Dissertations / Theses on the topic 'Curing'
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1
Tranter, Kenneth Shaun. "Remote cationic curing." Thesis, City University London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340378.
2
Fredheim, Rasmus. "Infrared Curing of Glass Fiber Composite Tube : Optimization of the curing cycle." Thesis, Karlstads universitet, Avdelningen för maskin- och materialteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-85466.
Abstract:
This thesis has investigated the possibility of optimizing curing time by changing the energy source from a conventional oven to infrared radiation (IR) and if it is possible to achieve similar results as the company's current production of glass fiber composite tubes. Many different parameters (time, temperature, heating rate, and rotation speed) might influence a cured composite tube's properties. Reduced factorial experiments were conducted to test all these parameters cost-efficient where each parameter was tested at a high and low level. However, every possible combination was not investigated. Temperature measurements during the curing cycles, energy calculations, three-point bending, and differential scanning calorimetry analysis were conducted to compare the two different curing methods, hot air and IR curing. The current production flexural strength and glass transition temperature (Tg) have acted as benchmark values that the tubes cured with IR would have to reach to be considered a reliable manufacturing method. Differential scanning calorimetry (DSC) analyses were conducted to measure the Tg and three-point bending to determine the flexural strength. Due to that no standard exist for three-point bending of composite tubes, an in-house method was created and verified with a finite element simulation in Abaqus, to measure the flexural strength. The simulated reaction force was circa 76.9% of the measured force at the same displacement during the three-point bending test of the tubes. The simulation found that the stress concentration did occur at the same locations as the fracture occurred in the three-point bending test. The temperature difference between the top of the laminate and the core was close to zero degrees for the current production by hot air in a thermal oven. A more significant temperature difference between the core and top of the laminate was found during curing with IR. However, a higher rotation speed was found to create a more evenly temperature distribution in the composite. No clear correlation between the Tg and the flexural strength was found, as the literature suggests while comparing each test cured with IR. Nevertheless, by comparing every test cured with IR with the current production of the tube, it was determined that a lower Tg could cause a lower flexural strength. However, the lower flexural strength for the tubes cured by IR could also be explained by the temperature difference found between the core temperature and the top of the laminate during the curing process. The reduced factorial experiments showed that it was possible to reach similar properties by curing with IR and reducing the curing time by 69.3%. Time and the combination of time and temperature were found to affect the result when it comes to the glass transition temperature. Regarding flexural strength, no parameters were found to impact the outcome. By investigating the time and temperature further, the curing time could be reduced to 71.3% compared with the current production and still achieve similar properties. Nevertheless, the energy use for curing with IR was found to require 8.3 times more than the current production.
3
Wilkinson, Susan Anne. "Aspects of radiation curing." Thesis, City University London, 1989. http://openaccess.city.ac.uk/7720/.
Abstract:
The electron beam induced polymerisation of dialkyltin diacrylates, as well as the UV and electron beam induced polymerisation of some novel silicon containing acrylates are discussed. The reactivity and film forming properties of these materials are compared with that of some commercial diluents such as, tripropyleneglycol diacrylate, TPGDA and trimethylolpropane triacrylate, TMPTA. Mechanistic studies concerning the initiation of free radical polymerisation of the acrylate ester, isodecylacrylate, IDA on electron beam irradiation are presented. Addition of electron and hole scavengers revealed that slow electrons contribute significantly to the initiation of electron beam induced polymerisation of acrylate esters. The film forming properties of phenyl acrylate and mono-, di- and tri- halophenyl acrylates on exposure to electron beam irradiation are evaluated in terms of their ability to produce tackfree films. The sensitivity of catechol diacrylate compared with t-butyl catechol diacrylate is also presented. Mechanistic studies concerning the initiation of both UV and electron beam induced cationic polymerisation of 3,4-epoxycyclohexylmethyl-31,41 -epoxycyclohexanecarboxylate, with the aid of diphenyliodonium hexafýuorophosphate, triphenylsulphonium hexafluorophosphate and (n -2,4-cyclopentadien- I-yl) [(I, 2,3,4,5,6-n) (-I-methylethyl) benzene] -iron(I+) hexafluorophosphate, as well as the radiolysis of 6,7-epoxy- 3,7-dimethyloctylacrylate in the presence of diphenyliodonium hexafluorophosphate are presented. The decomposition of the salts was monitored in situ by infrared and UV spectroscopy and hydrogen fluoride is credited as the true initiator of the cationic polymerisation of epoxides in an open system. The UV photolysis of the aforementioned onium salts led to the production of volatiles, resulting in the polymerisation of thin films of 3,4-epoxycyclohexylmethyl-31,41 - epoxycyclohexanecarboxylate, providing further evidence of hydrogen fluoride evolution. The use of FTIR- photoacoustic spectroscopy was proven to be an invaluable tool in monitoring the polymerisation of thin epoxide or acrylate films on an opaque substrate.
4
Khan, Niaz Ahmad. "Aspects of radiation curing." Thesis, City University London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241483.
5
Rostami, Vahid. "Development of early carbonation curing to replace steam curing for precast dry-mix concrete." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114470.
Abstract:
Early carbonation curing technology was developed to replace steam curing for precast dry-mix concrete production. To facilitate carbon dioxide diffusion in concrete within 24-h after casting, presetting is necessary. It was accomplished by a short steam curing or by a controlled air curing. Carbonation was carried out after presetting at a gas pressure of 0.15 MPa and in a period of two hours. The performance of carbonated concretes was characterized by their carbon uptake, strength gain, pH values, calcium hydroxide content, permeability, sorptivity, freeze-thaw damage resistance and sulphate and acid resistance. It was found that the early carbonation curing could produce concrete with comparable strength by steam curing and lead to reduced calcium hydroxide on surface while maintaining pH higher than the corrosion threshold at the core. Carbonated concretes also exhibited improved resistance to sulphate attack, water absorption, and ion penetration. The early carbonation curing also demonstrated CO2 sequestration potential as an added value to the process. The microstructure of the cement paste subject to early carbonation was studied to understand the mechanism of early carbonation of concrete. Calcium carbonates produced by the process were integrated in calcium-silicate-hydrate while maintaining its initial silicate structure. The wetting procedure applied in subsequent hydration was essential to produce more hydration products in the carbonated zone and increase strength and durability. Both ordinary Portland cement (OPC) and Portland limestone cement (PLC) were investigated for their carbonation behaviour. PLC was found to be more CO2 reactive.La technologie de cure par carbonatation précoce a été développée pour remplacer la cure par étuvage pour la production du béton mélange-à-sec préfabriqué. Afin de faciliter la diffusion du dioxyde de carbone dans le béton dans les 24 heures après le moulage, le préréglage est nécessaire. Ceci a été accompli par une cure par étuvage de courte durée ou par une cure par air contrôlé. Après le préréglage, la carbonatation a été effectuée à une pression de gaz de 0,15 MPa et dans une période de deux heures. La performance des bétons carbonatés a été caractérisée par leur absorption de carbone, le gain de résistance, les valeurs de pH, la teneur en hydroxyde de calcium, la perméabilité, la sorptivité, la résistance au gel-dégel ainsi qu'aux sulfates et à l'acide. Il a été constaté que la cure par carbonatation précoce pourrait produire du béton avec une résistance comparable à la cure par étuvage. Aussi, il a été noté que la carbonatation précoce pourrait résulter à une réduction de l'hydroxyde de calcium sur la surface tout en permettant le pH au coeur d'être supérieure à la valeur seuil de la corrosion. Des bétons carbonatés ont également présenté une résistance améliorée aux attaques des sulfates, à l'absorption de l'eau et à la pénétration des ions. En plus, la cure par carbonatation précoce a démontré le potentiel de séquestration du CO2 comme une valeur ajoutée au processus.La microstructure de la pâte de ciment soumise à la carbonatation précoce a été étudiée afin comprendre le mécanisme de carbonatation du béton. L'hydrate silicate de calcium (HSC) dans le ciment carbonaté était fortement intégré avec les carbonates de calcium tout en conservant sa structure silicatée initiale. La procédure de mouillage appliquée à l'hydratation ultérieure a été essentielle afin de produire plus de produits d'hydratation dans la zone carbonatée et d'augmenter la résistance et la durabilité. Le ciment Portland ordinaire (CPO) et le ciment Portland au calcaire (CPC) ont été étudiés pour comprendre leur comportement lors de la carbonatation. Le CPC est en mesure d'absorber plus de dioxyde de carbone et de produire une résistance plus élevée à un âge précoce.
