Este trabalho apresenta conceitos da fabricação de compósitos com o objetivo de avaliar a influência das condições do processo de fabricação nas propriedades mecânicas do laminado. É comum utilizar ensaios mecânicos para determinar as propriedades do produto final a fim de otimizar e adicionar confiabilidade ao projeto e o objetivo deste trabalho é estudar uma das fontes de variação das características em compósitos estruturais, que é o processo de cura. Embora pela regra das misturas se considere que a relação ponderada entre os elementos de matriz e reforço resulte na propriedade final do laminado, é necessário entender que existe influência do processo de fabricação para a obtenção deste potencial. O processo de cura é uma das etapas mais importantes na fabricação de componentes em polímeros reforçados e consiste na utilização de certo nível de energia que propicia a polimerização da matriz e formação da estrutura monolítica do material compósito. Para a simulação desta variação, através de ensaios laboratoriais são definidas condições de cura que reflitam uma diferença razoável de temperatura de transição vítrea. Com a definição dos parâmetros de cura, laminados bi diagonais são fabricados por processo de moldagem por transferência de resina assistida por vácuo e as características mecânicas destes laminados são mensuradas em ensaios que seguem padrões normalizados pela ISO em condições de tração, compressão e flexão. Os resultados destes ensaios são comparados entre si, a fim de direcionar o projetista em compósitos para a relevância e impacto do processo produtivo na vida do componente. / This work introduces manufacturing concepts for composites parts targeting to evaluate the influence of manufacturing process conditions in the final mechanical properties of the laminates. It is usual to utilize mechanical tests to define and predict properties of the actual component aiming to optimize and add reliability to the design. The main purpose of this study is to evaluate one of the main sources of variation that becomes form the curing process. Although from the mixture rules is possible to consider the final product property as the weighted relation between matrix and reinforcement properties, its needed to understand that the manufacturing process affects the achievement of this potential. Curing is one of the most important steps on the composites manufacturing and consists in the use of some source of energy to start matrix polymerization and formation of a monolithic structure with at least two phases from when becomes the composites concept. To simulate this variation through laboratorial tests, firstly the curing condition was defined to reflect a reasonable difference of glass transition temperature between the samples. After the definition of the curing condition bi diagonal laminate panels were prepared through vacuum assisted resin transfer molding and their mechanical characteristics evaluated by laboratory tests following international ISO standards in tensile, compression and flexural trials. Results of the tests are compared for the purpose of guiding composites designers for the relevance of manufacturing process and its impact on the component life.

Reinforced polymer composites consist of continuous fibers embedded in a polymer matrix. The matrix is usually a thermoplastic or thermosetting resin. When thermosetting matrices are cured during the manufacture of composite parts, residual stresses develop within the part during the manufacture due primarily the thermally and chemically induced volumetric strains imposed on them. This can lead to shape distortions and sometimes weakening of the structure itself. Curing is the manufacturing process in which the thermoset resin is transformed from a liquid to a solid material. The molecular mechanisms involved in this process are quite complex and not well understood. In the macro-level, in addition to volumetric strains, heat is also generated since most thermoset polymerization reactions are exothermic. The mechanical properties of the thermoset also undergo dramatic changes. The material changes from an initial liquid state to a rubbery gel and finally to a vitrified glassy state. In modern day composite manufacturing, to accommodate for the shape distortions caused due to residual stress formation, the mold geometry is compensated. To do this, accurate predictions of the distortion behavior is preferred via computer simulations. This in turn requires simple mathematical models that can replicate the complex processes that take place during manufacture. One such process that requires attention is the curing of the thermoset. While models exist that assume elastic behavior during cure, they are not accurate throughout the entire cure process. Models based on viscoelastic material during cure offer better prospects in this perspective. However, currently models that are based on full viscoelasticity are either not well defined or are computationally tasking. Viscoelastic materials can be classified further in to thermorheologically simple and complex materials depending on their molecular weights. In simpler terms, thermorheologically simple materials are those that obey the principles of time-temperature superposition (TTS). TTS requires that all response times (i.e., all relaxation or retardation time), depend equally on