Types Of Elastomers Research Articles

Damper for mobile installation of oil sludge pyrolysis

The article discusses the main types of dampers used in modern industry, their advantages and disadvantages. The reasons for their inefficient work on the mobile installation of pyrolysis of oil sludge. A new design of the collet elastomer type damper is proposed.

Robust Low Friction Antibiotic Coating of Urethral Catheters Using a Catechol-Functionalized Polymeric Hydrogel Film

Indwelling urethral catheters are widely used in hospitalized patients however they are associated with bacterial infection and biofilm formation due to the suboptimal surface properties of the elastic materials used for the catheters. Although there are several antibacterial coating technologies to modify the surface properties of the catheter including hydrophilic polymeric coating, the risk of infection is still high given the absence of reactive functional groups on the surface of elastomers. In this study, we describe the use of catechol-functionalized hydrophilic polymers and explore strategies to create antibacterial hydrogel coatings. Three different types of catechol-functionalized polymers, chitosan, hyaluronic acid, and human serum albumin were synthesized and deposited using simple dip-coating method. All of the tested polymers could coat different types of elastomers widely used for urethral catheters independent to the surface properties, and the thickness of the coating could be controlled by the number of depositions. The coating formed stable water-containing lubricant surface beneficial as a physical repellant of microbial attachment. In addition, the coating could be combined with additional antibacterial agents such as silver nanoparticles to maximize the antibacterial effect on the surface of urethral catheter materials.

Toughened High-Flow Polypropylene with Polyolefin-based Elastomers.

Polyolefin is the most widely used and versatile commodity polymer. In this work, three types of polyolefin-based elastomers (PBEs) were adopted to toughen a high-flow polypropylene to improve its overall performance. The chain microstructures of these PBEs, including ethylene/1-octene (E/O) random copolymer from Dow Chemical′s polyolefin elastomer (POE), olefin block copolymers (OBCs) of E/O from Dow, and ethylene/propylene random copolymer from ExxonMobil’s propylene-based elastomer, were elucidated by GPC, 13C NMR, TREF, and DSC techniques. The mechanical, thermal and optical properties, and morphology analysis of the PP/PBE blends were also studied to investigate the toughening mechanism of these PBEs. The results showed that all three types of PBEs can effectively improve the Izod impact strength of the PP/PBE blends by the addition of the rubber compositions, at the cost of the stiffness. PBE-1 and PBE-2 were found to have a great stiffness–toughness balance with about 1700 MPa of flexural modulus, about 110 °C of HDT and 3.6 kJ/m2 of impact strength on the prepared PP/PBE blends by forming separated rubber phase and refined spherulite crystals. As a result, the OBC with alternating hard and soft segments could achieve a similar toughening effect as the E/P random copolymer. Surprisingly, no obvious rubber phase separation was observed in the PP/PBE-4 blend, which might be due to the good compatibility of the E/P random chains with the isotactic PP; therefore, the PP/PBE blend obtains great toughness performance and optical transparency with the highest Izod impact strength of 4.2 kJ/m2 and excellent transparency.

Influence of the size of magnetic filler particles on the properties of hybrid magnetic elastomer with magnetically hard filler

The magnetic properties of hybrid magnetic elastomers (HME) featuring a type of magnetorheological elastomer filled with high-coercivity (a.k.a. magnetically hard) particles have been studied. Introduction of magnetically hard components into the formula significantly modifies both magnetic and rheological parameters of the composite. An additional factor having an influence on the overall behavior of the elastomer is based on the properties of the powder used as filler determined by its dispersion degree. Impregnation of the polymer matrix with a magnetically hard powder leads to a complex relationship between the magnetization and elasticity of the material and magnetic field as compared to the behavior demonstrated by composites based on magnetically soft filler, which is determined by the rotational motion of the particles inside the sample. Such a material exhibits asymmetrical magnetization hysteresis loops.

Self-Healing Polyurethane Elastomers Based on a Disulfide Bond by Digital Light Processing 3D Printing.