6
Pheeraphan, Thanakorn. "Microwave curing of cementitious materials." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12174.
7
Bettelli, Mercedes Amelia. "Effect of Induction-Heat Post-Curing on Residual Stresses in Fast-Curing Carbon Fibre Reinforced Composites." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80527.
Abstract:
Manufacturing induced shape distortions is a common problem for composite materials. Due to the non-isotropic nature of carbon fibre reinforced polymers (CFRP) unavoidable deformations occur during part production. During fabrication of polymer composites, the material obtains its final shape at elevated temperatures. The curing process involves a transition from the liquid state to the solid, glassy state, allowing bonding between fibres and matrix. As the material cools the mismatch in thermal expansion coefficients and cure shrinkage obtained during the matrix polymerization leads to residual stresses on the mechanical level within composite part. There is a great interest from the aircraft and automotive industries, to increase the ability to understand development of shape distortions and residual stresses during the cure, since these deformations often lead to dissatisfaction of tolerances and it is essential to predict the deformations beforehand in order to compensate time and cost. In this context, a study of residual stresses during the curing process of thermosetting resin composites is presented. A methodology is proposed for predicting the formation and development of manufacturing- induced residual stresses. The present project reports on a comprehensive experimental study on the dependency of different short curing cycles on the build-up of residual stresses in a carbon fibre/fast-curing epoxy system and evaluate of post-curing methods through induction heating and oven post-curing with unidirectional [904] and unsymmetrical [9020] laminates. It includes characterization in thermo-elastic properties and degree-of-cure of the material by Thermal bending test, thermal expansion test, mechanical tensile test and Differential Scanning Calorimetry (DSC) in non-post-cured and post-cured laminates. The results showed slight variation in the thermal properties and not effect in the mechanical properties at different cure and post-curing conditions. Analytical data by Laminate Analysis program validated the experimental thermo-elastic data with analytical simulations. In addition, it is shown improvements in the temperature distributions in the post-curing by induction heating with different experimental set-ups, however, oven post-curing showed a more systematic system, higher heat efficient a low cure temperature, with more consistent mechanisms of shape distortions and residual stresses compared to induction heating. These findings are relevant for the future development of prediction methods for process induced deformations of Fast Curing Epoxy Resins (FCER).
8
Wang, Jinsong. "Membrane curing and performance of concrete." Thesis, University of Dundee, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257442.
9
Folz, Diane C. "Variable Frequency Microwave Curing of Polyurethane." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/34567.
Abstract:
Historically, coatings were processed from natural oils, fats, and resins; the first well-known and widely used being lacquer [Meir-Westhues, 2007]. In the 20th century, synthetic resins were developed to achieve coatings with improved properties. Of these coating compositions, polyurethanes (PURs) were one of the most prevalent. Polyurethanes became possible in 1937 when Otto Bayer developed the diisocyanate polyaddition process [Randall et al, 2002]. Since that time, literally thousands of PUR compositions have been used commercially. The primary application of interest in this study is that of coatings for wood substrates.
It is well-known among materials researchers that there can be a number of differences between microwave and conventional materials treatment techniques [Clark et al, 1996], including enhanced reaction rates, lowered processing temperatures for some products, and selective interactions in composite systems.
The primary goals of this research were to determine (1) whether microwave energy affected the cure rate in a water-based, aliphatic PUR, and (2) if there was an effect of microwave frequency on the cure rate.
The primary tool for determining extent of cure in the PUR samples was Fourier transform infrared spectroscopy (FTIR). Using this characterization method, the changes in intensities of four bonds specific to the PUR composition were followed. It was determined that, in the particular PUR composition studied, microwave energy had an effect on the cure rate when compared with conventional heating, and that there was a frequency effect on the cure rate. Additionally, a deeper understanding of the use of FTIR spectroscopy techniques for studying cure kinetics was developed.Master of Science
10
Esteves, Luís Pedro. "Internal curing in cement-based materials." Doctoral thesis, Universidade de Aveiro, 2009. http://hdl.handle.net/10773/2413.
Abstract:
Doutoramento em Engenharia CivilO desenvolvimento de betões de elevado desempenho, durante o início da década de 80, revelou que este tipo particular de materiais com base em cimento é susceptível a problemas de cura. São bem conhecidos os efeitos dos fenómenos autogéneos em sistemas de elevado desempenho com base em cimento, nomeadamente a fissuração em idade jovem. Esta é, aliás vista como a maior limitação no desenvolvimento de novos materiais com durabilidade superior. Desenvolvimentos recentes de métodos de cura interna provaram ser uma boa estratégia de mitigação dos efeitos da auto-dissecação destes sistemas, onde a presente tese ganha o seu espaço no tempo. Este estudo centra-se essencialmente em sistemas de elevado desempenho com base em cimento com cura interna através de partículas superabsorventes, dando particular importância à alteração de volume em idade jovem. Da análise mais aprofundada deste método, resultam algumas limitações na sua aplicabilidade, especialmente em sistemas modificados com sílica de fumo. Conclui-se que a natureza física e química dos polímeros superabsorventes pode afectar significativamente a eficiência da cura interna. Em adição, os mecanismos de cura interna são discutidos mais profundamente, sendo que para além dos mecanismos baseados em fenómenos físicos e químicos, parecem existir efeitos mecânicos significativos. Várias técnicas foram utilizadas durante o decorrer desta investigação, com o objectivo, para além da caracterização de certas propriedades dos materiais, de perseguir as questões deixadas em aberto pela comunidade internacional, relativamente aos mecanismos que fundamentam a explicação dos fenómenos autogéneos. Como exemplo, são apresentados os estudos sobre hidratação dos sistemas para avaliação do problema numa escala microscópica, em vez de macroscópica. Uma nova técnica de cura interna emerge da investigação, baseada na utilização de agregados finos como veiculo para mitigar parcialmente a retracção autogénea. Até aqui, esta técnica não encontra par em investigação anterior, mas a extensão da cura interna ou a eficácia na mitigação baseada neste conceito encontra algumas limitações. A significância desta técnica em prevenir a micro fissuração é um aspecto que está ainda em aberto, mas pode concluir-se que os agregados finos podem ser benéficos na redução dos efeitos da restrição localizada no sistema, reduzindo o risco de micro fissuração. A utilização combinada de partículas finas de agregado e polímeros super absorventes pode ter como consequência betão sem microfissuração, ou pelo menos com nanofissuração.
