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This paper describes the testing methods used to determine the thermal properties of insulation materials and mechanical properties of materials used for the load-bearing structure for pressure tanks (up to 4 bar, relative) and cryogenic liquids (LNG, −166 °C to -157 °C at atmospheric pressure). Goal is to design a transportation tank that does not exceed 4 bars (relative) within 10 h, starting at atmospheric pressure. PUR-foam is a suitable material for the insulation. A 12,5 l small scale tank prototype reached 4 bar (relative) within 87 minutes, which is, regarding the influence of the size, a satisfying result. The mechanical properties change significantly at cryogenic temperatures. The bending modulus is similar at first, but decreases at a certain point by appr. 50 %. However, the maximum stress is much higher and could not be reached within this testing setup.
To reduce the emission of CO2, liquified natural gas (LNG) is used as fuel. As the pipeline network is not developed all around the globe, LNG needs to be transported via ship or truck. Double-walled tanks made of steel with a vacuum insulation are currently used to keep LNG at cryogenic temperatures (-162 °C; 111 K). The double-walled construction makes the tanks heavy and expensive. Furthermore, there are some restriction to carry out in-service inspection using a double-wall design. Main topics: Lightweight design, superior thermal properties of GRP compared to steel Aim of this project is to develop a single-walled tank made of glass-fiber reinforced plastic (GRP) and an insulator, so that the tank pressure will not exceed 5 bar within a certain time, relative, as a result of the rising fluid temperature. First, the thermal and mechanical properties of GRP and the insulator at cryogenic temperatures must be determined. Liquid nitrogen (-196 °C; 77 K) is used for all experiments at cryogenic temperatures for safety reasons. Mechanical properties are analyzed by performing 3-point bending tests on cooled specimen. The tests show, that there are now significant changes on the mechanical properties of GRP, so that this material can be used in a cryogenic environment. To examine the thermal conductivity of GRP, a test rig is designed, in which one side of a GRP-laminate plate is cooled down while the other side is at room temperature at the beginning. Temperature is measured on both sides of the plate as well as inside the laminate. The temperature curves are then implemented in a ANSYS simulation to calculate thermal material properties. The experiments show, that the thermal conductivity of GRP is much lower than the one of steel, but still not low enough to design a single walled tank without an additional insulation. Therefore, a closed GRP pipe with insolation inside is immersed in liquid nitrogen for a defined time. Sensors record the surface temperatures inside and outside the specimen, as well as between insulation and GRP. With the data gained in this experiment, another ANSYS model is done. For correct simulation of the heat transfer between insulation and liquid nitrogen (or LNG later), a fluid simulation is necessary, which simulates the phase change from liquid to gaseous nitrogen. After validation of the model, a parameter study in the material properties of the insulation is performed, until a satisfying setup is achieved.
Today glass is broadly used in modern architecture. For applications indoor it is possible to produce decor glass by using enamel colors and glass painting techniques without any problems. However, this is more limited for applications outdoor. Humidity and environmental pollution attack the surface of the coating and damage it strongly. There are only few colors on the market which are resistant towards acids and bases until now. Additionally, most of those colors are opaque. In order to extend the color palette, chemically resistant colored glasses are being developed which are transparent, relatively low melting and intensively toned even in thin coat thickness. To achieve such ambitious aim, many parameters have to match which act in complex manner. Metal oxides were used to color the glasses. A lead-free glass composition was developed to avoid an exposition of heavy metals to the environment. The glasses were characterized, in particular in terms of their thermal properties, their crystallization and corrosion behavior as well as their chemical and environmental durability. Different practical applications will be shown.
This presentation focusses on the thermal test of a typical storage container design for the German final storage repository KONRAD. The preparation of the container, the conduction of the fire test itself and results like the temperature evolution and as-sumptions for thermal material properties are shown.
As thermal test final storage containers have to be exposed to a fire of 800 °C (1472 °F) for 1 hour according to the final storage conditions provided by the federal com-pany for radioactive waste disposal (BGE). The here discussed cask contains a steel covered concrete layer of a thickness of 100/150 mm. Heating up concrete is a highly nonlinear process since the vaporization of residual water consumes high amounts of thermal energy and produce vast amounts of steam.
The constantly measured temperatures provide the basis to adjust common models of thermal properties for concrete esp. for FEAs. Finally in a later step this will allow predictions of similar designed container with different sizes.
One-part geopolymers, synthesized from three different silica sources and sodium aluminate, were investigated regarding their microstructure and the evolution of their compressive strength on curing at slightly elevated temperatures. The effect of thermal treatment was studied up to 1000 °C and for the investigation of the chemical durability specific samples were treated with sulfuric acid (H2SO4, pH = 1).
Depending on the silica feedstock, different degrees of reaction were observed. One of the silicas had a significantly higher reactivity. For two of the silicas, significant amounts of zeolites occurred as reaction products besides geopolymeric gel, whereas the more reactive silica source lead to the formation of a rather fully condensed geopolymeric network.
The composites indicated promising behavior on heating in so far as no distinct shrinkage step occurred in the temperature range of dehydration. Up to 400 °C the residual strength of those mixes increased. Above 800 °C the samples underwent new phase formation. After exposure to sulfuric acid (pH 1; 70 d) specimens showed a residual compressive strength of about 77 % of the reference, indicating high acid resistance.
