Properties Of Elastomeric Materials Research Articles

COMBINED TECHNIQUES AND RELEVANT IMAGE PROCESSING FOR QUANTITATIVE STATISTICAL CHARACTERIZATION OF INCLUSIONS IN ELASTOMERS

ABSTRACT The properties of elastomeric materials are strongly influenced by the inclusions resulting from the ingredients and the elaboration process. A methodology is proposed to differentiate the inclusions harmful for fatigue (larger than a few micrometers) in elastomers according to their chemical nature, and to characterize them quantitatively with sufficient statistics. Three techniques are used and compared: digital optical microscopy (OM), scanning electron microscopy (SEM) associated with energy dispersive X-ray spectroscopy, and X-ray micro-computed tomography (μ-CT). Six materials are used to challenge the methodology. In addition to the usual metal oxides and carbon black agglomerates, three atypical types of inclusions are highlighted, generating specific detection difficulties. A relevant image analysis procedure is developed to automatically detect the inclusions from the acquired images, more objectively and accurately than with the classical thresholding methods. The morphology and the spatial distribution of the different inclusions populations are then determined. μ-CT is the most comprehensive and accurate method for classification and statistical characterization of inclusions. Furthermore, relevant data on the size distribution of inclusions can be obtained using backscattered electrons (SEM-BSE) or digital OM. SEM-BSE provides more accurate results than digital OM.

Localizing the cross-links distribution in elastomeric composites by tailoring the morphology of the curing activator

The localization of the rubber vulcanization reaction close to the silica filler surface was investigated in isoprene rubber composites (IR NCs): the main goal was to highlight the role of curing agents’ dispersion and filler surface features on the spatial propagation of the rubber cross-links and the resulting mechanical behavior of the material. The study was realized by tailoring the morphology of the curing activator, i.e. by vulcanizing IR NCs with Zn@SiO2 double function filler, composed of Zn(II) single sites anchored on SiO2 filler, in comparison to silica filled IR NCs vulcanized with microcrystalline ZnO . The microscopic cross-links distribution was measured by Transmission Electron Microscopy for network visualization (NVTEM) and Time Domain Nuclear Magnetic Resonance (TD-NMR). Besides the NCs mechanical behavior was characterized both at small strain and at fracture. In the presence of Zn@SiO2, higher cross-link density in proximity to SiO2 particles was evidenced, which gradually spreads from the filler surface to the bulk, induced by localization of the Zn(II) centers. IR NCs with Zn@SiO2 resulted stiffer (+45%) and with a lower fracture toughness (less than one third), compared to m-ZnO based NCs, which shows a quite homogeneous structure of the rubber cross-links network. The results highlighted the correlation between the composites structural features and their macroscopic behavior, paving the way to modulating the mechanical properties of elastomeric materials by tuning the nature of the curing agents.

Influence of various factors on surface properties of elastomeric materials based on nitrile butadiene rubbers

Objectives. The influence of the technological additive content and accelerated aging conditions on the surface energy and elastic-strength properties of nitrile butadiene rubbers with an average acrylic acid nitrile content and rubbers based on them were studied in the paper.Methods. The free surface energy of the samples was determined under the standard conditions and in the accelerated aging conditions with the use of the Owens, Wendt, Rabel, and Kaelble method.Results. It was shown that the elastomeric materials surface energy is influenced by surfactants such as rosin and stearic acid, which are typical ingredients of rubber compounds. It was also found that the thermal aging effect on the physical and mechanical properties of rubbers based on nitrile butadiene rubbers depends on the method of rubber isolation from latex and on the nature of the surfactant components in the samples.Conclusions. The analysis of the results obtained shows that the change in the vulcanizates physical and mechanical properties, depending on the technological additive content and the temperature effect, occurs along with a change in the critical surface tension.

