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Elastomers, such as hydrogenated acrylonitrile-butadiene rubber (HNBR) are usually mechanically reinforced with high loadings of carbon black (CB) to achieve the properties demanded; high amounts of mineral flame retardants are used to fulfill fire safety requirements. These high filler loadings sometimes cause deterioration of the physical properties of the material. In this study, multilayer graphene (MLG), a nanoparticle made of only 10 graphene sheets, is applied in low loadings (3 phr) to reduce the total amount of filler or boost performance.1,2,3 In former studies nanofiller achieved increased flame retardancy at very low lowdings.4,5,6 The dispersion of the nanofiller is essential for the properties of the nanocomposites.7 The nanocomposites were prepared via master batch by an ultrasonically assisted solution mixing and subsequent conventional two-roll milling.
SEM and TEM micrographs and rheological measurements revealed that the MLG nanoparticles were well dispersed in the HNBR matrix. In the HNBR nanocomposites, 3 phr MLG replaced 15 phr CB, 3 phr ATH or 15 phr CB + 3 phr ATH and achieved large consistent improvement in curing, rheological and mechanical properties of the HNBR. The nanocomposites with partial replaced CB reduced the filler loading up to 60% without any deterioration of the properties. The HNBR/MLG nanocomposites achieved an even higher Young’s modulus, hardness and thermal conductivity. MLG achieved advanced flame retardancy by improving the protection layer. The layer is created during the burning phase and acted as an afterglow suppressor. This study proposed the combination of ATH with MLG as a promising approach to reduce the amount of filler, in addition to improving the mechanical properties and fire performance of HNBR rubbers.
Elastomers are used in a wide range of automotive and railway applications. However, a severe drawback of most rubbers are their high flammability. Therefore, flame retardants (FRs) are added to improve the performance in fire. Generally, rubber composites are filled with high amounts of mineral fillers such as aluminium trihydroxide (ATH) to fulfil fire safety regulations. These high loadings may cause deterioration of the physical properties of the material. This work shows the implementation of two new strategies to achieve the modern demands on non-toxic FRs and the reduction of fillers.
The first approach was the implementation of multilayer graphene (MLG), acting as a multifunctional filler, reinforcing agent and FR. The study presents filler combinations with a systematic variation of the fillers carbon black (CB), MLG and ATH. The nanocomposites were prepared via master batch by an ultrasonically assisted solution mixing. Afterwards the master batch was compounded into the rubber in a two-roll milling. MLG substituted high amounts of the conventional filler CB, leading to reduced filler loadings and a consistent improvement in curing, mechanical and FR properties.
The second strategy was the combination of phosphorous-containing FRs with a potential new polymeric char promoting agent polyaniline (PANI). Char promoting additives such as pentaerythritol (PER) improve the effectiveness of the FR system. The combination of ammonium polyphosphate (APP) with PER was successfully investigated for natural and styrene-butadiene rubber composites. This work investigates the flame retardancy of the combination of FRs with PANI and its capability to act as a char/barrier promoter in EPDM.
The morphology of the rubbers and homogenously dispersion of MLG was investigated via scanning/transmission electron microscope (SEM/TEM) micrographs. Rheological and mechanical measurements assessed the influence of the fillers on the physical properties of the rubber composites. Characterization via thermogravimetric analysis (TGA) led to a broader understanding of the decomposition. In order to determine the flame retardancy effect of these materials, a multi-methodical approach was selected. Limiting oxygen index (LOI) and UL-94 were used to quantify the flammability of the rubber composites. The cone calorimeter provided information about the fire behaviour in forced flaming conditions. Residues were investigated via elementary analysis and XPS to clarify the composition of the remaining material. Glow-Wire and FMVSS 302 tests revealed significant results in terms of flame retardancy. The flame retardancy investigation of rubber composites, combinations of ATH with MLG and ATH with phosphorous-containing FRs, broaden the horizons of rubber flame retardancy solutions. By examining alternate FR formulations and their effect on mechanical and physical properties of the rubber, new insight into the range of applicable additives for rubber composites may be won.
This presentation discusses the potentials of probabilistic methods in offshore foundation installation, from the perspective of probabilistic ground models and data-driven site characterization. We discuss about methodologies for utilizing site-specific geotechnical (CPT) and geological data, aiming to construct an integrated ground model that can predict stratigraphic profiles and useful for geotechnical design parameters at any location within a 3D domain. The predicted parameters and stratigraphy are then used to predict the probability of potential pile tip damage, upon collision with a boulder.
The aim of the study is to infer the soil stratification from the provided CPT and borehole data. We infer the soil type at any location within the domain of interest from the SBT index Ic (Robertson, 2009). This index can be directly related to the CPT data through an empirical correlation model. In addition, the soil classes contained in the borehole logs can be expressed as bounds on Ic. A log-transformation was applied to Ic, Y = ln(Ic), and Y was modelled by a 3D Random Field, with a fully Bayesian hierarchical Gaussian Process model to explicitly capture uncertainties.
Alkali-silica reaction (ASR) is a serious Problem concerning the deterioration of concrete. This leads to significant maintenance and reconstruction costs for concrete infrastructures all over the world. The geographical regions, which play a major role in concrete deterioration, are for example coastal Areas or in general, areas with a high air humidity/salinity due to closeness of rivers or lakes.
These exemplary results show, the application of Raman spectroscopy establishes a valuable approach for characterizing the chemical and structural composition of ASR-products. The results prove the potential to trace the kind of reaction products, developing in dependence on the aggregate and to follow up its local alteration from origin of the gel.