temperature. This is expressed using the temperature shift function. Master curves can be then generated extending the time scale beyond the range that could normally be covered in a single experiment. However to fully understand the development of viscoelasticity during cure it is also necessary that the effects of the degree of cure of the thermoset on these times be included in the model definition. This requires defining a cure shift function along with the temperature shift function. In the presented work, an attempt is made to develop a simplified methodology to characterize the viscoelastic material properties during curing. Two different methods are investigated in a DMTA instrument to determine the effects of curing on the glassy state of the resin system LY5052/HY5052. A cure shift function was identified in the process. Based on observations it was concluded that the total shift function could be possibly defined as a product of the temperature and cure shift functions. Unique super-master curves were generated as a result. However, these curves showed a dependency of the rubbery modulus on the degree of cure. Hence, in the second paper, the effect of the degree of cure on the rubbery modulus was investigated. Subsequently a model was reformulated from an existing one and this was used to further simplify the super-master curves. Following dynamic testing, it was necessary that macroscopic testing is performed to corroborate the results. The macroscopic experiments utilized for this purpose was stress relaxation tests to determine the viscoelastic Poisson’s ratio of neat resin. The Poisson’s ratio in particular is an important property to study, since it’s interaction with the fiber during curing is critical in the study of residual stresses. The focus of the study is to determine if there is a dependency of the Poisson’s ratio on degree of cure and whether master curves can be generated by horizontal shifting of data. Literature pertaining to the dependency of the Poisson’s ratio on degree of cure is scarce. If appropriate horizontal shifting can be performed, it can be easily compared to the results from dynamic testing to check if the shift factors are truly universal. Also presented is a brief study of the effect of degree of cure and time on the development of viscoplastic strains during curing. This is done by performing creep tests on composite specimens with varying degrees of cure. The experimental results were then used to validate the well-known Zapas-Crissman model for viscoplastic strain evolution with time and investigate how it is influenced by the cure state.

In this project, different MUF resins were synthesized with varying melamine content, F/NH2 molar ratio, number of addition steps and with varying addition order of the reactants during synthesis. Further, it was investigated how these synthesis parameters influenced resin properties including storage stability and free formaldehyde content. Additionally, NMR spectroscopy was used in order to study the resulting chemical structure of the resins and their molecular size and molecular size distribution were examined by SEC and MALDI-TOF-MS. The curing kinetics of the resins were studied by Raman spectroscopy. From the resins, cured glue joints were prepared and the mechanical properties and water resistance of these were tested through tensile shear testing after different pretreatments of the glue joints. It was confirmed that synthesis under both alkaline and acidic conditions resulted in a higher amount of ether bridges in the resin in comparison to synthesis under acidic conditions. Furthermore, a high melamine content and fewer urea additions resulted in resins with a higher amount of methylol groups and less substituted functional groups. Comparatively, when the F/NH2 molar ratio was increased or when formalin was added in two steps, a resin with higher amount of substituted groups and structures of higher degree of condensation was obtained. From the synthesis procedure it was concluded that a long condensation time at alkaline conditions was the most efficient way to achieve a low free formaldehyde content, while a high F/NH2 molar ratio resulted in the highest amount of free formaldehyde. Furthermore, a high amount of flexible ether bridges, low amount of methylol groups, low melamine content, high F/NH2 molar ratio and a high degree of branched chains seem to be important structural parameters for achieving resins with a long shelf life. Additionally, from the SEC-analysis it was found that the resins had an average molecular weight (Mn) between 1000-1600 g/mol and a broad molecular weight distribution, which were further verified by MALDI-TOF-MS. The resins with a high melamine content had shorter chains, and the molecular weight distribution was most significantly increased when the number of addition steps were changed. Through analysis of the curing process it was found that a higher hardener-to-resin mixing ratio resulted in a faster curing process and a higher final degree of cross-linking. Additionally, it appeared as the reaction of methylol groups was less pH-dependent than the reactions of ether bridges and methylene bridges, which both were favored at lower pH. From the kinetic profiles it was observed that the resin with a higher amount of ether bridges and lower amount of methylol groups had a more