Влияние технологии производства средств снижения шума и виб-рации на их физико-механические и акустические характеристики

Object and purpose of research. This paper discusses typical acoustic protection tools, like resilient mounts and sonar coatings. The purpose is to determine how manufacturing technology of acoustic protection tools affects their performance. Materials and methods. The study is based on the experiments intended to obtain physical, mechanical, operational and elastic-hysteresis properties of polyurethane material, as well as physical, mechanical and acoustic properties of acoustic protection tools manufactured as per various technologies. Main results. This research established the manufacturing technology effect of polyurethane compound upon the properties of elastomeric materials and acoustic protection tools made of it. Analysis of the results served to estimate pros and cons for each of the technologies under investigation in terms of their relevance with respect to advanced acoustic protection designs, as well as to estimate practicability of further studies in this direction. Conclusion. Dynamic shear modulus reduction of the material used in production of sonar coatigns and resilient mounts could be achieved through a technology where the components of polyurethane compound, prior to their use, are mixed (homogenized) separately without vacuum, which attracts additional air into them.

Bioinspired toughening of soft elastomer via embedded three‐dimensional printing

AbstractThe interest in soft elastomers has been revived because they are needed in the emerging soft robotics and wearable devices. It is imperative to adjust the mechanical properties of elastomeric materials for real‐life applications as well as to develop an approach to construct more complex and customized architectures. In this study, an embedded extrusion‐based three‐dimensional (3D) printing method was used to prepare silicone elastomeric composites. Cellulose nanocrystals were introduced to tailor the rheology of the ink and serve as reinforcements after solidification. The printing paths were carefully designed to write Bouligand structures, which have been widely found in arthropod cuticles and fish scales because of their exceptional damage resistance. Compared with the pure elastomer and randomly distributed composites, the 3D‐printed elastomeric composites with bioinspired structures exhibited simultaneously enhanced stiffness, extensibility, and toughness. This strategy may be extended to the realization of other biomimetic designs and paves the way for soft material manufacturing.

The Effect of Finishing Carbon Microfibers on Fire–Heat Resistant and Adhesion Properties of Elastomeric Materials

The Effect of Finishing Carbon Microfibers on Fire–Heat Resistant and Adhesion Properties of Elastomeric Materials

Simultaneous characterization of dielectric and dynamic-mechanical properties of elastomeric materials under static and dynamic load

The inner dynamics of carbon black filled elastomeric material under static and dynamic load are examined by means of simultaneous dielectric and dynamic-mechanical analysis at room temperature. The experiments are performed on styrene butadiene rubber (SBR) samples filled with carbon black well above the dielectric percolation threshold. By increasing the mechanical load, a decrease in the conductivity is found due to continuous mechanical damage to the filler network structure, which prevents the transport of charge carriers through the sample via the carbon black network. The Cole-Cole equation is applied to fit the experimental data. The resulting fit-parameters show different load dependence. The mechanical damage to the filler network makes the relaxation processes broader and leads to higher relaxation times, whereby the relaxation strength increases. This has been attributed to an increase in the correlation length of the filler network with increasing load.

Design of a self-unfolding delivery concept for oral administration of macromolecules

Delivering macromolecular drugs, e.g. peptides, to the systemic circulation by oral administration is challenging due to their degradation in the gastrointestinal tract and low transmucosal permeation. In this study, the concept of an oral delivery device utilizing an elastomeric material is presented with the potential of increasing the absorption of peptides, e.g. insulin. Absorption enhancement in the intestine is proposed as a result of self-unfolding of a polydimethylsiloxane foil upon release from enteric coated capsules. A pH-sensitive polymer coating prevents capsule disintegration until arrival in the small intestine where complete unfolding of the elastomeric foil ensures close contact with the intestinal mucosa. Foils with close-packed hexagonal compartments for optimal drug loading are produced by casting against a deep-etched silicon master. Complete unfolding of the foil upon capsule disintegration is verified in vitro and the insulin release profile of the final delivery device confirms insulin protection at gastric pH. In vivo performance is evaluated with the outcome of quantifiable plasma insulin concentrations in all rats receiving duodenal administration of the novel delivery device. By taking advantage of elastomeric material properties for drug delivery, this approach might serve as inspiration for further development of commercially viable biocompatible devices for oral delivery of macromolecules.

