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Modern rubber materials face high demands in terms of oxidation stability as well as thermal resistance and, in some cases, enhanced oil resistance. At the same time, their mechanical properties have to maintain a high level. Highperformance synthetic rubbers with highly sophisticated properties – like nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR) and peroxide-crosslinked ethylene – propylene – diene rubber (EPDM) – are thus becoming more and more important. Nevertheless, irreversible aging processes limit lifetime and result in the failure of these elastomer materials. Knowledge about chemical aging mechanisms, kinetics and the weak elements in the polymer chain and in the chemical network are fundamental to understanding and predicting lifetime as well as in arriving at appropriate measures for stabilizing the polymer matrix. Alongside the polymer’s microstructure, other determining parameters are temperature, exposure to oxygen, and its diffusion into the bulk in competition to reaction speed, which is responsible for the spatial changing of the material from the surface inward. Investigations by means of selected methods like nanoindentation, FT-IR spectroscopy, chemiluminescence, and physical testing in combination with artificial aging are used to describe quantitatively the mechanistic role of the polymer’s microstructure and of crosslinking during thermal-oxidative aging. [ABSTRACT FROM AUTHOR]

Abstract Vast amounts of rubber waste are produced every year, where end-of-life tires (ELT) mount up the largest share with several million tonnes in the EU each year. This points up the necessity for reusing end-of-life rubber material. The recycled material shows nearly the same advantages like the origin materials. In consequence, the recycled material is predestined for the use in sport facilities, which explains that around half of the recycled ELTs are used to produce artificial turf, sports flooring and injury-prevention pavements on playgrounds. Since tires contain potentially toxic components, there is worry concerning the release of such chemical substances stemming from these products. As tires contain highly aromatic oils and carbon black, the presence of polycyclic aromatic hydrocarbons (PAH) and their carcinogenic properties are discussed controversially. This review issues a comprehensive overview of PAH release and a conclusive assessment on human health risk. Analytical studies dealing with the PAH content of consumer goods made from recycled rubber material and associated risk assessments are reviewed. In conclusion PAHs can be detected in consumer goods made from recycled rubber and are released into the environment. They reach humans via leaching (soil, ground water, rivers), oral intake, dermal exposure and inhalation. Thereby, dermal contact or inhalation is the primary route of exposure, whereas oral intake and environmental pollution are regarded as secondary risks. The amount of PAHs that could potentially harm humans is in the magnitude of urban pollution. Risk assessment studies reviewed in this article show no serious risk potential. Graphical abstract Image 1 Highlights • Most recycled rubber is stemming from end-of-life tires. • Around half of the recycled rubber is used to produce artificial turf and similar. • PAHs can be detected in consumer goods made from recycled rubber. • Dermal contact or inhalation is the primary route of PAH exposure. • Reviewed risk assessment studies show no serious risk potential. [ABSTRACT FROM AUTHOR]

Two-dimensional hexagonal boron nitride (hBN) has attracted tremendous attention over the last few years, thanks to its stable structure and its outstanding properties, such as mechanical strength, thermal conductivity, electrical insulation, and lubricant behavior. This work demonstrates that hBN can also improve the rheological and mechanical properties of elastomer composites when used to partially replace silica. In this work, commercially available pristine hBN (hBN-p) was exfoliated and ball-mill treated in air for different durations (2.5, 5, and 10 h milling). Functionalization occurred with the -NH and -OH groups (hBN-OH). The functional groups were detected using Fourier-Transform Infrared pectroscopy (FT-IR) and were estimated to be up to about 7% through thermogravimetric analysis. The presence of an increased amount of oxygen in hBN-OH was confirmed using Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy. (SEM-EDS). The number of stacked layers, estimated using WAXD analysis, decreased to 8–9 in hBN-OH (10 h milling) from about 130 in hBN-p. High-resolution transmission electron microscopy (HR-TEM) and SEM-EDS revealed the increase in disorder in hBN-OH. hBN-p and hBN-OH were used to partially replace silica by 15% and 30%, respectively, by volume, in elastomer composites based on poly(styrene-co-butadiene) from solution anionic polymerization (S-SBR) and poly(1,4-cis-isoprene) from Hevea Brasiliensis (natural rubber, NR) as the elastomers (volume (mm3) of composites released by the instrument). The use of both hBNs in substitution of 30% of silica led to a lower Payne effect, a higher dynamic rigidity, and an increase in E′ of up to about 15% at 70 °C, with similar/lower hysteresis. Indeed, the composites with hBN-OH revealed a better balance of tan delta (higher at low temperatures and lower at high temperatures) and better ultimate properties. The functional groups reasonably promote the interaction of hBN with silica and with the silica's coupling agent, sulfur-based silane, and thus promoted the interaction with the elastomer chains. The volume of the composite, measured using a high-pressure capillary viscometer, increased by about 500% and 400% after one week of storage in the presence of hBN-p and hBN-OH. Hence, both hBNs improved the processability and the shelf life of the composites. Composites obtained using hBN-OH had even filler dispersion without the detachments of the filler from the elastomer matrix, as shown through TEM micrographs. These results pave the way for substantial improvements in the important properties of silica-based composites for tire compounds, used to reduce rolling resistance and thus the improve environmental impacts. [ABSTRACT FROM AUTHOR]