The development of high performance concrete in the early 80 revealed that this particular branch of cement-based materials is highly sensible to curing problems. It is well known the consequences of autogenous phenomena in high performance systems, namely the early-age cracking. This is seen as the major limitation on the further development of new materials with superior durability. Recent developments have returned internal curing methods as mean to mitigate such phenomena, where this thesis finds it space in time. Internal curing of cement-based materials by superabsorbent polymers is further analysed, with emphasis on the consequences of the volume-changes in plain Portland and SF-modified cement based systems at early age. Some limitations in the use of superabsorbent polymers are encountered, being concluded that the physical and chemical nature of superabsorbent polymers may significantly affect the efficiency of internal curing. In addition, the mechanisms of internal curing are discussed in more depth, from where it transpires that beyond the mechanisms with physical or chemical ground, significant mechanical effects do exist. Several techniques are used in the course of the investigation, which aimed, beside the characterisation of certain material properties, to pursue the open questions left by the international community, in respect with the fundamental mechanisms that may explain the autogenous phenomena. Examples of that are the hydration studies at a microscopic scale, rather than macroscopic. Furthermore, a new technique of internal curing is proposed, which is based on the use of very fine aggregate particles, as mean of partial mitigation of autogenous shrinkage. So far, this technique has not been reported in the research community as mean of mitigation, but the extent of internal curing that may potentially be obtained from this concept encounters several limitations. The significance of this technique in preventing microcracking is yet to be proved, but it is concluded that fine aggregate particles may be beneficial in reducing the restraint effects, and thus, reducing the potential for cracking events. The combined use of superabsorbent and fine aggregate particles may have as a consequence the development of concrete with nanocracking, rather than micro, during a period where the “culture” in the concrete technology is putting considerable effort in getting more intimate with the durability aspects of cement-based materials.
11
Bilyeu, Bryan. "Cure Kinetics and Processing Parameters of Neat and Reinforced High Performance Epoxy Resins: Evaluation of Techniques." Thesis, University of North Texas, 1999. https://digital.library.unt.edu/ark:/67531/metadc2281/.
Abstract:
Kinetic equation parameters for the curing reaction of a commercial glass fiber reinforced high performance epoxy prepreg composed of the tetrafunctional epoxy tetraglycidyl 4,4-diaminodiphenyl methane (TGDDM), the tetrafunctional amine curing agent 4,4-diaminodiphenylsulfone (DDS) and an ionic initiator/accelerator, are determined by various thermal analysis techniques and the results compared. The reaction is monitored by heat generated determined by differential scanning calorimetry (DSC). The changes in physical properties indicating increasing conversion are followed by shifts in glass transition temperature determined by DSC and temperature-modulated DSC (TMDSC), thermomechanical (TMA) and dynamic mechanical (DMA) analysis and thermally stimulated depolarization (TSD). Changes in viscosity, also indicative of degree of conversion, are monitored by DMA. Thermal stability as a function of degree of cure is monitored by thermogravimetric analysis (TGA). The parameters of the general kinetic equations, including activation energy and rate constant, are explained and used to compare results of various techniques. The utilities of the kinetic descriptions are demonstrated in the construction of a useful time-temperature-transformation (TTT) diagram for rapid determination of processing parameters in the processing of prepregs.
Copyright is held by the author, unless otherwise noted. All rights reserved.
Files: Thesis.pdf
Special Conditions
12
Konuray, Ali Osman. "Design and analysis of dual-curing systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/666325.
Abstract:
Dual-curing processing is a method to prepare thermoset materials through two polymerization reactions carried out
simultaneously or sequentially. In these processes, a firm understanding of reaction mechanisms enables the design of catalytic systems to control reaction kinetics and to impart sequentiality to the curing reactions. Material properties at different curing stages are dictated by the choice of monomers. Furthermore, by employing click-based approaches, eco-friendly and efficient dual-curing processes can be designed.
In this thesis, a number of sequential dual-curing systems were prepared and characterized. Sequentiality was either
intrinsic due to the monomers used or it was achieved by employing latent catalysts. The dual-curing systems were designed with an objective of improved physical and mechanical properties of the fully cured materials. The majority of the monomers were processable through click reactions, although a few processes did not strictly fit click criteria. In terms of the characterized properties, this did not pose any shortcoming.
Due to the limited number of related publications, the thiol-epoxy reaction was investigated in more detail. Accurate
phenomenological and mechanistic models of reaction kinetics were developed to study reaction kinetics in and out of dual- curing context.
For reactive latency, a new family of photobase generators (PBGs) were developed. As the name implies, these PBGs
liberated base catalysts upon UV irradiation. The possibility of thermal initiation of some of these PBGs was also
demonstrated. Storage stabilities of uncured and partially-cured (i.e. intermediate) materials were significantly improved since PBGs allowed temporal control over curing stages.
In some dual-curing systems, step-wise click polymerizations such as Michael additions were combined with chain-wise
homopolymerizations such as acrylate photopolymerizations. In these systems, the initial step-growth proces delivered intermediate materials with desirable properties such as polymer network homogeneity, high gel point conversion, and low polymerization shrinkage. The chain-wise process was carried out as a second curing stage, at the end of which final
materials were obtained with increased crosslinking density, hardness and Tg. In all dual-curing systems presented here, final materials had significantly improved properties compared to intermediate materials, regardless of the nature of the curing processes.
In one part of the project, a new set of catalyst comonomers were designed. These comonomers, which were also prepared using click-based procedures, had pendant allyl functionalities and wielded tertiary amine groups in their structure. The tertiary amines catalyzed a thiol-acrylate reaction carried out as a first curing stage in a dual-curing system. Later, as a
second curing stage, the pendant allyl groups of the comonomers participated in thiol-ene polymerizations with the excess thiols initially present in the formulation, thereby getting incorporated into the final polymer network.
The dual-curable materials developed here can be used in diverse applications ranging from high-performance adhesives,
to rigid shape-memory materials. As a matter of fact, a preliminary demonstration of these two applications is provided. Prospectively, the materials presented here could benefit from a more detailed characterization in the context of specific applications. Without a doubt, such an effort would increase the possibility of successful commercialization of these formulations.El curat dual és una metodologia utilitzada per preparar materials termoestables mitjançant la combinació de dos processos de polimerització que poden tenir lloc de forma simultània o seqüencial. Conèixer en profunditat els mecanismes de reacció que regeixen aquests processos és l'eina clau per al disseny de sistemes catalítics que permetin controlar la cinètica de la reacció i aconseguir la seqüencialitat de les etapes de curat. Les propietats del material en les diferents etapes de curat estan determinades per l'elecció dels monòmers. A més, la utilització de reaccions de tipus click permet dissenyar processos de curat més ecològics i eficients. En aquesta Tesi, es van preparar i caracteritzar diferents sistemes de curat seqüencials. La seqüencialitat en el curat es va aconseguir amb la selecció adequada de monòmers o mitjançant l'ús de catalitzadors latents. Els sistemes de curat dual es van dissenyar també amb l'objectiu de millorar les propietats físiques i mecàniques dels materials completament curats. La majoria dels monòmers van ser curats mitjançant reaccions de tipus click. Encara que algunes de les etapes de curat no s'ajustaven estrictament als criteris acceptats per les reaccions click, això no va suposar un problema pel que fa a les propietats dels materials preparats. La cinètica de reacció tiol-epoxi es va investigar amb més detall, atès el nombre limitat de publicacions existents sobre aquest tema. Es van desenvolupar models fenomenològics i mecanístics avançats per estudiar la cinètica d'aquesta reacció dins i fora del context del curat dual. Per aconseguir sistemes latents, es va desenvolupar una nova família de fotobases latents. Com el seu nom indica, aquestes fotobases, després de ser irradiades mitjançant llum UV, alliberen una base que actua com a catalitzador del curat. També es va demostrar la possibilitat d'activar tèrmicament les fotobases. La utilització d'aquestes va permetre el control temporal de les etapes de curat, augmentant significativament l'estabilitat durant l'emmagatzematge dels materials no curats i parcialment curats, després de la primera etapa. En alguns sistemes duals, es van combinar polimeritzacions click per etapes com ara les addicions de Michael amb homopolimeritzacions en cadena tals com la fotopolimerització d'acrilats. En aquest tipus de sistemes, la polimerització per etapes en la primera etapa de curat permet obtenir materials intermedis amb propietats desitjables com ara alta homogeneïtat i conversió a la gelificació i baixa contracció durant el curat. La polimerització en cadena que té lloc durant la segona etapa de curat, va permetre obtenir materials finals amb major densitat d'entrecreuament, duresa i temperatura de transició vítria. Independentment de la naturalesa dels processos de curat utilitzats, tots els materials finals van presentar propietats tèrmiques i mecàniques significativament millorades en comparació amb els materials intermedis. En una part d'aquesta Tesi, es va dissenyar una nova família de comonòmers que actuaven simultàniament com a catalitzadors. Aquests comonòmers, que també es van preparar mitjançant procediments basats en la química click, tenien funcionalitats alíliques terminals i amines terciàries en la seva estructura generades durant la seva síntesi. Aquestes amines van actuar com a catalitzadors de la primera etapa de curat tiol-acrilat en un sistema de curat dual. En la segona etapa de curat, els grups al·lil terminals dels comonòmers van reaccionar amb grups tiols en excés presents en la formulació mitjançant una reacció tiol-è fotoinduïda. Els materials preparats mitjançant curat dual en aquest treball es poden utilitzar en una àmplia gamma d'aplicacions avançades que van des d'adhesius d'alt rendiment fins a materials amb memòria de forma.