CaproGlu: Multifunctional tissue adhesive platform

Driven by the clinical need for a strong tissue adhesive with elastomeric material properties, a departure from legacy crosslinking chemistries was sought as a multipurpose platform for tissue mending. A fresh approach to bonding wet substrates has yielded a synthetic biomaterial that overcomes the drawbacks of free-radical and nature-inspired bioadhesives. A food-grade liquid polycaprolactone grafted with carbene precursors yields CaproGlu. The first-of-its-kind low-viscosity prepolymer is VOC-free and requires no photoinitiators. Grafted diazirine end-groups form carbene diradicals upon low energy UVA (365 nm) activation that immediately crosslink tissue surfaces; no pre-heating or animal-derived components are required. The hydrophobic polymeric environment enables metastable functional groups not possible in formulations requiring solvents or water. Activated diazirine within CaproGlu is uniquely capable of crosslinking all amino acids, even on wet tissue substrates. CaproGlu undergoes rapid liquid-to-biorubber transition within seconds of UVA exposure–features not found in any other bioadhesive. The exceptional shelf stability of CaproGlu allows gamma sterilization with no change in material properties. CaproGlu wet adhesiveness is challenged against current unmet clinical needs: anastomosis of spliced blood vessels, anesthetic muscle patches, and human platelet-mediating coatings. The versatility of CaproGlu enables both organic and inorganic composites for future bioadhesive platforms.

Tunable Photonic Materials via Monitoring Step‐Growth Polymerization Kinetics by Structural Colors

AbstractThe functional and responsive properties of elastomeric materials highly depend on crosslink density and molecular weight between crosslinks. However, tedious analytical steps are needed to obtain polymer network structure–property relationships. In this article, an in situ structure–property characterization method is reported by monitoring the structural color change in a photonic elastomeric material. The photonic materials are prepared in a two‐step polymerization process. First, linear chain extension occurs via Michael addition. Second, photopolymerization ensures crosslinking, resulting in the formation of an elastomeric photonic network. During the first step, the step‐growth polymer process can be monitored by following the photonic reflection band redshift, allowing to program the molecular weight between the crosslinks. During network formation, the crosslink density, chain length between crosslinks, and the colors are “frozen in.” These processes can be locally controlled creating both single‐layered multicolor patterned and broadband reflective coatings at room temperature. The scalability of the coating process is further demonstrated by using a gravure printing technique. Additionally, the final coatings are made responsive toward specific solvents and temperature. Here the modulus, response, and color of the coating are controlled by tuning the crosslink density and molecular weight between crosslinks of the elastomeric material.

Hyper-viscoelastic constitutive models for predicting the material behavior of polyurethane under varying strain rates and uniaxial tensile loading

Non-linearity, loading rate, as well as temperature and pressure dependency present major challenges in the investigation of properties, particularly the mechanical properties of elastomeric polymers. Recently, material and structural engineers have focused on investigating the mechanical behavior of hyper-elastic materials under varying strain rate conditions. In addition, they have been developing constitutive models to define the non-linear behavior of these materials, combined with the strain rate effect, which simulates behavior under different loading conditions. In this study, a new viscoelastic model is proposed to simulate the variation in the mechanical properties of elastomeric materials. Hyper-viscoelastic constitutive models were also developed by modifying existing hyper-elastic models (Mooney–Rivlin and Ogden) with existing viscoplastic models (Cowper–Symonds and Johnson–Cook) and the proposed viscoelastic model. The proposed models were verified through experimental results by investigating the uniaxial tensile behavior of an elastomeric polyurethane (PU) sample under varying low strain rate regimes (0.001 s−1–0.1 s−1). The proposed viscoelastic model exhibited the best correlation to present the enhancement of mechanical properties under varying strain rate conditions compared with the Cowper–Symonds and Johnson–Cook models. The proposed hyper-viscoelastic models could be used to predict material behavior using only one set of hyper-elastic model parameters at a certain strain rate, combined with viscoelastic model parameters. The hyper-viscoelastic cumulative strain energy and stress–strain models, which were developed with the proposed viscoelastic model, demonstrated high accuracy in predicting material behavior with the strain rate effect of elastomeric PU or similar materials.