In this work, the hysteresis of elastomer composites suitable for tire compounds was reduced by using CB functionalized with pyrrole compounds containing sulfur-based functional groups reactive with the elastomer chains. CB was functionalized with bio-based pyrrole compounds: 2-(2,5-dimethyl-1H-pyrrol-1-yl)ethane-1-thiol (SHP) and 1,2-bis(2-(2,5-dimethyl-1H-pyr-rol-1-yl)ethyl)disulfide (SSP), bearing an -SH and an -SS- functional group, respectively. SHP and SSP were synthesized via a one-pot two-step synthesis, with yields higher than 70%, starting from biosourced chemicals as follows: 2,5-hexanedione from 2,5-dimethylfuran, cysteine and cysteamine. The functionalization of CB was carried out by mixing the CB with PyC and heating, with quantitative yields ranging from 92 to 97%. Thus, the whole functionalization process was characterized by a high carbon efficiency. The formation of the covalent bond between SHP, SSP and CB, in line with the prior art of such a functionalization technology, was proven by means of extraction and TGA analyses. The reactivity of the sulfur-based functional groups with unsaturated polymer chains was demonstrated by using squalene as the model compound. Poly(styrene-co-butadiene) from solution anionic polymerization and poly(1,4-cis-isoprene) from Hevea Brasiliensis were the elastomers employed for the preparation of the composites, which were crosslinked with a sulfur-based system. Pristine CB was partially replaced with CB/SHP (33%) and CB/SSP (33% and 66%). The PyC resulted in better curing efficiency, an increase in the dynamic rigidity of approximately 20% and a reduction in the hysteresis of approximately 10% at 70 °C, as well as similar/better ultimate tensile properties. The best results were achieved with a 66% replacement of CB with CB/SSP. This new family of reactive carbon blacks paves the way for a new generation of 'green tires', reinforced by a CB reactive with the polymer chains, which provides high mechanical properties and low rolling resistance. Such a reactive CB eliminates the use of silica, and thus the ethanol emission resulting from the condensation of silane is used as a coupling agent. In addition, CB-based tires are characterized by a higher mileage, at a moment in which the reduction in tire wear has become a primary concern. [ABSTRACT FROM AUTHOR]

Elastomer composites for dynamic mechanical applications with a low dissipation of energy are of great importance in view of their application in tire compounds. In this work, furnace carbon black functionalized with 2-2,5-dimethyl-1H-pyrrol-1-yl-1,3-propanediol (SP) was used in place of silica in an elastomer composite based on poly(styrene-co-butadiene) from solution anionic polymerization and poly(1,4-cis-isoprene) from Hevea Brasiliensis. The traditional coupling agent used for silica was also used for the CB/SP adduct: 3,3′-bis(triethoxysilylpropyl)tetrasulfide (TESPT). The composite with the CB/SP + TESPT system revealed a lower Payne effect, higher dynamic rigidity, and lower hysteresis, compared to the composite with CB + TESPT, although the latter composite had a higher crosslinking density. The properties of the silica and the CB/SP + TESPT-based composites appear similar, though in the presence of slightly higher hysteresis and lower ultimate properties for the CB/SP-based composite. The use of CB in place of silica allows us to prepare lighter compounds and paves the way for the preparation of tire compounds with lower environmental impacts. [ABSTRACT FROM AUTHOR]