13
Lindberg, Anders. "Resin composites : Sandwich restorations and curing techniques." Doctoral thesis, Umeå : Umeå University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-510.
14
Farnsworth, Kimberly Dawn Richards. "Variable frequency microwave curing of polymer dielectrics." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/10928.
15
DiBartolomeo, Franklin. "HIGH SPEED CONTINUOUS THERMAL CURING MICROFABRICATION SYSTEM." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_theses/105.
Abstract:
Rapid creation of devices with microscale features is a vital step in the commercialization of a wide variety of technologies, such as microfluidics, fuel cells and self-healing materials. The current standard for creating many of these microstructured devices utilizes the inexpensive, flexible material poly-dimethylsiloxane (PDMS) to replicate microstructured molds. This process is inexpensive and fast for small batches of devices, but lacks scalability and the ability to produce large surface-area materials. The novel fabrication process presented in this paper uses a cylindrical mold with microscale surface patterns to cure liquid PDMS prepolymer into continuous microstructured films. Results show that this process can create continuous sheets of micropatterned devices at a rate of 1.9 in2/sec (~1200 mm2/sec), almost an order of magnitude faster than soft lithography, while still retaining submicron patterning accuracy.
16
Degamber, Balkarransingh. "Microwave curing and process monitoring of thermosets." Thesis, Cranfield University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396488.
17
Pheeraphan, Thanakorn. "Accerlated curing of concrete with microwave energy." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10733.
18
Heritage, Ian. "Direct electric curing of mortar and concrete." Thesis, Edinburgh Napier University, 2001. http://researchrepository.napier.ac.uk/Output/6571.
Abstract:
Direct electric curing is the method by which the hydration reactions within concrete are thermally accelerated by passing an alternating electric current through the sample. This use of electricity as a means of supplying heat to young concrete and mortar has become recognised as a more effective and energy efficient form of accelerating the curing process than traditional steam curing. The present investigation involves studying the affects of thermally accelerated curing of cementitious materials in comparison to normally non-heated curing. Prior to mixing, tests are performed on the constituents of the cementitious mixes. Results of these tests are used in the creation of mix designs for mortar and concrete samples. A range of concrete mixes are designed with and without additives and admixtures are used to make cubes, slabs and beams. From the testing results, the factors affecting the short and long term properties of electrically cured cementitious materials are investigated and heating regimes are presented to achieve specific properties of both strength and durability at specific ages. A substantial section of reinforced concrete is required to gain representative results in electrically curing reinforced concrete slabs. Compressive strength is difficult to measure due to the electrical distortion affects of inserts and the damage caused by coring so that at present, basic maturity concepts are used as a compressive strength guide which limits the validity of results obtained. This research looks at refining these concepts to include early age heating effects induced by direct electric curing. The microstructural development of concrete when subjected to accelerated curing is also considered. The affect of delay periods and maximum temperature is studied using a scanning electron microscope and the results presented.
19
JANSEN, JOSE U. "Síntese e caracterização de verniz eletroisolante para cura dual UV/termica." reponame:Repositório Institucional do IPEN, 2005. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11374.
Abstract:
Made available in DSpace on 2014-10-09T12:51:13Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:10:37Z (GMT). No. of bitstreams: 1 11257.pdf: 9782449 bytes, checksum: 9692d0a5b3355b0291e58320e6dc078d (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
20
Desai, Ajay Kumar. "Studies on process variables in mixing and curing of animal feed block supplements for reducing the curing cycle time." Thesis, Queensland University of Technology, 2007.
Abstract:
The animal feed block processing is multi billion dollar industry with impact on huge livestock sector. Production of animal feed block supplements comprises mixing of ingredients in set sequence, time interval, stirring speed, pouring the mix and curing before despatch to customers. There is a huge variability in curing time in the current process. This leads to quality problem due to non-compliance of product hardness and supply problems.
Longer curing time leads to bottleneck in the production and storage area because products can not be physically transported if the hardness is below certain level. Softer products lead to safety problems for animal due to increased consumption and toxicity. It can lead to rejection, product recall and liability for huge compensation. Harder products can lead to inadequate consumption leading to customer complaints. There is a need in the industry to reduce the variability of curing time and hardness to maintain the quality of the product and to overcome the bottleneck problem in the shop floor and warehouse. This Thesis investigates the production and curing process to enhance the knowledge for reducing process variation.
21
Sopanangkul, Anongnat. "Diffusion phenomenon in high pressure processed foods." Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250688.
22
Li, Chun. "Simulation of process induced residual stresses in thick filament wound tubes." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272044.
23
Glauser, Thierry. "Electron-beam curing of thermoset resins for composites." Doctoral thesis, KTH, Polymer Technology, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2837.
Abstract:
Electron-beams (EB) are an alternative to traditionalthermal curing when manufacturing thick thermoset composites.It is a quick and energetically efficient technique when curinglarge fiber reinforced parts. Most of the published work onEB-curing deals with curing of thin layers of resin or withcrosslinking of polymers.
In this thesis, the curing of acrylic resins is studied tohighlight the critical parameters and the particularities ofEB-curing. Tgof the thermoset increases with increasingirradiation dose and levels-off at Tg∞, when the resin is fully cured. As inthermal curing, the temperature during cure strongly affectsthe crosslinking of the resin and the thermo-mechanicalproperties of the cured thermoset. Up to Tg∞, a linear relationship between the maximumtemperature during cure and Tgwas found.
Carbon and glass fiber composites were EB-cured and tested.Adding fibers to the acrylic resins lowered the exotherm, whichclearly confirmed the importance of temperature during cure tofully crosslink the polymer matrix.
Comparing EB-, UV- and thermal cure showed that the curingmethod was not the factor that most influenced the propertiesof the cured thermoset. The curing technique imposesconstraints, such as starting temperature and curing time, butit does not influence directly the polymerization and thenetwork formation. These properties are inherent to the monomerused.
An acrylate resin was blended it with a series of alkyl andmethacrylate functionalized hyperbranched polyester. Thephase-separated thermoset exhibited increased toughness.
Keywords:electron-beam, thermoset, acrylic resin,hyperbranched polyester, thermal effect, toughening
24
Wikström, Malin. "Synthesis and protein curing abilities of membrane glycolipids." Doctoral thesis, Stockholm University, Department of Biochemistry and Biophysics, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-1361.