A type of polyurethane elastomer with excellent self-healing ability has been fabricated through digital light processing 3D printing. First, a type of polyurethane acrylate containing disulfide bonds is synthesized and then compounded with reactive diluent and photoinitiators to get a photopolymer resin. Due to the good fluidity and high curing rate, the photopolymer resin can be applied in DLP 3D printing, and various 3D objects with complicated structures, high printing accuracy, and remarkable self-healing ability have been printed. The tensile strength and elongation at break of the polyurethane elastomer are 3.39 ± 0.09 MPa and 400.38 ± 14.26%, respectively, and the healing efficiency can get to 95% after healing at 80 °C for 12 h and can be healed for multiple times. With the ease of fabrication and excellent performance, the polyurethane elastomers from DLP 3D printing have great potential applications in flexible electronics, soft robotics, and sensors.

Predicting the electrical breakdown strength of elastomers

Elastomers have extensive applications in engineering and industrial fields, such as stretchable electronics and soft robotics. Among the various properties of elastomers, electrical breakdown strength strongly affects their application and design due to safety reason. Nevertheless, measuring and determining the electrical breakdown strength of elastomers is a difficult challenge. This work proposes a general predictor and relation for the electrical breakdown strength of various types of elastomers. Based on configurational mechanics, the proposed predictor captures the stretch dependence, the voltage ramping-rate dependence and the elastic modulus dependence of the breakdown strength through the evolution of defects within the material and can effectively keep track of the variation of the electrical breakdown strength. The proposed predictor and relation can serve as a significant tool for the optimal design of elastomer-based electronics or devices and open new door for improving the electrical breakdown strength of elastomers.

Multi-stimuli-responsive poly(hydroxyethyl methacrylate-co-N-vinyl pyrrolidone-co-methacrylic acid-co-N-isopropylacryl amide) hydrogel: synthesis, characterization and application in drug release

Multi-stimuli-responsive hydrogels are being increasingly studied due to their sensitive response to small stimuli and wide applications in biosensors and drug delivery. In this study, a multi-stimuli-responsive hydrogel, poly(hydroxyethyl methacrylate-co-N-vinyl pyrrolidone-co-methacrylic acid-co-N-isopropylacryl amide) [poly(HEMA-co-NVP-co-MAA-co-NIPA)], was synthesized by radical polymerization and characterized by Fourier transform infrared (FTIR) and 13C NMR spectroscopy techniques. With the aids of scanning electron microscopy (SEM) characterization, it was confirmed that the sensitive stimuli-responsive behavior of the hydrogel stemmed from its microstructure variation with those external stimulus. Rheological study showed that the hydrogel had rheological feature of typical elastomer. Compression tests revealed that the poly(hydroxyethyl methacrylate-co-N-vinyl pyrrolidone) [poly(HEMA-co-NVP)] played an important role in enhancing the compressive modulus of such hydrogel. More interestingly, the equilibrium swelling ratio (ESR) studies further confirmed that the composite hydrogel displayed response sensitively to the stimulus of temperature, pH, and ionic strength. Herein, theophylline as a drug model was adopted due to the multi-stimulus properties of hydrogels, which were a potential candidate for drug loading and delivering. Releasing drug continuously in a given period was dependent on the characteristics of solution and loading time. The mechanisms for drug release from the hydrogels were studied by Ritger–Peppas model.

Temperature and trap distribution dependence of electrical tree growth characteristics in polypropylene/elastomer blends for recyclable cable insulation

Polypropylene (PP)/elastomer blends as a promising cable insulation material have to face the challenge of electrical treeing which possibly leads to unexpected insulation failure. In this work, two types of elastomers, i.e. polyolefin elastomer and propylene-based elastomer, have been blended into isotactic PP. Effects of the elastomer content and type on electrical treeing behaviours have been investigated under different ambient temperatures. Isothermal surface potential decay measurement has been performed to explore the influence of trap distribution on the treeing behaviour, scanning electron microscope and differential scanning calorimetry measurements were performed to characterise the structure of blends. It was found that with the increase of elastomer content, the trap energy level was reduced and the shallow trap density was increased, which resulted in the enhancement of the tree growth rate and the decrease in the breakdown time. With the temperature changing from 20 to 100°C, the growth rate tended to be increased except that an anomalous reduction in the rate occurred at 80°C. It is suggested that the compatibility between PP matrix and elastomer plays an important role in determining the morphology of blends, which in turn influences the trap distribution and the temperature dependent treeing behaviours.