The additive manufacturing (AM) of elastomeric parts based on high-viscosity reinforced rubbers has increasingly become a topic of scientific research in recent years. In addition to the viscosity, which is several decades higher during processing than the viscosities of thermoplastics, the flowability of the compound after the printing process and the necessary chemical crosslinking of the printed component play a decisive role in producing an elastic, high-quality, and geometrically stable part. After the first technological achievements using the so-called additive manufacturing of elastomers (AME) process, the knowledge gained has to be transferred first to concrete industrial parts. Therefore, in this study, the cure kinetics of a conventional rubber compound are tailored to match the specific requirements for scorch safety in the additive manufacturing of an industrial 2-component rod seal based on an acrylonitrile butadiene rubber O-ring in combination with a thermoplastic polyurethane as the base body. Experimental tests on a test rig for rod seals demonstrate the functionality of this additively manufactured 2-component rod seal. [ABSTRACT FROM AUTHOR]

Elastomer composites with low hysteresis are of great importance for sustainable development, as they find application in billions of tires. For these composites, a filler such as silica, able to establish a chemical bond with the elastomer chains, is used, in spite of its technical drawbacks. In this work, a furnace carbon black (CB) functionalized with polar groups was used in replacement of silica, obtaining lower hysteresis. CBN326 was functionalized with 2-(2,5-dimethyl-1H-pyrrol-1-yl)-1,3-propanediol (serinol pyrrole, SP), and samples of CB/SP adducts were prepared with different SP content, ranging from four to seven parts per hundred carbon (phc). The entire process, from the synthesis of SP to the preparation of the CB/SP adduct, was characterized by a yield close to 80%. The functionalization did not alter the bulk structure of CB. Composites were prepared, based on diene rubbers—poly(1,4-cis-isoprene) from Hevea Brasiliensis and poly(1,4-cis-butadiene) in a first study and synthetic poly(1,4-cis-isoprene) in a second study—and were crosslinked with a sulfur-based system. A CB/silica hybrid filler system (30/35 parts) was used and the partial replacement (66% by volume) of silica with CB/SP was performed. The composites with CB/SP exhibited more efficient crosslinking, a lower Payne effect and higher dynamic rigidity, for all the SP content, with the effect of the functionalized CB consistently increasing the amount of SP. Lower hysteresis was obtained for the composites with CB/SP. A CB/SP adduct with approximately 6 phc of SP, used in place of silica, resulted in a reduction in ΔG′/G′ of more than 10% and an increase in E' at 70 °C and in σ300 in tensile measurements of about 35% and 30%, respectively. The results of this work increase the degrees of freedom for preparing elastomer composites with low hysteresis, allowing for the use of either silica or CB as filler, with a potentially great impact on an industrial scale. [ABSTRACT FROM AUTHOR]

Incorporating nanofillers into elastomers leads to composites with an enormous potential regarding their properties. Unfortunately, nanofillers tend to form agglomerates inhibiting adequate filler dispersion. Therefore, different carbon nanotube (CNT) pretreatment methods were analyzed in this study to enhance the filler dispersion in polydimethylsiloxane (PDMS)/CNT-composites. By pre-dispersing CNTs in solvents an increase in electrical conductivity could be observed within the sequence of tetrahydrofuran (THF) > acetone > chloroform. Optimization of the pre-dispersion step results in an AC conductivity of 3.2 × 10−4 S/cm at 1 Hz and 0.5 wt.% of CNTs and the electrical percolation threshold is decreased to 0.1 wt.% of CNTs. Optimum parameters imply the use of an ultrasonic finger for 60 min in THF. However, solvent residues cause a softening effect deteriorating the mechanical performance of these composites. Concerning the pretreatment of CNTs by physical functionalization, the use of surfactants (sodium dodecylbenzenesulfonate (SDBS) and polyoxyethylene lauryl ether ("Brij35")) leads to no improvement, neither in electrical conductivity nor in mechanical properties. Chemical functionalization enhances the compatibility of PDMS and CNT but damages the carbon nanotubes due to the oxidation process so that the improvement in conductivity and reinforcement is superimposed by the CNT damage even for mild oxidation conditions. [ABSTRACT FROM AUTHOR]

