scales have resulted in not only improved electromechanical performance but also better mechanistic understanding. We first review the fundamental operating principles of DEs developed from conventional elastomers that undergo isotropic electroactuation and then consider more recent advances at different length scales. At the macroscale, incorporation of oriented fibers within elastomeric matrices is found to have a profound impact on electroactuation by promoting an anisotropic response. At the mesoscale, physically cross-linked thermoplastic elastomer gel networks formed by midblock-swollen triblock copolymers provide a highly tunable alternative to chemically cross-linked elastomers. At the nanoscale, the chemical synthesis of binetwork and bottlebrush elastomers permits extraordinarily enhanced electromechanical performance through targeted integration of inherently prestrained macromolecular networks.

High-performance electromechanical transduction using laterally-constrained dielectric elastomers part I: Actuation processes

A dielectric elastomer transducer is a deformable capacitor, and is under development as a sensor, actuator, or generator. Among various geometric configurations, laterally-constrained transducer, also known as pure-shear transducer, is easy to implement and effective to couple mechanical force and electrical voltage. This analytical study reveals that lateral pre-stretch enhances actuation, far exceeding previously reported actuation strokes. Laterally-constrained transducers exhibit complex electromechanical behavior. As voltage increases, an actuator may undergo electromechanical instability, or form wrinkles, or suffer electrical breakdown. We survey the behavior of actuators under all possible states of pre-stretches, and identify five modes of actuation. Our analysis predicts that laterally-constrained actuators can achieve actuation stroke of 1000% for an acrylic elastomer, and 230% for natural rubber. This analysis opens the door to design actuators of simple geometry capable of a very large range of electromechanical actuation.