Architectural Code for Rubber Elasticity: From Supersoft to Superfirm Materials

The current approach to regulating mechanical properties of elastomeric materials is predominately based on the exploratory mixing of different polymers, solvents, and fillers—which is both inflexi...

Determination of the Crosslinking Density of a Silicone Elastomer

A laboratory experiment for the determination of the cross-linking density of silicone elastomers is described on the basis of swelling experiments and mechanical tests. In the experiment, the macroscopic swelling and mechanical behaviors of the elastomers were discussed as a function of the cross-linking density, which can be easily controlled by varying the base-to-curing-agent ratio during elastomer synthesis. The cross-linking density and the average molecular weight between cross-links were calculated from the swelling degree at equilibrium through the Flory–Rehner theory and from a simple mechanical model. The results have shown a good convergence of the average molecular weight between cross-links calculated from the two methods, respectively. On a more general note, the suggested experiments and the associated results offered numerous opportunities for discussions on macromolecular architectures, interactions between polymers and solvents, and mechanical properties of elastomeric materials.

The influence of combined active fillers on the properties of elastomeric materials for eco-friendly tyres

Reinforcing of elastomers by the addition of various nanofillers has led to significant improvements in elastomer properties, and therefore, to the increase of potentials for use as suitable materials for special applications. The aim of this study was to investigate the effects of combinations of two active fillers (carbon black and synthesized silica (50/0; 35/15; 25/25; 15/35; 0/50; phr)) on the morphology, curing, as well as thermal, dynamic-mechanical and mechanical properties of nanocomposites based on the styrene-butadiene rubber as the network precursor. Based on SEM results, the largest agglomerates were observed in the structure of the nanocomposite containing 25 phr of carbon black and 25 phr of SiO2. Determination of curing characteristics indicated that the minimum torque at 100, 150 and 160?C had higher magnitudes for the compounds with silica filler, which is in accordance with the tendency of SiO2 to form filler-filler interactions. Values of the scorch time and the optimal time of crosslinking increased by increasing the silica phr content in the fillers mixture. It could be thus supposed that the fraction of occluded and trapped chains in the structure of elastomer reinforced by SiO2 is higher due to the almost 2-fold higher value of the silica NDBP number as compared to the NDBP number of carbon black particles. On the basis of MDSC results, it was assessed that the addition of combined active fillers had negligible effects on the glass transition temperature, registered at about -47?C for all tested samples. The obtained DMA data, concerning storage moduli in the temperature range from -20 to 0?C, (characteristic for "Payne" effect) are very significant for predictions of the properties of the tyre tread such as the slip resistance on the road on ice and in the wet conditions. The increase of silica content in the combined filler induced a decrease of the dynamic mechanical loss factor of prepared nanocomposites in the temperature range from 40 to 80?C. The obtained results are very important for the structuring of elastomeric materials aimed for production of tyres with reduced rolling resistance and fuel consumption. The elastomer containing the highest content of carbon black showed the highest value of the tensile strength (21.8 MPa). The abrasion resistance of the synthesized nanocomposites increased as the silica content was reduced in the combined fillers.

Influence of physico-mechanical properties of elastomeric material for different cell growth

The tunable mechanical and physical properties of polydimethylsiloxane (PDMS) are commonly utilized for studying cellular dynamics. However, the inherent hydrophobic nature of PDMS limits its application as a cell culture film. Various surface modification techniques render PDMS films hydrophilic, altering their surface chemistry, elasticity, roughness and the cell attachment of anchorage-dependent cell types to the films. The surface properties of thin films lead to the alteration of the biomechano-physical properties of cells, so they can be used as a mechanical signature for the viability testing of different types of cell, such as normal and cancerous ones. In this study, 3T3 fibroblast and HaCaT keratinocyte cells were grown on different pristine and oxidized PDMS compositions by varying their base-to-curing-agent ratios (w/w). The enhanced wettability favors the cell spreading and growth rate of both 3T3 and HaCaT cells, and it varies with the film’s surface chemistry and elasticity. This study focuses on the importance of understanding how various surface modification methods, like oxygen plasma and piranha treatment, can impact cell–cell and cell–substrate interaction for different cell types, thereby assisting in the preparation of various PDMS-based biomedical devices.