prolonged curing process. Furthermore, the mechanical testing of the resulting cured glue joints showed no significant difference in tensile strength between the resins when tested in the dry state. However, a reduced tensile strength were observed for the resin with higher melamine content when tested in the wet state, hence indicating that the increased melamine content used in this project is not enough in order to significantly improve the mechanical properties or water resistance of the cured glue joint observable with the used method. / I detta arbete har MUF-hartser syntetiserats med varierande melaminhalt, F/NH2 molkvot och satsningsförfarande av reaktanter under syntes. Vidare undersöktes det hur dessa syntesparametrar påverkar hartsernas egenskaper så som lagringsstabilitet och fri formaldehyd innehåll. Dessutom tillämpades NMR spektroskopi för att studera hartsernas kemiska struktur medan SEC och MALDITOF-MS analyser utfördes för att få en uppfattning om hartsernas molekylvikt samt molekylviktsfördelning. Vidare analyserades hartsernas härdningskinetik med Raman spektroskopi. Från de syntetiserade hartserna förbereddes härdade limfogar vars mekaniska egenskaper och vattenbeständighet studerades genom dragprovstestning efter olika förbehandlingar av fogarna. Från hartsernas kemiska struktur kunde det bekräftas att då syntes utfördes under både basiska och sura betingelser erhölls en högre mängd eterbryggor i hartserna i jämförelse med syntes under endast sura betingelser. Vidare konstaterades det att hartserna med högre melaminhalt samt hartset som tillverkades med färre ureasatsningar bestod av en högre mängd metylolgrupper och en mindre andel substituerade grupper på melamin och urea. Jämförelsevis resulterade en högre F/NH2 molkvot samt två formalinsatsningar under syntes i en större mängd substituerade grupper och i en högre andel större molekylstrukturer. Från den erhållna mängden fri formaldehyd i hartsen kunde det konstateras att en lång kondensationstid under basiska betingelser var det mest effektiva sättet att sänka detta värde. Jämförelsevis hade hartserna med hög F/NH2 molkvot det högsta innehållet av fri formaldehyd. Då hartsernas lagringstabilitet undersöktes visade det sig att en hög andel flexibla eterbryggor, en låg andel metylolgrupper, en låg melaminhalt, en hög F/NH2 molkvot och en hög andel grenade kedjor resulterade i förbättrad lagringsbeständighet. Från SEC-analysen erhölls hartsernas molekylvikter (Mn) i området 1000-1600 g/mol samt en bred molekylviktsfördelning. Resultaten var vidare bekräftade med MALDI-TOF-MS. Det observerades att hartserna med högre melaminhalt hade lägre molekylvikt samt att hartserna tillverkade med olika antal satsningar hade högst dispersitet. Då hartsernas härdningsförlopp studerades kunde det konstateras att ett högre bladningsförhållande av härdare/harts resulterade i en snabbare härdningsprocess samt i en större andel tvärbindningar i systemet. Dessutom visade det sig att reaktionen med metylolgrupper är mindre pH-beroende än omlagringen av eterbryggor och bildandet av metylenbryggor. De två sistnämda reaktionerna gynnas vid lägre pH. Då de kinetiska profilerna av hartserna jämfördes noterades det att hartset med en högre mängd eterbryggor och en lägre andel metylolgrupper hade en långsammare härdningsprocess. Från resultaten av de mekaniska analyserna på de härdade limfogarna kunde det konstateras att ingen signifikant skillnad i dragstyrka fanns mellan de olika fogarna då de testades i torrt tillstånd. Däremot observerades en minskad dragstyrka för hartset med högre melaminhalt då fogarna undersöktes i vått tillstånd. Detta visar på att den ökade melaminhalten som används i hartserna i detta projekt inte är tillräcklig för att resultera i en, med den använda metoden observerbar, förbättrad dragstyrka eller vattenbeständighet hos den motsvarande härdade limfogen.

Replacing solventborne coating with waterborne can reduce emission of VOC from paint shops, and decrease the amount of CO2 released from after-burners. The chemistry of 2K WB urethane coatings includes complex kinetics, with a selectivity which is highly dependent on application and curing conditions. To be able to design a coating process producing stable high quality coatings, it is important to know what factors affect the material properties. In this project, the effect of variations in temperature during curing of 2K WB and 2K SB topcoats have been evaluated in order to determine if there are any measurable effects on the material. The significance of these difference have also been evaluated to substantiate the need for thorough design of the curing process. After evaluation of visual, mechanical and chemical properties, as well as the durability of the cured topcoats, it was found that the effect of curing temperature on the level of gloss on 2K WB topcoats could be seen with the naked eye. Effects on colour, hardness, flexibility, adhesion and durability could also be measured, and revealed apparent changes in the material. Increased curing temperature had effects on both cross-linking density and isocyanate conversion. The heightened temperature contributed to the formation of topcoats with significantly decreased level of gloss and reduced stone-chip resistance, but also increased hardness and chemical resistance to an extent that was deemed significant. Varied