Purpose: Elastomer seals are used in many applications. They are exposed to lubricants and additives at elevated temperatures, as well as mechanical stresses. They can only provide good sealing function when they have resistance to those factors. There are many elastomer-lubricant compatibility tests based on DIN ISO 1817 in industry. However, they are insufficient and costly. Correlations between the tests and the applications are inadequate. The purpose of this study is investigating lubricant compatibility of fluoroelastomers (FKM) seals in polyethylene-glycol (PG)- and polyalphaolefin (PAO)- based synthetic oils and developing a methodology to predict seal service life. Design/methodology/approach: A new compatibility test which is more sufficient in terms of time and cost was developed and compared with a standard test, currently used in industry. Compatibility of FKM radial lip seals with PG- and PAO-based synthetic oils with different additives was investigated chemically and dynamically. Failure mechanisms were examined. Findings: The new method and the Freudenberg Flender Test FB 73 11 008 showed similar results concerning damages and similar tendencies regarding wear. The additive imidazole derivative was the most critical. Static tests give indications of possible chemically active additives, but alone they are insufficient to simulate the dynamic applications. Originality/value: The paper describes a new method to investigate elastomer-lubricant compatibility and gives first results with a variety of lubricants. [ABSTRACT FROM AUTHOR]

The purpose of the current study was to establish an in vitro model for osteoarthritis (OA) by co-culture of osteochondral and synovial membrane explants. Osteochondral explants were cultured alone (control-1) or in co-culture with synovial membrane explants (control-2) in standard culture medium or with interleukin-1β (IL1β) and tumor necrosis factor (TNFα) added to the culture medium (OA-model-1 = osteochondral explant; OA-model-2 = osteochondroal-synovial explant). In addition, in OA-model groups a 2-mm partial-thickness defect was created in the centre of the cartilage explant. Changes in the expression of extracellular matrix (ECM) genes (collagen type-1 (Col1), Col2, Col10 and aggrecan) as well as presence and quantity of inflammatory marker genes (IL6, matrix metalloproteinase-1 (MMP1), MMP3, MMP13, a disintegrin and metalloproteinase with-thrombospondin-motif-5 (ADAMTS5) were analysed by immunohistochemistry, qPCR and ELISA. To monitor the activity of classically-activated pro-inflammatory (M1) versus alternatively-activated anti-inflammatory/repair (M2) synovial macrophages, the nitric oxide/urea ratio in the supernatant of osteochondral-synovial explant co-cultures was determined. In both OA-model groups immunohistochemistry and qPCR showed a significantly increased expression of MMPs and IL6 compared to their respective control group. ELISA results confirmed a statistically significant increase in MMP1and MMP3 production over the culturing period. In the osteochondral-synovial explant co-culture OA-model the nitric oxide/urea ratio was increased compared to the control group, indicating a shift toward M1 synovial macrophages. In summary, chemical damage (TNFα, IL1β) in combination with a partial-thickness cartilage defect elicits an inflammatory response similar to naturally occurring OA in osteochondral explants with and without osteochondral-synovial explant co-cultures and OA-model-2 showing a closer approximation of OA due to the additional shift of synovial macrophages toward the pro-inflammatory M1 phenotype. [ABSTRACT FROM AUTHOR]