Study of the enhanced burning rate during the plasma-propellant interaction process

Plasma ignition technology has been widely used for decades due to its great improvement in enhanced burning rate. However, the interaction process between the plasma jet and the solid propellant is still far from being elucidated. In this paper, coupling the flow model of plasma jet and the chemical reaction model of propellants, a more comprehensive model for predicting the plasma enhanced burning rate is presented. Three types of energetic thermoplastic elastomers propellant are involved. In addition, the closed bomb vessel test is conducted to investigate the burning characteristics of propellant under the action of plasma for comparison. It demonstrates that the enhanced combustion phenomenon of propellants in the experiment can be well described by an enhanced burning rate coefficient epsilon calculated with the model, which could reflect the effect of plasma jet to some extent. The results show that the composition of the energetic material and its surface temperature are the key factors influencing the plasma-enhanced combustion. This model would bring some insight on the interaction mechanisms between plasma and different propellants.

Textile-Integrated Elastomer Surface for Fiber Reinforced Composites

Elastomer layers offer a wide range of surface functionalization options for fiber-reinforced polymer composites (FRPC), e.g. erosion protection or increased impact resistance. Goal of this study was to investigate if it is possible to prepare a textile-based semi-finished product with elastomeric surface, which can easily be used as outermost layer in different liquid composite molding (LCM) processes. For this purpose, different types of elastomer were pressed and vulcanized onto a biaxial glass fiber fabric. Target of this procedure was to reach partial immersion of the elastomer into the textile with remaining dry textile areas. The dry areas of the textile can later be impregnated with a thermoset resin system. The strategy is to have the transition region between elastomer and thermoset within one textile layer and to give a robust and easy to handle semi-finished-product in order to achieve a maximum bonding strength of the elastomer surface to the final composite part. It could be shown by micrographs and computer tomography that the elastomer only penetrates the textile at its boundary. A remarkable microimpregnation of individual filaments within the rovings does not take place. Concerning the manufacturing, since water evaporates during vulcanization, a sufficient process pressure must be maintained throughout the entire vulcanization process to ensure a pore-free elastomer. Peel-off tests similar to DIN EN 28510-1 on the finished composite showed a failure in the laminate and not in the boundary layer between laminate and elastomer, so that the desired high joint strength could be demonstrated.

Finite Element Model Updating Combined with Multi-Response Optimization for Hyper-Elastic Materials Characterization.

The experimental stress-strain curves from the standardized tests of Tensile, Plane Stress, Compression, Volumetric Compression, and Shear, are normally used to obtain the invariant λi and constants of material Ci that will define the behavior elastomers. Obtaining these experimental curves requires the use of expensive and complex experimental equipment. For years, a direct method called model updating, which is based on the combination of parameterized finite element (FE) models and experimental force-displacement curves, which are simpler and more economical than stress-strain curves, has been used to obtain the Ci constants. Model updating has the disadvantage of requiring a high computational cost when it is used without the support of any known optimization method or when the number of standardized tests and required Ci constants is high. This paper proposes a methodology that combines the model updating method, the mentioned standardized tests and the multi-response surface method (MRS) with desirability functions to automatically determine the most appropriate Ci constants for modeling the behavior of a group of elastomers. For each standardized test, quadratic regression models were generated for modeling the error functions (ER), which represent the distance between the force-displacement curves that were obtained experimentally and those that were obtained by means of the parameterized FE models. The process of adjusting each Ci constant was carried out with desirability functions, considering the same value of importance for all of the standardized tests. As a practical example, the proposed methodology was validated with the following elastomers: nitrile butadiene rubber (NBR), ethylene-vinyl acetate (EVA), styrene butadiene rubber (SBR) and polyurethane (PUR). Mooney–Rivlin, Ogden, Arruda–Boyce and Gent were considered as the hyper-elastic models for modeling the mechanical behavior of the mentioned elastomers. The validation results, after the Ci parameters were adjusted, showed that the Mooney–Rivlin model was the hyper-elastic model that has the least error of all materials studied (MAEnorm = 0.054 for NBR, MAEnorm = 0.127 for NBR, MAEnorm = 0.116 for EVA and MAEnorm = 0.061 for NBR). The small error obtained in the adjustment of the Ci constants, as well as the computational cost of new materials, suggests that the methodology that this paper proposes could be a simpler and more economical alternative to use to obtain the optimal Ci constants of any type of elastomer than other more sophisticated methods.