curing temperature was found to give variations in durability, which with time may give different ageing properties of parts coated under different conditions. Before implementation of this type of waterborne topcoat, it is recommended that several properties be further evaluated, such as the effect of humidity and wet paint viscosity on the material properties. / Genom att ersätta lösningsmedelsburna ytbehandlingar med vattenburna kan man kraftigt reducera utsläppen av VOC från lackeringsverkstäder och minska mängden CO2som frigörs från efterbrännare. Kemin för 2K WB uretanlacker innefattar komplex kinetik med selektivitet som är starkt beroende av applicerings- och härdningsbetingelser. För att kunna konstruera en ytbehandlingsprocess som producerar stabila högkvalitativa ytbehandlingar är det viktigt att känna till vilka faktorer påverkar materialegenskaperna. I detta projekt har effekten av variationer i temperatur under härdning av 2K WB och 2K SB topplack utvärderats för att fastställa om det resulterar i mätbara effekter på den färdiga topplacken. Även signifikansen av dessa skillnader har utvärderats för att bedöma behovet av noggrann utformning av härdningsprocessen. Efter utvärdering av visuella, mekaniska och kemiska egenskaper samt hållbarheten hos de härdade lackerna, fanns det att effekten av härdningstemperaturen på nivån av glans för 2K WB topplacker kunde ses med blotta ögat. Effekter på färg, hårdhet, flexibilitet, vidhäftning och hållbarhet visades också mätbara, och visade på tydliga förändringar i materialet. Förhöjd härdningstemperatur visade sig ha effekter på både tvärbindningsdensiteten och omsättning av isocyanater hos härdaren. En förhöjd härdningstemperatur påvisades även bidra till bildandet av en topplack med avsevärt minskad glansnivå och visst minskad stenskottsbeständighet, men även ökad hårdhet och kemikalietålighet i en omfattning som fanns signifikant. Varierad härdningstemperatur visade sig ge variationer i hållfasthet, som med tiden riskerar att ge olika åldringsegenskaper hos komponenter belagda under olika förhållanden. Innan denna typ av vattenburen täckfärg implementeras i produktion rekommenderas att ytterligare egenskaper utvärderas, såsom inverkan av fukt och våtfärgsviskositet på ytbehandlingens slutegenskaper

The effect of preharvest foliar applications of ethephon and postharvest curing on baked sweet potatoes (Ipomoea batata) were analyzed. Ethylene had negative effects on appearance of baked roots while curing increased the total phenolics in sweet potatoes. Panelists preferred the non-ethylene treated and green or cured over ethylene treated sweet potatoes with respect to texture, color and flavor. No differences in chemical or color properties were found between treatments. The effect of curing time (0, 7, 14 days) on baked sweet potatoes was studied. Curing caused more browning on flesh of sweet potatoes. Moreover, panelists preferred the texture of the green over the cured roots but did not find any differences in flavor sensory quality. The effect of hot water treatment on sprouting and spoilage of cured sweet potatoes was investigated. The most effective treatment was at 53-56 °C for less than 10 min, resulting in less than 60% (control=80%).

No / Degrading infrastructure and applications of structural demolition create tremendous amounts of construction and demolition waste (CDW) all around the world. To address this issue in an effective way, recycling CDW in a most appropriate way has become a global concern in recent years. To this end, this study focused on the utilization of CDW-based materials such as hollow brick (HB), red clay brick (RCB), roof tile (RT), glass (G) and concrete (C) in the production of geopolymer mortars. These materials were first collected from an urban transformation area and then subjected to an identical two-step crushing-milling procedure to provide sufficient fineness for geopolymerization. To investigate the influence of blast furnace slag (S) addition to the CDW-based mixtures, 20% S substituted mixture designs were also made. Fine recycled concrete aggregates (FRCA) obtained from crushing and sieving of the waste concrete were used as the aggregate. A series of mixtures were designed using different proportions of three distinct alkali activators such as sodium hydroxide (NaOH), sodium silicate (Na2SiO3) and calcium hydroxide (Ca[OH]2). To improve their applicability, the mixtures were left to cure at room temperature rather than the heat curing which is frequently applied in the literature. After 28 days of ambient curing, the 100% CDW-based geopolymer mortar activated with three different activators reached a compressive strength of 31.6 MPa, whereas the 20% S substituted geopolymer mortar achieved a compressive strength of 51.9 MPa. While the geopolymer mortars activated with only NaOH exhibited poor performance, it was found that the use of Na2SiO3 and Ca(OH)2 improved the compressive strength. Main geopolymerization products were related to NASH, CASH, and C(N)ASH gel formations. Our results demonstrated that mixed CDW-based materials can be employed in the manufacturing geopolymers, making them potential alternatives to Portland cement-based systems by being eco-friendly, energy-efficient, and comparable in compressive strength. / This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 894100.