This work presents the lifetime prediction of elastomer component based on the particle distribution in the specimen, the crack growth properties and the appropriate crack criterion. A lifetime prediction using numerical simulation saves both cost and time and can be very helpful in the development phase of a product. On the basis of the obtained results, lifetime can be estimated and thus an appropriate measure such as geometry change or load adjustment can be adopted. The prediction is demonstrated using two kinds of elastomer samples: EPDM and NR under different load amplitudes. Lifetime prediction is accomplished by Monte Carlo simulation, which is based on the correlation between the value of J-integral and total energy density of the single-edge notched tension (SENT) sample. Due to the choice of an inelastic material law the J-integral is evaluated after establishment of stable load cycles as the stable value for a J-integral contour curve as a function of the contour curve distance from the crack tip. For lifetime prediction, a Python script was implemented for the commercial FEA system Abaqus as a postprocessing routine. The script is based on local lifetime evaluation, where evaluation is done element by element followed up by an accumulation. In addition, physical experiments are used for counting the particles in the materials, to characterise the crack growth and also to measure lifetime. [ABSTRACT FROM AUTHOR]

For carbon black reinforced Ethylene-Propylene-Diene Monomer Rubber (EPDM) fracture mechanics investigations by using a Single Edge Notched Tension sample (SENT) are presented. Filled elastomers under cyclic loading typically display inelastic effects like permanent set, strong nonlinear S-shaped stress-strain behaviour and stress induced softening (discontinuous damage) as well as cyclic softening (continuous damage) better known as Mullins effect. These unique properties give this material class an interesting and a complex aspect regarding the experimental observations and numerical modelling of fracture mechanics. In simulations with homogenous material, the J-integral given as the evaluation of the Eshelby stress tensor along a path integral around the crack shows no dependency on the chosen integration path. In contrast, dissipative materials show strong path dependency of the J-integral. When the chosen path is near to the crack tip, this effect is pronounced, due to the inelastic effects, which are very high at the crack tip compared to the rest of the sample. In the process zone, the J-integral value depends strongly on the chosen path around the crack tip. This phenomenon occurs due to the intensity of inelastic effects near the crack tip. The path-dependency of J-integral using the variational formulation of a crack problem in a dissipative material has been given in [16]. Stumpf and Le have proposed a new formulation of the boundary value problem for elastoplastic cracked body using variational formulation, where the finite deformation was considered. For cyclic displacement controlled loading, the elastomers show typical stress softening behaviour, i.e. the force-displacement curve of each cycle is lower than the previous cycle and higher than the following cycle. This occurs due to the continuous damage, whereby the bondings between polymer chains and the filler particles are partially damaged. At small external amplitudes, the stress softening effect is significant only in the vicinity of the crack tip, because of the hysteresis which is large compared to the rest of the sample. The evaluation of the J-integral for an SENT sample under cyclic displacement controlled loading shows clearly that the resulting energy flux at the crack tip decreases from the virgin curve until the last repetition. The values found are in good agreement with experimentally evaluated tearing energy. Hence J-integral evaluation while considering a stress softening reflecting material model can be a promising approach used for estimation of the crack propagation or for lifetime prediction. [ABSTRACT FROM AUTHOR]

A stretch intensity factor for filled and unfilled elastomers is introduced for different mixtures. This stretch intensity factor allows for prediction of the analytically evaluated energy release rate for a cracked sample under uniaxial tension. Considering the opening mode from fracture mechanics (mode I ) was investigated. The continuum mechanical derivations are based on non-linear hyperelastic material behaviour, where the energy release rate is evaluated through a closed path integral very near to the crack tip. Here, the integrand includes asymptotic solution for strain, stress and energy density using the Ogden model. The decisive advantage of this method is to predict well the critical tearing energy values by the crack growth using the analytical energy release rate term. In this work the Mullins effect is not considered, since the cracked samples are tested without any preconditioning. [ABSTRACT FROM AUTHOR]