Abstract:
There are many types of membrane lipids throughout Nature. Still little is known about synthesizing pathways and how different lipids affect the embedded membrane proteins. The most common lipids are glycolipids since they dominate plant green tissue. Glycolipids also exist in mammal cells as well as in most Gram-positive bacteria. Glycosyltransferases (GTs) catalyze the final enzymatic steps for these glycolipids. In the bacteria Acholeplasma laidlawii and Streptococcus pneumonie and in the plant Arabidopsis thaliana, GTs for mono-/di-glycosyl-diacylglycerol (-DAG) are suggested to be regulated to keep a certain membrane curvature close to a bilayer/nonbilayer phase transition. The monoglycosylDAGs are nonbilayer-prone with small headgroups, hence by themselves they will not form bilayer structures.
Here we have determined the genes encoding the main glycolipids of A. laidlawii and S. pneumonie. We have also shown that these GTs belong to a large enzyme group widely spread in Nature, and that all four enzymes are differently regulated by membrane lipids. The importance of different lipid properties were traced in a lipid mutant of Escherichia coli lacking the major (75 %), nonbilayer-prone/zwitterionic, lipid phosphatidylethanolamine. Introducing the genes for the GTs of A. laidlawii and two analogous genes from A. thaliana yielded new strains containing 50 percent of glyco-DAG lipids. The monoglyco-DAG strains contain significant amounts of nonbilayer-prone lipids while the diglyco-DAG strains contain no such lipids. Comparing these new strains for viability and the state of membrane-associated functions made it possible to connect different functions to certain lipid properties. In summary, a low surface charge density of anionic lipids is important in E.coli membranes, but this fails to be supportive if the diluting species have a too large headgroup. This indicates that a certain magnitude of the curvature stress is crucial for the membrane bilayer in vivo.
25
Strömberg, Helen. "Sjukvårdens industrialisering : Mellan curing och caring –sjuksköterskearbetets omvandling." Doctoral thesis, Umeå universitet, Ekonomisk historia, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-257.
Abstract:
This dissertation examines changes in the Swedish health care system during the period 1962-2000. During this period, three legislative changes affected the development of the health care system. Firstly, the Health care act of 1962 that increased the county councils responsibility for the health care. Secondly, the Health care act of 1983, which resulted in a new definition of concept health at the same time as it changed the hospitals responsibility for care and illness. Thirdly, from 1992 to 1995, three reforms changed the hospitals position in the health care system. Together with the general technological development of the health care sector, these three legislative changes have led to new way of producing care as well as it has created new jobs, new work specialities and it has also effect the gender division in work. Women have always dominated the work in the health care sector. The way of care production have however also created new jobs mainly consisting of technological work assignments that have better status than traditional care work with the patients. The new technological jobs are furthermore primarily occupied by men, which leads to a organizational development than reemphasizes the hierarchical structure of the health care sector, where women work in the lower position and men in the upper positions. This development is also evident when nurses begin to work with technology. This express a new gender system in which men dominate in curing and nursing work-assignments at care wards with high technological level, but not in the caring assignments. And at care wards with low technological level the situation is the opposite, women dominate in all three assignments e.g. curing, nursing and caring care work.
26
Lele, Stephen, and slele@bigpond net au. "Additives on the Curing of Phenolic Novolak Composites." RMIT University. Applied Sciences, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070205.095402.
Abstract:
The research programme studied the cure reaction of a phenolic novolak resin and the effects of various additives and fillers on the reaction. The programme utilised the recently developed thermal analysis technique of temperature-modulated differential scanning calorimetry (TMDSC) performed in conjunction with other available thermal analysis techniques. TMDSC enables the signal for the heat of reaction to be separated from the underlying specific heat change in the resin. This meant that the reaction could be studied without interference from any physical changes in the resin. The manufacture of composite brake materials required the use of numerous additives and fillers to produce the desired properties. The influence of such additives on the cure rate and final properties of the resin was known to occur but had not previously been measured due to the difficulties presented by the presence of opaque additives. Some additives also underwent thermally induced physical changes in the temperature range of the cure. The final properties and the processing of new brake materials undergoing development often required trial and error adjustments to compensate for changes in cure rate. An understanding of the influence of additives would enable more rapid commercial development of brake materials through an improvement in the ability to predict both the properties of the product and the optimal processing parameters. Processing efficiency could also be improved through detailed knowledge of the kinetics. Moulding cycle times and post-baking times and temperatures were longer than necessary in order to ensure adequate cure at the end of each stage because of the lack of kinetic data. The cure of phenolic resin has been shown to be highly complicated with numerous alternate and competing reactions. For the manufacture of composite materials, knowledge of the kinetic parameters of individual reactions is not considered to be important; rather the overall kinetic parameters are required for prediction. Therefore the kinetic model parameters that best described the observed behaviour were chosen even though the model had no basis in the molecular interaction theory of reaction. Rather it served as a convenient tool for predictions. Characterisation of the resin proved to be difficult due to the presence of overlapping peaks, and volatile reaction products. TMDSC was successfully used to determine the reaction kinetics of the pure resin and the influence of certain additives on the reaction kinetics. The determination of the kinetic parameters using TMDSC agreed well with the traditional Differential Scanning Calorimetry isothermal and non-isothermal techniques. Both the Perkin-Elmer and TA Instruments were utilised for the research and were found to provide reasonably good agreement with each other. The capabilities and limitations of the individual instruments were critically examined, frequently beyond the manufacturers' specifications. TMDSC suffers from a limitation in the heating rate of the sample compared to DSC. However, it was observed that valuable information could still be obtained from TMDSC despite using heating rates that were higher than specified by manufacturers. Hot Stage Microscopy and thermogravimetry were additional experimental techniques used to aid in the characterisation of the resin. Some inhomogeneity of the resin was identified as well as differences in the behaviour of the cure between open (constant pressure) and closed (constant volume) environments were observed. A novel method of determining the orders of the cure reactions and their kinetic parameters was utilised. Reaction models for the overall cure reactions were postulated and tested by fitment to sections of experimental data in temperature regions which appeared to be free of interference from overlapping peaks. Once an individual peak was reasonably well modelled, adjacent overlapping peaks were able to be modelled both individually and in combinations by fitment to experimental data. The Solver function in Microsoft Excel was utilised to find the best fitting model parameters for the experimental data. The model parameters were able to be refined as overlapping peaks were progressively incorporated into the calculations. This method produced results that agreed well with the traditional method of analysing reaction peak temperatures at multiple scanning rates. Model fitment was shown to be of benefit where overlapping reactions occur. Various model scenarios could be tested and optimised to particular sections of experimental data. This enabled the researcher to easily identify areas of possible anomalies and postulate alternative scenarios. The accuracy of the postulated model was able to be determined by its successful fitment to experimental data from experiments run under different conditions.
27
Wikström, Malin. "Synthesis and protein curing abilities of membrane glycolipids /." Stockholm : Department of Biochemistry and Biophysics, Stockholm University, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-1361.
28
Strömberg, Helén. "Sjukvårdens industrialisering : mellan curing och caring - sjuksköterskearbetets omvandling." Umeå: Univ, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-257.
29
Manepalli, Rahul Nagaraj. "Electron beam curing of thin film polymer dielectrics." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/11036.
30
He, Zhanqi. "A cycloaddition approach to the curing of polyimides." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/27301.
31
Lewis, Matthew Carrington. "Heat curing and delayed ettringite formation in concretes." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321775.
32
Nightingale, Clare. "Microwave assisted curing of epoxy resins and composites." Thesis, University of Manchester, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.577136.
33
McCusker, Neil. "Light curing in orthodontics : should we be worried?" Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551289.