Experimental investigation of modern ORC working fluids R1224yd(Z) and R1233zd(E) as replacements for R245fa

The Organic Rankine Cycle (ORC) is a promising technology to convert low temperature heat to electrical power. It utilizes organic substances, which are often refrigerants, as working fluids. With the groups of hydrofluoroolefines (HFO) and hydrochlorofluoroolefines (HCFO), a new generation of refrigerants has been introduced within the last years. These refrigerants have a significantly smaller Global Warming Potential (GWP) compared to the currently dominating fluids, which are within the group of hydrofluorocarbons (HFC). A typical representative of HFC fluids for ORC applications is R245fa, with an GWP value of 1030. According to the thermophysical properties, promising low-GWP alternatives for this fluid are R1233zd(E) and R1224yd(Z) with a three orders of magnitude lower GWP value.The purpose of this paper is to investigate the applicability of these modern fluids as drop-in replacements for R245fa in existing ORC systems. For the evaluation of drop-in replacements, it has to be ensured, that on the one hand side, the materials within the system are compatible with the new fluid. On the other hand side, the operation condition and the performance of the system should be similar to the case with the HFC fluid. Therefore, a twofold approach is followed in this study: First, the material compatibility between the three fluids and typical elastomers is investigated. Second, all three fluids are tested in an ORC system under a wide range of operational conditions. With that approach, a general evaluation of the feasibility of a drop-in replacement can be made.As a conclusion, it can be stated, that both novel fluids R1233zd(E) and R1224yd(Z) are suitable for the drop-in replacement of R245fa in ORC systems. However, the results show, that the compatibility of R1233zd(E) with the investigated typical polymers is worse compared to R245fa and R1224yd(Z), pointing out the need for individual compatibility investigations when R1233zd(E) should be applied. Concerning system performance, the highest power output is still obtained with the high-GWP fluid R245fa. The maximum power output with R245fa is 326 W, which is 9% higher compared to R1233zd(E) and 12% higher compared to R1224yd(Z). In terms of thermal efficiency of the ORC system, R1233zd(E) leads to approximately 2% higher values compared to R245fa. In contrast to that, the thermal efficiency of R245fa and R1224yd(Z) is equal over a wide range of operation conditions.

Elastomeric Prepregs for Soft Robotics Applications

Typically, soft robots that are driven with compressed air consist of two parts which are bonded together, a top and a strain‐limiting bottom part. This communication describes the possibility to simplify the manufacturing process by using textile semi‐finished products preimpregnated with liquid elastomer (prepregs) as the strain‐limiting part, which can be stored at low temperatures with significant slower cross‐linking reaction. For this, in long‐term tests, three typical elastomers (Elastosil M 4601, Ecoflex 00–30, and Sylgard 184) are stored at −25 °C, and in a weekly cycle over 12 weeks, the viscosity is measured to determine the curing characteristics. It turns out that Elastosil M 4601 and Sylgard 184 are suitable for this application. For comparison, short‐term viscosity measurements are conducted at room temperature in a 10 min cycle. The impregnability of several textiles (polyester/cotton blended fabric, nylon fabric, fleece, and flax fabric) is tested with the suitable elastomers. The applicability of prepregs for soft robotic applications is demonstrated by manufacturing soft bending actuators with various textile‐elastomer combinations.

Unraveling the high strain-rate dynamic stiffening in select model polyurethanes − the role of intermolecular hydrogen bonding

This study elucidates the influence of molecular attributes on the observed dynamic stiffening in select two-component polyurethanes upon high strain-rate impact. Unlike typical segmented elastomers, polyurethanes consisting of poly(tetramethylene oxide), PTMO, and a diisocyanate, but without a chain extender, are investigated. The hexamethylenediisocyanate (HDI)-based polyurethane, HDI−PU, exhibits crystallinity and a much higher ambient storage modulus, as determined by dynamic mechanical analysis at 1 Hz, than that of 4,4′-methylenediphenyldiisocyanate (MDI)-based polyurethane, MDI−PU. In contrast, MDI−PU exhibits a higher glass transition temperature than that of HDI−PU, and a greater dynamic stiffening against silica micro-particle impacts at strain rates between 107 and 108 s−1. The variation in dynamic stiffening corroborates well the observed dynamics at the molecular level, as determined via solid-state nuclear magnetic resonance (ssNMR) spectroscopy. The presence of a slower-dynamics component in MDI−PU, as evidenced in the 13C ssNMR dipolar dephasing time, is used to explain the observed enhanced dynamic stiffening response.