Elastomers composites are viscoelastic materials and show a complex behaviour due to their non-linear response to external load, characterised in general by energy dissipation, residual set and material softening. For production reasons defects like micro-cracks and pores may be contained. A micro crack in a filled elastomer can occur between polymer-polymer, filler-polymer or filler-filler interfaces. Such a crack grows when the energy flux at the crack tip exceeds a critical value. Energy considerations at the crack shows that the energy released during the crack growth is not the total dissipated energy. The remaining energy is dissipated in the rest of the elastomer composite. In this study three different fracture criteria are compared: the tearing energy (Rivlin and Thomas, 1953), energy release rate (Groß and Seelig, 2011) and the J-integral (Rice, 1968). Tearing energy and energy release rate are based on the global energetic consideration and J-integral is based on the local energy observation. As a global criterion the tearing energy can be determined experimentally and numerically, whereas the J-integral is a local criterion at the crack tip and can be evaluated only numerically. The importance of local calculations lies in the determination of actually required tearing energy as well as the description of inelastic effects of elastomers at the crack tip. The analytical evaluation of the energy release rate allows for the prediction of the driving force at the crack tip without carrying out experiments for the determination of the tearing energy. Stumpf and Le (1990) have applied the variational principle to determine the energy flux at the mode I crack tip for a hyperelastic body. In this work only the trouser-sample is analysed. The load on this sample corresponds to the presented mode III from linear fracture mechanics. Here, the Ogden model is chosen (ABAQUS, 1998) as hyperelastic material model. The analytical determination of the energy release rate is calculated from the energy density function of this model. Results obtained from the experiments, simulations and analytical calculations are compared, where the analytical energy release rate turned out to be in closer accordance with the experimentally evaluated tearing energy than the J-Integral. [ABSTRACT FROM AUTHOR]

This study presents rice husk silica-reinforced elastomer composites fabricated by wet compounding, exhibiting 10% higher dynamic friction coefficients than the reference composites made by conventional dry compounding. Depending on the fabrication method, the filler micro-dispersion was characterized to correlate the measured friction coefficients with the viscoelastic properties with respect to sliding velocity and substrate lubrication. The effect of viscoelastic properties of the elastomer composites on the adhesion and hysteresis friction coefficients was investigated based on the elastomer friction theory. It was found that the constructed friction master curves showed a reasonable correlation with the theory. This study demonstrates that the rice husk silica can be used as a reinforcing filler for sustainable tires. More importantly, the well-dispersed filler microstructures can ensure the higher friction coefficients of the elastomer composites on rough surfaces, improving the tire performances (e.g., wet traction, cornering, and acceleration) of the ever-growing electric vehicles and future mobility. • Wet compounding of rice husk silica/SBR composites ensured a good filler dispersion. • Wet-compounded rich husk silica/SBR composites exhibited 10% higher friction coefficient. • Constructed friction master curves showed a reasonable correlation with rubber friction theory. [ABSTRACT FROM AUTHOR]

In this paper the separation of the binary mixture H 2 /CH 4 on (i) neat supported ZIF (zeolitic imidazolate framework) membranes of types ZIF-8 and ZIF-90, (ii) a neat supported Matrimid polymer membrane, and (iii) Mixed Matrix Membranes (MMMs) with 10, 20 and 30 vol-% ZIF-8 and ZIF-90 nanocrystals in Matrimid is compared. A high separation performance was found surprisingly for the MMMs and it was concluded that the polymer matrix prevents the framework flexibility of the embedded Metal Organic Framework (MOF) particles, thus increasing the selectivity of MMMs with particle loadings ≤20 vol-%. Higher loadings, however, lead to agglomerations and segregations, which result in MMMs with lower selectivities. To approve the idea of the hindered linker distortion caused by the surrounding polymer, we coated the top of neat supported ZIF-8 and neat ZIF-90 membranes with an additional Matrimid polymer layer (dual-layer membrane). Indeed, the polymer coating also caused a suppression of the linker distortion of the ZIF layer in contact with the polymer which results in an enhanced H 2 /CH 4 selectivity. [ABSTRACT FROM AUTHOR]

Polymer matrix nanocomposites filled with metallic and alloy nanoparticles add functionality in various applications such as optical devices and in the energy sector. However, matrix coupling agents or nanoparticle ligands may be unwanted additives, potentially inhibiting the resulting nanocomposite to be processed by injection molding. The generation of stabilizer-free Au, Ag, and AuAg alloy nanoparticle acrylate composites is achieved by picosecond-pulsed laser ablation of the respective metal target in the liquid monomer. Complementary to laser ablation of the solid alloy, we have alloyed nanoparticles by post-irradiation of Au and Ag colloids in the liquid monomer. The optical properties of the colloidal nanoparticles are successfully transferred to the solid poly(methyl methacrylate) matrix and characterized by their plasmon resonance that can be easily tuned between 400 and 600 nm by laser alloying in the liquid monomer. [ABSTRACT FROM AUTHOR]

