German Institute of Rubber Technology

MaterialDigital Initiative The cover image illustrates the concept of advancing digital transformation within the MaterialDigital Initiative through workflows, as discussed in article number 2402149 by Jörg Schaarschmidt and co-workers. The projects within this initiative utilize various concepts and tools, applied to a broad range of material classes. A digital library, the PMD Workflow Store, has been established to disseminate these workflows enabling FAIR principles. The image shows an examplary workflow developed within StahlDigital, discussed in detail in article number 2402148. Graphical Design: Christine Heinrich.

Magnetorheological elastomers are smart materials, that have great potential for many technical applications like intelligent semi-active dampers or energy harvesting applications. We investigate soft- and hard-magnetic filler types in typical technical elastomers under cyclic deformation regarding their influence on the electromagnetic induction and magnetic switching-ability of the compounds. The effect of vulcanization in an external magnetic field is considered leading to anisotropic samples with aligned filler particles. It is found that the soft magnetic fillers show a higher switching-ability compared to hard magnetic fillers in anisotropic samples, which is related to hysteretic and slow magnetization behaviour of hard magnetic fillers. This also leads to a negative switching effect or softening of the samples if the direction of the magnetic field is opposite to that during vulcanization, suggesting rotational motion of the particles in dependence of the outer field. The stress values and mechanical hysteresis are generally higher for the anisotropic samples, both for soft and hard magnetic fillers. This is found for quasistatic and dynamic excitations at different frequencies and can clearly be related to the alignment of particles. Nevertheless, the energy harvesting ability seems to be widely independent of this since no significant different inductive properties are found for isotropic and anisotropic samples. The possibility of a combined magnetorheological and energy harvesting application is discussed.

ABSTRACT Rubber-based polymers with high carbon black content can be three-dimensionally (3D) printed using the additive manufacturing of elastomers process. However, high-viscosity materials limit printing resolution, making it difficult to produce fine structures and high-precision parts, especially two-component (2K) parts. The viscosity of a rubber compound used for rod seal applications was reduced and adjusted using Nipol® 1312 liquid rubber and the alkyl sulfonic phenyl ester Mesamoll® II as plasticizers to lower the torque level during extrusion when a reduced nozzle diameter of 0.4 mm is used in 3D printing. In addition, the flowability of the compound was enhanced prior to vulcanization of the part, which could increase the layer–layer bond and thus reduce the mechanical anisotropy typically induced by fused filament fabrication. Using a viscosity-optimized rubber compound, a 2K rod seal consisting of a thermoplastic polyurethane with elastomeric properties and an acrylonitrile rubber-based O-ring was produced and dynamically tested for leakage.

Environmental microplastic (MP) is ubiquitous in aquatic and terrestrial ecosystems providing artificial habitats for microbes. Mechanisms of MP colonization, MP polymer impacts, and effects on soil microbiomes are largely unknown in terrestrial systems. Therefore, we experimentally tested the hypothesis that MP polymer type is an important deterministic factor affecting MP community assembly by incubating common MP polymer types in situ in landfill soil for 14 months. 16S rRNA gene amplicon sequencing indicated that MP polymers have specific impacts on plastisphere microbiomes, which are subsets of the soil microbiome. Chloroflexota, Gammaproteobacteria, certain Nitrososphaerota, and Nanoarchaeota explained differences among MP polymers and time points. Plastisphere microbial community composition derived from different MP diverged over time and was enriched in potential pathogens. PICRUSt predictions of pathway abundances and quantitative PCR of functional marker genes indicated that MP polymers exerted an ambivalent effect on genetic potentials of biogeochemical cycles. Overall, the data indicate that (i) polymer type as deterministic factor rather than stochastic factors drives plastisphere community assembly, (ii) MP impacts greenhouse gas metabolism, xenobiotic degradation and pathogen distribution, and (iii) MP serves as an ideal model system for studying fundamental questions in microbial ecology such as community assembly mechanisms in terrestrial environments.

Abstract This work analyses the impact of the sample geometry on the stress or strain concentration and the occurrence of big agglomerates in the investigated test volume. Although the three investigated dumbbell test specimens were loaded at the same stress level, there were significant differences in measured lifetime. These differences in the lifetime are due to the occurrence of the large agglomerates in the tested volume. The probability of occurrence of large agglomerates increases with increase in the investigated volume. In the lifetime prediction by Monte Carlo method, this effect is realized by changing the quantity of the distributed agglomerates in the mesh of the simulated model. The prediction of the different sample geometries shows a very good agreement with the measurement points. The numerical simulations illustrate the stress increase for the three used lifetime test samples.

Abstract For investigations on a two‐stage multicomponent injection molding process adhesion‐modified polyamide 6 and EPDM with sulfur‐curing system are used. The influence of different process temperatures is investigated on the basis of a DoE test plan with 15 factor level combinations. Within the scope of additional, more in‐depth investigations, special focus was given to the preheating temperature of the thermoplastic insert. In addition to the experimental work, results from simulations are used to assess the influencing factors. This approach allows a more precise description of the influence of temperature equilibration processes on the crosslinking reaction, especially near the interface between the two components. It is shown that the preheating temperature of the hard component (thermoplastic) in particular has a significant influence on the time course of the crosslinking reaction and ultimately on adhesion to the thermoplastic substrate.

The integration of sensor-systems into elastomer bodies or onto flexible surfaces is a challenging task. Therefore, a new approach has been developed and investigated to create thin-film-based structures via PVD (physical vapor deposition) processes on water-soluble substrates such as polyvinyl-alcohol (PVA) and subsequently transferring the sensor structures onto unvulcanized rubber substrates. A contacting method using conductive polymer composites creates a reliable technique to electrically contact transferred thin film layers within an elastomer sandwich matrix.