Effect of radiation on vinyl-methyl-polysiloxane and phenyl-vinyl-methyl-polysiloxane elastomers cured with different co-agents: Comparative study of mechanical and relaxation properties

The objective of this comparative study is to investigate the effects of electron-beam irradiation on the mechanical and stress relaxation properties of vinyl-methyl-polysiloxane (VMQ) and phenyl-vinyl-methyl-polysiloxane (PVMQ), as well the variation of these properties with irradiation depending on the silicone and co-agent type. For this purpose, firstly a series of silicone mixtures was prepared using 2,5-bis(tert-butylperoxy)−2,5-dimethylhexane as the peroxide and either a Type I (ZDA) or Type II co-agent (TAIC). The rheological properties and curing conditions of the prepared mixtures were investigated by rubber process analyzer. In the second step, cured elastomers were irradiated with electron beams at doses of 0–80 kGy. The percent gelation of elastomers before and after irradiation was determined by sol–gel analysis. In order to investigate the effects of irradiation on the mechanical properties and cross-link density, the stress–strain behavior was determined. The stress relaxation properties of samples were determined by temperature scanning stress relaxation technique. After the irradiation, it was found that the main effect of irradiation on the silicone elastomers is cross-linking. Irradiation increased the cross-link density for both the silicone and gel fraction up to 94.3% for PVMQ and 96.7% for VMQ. A higher cross-link density was achieved for all of the non-irradiated and irradiated PVMQ elastomers than for VMQ elastomers. The relaxation studies revealed that elastomer type and irradiation are two important parameters affecting the relaxation behaviors of silicone elastomers. Increasing the irradiation dose resulted in maintaining of mechanical properties owing to the isothermal relaxation of both VMQ and PVMQ elastomers. This improvement was higher in the VMQ elastomers. In non-isothermal or temperature scanning stress relaxation behavior, an increase in the irradiation dose resulted in an improvement in the properties of the VMQ elastomers and a decrease for the PVMQ elastomers. The reason for this reduction is thought to be some undesirable side reactions occurring with the free radicals stabilized by the phenyl groups during irradiation and that these groups accelerate the decomposition at high temperatures during the relaxation experiments.

A new hybrid energy dissipation system with viscoelastic and flexural yielding strips dampers for multi-level vibration control

In this study, a new hybrid damper (HD) is introduced that consists of elastomeric layers, which act as a viscoelastic damper (VED), and metallic dampers (MDs). Metallic part is composed of flexural yielding strips. This HD not only removes the limitations of each of these two types of dampers, but also facilitates its application for multi-level vibration control. Based on operational mechanism and design objectives of the proposed HD, three specimens have been manufactured and tested under quasi-static cyclic loading to evaluate the functional objectives. Two types of elastomers and two types of metallic dampers are used in these specimens. Experimental results show stable hysteretic behavior and high energy dissipation capacity. Also, the multi-phase behavior of the proposed HD confirms the proper function that is intended. However, the HD that is made of natural rubber (NR) and comb-teeth damper (CTD) can tolerate more cycles and possesses more ductility in comparison with the HD made of butyl rubber (IIR) and steel slit damper (SSD). A finite element model (FEM) is also used to simulate the behavior of the proposed HD. A good correlation between numerical outputs, analytical equations and experimental results indicates the accuracy of the proposed FEM.

Evaluation of Shore A hardness of maxillofacial silicones: the effect of dark storage and nanoparticles.