Experimental analysis of the effect of carbon nanoparticles with different geometry on the appearance of anisotropy of mechanical properties in elastomeric composites

The paper presents studies of the properties of elastomeric materials based on the solution-polymerized styrene-butadiene rubber (S-SBR) filled with nanoparticles of different geometry – grainy (nanodiamonds), layered (graphene nanoplates) and fibrous (nanotubes). Despite the introduction of a small amount of fillers, the significant strengthening of the matrix is exhibited. Of particular interest is the behavior of the nanodiamond-filled elastomer composite, for which a double increase in rupture stress with an increase in rupture strain is observed at the filler volume fraction approximately equal to 2%. The structure of composites is investigated by optical and atomic force microscopy. In addition to standard mechanical testing, experiments of successive cyclic loading along each of two mutually perpendicular axes of plane elastomeric samples were conducted with use of a Zwick 4-vector test stand (biaxial testing machine). The phenomenon of induced anisotropy in materials is analyzed. A hypothesis to explain its manifestation is suggested.

An Explicit Finite-Element Model to Investigate the Effects of Elastomeric Bushing on Bearing Dynamics

This work presents a numerical simulation which studies the effect of elastomeric bushing on the dynamics of a deep-groove ball bearing. To achieve the objective, a three-dimensional (3D) explicit finite element method (EFEM) was developed to model a cylindrical elastomeric bushing, which was then coupled with an existing dynamic bearing model (DBM). Constitutive relationship for the elastomer is based on the Arruda–Boyce model combined with a generalized Maxwell-element model to capture both hyperelastic and viscoelastic behaviors of the material. Comparisons between the bushing model developed for this investigation and the existing experimental elastomeric bushing study showed that the results are in good agreement. Parametric studies were conducted to show the effects of various elastomeric material properties on bushing behavior. It was also shown that a desired bushing support performance can be achieved by varying bushing geometry. Simulations using the combined EFEM bushing and DBM model demonstrated that the elastomeric bushing provides better compliance to bearing misalignment as compared to a commonly used rigid support model. As a result, less ball slip and spin are generated. Modeling with a bearing surface dent showed that vibrations due to surface abnormalities can be significantly reduced using elastomeric bushing support. It has also been shown that choosing a proper bushing is an efficient way to tuning bushing vibration frequencies.

Effect of Carbon Black Activation on Physicomechanical Properties of Butadiene-nitrile Rubber

E-mail: jinhcho@mju.ac.krReceived April 28, 2014, Accepted June 3, 2014The effects of mechanical activation of carbon black on the processing and properties of butadiene nitrilerubber were studied. Mechanical activation of carbon black caused an improvement in the physical andmechanical properties of the butadiene-nitrile rubber, BNR-18AMN. The optimum activation time that wouldafford rubber with improved properties was established.Key Words : Carbon black, Butadiene-nitrile, Rubber, Mechanical activationIntroductionManufacturing of low-cost but high-quality rubber pro-ducts has continued to be a challenging but attractive taskgiven its potential benefits. One of the more popularmethods to control the physical and mechanical properties ofelastomeric materials is the use of dispersed fillers,

Flammability and other properties of elastomeric materials and nanomaterials. Part I. Nanocomposites of elastomers with montmorillonite or halloysite

Flammability and other properties of elastomeric materials and nanomaterials. Part I. Nanocomposites of elastomers with montmorillonite or halloysite

Investigating the Influence of the Degree of Dispersion of Mineral Shungite on the Properties of Elastomeric Materials Based on Butadiene–Styrene Rubber

Investigating the Influence of the Degree of Dispersion of Mineral Shungite on the Properties of Elastomeric Materials Based on Butadiene–Styrene Rubber