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Yes / This paper evaluates the influence of mineral admixtures partially replacing cement, sea sand replacing quartz, sea water replacing fresh water on ultra-high performance concrete (UHPC). The fluidity and mechanical properties were studied. Besides, the impermeability, chloride resistance and freeze-thaw resistance were investigated. Failure modes, scanning electron microscope (SEM) analysis, mass loss, relative dynamic modulus of elasticity and mechanical properties of UHPCs after freeze-thaw cycles were conducted. The results showed the fluidity of UHPC paste gradually increases with the improvement of water-binder ratio. It is recommended that the water-binder ratio of UHPC be set at 0.19. The fluidity also increases with the improvement of the content of slag, fly ash and water reducer, but decreases with the improvement of silica fume content. The flexural and compressive strengths of UHPC enhance with the improvement of the content of silica fume, but reduce with the improvement of the content of fly ash and slag. The UHPCs made of quartz sand, river sand and sea sand, all, achieve a high strength. UHPCs prepared at standard curing conditions, with or without steel fibers, mixed by artificial seawater and made of sea sand, exhibited excellent impermeability and chloride resistance. The frost resistant grade of all UHPC specimens prepared by standard curing are greater than F500 exhibiting excellent freeze-thaw resistance and sustainability.

Syfte: Att undersöka och jämföra effekten av olika LED-lampor genom mätning av konversionsgrad, härdningsdjup och mikro-hårdhet på en universal nano-komposit. Detta utifrån frågeställningarna: - Stämmer härdningslampornas verkliga irradians överens med den som uppges i produktdatabladen?- Kan härdningsprocessen effektiviseras genom att ljushärda med högre irradians och kortare härdningstid?Material & Metod: Materialegenskaperna - konversionsgrad, härdningsdjup och mikro-hårdhet mättes för kompositen Filtek Supreme XTE (3M ESPE) med fem LED-härdningslampor och olika härdningstider (kort, medellång, lång tid). LED-lamporna som användes i studien var L.E.Demetron II (Kerr), Mini LED (Satelec), D-Light Pro (GC), Epilar Deepcure-S (3M ESPE) och Flashmax P3 (CMS Dental). LED-lampornas spektralfördelning erhölls med en CCD-spektrometer (Avantes Inc.) kopplad till en integrerande sfär (Gooch & Housego) med en fiberoptisk kabel (Avantes Inc.). Data analyserades med ensidig och tvåsidig variansanalys (ANOVA-test) följt av Tukey-test. Resultat: En kort härdningstid och en härdning med låg irradians gav en lägre konversionsgrad, härdningsdjup och mikro-hårdhet jämfört med härdning med längre tid och hög irradians.Slutsats: Härdningslampornas verkliga irradians överensstämmer med irradiansen som uppges i produktdatabladen. En tillräcklig polymerisering uppnås med alla härdningslampor vid samtliga härdningstider. Härdningsprocessen kan effektiviseras och/eller förbättras genom att tillföra mer energi på kortare tid. Att förlänga härdningstiden utöver tillverkarens rekommendationer har en positiv effekt på materialegenskaperna – ökad konversionsgrad, härdningsdjup och mikro-hårdhet. / Aim: To investigate and compare the effect of different LED curing devices by measuring degree of conversion, curing depth and micro-hardness of a universal nanocomposite, based on the questions:- Does the actual irradiance of the curing lamps match the one specified in the product data sheets?- Can the curing process be done more efficiently by light curing with a higher irradiance and a shorter curing time?Materials & Methods: The material properties degree of conversion, curing depth and microhardness were measured for the Filtek Supreme XTE (3M ESPE) composite with different LEDs and after curing at different curing times (short, medium, long). The light curing units used in the study were L.E.Demetron II (Kerr), Mini LED (Satelec), D-Light Pro (GC), Epilar Deepcure-S (3M ESPE) and Flashmax P3 (CMS Dental). The spectral irradiance of the LEDs was obtained with a CCD spectrometer (Avantes Inc.) connected to an integral sphere (Gooch & Housego) with a fiber optic cable (Avantes Inc.). Data were analyzed with one- and two-way ANOVA test followed by Tukey test. Results: Short curing times and low irradiance results in lower values of the material properties compared to longer curing times and higher irradiance.Conclusion: The actual irradiance of the curing lamps is consistent with that stated in the product data sheets. Sufficient polymerization was achieved with all curing lamps at all curing times. The curing process can be made more efficient and/or be improved by adding more energy in less time. Extending the curing time has a positive effect on the material properties – an increased degree of conversion, depth of cure and micro-hardness.