Abstract:
There were four aims to this study; to assess the profile of orthodontists, their light curing processes and knowledge of the appliances they use. To calculate the maximum permissible daily exposure times for a number of different types of currently available light curing units. To evaluate the effect of orthodontic brackets to the blue light hazard. To test the hypothesis that routine use of dental curing units may lead to problems with colour discrimination in clinicians, namely orthodontists, when compared with a non- dental control. A self administered questionnaire was designed to assess the profile of orthodontists and the procedures used for light curing. This was completed by 104 orthodontists. The maximum permissible daily exposure times of a variety of curing lights (8 LED, 2 Quartz Tungsten Halogen, and 1 plasma) were calculated at distances of 2cm, 10cm, 20cm, 30cm, 40 cm, 5Ocm and 60 using a spectroradiometer. A phantom head unit with acrylic teeth was used to assess the effect of different bracket materials (metal and aesthetic) on reflected light and the maximum daily exposure limits. The Farnsworth Munsell l00 hue test was used to assess the colour discrimination and deficiency of 15 orthodontists and 15 controls. The results demonstrate that Orthodontists knowledge about the properties of light curing units that are important for orthodontic bonding and safety is low. Blue light hazard decreases as distance from the eye increases. Current light curing units a-re unlikely to reach maximal daily exposure for blue light at normal working distances . • Orthodontic bracket materials do affect reflected light but the differences are unlikely to be of clinical significance. Continued use of current dental light curing units does not lead to problems with colour discrimination.
34
Jepson, Peter. "Development of novel curing agents for epoxy resins." Thesis, University of Surrey, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395555.
35
Agbasi, Chukwuemeka Chijioke. "New approaches for assessing the curing of concrete." Thesis, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249326.
36
Moloto, Percy Kgothatso. "Laboratory accelerated curing protocol for bitumen stabilized materials." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4187.
Abstract:
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: The research conducted in this study forms part of the Phase II process of the Bitumen Stabilized Materials (BSMs) Guideline improvement initiative. The initiative aims to address areas of concern in the cold mix design procedures for BSMs. Current road rehabilitation using the bitumen stabilization process requires testing of representative specimens as means to evaluate pavement performance over time. In order to adequately acquire specimens representative of field conditions, it is necessary to condition the materials in a process called curing. Although curing procedures have been standard in many countries on different continents, the protocols are varied and an acceptable procedure is currently not available. In order to develop an acceptable curing protocol for BSMs, both field and laboratory environments were investigated. Considering that curing takes time in the field, production of representative samples intended for laboratory testing must undergo accelerated curing in the laboratory. Given the complexities involved in achieving close correlations between field and laboratory environments, the research strived to reconcile field and laboratory material behaviour. In particular, the main objective of the research was to unify the curing protocol for BSMs, with the standardization of the curing protocol being top priority. In this study, laboratory results have confirmed that the different natures of curing mechanisms inherent in a BSM-foam and BSM-emulsion contribute to irreconcilable material behaviour(s). Results have confirmed that curing of BSM-foam is largely a function of water repulsion, with the addition of active filler dominating material performance almost immediately. Unlike BSM-foam, curing of BSM-emulsion is both a function of the breaking of emulsion during the initial phase and the gradual release of moisture with time. In this instance, BSM-emulsion material performance resembled active filler influences past the breaking of the emulsion cycle. Consequently, given the observed differences regarding material behaviour(s), the unification of the curing protocol for BSMs has not been successful. In terms of accommodation of active filler in the final curing protocol for BSMs, findings in this research have revealed that active filler’s tendency to absorb moisture in the initial stages requires longer curing time to help extract the absorbed moisture during the curing process. Although the use of active filler has an impact on curing, its inclusion in a BSM does not justify its extension in the curing time as cementation is not one of the desired properties of these materials. BSMs are primarily desirable for their flexibility in pavement structures. For this reason, active filler was omitted in the final curing protocol due to reasons of simplifying the mix design process. In conclusion, different curing protocols were tested and developed to help produce reconcilable material behaviour in both the field and laboratory environments. Through the reconciliation of key material properties such as the resilient modulus, long term equilibrium moisture conditions and shear parameters, an acceptable standardized curing protocol for BSM-foam and BSMemulsion intended for application in industrial laboratories across South Africa was successfully developed.
AFRIKAANSE OPSOMMING: Die navorsing tydens hierdie studie gedoen, vorm deel van die Tweede fase van die Bitumen Gestabiliseerde Materiale Riglyne verbeteringsinisiatief. Die inisiatief het ten doel om areas van bekommernis in die kouemengsel-ontwerp-prosedures vir Bitumen Gestabiliseerde Materiale aan te spreek. Huidige padrehabilitasie wat gebruik maak van die Bitumen Gestabiliseerde Materiale proses, vereis toetsing van verteenwoordigende monsters om sodoende plaveiselgedrag oor ‘n tydperk te evalueer. Materiale moet deur die verouderingsproses gekondisioneer word, om sodoende monsters te verkry wat akkuraat verteenwoordigend van veldtoestande is. Alhoewel verouderingsprosesse in meeste lande - op verskillende kontinente - gestandariseerd is, is die protokol verskillend en ‘n aanvaarbare prosedure is nie tans beskikbaar nie. Beide veld- en laboratoriumomgewings is ondersoek, om sodoende ‘n aanvaarbare verouderings-protokol vir Bitumen Gestabiliseerde Materiale te ontwikkel. Wanneer in ag geneem word dat veroudering in die veld tydrowend is, moet vervaardiging van verteenwoordigende monsters vir laboratoriumgebruik versnelde veroudering in die laboratoruim ondergaan. Gegee die kompleksiteite betrokke om goeie korrelasie tussen velden laboratoriumomgewings te verkry, het die navorsing daarna gestreef om die veld- en laboratoriummateriaalgedrag te verenig. Die hoofdoel van die navorsing was om die verouderingsprotokol vir Bitumen Gestabiliseerde Materiale te verenig met die stardaardisering van die verouderingsprotokol as top prioriteit. In hierdie studie het laboratorium resultate bevestig dat die verskillende aard van voorbereidings- meganismes inherent in BSM-skuim en BSM-emulsie bydra tot onversoenbare materiaalgedrag. Resultate het bevestig dat voorbereiding van BSM-skuim ’n funksie van waterrepulsie het en met die byvoeging van aktiewe vullers dominieer dit die materiaalgedrag byna onmiddelik. Anders as BSM-skuim is die voorbereiding van BSM-emulsie beide ’n funksie vir die breek van emulsie tydens die begin fase en die geleidelike vrystelling van vog oor tyd. In hierdie geval het BSM-emulsie se materiaalgedrag die invloed van aktiewe vuller getoon nadat die emulsie gebreek het. Gevolglik, weens die waargenome verskille rakende materiaalgedrag is die vereniging van die voorbereidings- protokols vir BSMs nie suksesvol nie. In terme van inagneming van aktiewe vullers in die finale voorbereidingsprotokol vir BSM’s, is deur navorsing bevind dat aktiewe vullers neig se neiging om vog te absorbeer in die beginstadia dit benodig dus ‘n langer verouderingstyd vir die ontrekking van die geabsorbeerde vog. Hoewel die gebruik van aktiewe vullers ’n impak het op die voorbereiding, reverdig dit nie die verlenging van die verouderingstyd vir die insluiting daarvan in BSM nie, siende dat sementering nie een van die gewenste eienskappe van hierdie materiaal is nie. BSMs word hoofsaaklik verkies vir sy buigsaamheid in paveiselsturkture. Om die mengselontwerp prosesse te vereenvoudig, was aktiewe vullers dus weggelaat in die finale voorbereidingsprotokol. Ter afsluiting was verskeie voorbereidings protokolle getoets en ontwikkel om te help met die vervaardiging van versoenbare materaalgedrag in beide veld-en-laboratoriumomgewings. Deur die versoening van kern materiaal eienskappe soos die elastisiteitsmodulus, lang termynewewigvog kondisies en skuifparameters, is ’n aanvaarbare gestandariseerde voorbereidingsprotokol vir BSM-skuim en BSM-emulsie bedoel vir aanwending in industriele laboratoriums regoor Suid Afrika suksesvol ontwikkel.