Abstract: For the validation of the quantification of the newly-developed method of 3D Micro X-ray fluorescence spectroscopy (3D Micro-XRF) samples with a low average Z matrix and minor high Z elements are best suited. In a light matrix the interferences by matrix effects are minimized so that organic polymers are appropriate as basis for analytes which are more easily detected by X-ray fluorescence spectroscopy. Polymer layer systems were assembled from single layers of ethylene–propylene–diene rubber (EPDM) filled with changing concentrations of silica and zinc oxide as inorganic additives. Layer thicknesses were in the range of 30–150 μm. Before the analysis with 3D Micro-XRF all layers have been characterized by scanning micro-XRF with regard to filler dispersion, by infrared microscopy and light microscopy in order to determine the layer thicknesses and by ICP-OES to verify the concentration of the X-ray sensitive elements in the layers. With the results obtained for stacked polymer systems the validity of the analytical quantification model for the determination of stratified materials by 3D Micro-XRF could be demonstrated. [Copyright &y& Elsevier]

[Display omitted] • Natural cork and potato periderm were depolymerized to obtain suberin derivatives. • Bio-based composites were prepared with suberin derivatives as coupling agents. • Bio-based composites exhibited high strength, toughness, and energy-absorption. • Cork suberin derivatives offered higher damping and tunable viscoelasticity. • Natural cork and potato periderm can be potential resources for advanced materials. Suberin is a natural polyester providing the impermeability and mechanical damping of the plant cell walls. It is fascinating because ester bonds in the suberin can be easily hydrolyzed to provide various functional chemical precursors for further applications. This study investigates an unprecedented way to tailor energy-absorbing capabilities in silica-reinforced styrene-butadiene rubber (SBR) composites by introducing depolymerized suberin derivatives (DSDs) extracted from cork and potato periderm. The filler–matrix couplings were experimentally and analytically investigated through dynamic mechanical analysis (DMA) and the Huber–Vilgis model. The DSDs modified silica–polymer interfaces seem to offer a substantial increase in strength, toughness, and energy-absorption by nearly 47 %, 336 %, and 126 %, respectively, compared to bis(3-triethoxysilylpropyl)-tetrasulfide (TESPT)-coupled elastomers, without sacrificing the modulus. These findings could inspire natural materials enabled composite design for high energy-absorbing materials and provide a breakthrough in utilizing natural resources for next-generation structures such as urban air mobility or autonomous electrical vehicle, which typically require multifunctional performances including lightweight, high strength, and energy-absorbing capability. [ABSTRACT FROM AUTHOR]

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. Image 1 • Simultaneous dielectric and dynamic-mechanical analysis. • Dielectric properties of elastomeric materials under static and dynamic loads. • Dynamics of filler network and structural change due to mechanical loads. • Density of conductive paths. • Advanced data analysis: relaxation time, relaxation strength and broadness parameter from Cole-Cole equations. [ABSTRACT FROM AUTHOR]

The wetting of rough polymer surfaces is of great importance for many technical applications. In this paper, we demonstrate the relationship between the mean roughness values and the fractal dimension of rough and self-affine PTFE surfaces. We have used white light interferometry measurements to obtain information about the complex topography of the technical surfaces having different height distributions. Two different methods for the calculation of the fractal dimension were used: The height difference correlation function (HDC) and the cube counting method. It was demonstrated that the mean roughness value (Ra) correlates better with the fractal dimension Df determined by the cube counting method than with the Df values obtained from HDC calculations. However, the HDC values show a stronger dependency by changing the surface roughness. The advancing and receding contact angles as well as the contact angle hysteresis of PTFE samples of different roughness were studied by the modified Wilhelmy balance technique using deionized water as a liquid. The modified Wilhelmy balance technique enables the possibility for future analysis of very rough PTFE surfaces which are difficult to investigate with the sessile drop method. [ABSTRACT FROM AUTHOR]