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| case 1: retrofitting for hydrogen transport using epoxy coating? | |
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In the near future, natural gas pipelines (type X-52, X-60, X-65 and X-70) may also
be used for transport of Hydrogen or even Carbon Dioxide. In case of Hydrogen conveyance, Hydrogen might be mixed with Natural Gas (parallel gas transport, using a membrane to seperate the gases at the outlet) or transported solely. Discarded natural gas pipelines may also be completely retrofitted for Hydrogen or Carbon Dioxide transport. With regard to Hydrogen, a service life concern could be HISC (Hydrogen Initiated Stress Cracking) of steel. Hydrogen embrittlement or HISC results from combining of diffusing Hydrogen atoms into molecular Hydrogen - or the formation of molecular Methane - in internal metal voids of nanoscopic size. The generated pressure - in combination with intrinsic circumferential stress in the material - can exceed the restrain pressure of steel, especially near the loading surface. Whether HISC is an issue is largely dependent on the sort of steel, internal pressure and temperature. If HISC takes place, the strength of the pipeline will reduce, Hydrogen will escape and in a worst case, even buckling could occur. (continued on next page) To enhance the lifetime of these pipelines or to improve the reliability of these
pipelines, nowadays several organic and inorganic material combinations (in a composite or multilayer configuration) are being researched. One suggestion for large diameter X-60 pipelines is the application of an internal Fusion Bonded Epoxy (FBE) coating. In this case study a diffusion-chemical-mechanical simulation will be carried out for a retrofitted Natural Gas pipeline, in order to transport Hydrogen. The material under evaluation consists of (1) an inside Fusion Bonded Epoxy coating,(2) structural high strength steel and (3) an outside PE (Polyethylene) weathering coating. Key issues are: coating? and if a metal crack due to HISC would appear under the coating (severe conditions or long times)? |
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| case 2: ageing and fatigue of thermoplastic rotor blades | |
| Proper mechanical and corrosion resistance properties of polymer based materials is of major importance in many applications. Traditional chemical resistance guides can provide valuable information with this regard. However, analysis becomes more complex if the polymer is reinforced with filler material and is sequenced in a composite laminate. Because of the discontinuous nature of diffusion rate, solubilities and restraints in the different layers, corrosion prediction and forthcoming mechanical retention of the composite is still a concern for long term rotor blade operation. Here, we demonstrate an integrated diffusion-chemical-mechanical approach for composite service life prediction of a thermoplastic rotor blade, going beyond the standard lifetime of 20 years. We use CheFEM software for chemical driven degradation (salt water, bird droppings, UV light) in combination with existing FEA multiphysics tools for rigorous stress / strain modelling. |
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| case 3: service life behaviour of thin film flexible solar cells | |
In this case study the lifetime of a thin film flexible solar cells is assessed. The multilayered solar cell will be applied in curved body parts for vehicles. The long term mechanical and corrosion resistant properties are focus of the study. Below a short introduction. For sake of corrosion prevention of the subsequent functional layers, on one hand crystallinity and thickness of the transparent surface polymer must be as high as possible. As such, the permeation rate of Oxygen and Water through the surface layer is kept low. On the other hand, adhesion of the polymer to the substrate decreases as function of thickness. The robustness of the interface is of major importance in restraining the mass solubility and temperature driven swelling stresses and mechanical stresses at the surface. To complicate things even more, the impact resistance / fracture toughness of the surface polymer decrease as function of the degree of crystallinity. (continued on next page) In this study it is found that for each material configuration (inorganic coating and
several substrates, possibly in series) there is an optimal thickness with regard to overall long term permeation, corrosion resistance and mechanical properties in real- life circumstances. The analysis and simulation was carried out using CheFEM software (diffusion & corrosion simulation) and FEM stress & strain simulation tools. |
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| case 4: carbon dioxide diffusion loss from PET bottle | |
| An interesting case is the diffusion of CO2 (carbon dioxide) through the wall of a PET (polyethylene terephthalate) bottle that contains soft or alcoholic drinks. You can think of cola or beer. Reason for putting gaseous CO2 in drinks is taste. The gas gives a sparkling feeling and a reduction in tasted sweetness. One can imagine that diffusion of CO2 through the wall is a problem because of loss of these features in time; in other words, a loss of quality in time. In this case story, the CO2 diffusion from a bottle as a function of time is demonstrated in real-life circumstances.Carbon Dioxide Diffusion from PET |
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| case 5: composite water permeation and chemical resistance | |
| In new composite equipment, such as in windmill turbines, aerospace parts, body parts for car and trains, electronic packages, medical packaging, membranes for simultaneous carbon dioxide / water vapour removal and other membrane applications, the mechanical retention if the composite is exposed to hygrothermal conditions is one of the main interests. The fact that water diffuses with a considerable rate in polymers, in combination with the anomalous diffusion and uptake behaviour, have lead to a variety of different theories with regard to water behaviour in composites. In this preliminary paper we present our view on water diffusion and mechanical retention in an unreinforced and glass fibre reinforced Derakane 411 Epoxy Vinyl Ester Resin (from Dow Chemicals). We have used CheFEM to interpret gravimetric data using two main concepts: [1] localized water adsorption theory, [2] multilayer diffusion simulation. The composite configuration that we tested did not show chemical degradation, but swells to a small extent under the continuous load of water. composite chemical resistance in hygrothermal conditions |