37
Gowenlock, Cathren. "Near infrared curing of high performance coil coatings." Thesis, Swansea University, 2014. https://cronfa.swan.ac.uk/Record/cronfa42537.
Abstract:
This thesis has investigated Near Infrared (NIR) curing, a fast thermal curing technique for polyester coil coatings used in exterior building applications where fast line speeds are required. The aim has been to further understanding of the NIR cure mechanism. UV/Vis/NIR spectroscopy and curing trials with two types of AdPhos NIR ovens were used to assess the influence of NIR absorbing pigment locus on cure. Firstly, carbon black was removed from red and brown coatings and this resulted in a wider cure window, but re-siting this pigment in the primer layer was unable to maintain coating colour due to top coat opacity. Then the addition of 1 wt.% NIR absorbing pigment to the backing coat was shown to increase top coat PMT by ca. 46°C, thus enabling line speed or oven power settings to be reduced. The convection cure of white coatings with carbon black primers was investigated and a 5 wt.% loading was able to reduce top coat cure time by ca. 3s. In-situ scanning Kelvin probe (SKP) studies showed that rates of coating delamination by cathodic disbondment remained unchanged for primer carbon black loadings of up to 3.5 wt.%. Silver coatings are particularly difficult to cure by NIR, so glass and mica coated flake were investigated as alternatives to aluminium flake, but resulted in coatings with hiding powers reduced by more than 75%. Further formulation suggestions for silver coatings were made, and emissivity and pigment morphology were suggested as potential factors in cure. Finally, NIR pigment additions of up to 10 wt.% to transpired solar collector (TSC) coatings were investigated, and were found to have a much smaller influence on TSC steady state surface temperature than reducing wind speed. An outdoor study of TSC temperature profile revealed that this closely mirrored the incident solar irradiation profile.
38
Catley, David Gerald. "Thermal curing of concrete with conductive polymer technology." Thesis, Sheffield Hallam University, 2009. http://shura.shu.ac.uk/19431/.
Abstract:
Concrete is used on the majority of all construction projects. It is manufactured using the core constituents of a cement binder, typically Portland Cement, proportions of coarse and fine aggregates and water. The strength development of concrete is achieved by the addition of water that reacts with the binder in the form of a hydration reaction. This hydration reaction or strength development is dependant on two primary curing factors, time and temperature. Increasing the rate of strength development of concrete by elevating the curing temperature at early ages has advantages of maximising concrete production and reducing manufacturing time. Increasing the temperature of early age concrete up to 70 deg C is used in precast plants where it is critical for a minimum strength to be achieved within a certain time period to allow the removal of the concrete sections from moulds and forms. Various practices are adopted by precast concrete manufacturers to achieve the early strengths required to maximise production, both thermal and non-thermal. These include heating the various mix constituents of the concrete, using unnecessarily high cement contents within the mix, using large quantities of chemical admixtures or by increasing the ambient temperature of plants within which the elements are manufactured. In precast concrete plants the use of steam to elevate the curing temperature of the concrete is the most commonly adopted technique. However, it is inefficient and rarely provides controlled temperatures to the concrete as recommended in approved codes of practices and standards. This research programme has investigated the use of an alternative heating technology for concrete curing, optimising a unique Conductive Polymer Technology (CPT). The application and optimisation of the CPT material to provide heat curing to concrete within the laboratory, in-situ and within precast concrete plants has been investigated. The electrical properties of the CPT were investigated to determine their relationship with the size of the concrete elements. This was done for various CPT materials with different Characteristic Resistances. Having gained an in depth understanding of the electrical properties of the CPT, various heating Jackets were designed and manufactured to thermally cure concrete elements at early ages. The Jackets were designed with various outer protective materials. The effect of CPT curing on the strength and shrinkage, both at early ages and long-term, was determined. The thermal performance of the heating jackets was determined for each application including the uniformity of the heating provided into the concrete element. The interaction of the heat generated by hydration and CPT heating for larger elements was also investigated. The results showed that the CPT materials varied depending upon their manufacture and required target resistance. The thermal blankets had the capability to uniformly heat concrete elements at various ambient temperatures, to temperatures required by standards and approved codes of practice for accelerated curing of concrete. This uniform heating resulted in greater compressive strength of laboratory scale concrete elements with reduced shrinkage. The research identified the important parameters for CPT jacket design andmaterials selection e.g. the importance of the contact between CPT heating elements and the concrete element and the selection of appropriate insulation materials. The test programme also investigated the durability of CPT under different exposure conditions. The results from testing the CPT material under conditions such as freeze thaw, heating & cooling and wetting & drying showed that wetting and drying had the most significant affect on the CPTs resistance, altering by 10%. Other tests of durability included punching holes of various sizes into the CPT samples to determine their effect on the CPT's resistance. This was found to be directly linked to the area of CPT material removed. The manufacture, performance and operation of the CPT materials has also been investigated to provide an understanding of its mode of heating and its effect on concrete curing. The concept of maturity has been used to determine relationships between strength development and thermal curing and energy requirement for thermal curing when using CPT.
39
Wehrle, Robert J. "The Curing and Degradation Kinetics of EPDM Rubber." Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1420455803.
40
Fu, Liwei. "Laser curing of inks for plastic electronic applications." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/2005999/.
Abstract:
The development of the plastic electronics industry has drawn great interest and inspired technology innovations in a broad area. This has stimulated the rapid development of flexible circuitry manufacturing technologies, including advances in conductive inks, printing technology and most importantly the novel curing technology - laser based curing (or Laser Direct Write). This has the ability to replace the conventional environmentally damaging and time consuming chemical etching method in current Printed Circuit Board (PCB) manufacturing. The work presented in this thesis is an investigation into a frequency doubled Nd:YAG laser curing process of epoxy-based micro-sized particulate silver inks. This 532nm laser curing process filled the gap as no research reported for solidifying conductive microparticle silver ink using this particular laser wavelength at 532nm. This 532nm laser curing process also extended the curing technology with a fast localized heating process. The composition of the epoxy-based conductive silver ink was studied in this investigation. The laser wavelength of 532nm was selected as the silver microparticles can absorb the laser energy more efficiently without the risk of damaging the material compared to infrared wavelength. Liquid-phase epoxy-based particulate silver inks deposited on flexible substrates were irradiated by laser beam at the wavelength of 532nm. This produced a smooth and cured ink with an effectively reduced electrical resistivity. A new laser curing mechanism theory was proposed based on the presented experimental research. 532nm has shown benefits in protecting the flexible substrate used from thermal damage, owing to the high transmittance of the wavelength through the substrate material. Unlike massive solvent evaporation observed in CO2 laser curing at 10.6µm, laser curing at 532nm, transported the solvent component by expelling solvent liquid from the ink system as a result of a radical change in solvent dynamic viscosity at an increased temperature and the molecular excitation followed by the Marangoni effect. Chemical cross-linking reactions to resin system were evidenced by Fourier Transform Infrared Spectroscopy (FTIR), resulting in a fully cured ink with reduced electrical resistivity. Epoxy-based silver ink's physical properties such as density, thermal conductivity were mathematically defined based on a new temperature evolution for use in a 3-D finite element (FE) modelling. A Time-dependent solver was chosen for modelling the thermal field in a 532nm laser curing process of epoxy-based conductive silver ink within COMSOL Multiphysics 4.3b. The modelling results were compared to the experimental thermal images for FE model validation. The impact to laser curing results by changing the absorption of the epoxy-based conductive silver ink was investigated in this FE model.