The key objective of this work is to create a comprehensive comparison between experimental analysis methods for detecting crosslinking reaction in EVA encapsulant material during PV module fabrication process. Several analytical methods, spanning from classical gel content extraction measurements over different thermo-analytic and mechanical approaches to spectroscopic analysis as Thermally Stimulated Current (TSC), have been investigated as to their ability to reveal the crosslinking state of ethylene vinyl acetate (EVA). The basic results show that TSC complements perfectly other thermal analysis methods like as Differential Scanning Calorimetry (DSC), Dynamic Mechanical Thermal Analysis (DMTA) to determine fundamental properties of EVA such as molecular mobility characteristics and also to monitor the crosslinking reaction. Exothermic peak as revealed by DSC analysis can be used to estimate the crosslinking rate of EVA during PV module encapsulation process as fast quality control test. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
L'objectif principal de ce travail est de permettre une meilleure compréhension entre les différentes techniques analyses expérimentales pour détecter la réaction de réticulation au niveau de lencapsulant Ethylène-Vinyle Acétate (EVA), durant le process de fabrication d'un module PV. Plusieurs méthodes d'analyse, allant du test classique d'extraction du taux de gel aux différentes techniques d'analyses thermomécaniques ainsi que les techniques d'analyse de spectroscopie comme le courant stimulé thermiquement (TSC), ont été étudiés pour permettre de révéler le phénomène de la réaction de réticulation de l'encapsulant l'EVA. Les résultats de base montrent que la TSC complète parfaitement d'autres méthodes d'analyses thermiques comme la calorimétrie différentielle à balayage (DSC), l'analyse mécanique dynamique (DMTA) pour déterminer les propriétés fondamentales de l'EVA. Ces techniques permettent de déterminer les caractéristiques relatives à la mobilité moléculaire et aussi pour mieux mettre en évidence la réaction de réticulation. Le pic exothermique comme révélé par l'analyse par DSC, peut être utilisé pour estimer le taux de réticulation de l'EVA au cours du process d'encapsulation du module PV comme un test rapide de contrôle de qualité.
The influence of distinct carbon based nanofillers: expanded graphite (EG), conducting carbon black (CB), thermally reduced graphene oxide (TRGO) and multi-walled carbon nanotubes (CNT) on the thermal, dielectric, electrical and rheological properties of polybutylene terephthalate (PBT) was examined. The glass transition temperature (Tg) of PBT nanocomposites is independent of the filler type and content. The carbon particles act as nucleation agents and significantly affect the melting temperature (Tm), the crystallization temperature (Tc) and the degree of crystallinity of PBT composites. PBT composites with EG show insulating behaviour over the tested concentration range of 0.5 to 2 wt.-% and hardly changed rheological behaviour. CB, CNT and TRGO induce electrical conductivity to their particular PBT composites by forming a conducting particle network within the polymer matrix. CNT reached the percolation threshold at the lowest concentration (<0.5 wt.-%), followed by TRGO (<1 wt.-%) and CB (<2 wt.-%). With the formation of a particle network, the flow behaviour of composites with CB, CNT and TRGO is affected, i.e., a flow limit occurs and the melt viscosity increases. The degree of influence of the carbon nanofillers on the rheological properties of PBT composites follows the same order as for electrical conductivity. Electrical and rheological results suggest an influence attributed to the particle dispersion, which is proposed to follow the order of EG<< CB<TRGO<CNT.
Cure monitoring of epoxy films by heatable in situ FTIR analysis: Correlation to composite parts
(2014)
The curing mechanism of an epoxy film containing dicyandiamide (DICY) and an epoxy formulation based on diglycidyl ether of Bisphenol A (DGEBA) polymer was studied as a function of various temperature programs. The investigation was performed in situ, using a thin film of the epoxy mixture on a silicon wafer substrate in a heatable transmission tool of a FTIR spectrometer. Based on these model-curing experiments, a major curing mechanism was proposed, taking into account the appearance, the decrease, and the development of characteristic bands at various temperatures. The conclusions of the model curing were correlated to FTIR measurements on a real, 50-mm-thick glass fiber reinforced component composite part from a technical process. It could be shown that characteristic bands that develop at curing temperatures above 150°C appear especially in the center of the thick sample. From the chemical or molecular point of view, this demonstrates the established technician's understanding that temperature control inside a large-scale fiber composite of, for example, aircraft, wind-turbine, automotive applications component is of major importance.
Electron magnetic resonance (EMR) spectroscopy, X-ray-fluorescent microscopy (XFM) and thermal analysis (TGA/DTA) are used to characterize the carbon nano-phase obtained in the reaction between fine-dispersed aluminium and dichlorethane in the liquid paraffin medium and its modified with Mn(II), Fe(III), Ni(II), Cu(II) chlorides forms were studied. It was shown that the solid nano-structured functionalized carbon systems containing metals possess specific magnetic and thermal properties. Key parameters of the process, influencing on the size and structure of the formed carbon nano-phase were determined. Results and regularities established in this work create presumably the certain basis for optimization of physical and chemical properties of similar systems.