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| case 6: polyimide for flexible thin film solar cells | |
| One of the candidate substrate materials for polymer based solar cells and Organic Light Emitting Diodes (OLED's) are transparant polyimides. Because of their combination of mechanical, moisture barrier and corrosion resistance (among which are UV light and extreme high Oxidation resistance) properties - even at high temperatures - they might be suitable. In this case study the water absorption characteristics of a new polyimide in real life circumstances is evaluated. By means of gravimetric, free volume and electrical impedance (EIS) data, it is found that water absorption in this specific polyimide can be rigorously modelled using the dual mode sorption model. According to this model, a part of the water molecules is adsorbed on hydrophilic sites in the polymer with a Langmuir isotherm. This part is immobile. Another part dissolves in the polymer and can move by normal (Fickian) diffusion. The implications of this significant anomaly on water breakthrough times, on water mass flux into the device, on accelerated weathering tests and on dimensional change are explained thoroughly. water diffusion polyimide based solar cells |
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| case 7: lifetime prediction of thermoplastic joint for bridge decks | |
| Thermoplastics joints have been developed to solve the corrosion problem of bridges, sluices, dams and other structures. The different steel reinforements are to a greater or lesser extent susceptible to corrosion in the highly alkaline environment of concrete. As a consequence, the thermoplastic joint could provide some basic protection for the less durable materials solutions against diffusion and deterioration. In this paper, the combined aqueous immersion and sustained stress on the service life of a plastic joint is chararacterized. This is done by mechanical testing and simultaneous chemicals exposure.osmosis in composite materials |
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| case 8: 100% nitrogen in polyisobutylene tyre | |
| Usually we fill our tyres with Air. Nowadays there are several discussions in magazines and internet on whether it would be better to fill tyres with 100% Nitrogen or Carbon Dioxide instead of Air. The diffusion resistance layer of tyres are made from a polymer rubber called Polyisobutylene, and a few percent of Isoprene. In this case history it is shown that this polymer has a better diffusion resistance against Nitrogen than Oxygen. Moreover the practical implications of this difference are described.Pure nitrogen in tyres |
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| case 9: methanol diffusion in GFRP | |
| Here we demonstrate how mass transfer of liquids and saturated vapours is applied in an industrial application. We were commissioned to assess whether it is possible to use a GFRP (Unsaturated Polyester Glass Fibre Reinforced Plastic) pipeline for the transport of methanol. Apart from past effects of alkaline water transport on sustainability of this pipeline, it is shown how the methanol flux changes in the time period evaluated. In this example the counter diffusion of polluting chemicals in ground water was not taken into account.Methanol Diffusion GFRP |
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| cases 10: polyethylene liner on tank for gasoline | |
| In a wide range of industries, various composite and lining systems are used with the objective to combine good mechanical and chemical resistance properties. Key to a sustainable and - sometimes even - a multi-purpose service life, is chemical resistance and diffusion analysis in an early development stage. The case of gasoline in a HDPE lined / coated Epoxy tank gives a clear insight in our approach. We have more information available on similar configurations, like hoses, tubes, adhesives, rubbers and elastomers for gasoline based on PA, PVDF, PPS including different kinds and degrees of reinforcements.Gasoline Diffusion HDPE Epoxy |
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| case 11: Hildebrand solubility parameters for material selection | |
| We want to assess what sort of thermoplastic polymer we can use for containment of toluene at ambient conditions. A special design requirement is prevention of plasticizing of the material by toluene. This requirement is related to diffusion resistance: in many instances plasticizing causes the initial diffusion rate to increase several orders of magnitudes. This can be noticed from the figures in the table for liquid diffusion on the website. If a chemical has a high solubility in the polymer, then the weighted average diffusion rate (D|) becomes much larger than the initial rate (D0).solubility parameters for polymer material decision |
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| case 12: hygrothermal resistance of epoxy - polyester composites | |
| In glass fibre reinforced plastics (GFRP) or glass fibre metal laminates (FML's) the combination of the different components do substantially increase the mechanical properties of the material, think for example of high toughness, very long critical crack lengths, etc. At the same time the behaviour of these materials when exposed to chemicals, high pressure and high temperature is becoming more and more complex. For fully integrated chemical-physical service life time predictions, the situation at the interface should often be the focal point of analysis and simulation. Here, possible voids do appears, temperature or swelling stress beyond the interfacial strength may come into play, cohesive strength, adhesive work, interlaminar shear strength values, pull and peel tests, etc. The attached paper is one of our first works on this subject and was published in the framework of ESAT 2006.aterials |
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