41
Zilic, Elvis. "Radiation curing and grafting of charge transfer complexes." Thesis, View thesis, 2008. http://handle.uws.edu.au:8081/1959.7/19385.
Abstract:
Charge transfer (CT) complexes have been used in a number of radiation polymerisation processes including grafting and curing. The complexes studied include donor (D) monomers like vinyl ethers and vinyl acetate (VA) with acceptor (A) monomers such as maleic anhydride (MA). Both UV and EB have been utilised as radiation sources. The complexes are directly grafted to these substrates in the presence of radiation. The complexes yield novel copolymers when radiation cured with concurrent grafting improving the properties of the finished product. The term cure grafting has been proposed for this concurrent grafting process. Studies in basic photografting work to complement the cure grafting have been proposed. The role of solvent in grafting is discussed, particularly the effect of aromatics in photografting to naturally occurring trunk polymers like wool and cellulose. The effect of the double bond molar ratio (DBMR) of the DA components in grafting is examined. The ultraviolet (UV) conditions for gel formation during photografting, hence the importance of homopolymer yields in these processes is reported. A plausible mechanism to explain the results from this photografting work is proposed. The significance of these photografting studies in the related field of curing, especially in UV and ionising radiation (EB) systems, is discussed. EB curing and cure grafting of charge transfer (CT) monomer complexes is investigated. The EB results are compared with UV curing and cure grafting of the same complexes. The work has been extended to include EB/UV curing and cure grafting of thiolene systems. The significance of these results in the potential commercial application of these complexes is discussed. Variables affecting the UV/EB curing and cure grafting of thiolenes on cellulose have been studied. These include effect of varying the type of olefin, increasing the functionality of the thiol, use of acrylate monomers and oligomers in hybrid systems, altering the surface structure of the cellulose and finally the role of air in these processes particularly with EB. Photopolymerisation of the thiol-enes in bulk has also been investigated. The thesis content is based on the published work of 14 research papers over the course of the project.
42
Zilic, Elvis. "Radiation curing and grafting of charge transfer complexes." View thesis, 2008. http://handle.uws.edu.au:8081/1959.7/19385.
Abstract:
Thesis (Ph.D.)--University of Western Sydney, 2008.Thesis submitted to the University of Western Sydney, College of Health and Science, School of Natural Sciences, in fulfilment of the requirements for admission to the Doctor of Philosophy. Includes bibliography.
43
Goldblatt, Nicholas Zalmon. "The characterisation of manganese (IV) compounds and the study of the thermal decomposition of potassium chlorate alone and with Mn(IV) and other oxides and salts." Thesis, Brunel University, 1998. http://bura.brunel.ac.uk/handle/2438/5260.
Abstract:
Manganese dioxide compounds are preferred curing agents for Polysulphide resins used as sealants in industry. These are required to have consistent setting characteristics and the investigation was initiated to characterise a number of proffered compounds of this type an to establish criteria by which an informed choice could be made of an optimum curing ages for a specific set of conditions. Several different chemical and physical properties were examined and critical parameters were established. A compound - sodium birnessite- was identified as a significant agent in the determination of curing properties. It was synthesised and its curing properties alone and in combination with other manganese dioxide compounds was evaluated. In an effort to find a specific reaction which might be used to characterise manganese dioxide curing agents it was decided to examine the classical reaction between these compounds and potassium chlorate. A literature search revealed major contradictions in the reported conditions under which potassium chlorate undergoes thermal decomposition as result of which it was decided to study the decomposition of potassium chlorate alone and in the presence of manganese dioxide and other catalysts. During this investigation a hitherto unreported high temperature structural change in potassium chlorate at 341° C was identified. The existence of this reversible change was confirmed by Powder Diffraction X-Ray analysis and an orthorhombic (near tetragonal) more open structure was assigned to it. It is suggested that the rapid decomposition of potassium chlorate in the solid state presence of catalysts is related to this change to a more open structure.
44
Prada, Julian Ignacio. "Development of high performance concrete for prestressed bridges." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/19487.
45
陳哲明. "Spectrum analysis and curing ability comparison among curing units." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/18426667528186709636.
46
杜方祥. "self-curing concrete." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/80839335881898391912.
47
Wang, ShengCheng, and 王生城. "Study of Curing Kinetics and Properties of Epoxy/Amine Curing Reactions." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/02391550030852802145.
Abstract:
碩士國立中興大學
材料工程學研究所
85
Epoxy resins has excellent properties,but its brittleness makes someapplication restricted.This study uses ether diamine and polymeric aminecuring agents containing different gel content to cure epoxy resin, the kinetics and physical properties are studied. This study uses three kinetic models to describe the curing behavior of different curing agent.No any of kinetic models can completely correspond to curing reactions accurately,especially when the conversion exceeds 60%.The model with equation dx/dt=(K1+K2x^m)(1-x)^n,includes the n order reaction rate constant and autocatalytic reaction rate constant ,can describe the curing behavior of epoxy resins better than other models .The polymeric amine curing agents with more gel content show a higher loss modulus.The low temperature fractal surface exhibits a local circle-like crack pattern for polymer amine curing agents.This shows the addition of polymer amine curing agents can disperse impact energy and increase the toughness.
48
Faller-Shackleton, Nancy. "A comparison of bond strengths using the plasma arc curing system, the visible light curing system and the argon laser curing system." 1997. http://catalog.hathitrust.org/api/volumes/oclc/48225406.html.
49
林凡皓. "The Optimum Dosage of Self-Curing Admixture for Curing Concrete at Low Relative Humidity." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/33089795702516818188.
Abstract:
碩士國立交通大學
土木工程學系
101
Curing is a very important step toward a more durable, higher strength, and less shrinkage concrete. Since sustainability has been the main stream to counteract global warming, supplementary cementitious materials, such as fly ash and slag, have been used widely to partly replace cement. This makes curing even more important. This study is trying to improve the quality of concrete under low relative humidity with various self-curing admixtures(SCA) and dosages. The compressive strengths, volume change, RCPT, and bond strengths were investigated for concrete specimens with and without SCA. It is found that the optimum SCA dosage is 1% of cementitious material. A 3 days wet cure of specimens with SCA showed comparative strength of specimens without SCA under standard curing. For RCPT, a 5 day wet curing of specimens with SCA showed better resistance than standard cured specimens without SCA. The bond strengths of specimens with SCA, regardless of wet curing regime, are better than specimens without SCA and wet-cured for 28 days. The specimens with SCA demonstrated better bond strength compared to the control specimens at all curing regimes. Keywords: concrete, self-curing, wet curing, compressive strength, RCPT, bond
50
Hsu, Pi-Yu, and 許璧伃. "Effect of curing protocol on degree of conversion and softening of light-curing polymers." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/47140673964093127361.
Abstract:
碩士高雄醫學大學
牙醫學研究所
100
Objective. The purpose of this study was to investigate the effect of light-curing protocol on degree of conversion (DC), and softening of dental composite polymers. Methods. Different curing-protocols were used to investigate the influence of power density and mode of cure on the properties. The modes of cure were continuous with different power intensity, ramp, and pulse-delay irradiation. Degree of conversion was measured by Fourier transform infrared spectroscopy (FTIR). Softening of composite polymers was measured with microhardness before and after ethanol storage. Data were submitted to one-way ANOVA, and correlation analysis with SPSS software. Results. Modes of cure influenced the degree of conversion, microhardness and softening of the polymer. Pulse-delay mode has lower degree of conversion on the bottom of resin. Compare lower power density in continuous mode to other curing modes: lower power density in continuous mode resulted in decreased microhardness of bottom surfaces. Ramp-curing mode has the least softening of composite resin. Conclusion. The ramp curing mode has the best overall performances of degree of conversion, microhardness and softening in ethanol.