Little has been reported how the addition of nanoparticles could affect the hardness of maxillofacial silicones. The purpose of this study was to evaluate the effects of different types of nanoparticle additives and dark storage for 2-years on the Shore A hardness of two types of maxillofacial silicone elastomers. A-2000 and A-2006 Room Temperature Vulcanized (RTV) silicone elastomers were tested in this study. Silaned silica, fumed silica and titanium dioxide nanoparticles at concentrations of 10% by volume were used as fillers for the maxillofacial silicone elastomers. A total of 64 silicone specimens were fabricated, which includes 8 samples, 30 × 10 mm in size, from each silicone elastomers for each subgroup and also controls. After the initial Shore A hardness measurements, specimens were kept in dark conditions at room temperature for 2 years. The final measurements were then taken from the silicone specimens. All data were statistically analyzed. For both types of silicones, there was statistically significant differences among study groups (p<0.001). Fumed silica group showed the lowest hardness values in A-2000 after storage. However, no significant difference was observed between control and fumed silica groups. Control group showed the lowest hardness values in A-2006, while the highest hardness values were found in fumed silica group; there was no significant difference between silica and silane groups. Shore A values of the specimens were within the acceptable range for the maxillofacial silicones after aging. Nanoparticle addition did not prevent hardening of the silicone elastomers with time.

Damping Characterization of Hybrid Carbon Fiber Elastomer Metal Laminates using Experimental and Numerical Dynamic Mechanical Analysis

Lightweight structures which consist to a large extent of carbon fiber reinforced plastics (CFRP), often lack sufficient damping behavior. This also applies to hybrid laminates such as fiber metal laminates made of CFRP and aluminum. Since they are usually prone to vibrations due to their high stiffness and low mass, additional damping material is required to meet noise, vibration and harshness comfort demands in automotive or aviation industry. In the present study, hybrid carbon fiber elastomer metal laminates (HyCEML) are investigated which are intended to influence the damping behavior of the laminates by an elastomer interlayer between the CFRP ply and the aluminum sheets. The damping behavior is based on the principle of constrained layer damping. To characterize the damping behavior, dynamic mechanical analyses (DMA) are performed under tension on the elastomer and the CFRP, and under three point bending on the hybrid laminate. Different laminate lay-ups, with and without elastomer, and two different elastomer types are examined. The temperature and frequency dependent damping behavior is related to the bending stiffness and master curves are generated by using the time temperature superposition to analyze the damping behavior at higher frequencies. A numerical model is built up on the basis of DMA experiments on the constituents and micro mechanical studies. Subsequently, three point bending DMA experiments on hybrids are simulated and the results are compared with the experimental investigations. In addition, a parameter study on different lay-ups is done numerically. Increasing vibration damping is correlated to increasing elastomer content and decreasing elastomer modulus in the laminate. A rule of mixture is used to estimate the laminate loss factor for varying elastomer content.

Strain-induced structural and dynamic changes in segmented polyurethane elastomers

Polyurethane elastomers have been widely used in the industry and daily life due to their versatile physical and chemical properties. Therefore, a fundamental understanding of the structures and dynamics at a molecular level will provide piercing insights into the precise design and application of new polyurethane materials. In this study, we mainly focused on investigating the strain-induced structural and dynamic changes in a typical polyurethane elastomer composed of poly(ε-caprolactone) (PCL) and 4,4′-diphenylmethylene diisocyanate (MDI) as the soft and hard segments, respectively. Obvious strain-hardening phenomenon was observed during the mechanical tensile test, and a systematic comparison was performed on the fractured and pristine samples. DSC results revealed that the crystallization of PCL chains was still going on after the sample was fractured, and the crystallite structures became stable after physical aging at 25 °C for two days. 1H solid-state nuclear magnetic resonance (NMR) experiment was further employed to determine the fraction of mobile PCL chains that were converted to crystallites during stretching. Besides, the microphase separation was also significantly enhanced in the fractured sample. The mobility of amorphous PCL chains was largely reduced due to the strain-induced crystallization of nearby PCL segments, as revealed by the 1H magic-sandwich echo (MSE) NMR experiments. 1H multiple quantum (MQ) NMR experiments also quantitatively revealed the strain-induced orientation of amorphous PCL chains in the fractured sample, indicating that the PCL crystallites were acting as the physical cross-linkages to prevent the contraction of the elongated PCL chains when the sample is fractured.

Adaptive Damping of a Double‐Beam Structure Based on Magnetorheological Elastomer

A method of vibration reduction based on activation of an MRE block that couples twin cantilever beams at their free ends is investigated. Four types of magnetorheological elastomers have been manufactured, and their rheological properties in a range of magnetic field intensities are established. Free vibrations of several double‐beam structures with controllable damping members made of these MREs are investigated, and a method of semiactive control of such structures is proposed. The effects of compression of the elastomers and alignment of the magnets used to activate them are reported. The mathematical modeling of the system is verified experimentally.