Corrosion testing in a laboratory container: Corrosion testing with artificial seawater and sediment
(2022)
Electricity generation by offshore wind turbine generators (WTG) is an important pillar of the energy transition. Corrosion processes on WTGs pose a particular challenge with regard to safe operation over longer periods of time due to the highly corrosive conditions in the offshore area. BAM is therefore conducting research to ensure a safe operation of the turbines over their intended service life to protect people and the environment.
In a joint research project, different corrosion-relevant areas of a WTG foundation structure were specifically simulated in test basins within a laboratory container. The aim of the work was, on the one hand, the gravimetric and electrochemical determination of corrosion rates in the different areas of an WTG that are relevant for cathodic corrosion protection (CCP): Underwater and sediment zone as well as the transition area between these two zones. Also, targeted tests were carried out under CCP. In addition, investigations regarding calcareous deposition during CCP were carried out on idealized specimens under laboratory conditions to better assess its influence on the protection process. The investigations were carried out in a laboratory container with different basins, which were filled with sand as sediment and artificial seawater according to ISO 15711and connected via a closed water circuit.
The poster at EURCORR 2022 provides an overview of the investigations and the most important results. It will be evaluated, if a simulation of offshore corrosion conditions is possible to a certain extent in an idealized system with artificial seawater and sediment.
In the maritime context of offshore operation, corrosion, in combination with the materials used, poses a particular challenge to ensure safe operation over long indefinite periods and to minimise susceptibility to failure. Until today, only a few corrosion protection systems have proven themselves for the interaction of efficiency, installation, and maintenance in the offshore sector. In addition, available corrosion test methods sometimes have major deficits about conclusions of the durability. Therefore, there is more research and development needed.
The flagship project H2Mare of the Federal Ministry of Education and Research aims to enable the production of green hydrogen and PtX products at high seas. Research is being driven forward by the partners in four individual projects, where BAM is involved in two.
In PtX-Wind, major kinds of corrosion attacks at offshore constructions are characterized and investigated, and suitable corrosion protection measures determined. In TransferWind, attention focusses on transferring scientific results into standardization.
This poster at the H2Mare Conference 2023 presents an overview of the investigation methods and contribution of the department “Corrosion and Corrosion Protection”.
The development of offshore wind turbines (WTGs) presents many challenges in terms of safe operation over extended periods of time. One of these is the corrosive environment towards metallic materials, which can lead to a loss of material thickness and thus to a deterioration of mechanical performances, especially the strength of infrastructures. This can be counteracted by painting and cathodic protection (CP). Much research has already been done in this area about inhibiting the corrosion process. However, gaps exist regarding free corrosion. This plays a greater role especially for time intervals during the installation of the systems and their maintenance, during which often no CP can be operated. This is especially true for areas where painting surfaces is impossible e.g., sediment areas. This problem is exacerbated by the different corrosion rates caused by the different zones (water and sediment), with their different amounts of dissolved oxygen.
This presentation deals with experiments in artificial seawater and sediment. Classical S355J2 steel samples in the form of coupons were fitted with welding wires that carried out the electrical contact to the outer side of the basin. Inside the basins, the specimens are stored in different zones like water and sediment which should simulate the foundation situation of monopiles. The mass loss was determined gravimetrically, elemental currents between specimens in water and sediment were measured and electrochemical investigations were carried out. The influences of the zones, based on different solved oxygen contents, and the rolling skin towards the corrosion behavior of the mild steel samples were determined in this work. Especially the influence of the sediment showed unexpected behavior, determined by electrochemical investigations. These results allow better conclusions to be drawn about the corrosion behavior of low alloy steels in offshore environments used in sediment and seawater, which cannot always be protected.
Maritime exposure poses particular challenges for corrosion
protection in plant construction. In addition to the right choice
of materials, special design features that can have an impact
on corrosion resistance must also be taken into account to
ensure long-lasting corrosion protection. In practice, structural
crevice arrangements are unavoidable, and therefore the
crevice corrosion resistances of stainless steels are of
particular importance. These and other influences are being
investigated in this joint project.
Polymeric membranes represent a low-cost, energy efficient solution for gas separation. Recently polymers of intrinsic microporosity (PIMs) have emerged as prestigious membrane materials featuring a large concentration of pores smaller than 1 nm, a BET surface area larger than 700 m2/g and high gas permeability and selectivity. Unusual chain structure combining rigid segments with sites of contortion gives rise to the intrinsic microporosity. However, this novel class of glassy polymers are prone to pronounced physical aging. The initial microporous structures approach a denser state via local small scale fluctuataions, leading to a dramatic reduction in the gas permeabilities. For the first time, dielectric relaxation spectroscopy with state-of-the-art high-resolution analyzers was employed to investigate three representative PIMs with a systematic change in chain rigidity: PIM-EA-TB 〉 PIM-1 〉 PIM-MDPH-TB. The molecular mobility, the charge transport and their response upon heating (aging) in the polymers were measured in a broad temperature range through isothermal frequency scans during different heating / cooling cycles. Multiple dielectric processes following Arrhenius behavior were observed for the investigated polymers. Local fluctuations, Maxwell-Wagner-Sillars (MWS) polarization and structural relaxation phenomena were discussed and attempted to be correlated with the structural features of PIMs. Moreover, all PIMs showed conductivity in the glassy state. The significant increase in the conductivity with increasing temperature far below the glass transition temperature of PIMs is explained in terms of the loosely packed microporous structure and the formation of local intermolecular agglomerates due to interaction of π-electrons in aromatic moieties of the polymer backbone.