Orientador: Edison Bittencourt / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-01T10:14:18Z (GMT). No. of bitstreams: 1 Trochmann_JoseLuizLino_M.pdf: 3861994 bytes, checksum: 5b3f668441856f2e55953e941160192b (MD5) Previous issue date: 2000 / Resumo: Existem fortes demandas por novos materiais poliméricos para lentes oftálmicas, com melhores propriedades físicas e menores custos. As resinas de policarbonatos são de longe as mais utilizadas comercialmente, porém apresentam baixo índice de refração, resistência ao calor e ao impacto. Alternativas aos policarbonatos são necessárias. A compatibílização das especificações de resistência ao calor e de resistência ao impacto é um dos maiores desafios na obtenção destas resinas. Neste trabalho investigou-se o uso de modelos de predição de propriedades físicas, como ferramenta no desenvolvimento de resinas ópticas. Foram estudadas as copolimerizações altemada e em bloco do estireno com di - metacrilatos do etileno glicol. Fazendo uso de modelos e com as especificações de: massa específica P I índice de refração n20o, temperatura de transição vítrea Tg, módulo de cisalhamento G, resistência ao calor e ao impacto foram selecionados os agentes de reticulação, que atendiam a todas especificações ao mesmo tempo. Foram estimadas as frações de alimentação dos agentes de reticulação da mistura reacional. O processo de cura escolhido foi o fotoquímico, por ser mais rápido e de menor custo que os processos de cura termoquímica convencionais. Diversos tipos e concentrações de fotoiniciadores foram testados. Os índices de refração foram medidos em refratômetro de Abbe e comparados com os valores previstos pelo modelo de Lorentz Lorenz. As temperaturas de transição vítrea foram medidas por análise termo e foto calorimétrica, DPC / Abstract: There is a large demand form new polymeric material for use in ophthalmic lens with improved physical properties and lower costs. The polycarbonates resins are by far the most used in the industry. To meet the heat and strength resistance specífications at the same time is one of the most challenges in the development of those resins. There is a large demand form new polymeric material for use in ophthalmic lens with improved physical properties and lower costs. The polycarbonates resins are by far the most used in the industry. To meet the heat and strength resistance specífications at the same time is one of the most challenges in the development of those resins. The photochemical process was elected due to the simplicity and general lower costs compared with the conventional thermochemical processo Several different photoinitiators and concentrations were tested. The refractive index of comonomers separately, cured and uncured resins were measured in an Abbe's refratometer and compared with the data trom the Lorentz - Lorenz prediction model. The glass transition temperature of cured resins were measured using the thermo - calorimetric techniques analyses, DSC-DPC, and compared with data from the van Krevelen's prediction model, for addictive contribution groups. The shear moduli of cured resins were measured with DMA and compared with data trom Treloar - Smith's prediction model, for the respective crosslinking density and length. The formulations selected by using the models, were casting and UV - irradiated with several different UV-light and dark period ratios at constant temperature. Samples were take at predefined curing times for analysis of: conversion, Shore "D" hardness, refractive index, glass transition temperature, shear modulus, softening temperature, strength resistance, heat resistance and visual inspection for defects. The deviation between lhe predicted density data and measured values was about + 1.5%. lhat can be considered a good approximation; for the refractive indexdeviation was about +0,4% Ihat is an excellent approximation; . the glass transition temperature deviations were around +5%. Ihat is also excellent approximation considering the nature of Ihis physical property and finally for lhe shear modulus deviation were between + 1 O a 20% for the less rich in di- melhaaylates, 0.33 til! 0.5. Above those values the model showed a much larger deviation due to lhe entropy elasticity associated to the thennal movements of the bridged segments of the crosslinking agents in the network / Mestrado / Ciencia e Tecnologia de Materiais / Mestre em Engenharia Química

<p>The use of atomistic level simulations like molecular dynamics are becoming a key part in the process of materials discovery, optimization and development since they can provide complete description of a material and contribute to understand the response of materials under certain conditions or to elucidate the mechanisms involved in the materials behavior.</p> <p>We will discuss to cases in which molecular dynamics simulations are used to characterize and understand the behavior of materials: i) prediction of properties of small organic crystals in order to be implemented in a multiscale modeling framework which objective is to predict mechanically induced amorphization without experimental input other than</p> <p>the molecular structure and ii) characterization of temperature dependent spatio-temporal domains of high mobility torsions in several bulk polymers, thin slab and isolated chains; strikingly we observe universality in the percolation of these domains across the glass transition.</p> <p>However, as in any model, validation of the predicted results against appropriate experiments is a critical stage, especially if the predicted results are to be used in decision making. Various sources of uncertainties alter both modeling and experimental results and therefore the validation process. We will present molecular dynamics simulations to assess uncertainties associated with the prediction of several important properties of thermoplastic polymers; in which we independently quantify how the predictions are affected by several sources. Interestingly, we nd that all sources of uncertainties studied influence predictions, but their relative importance depends on the specific quantity of interest.</p>

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The non-reactive Dreiding and the reactive ReaxFF atomic potentials were applied within a family of atom molecular dynamics (MD) simulations to investigate and understand interfacial adhesion in graphene/vinyl ester composites. First, a liquid vinyl ester (VE) resin was equilibrated in the presence of graphene surfaces and then cured, resulting in a gradient in the monomer distribution as a function of distance from the surfaces. Then the chemically realistic relative reactivity volume (RRV) curing algorithm was applied that mimics the known radical addition regiochemistry and monomer reactivity ratios of the VE monomers during three-dimensional chain-growth polymerization. Surface adhesion between the cured VE resin and the graphene reinforcement surfaces was obtained at a series of VE resin “crosslink densities.” Both pristine and oxidized graphite sheets were employed separately in these simulations using a Dreiding potential. The pristine sheets serve as a surrogate for pure carbon fibers while oxidizing the outer graphene sheets serve as a model for oxidized carbon fibers. Hence, the effects of local monomer distribution and temperature on the interphase region formation and surface adhesion can be investigated. Surface adhesion was studied at various curing conversions and as a function of temperature. Uniaxial loading simulations were performed at different curing conversions for both models to predict the composites’ modulus of elasticity, Poisson’s ratio, and yield strength. The same analysis was performed for the neat cured matrix. The glass transition temperature (Tg) for the homogenized composite and neat VE matrix was determined at different degrees of curing. Subsequent MD simulations were performed to predict structural damage evolution and fracture in the neat VE matrix. The ReaxFF potential was used to quantify irreversible damage due to bond breakage in the neat VE matrix for different degrees of cure, stress states, temperatures, and strain rates. The predicted damage mechanisms in the bulk VE thermosetting polymer were directly compared to those for an amorphous polyethylene (PE) thermoplastic polymer.

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The initial objective of this research project was to determine the feasibility of manufacturing carbon fiber-reinforced (CFR) composites with a matrix consisting of a phenylethynyl-terminated version of a thermoplastic poly(etherimide) termed PETU. Successful composite manufacture with 3,000 g/mol (3k) PETU led to a survey of CFR 3kPETU mechanical properties for comparison with other high-performance composites. Encouraging results led to a study of moisture sorption effects on CFR 3kPETU properties. The success of these initial studies spawned the large scale production of 2,500 g/mol (2.5k) PETU. Thermal characterization of neat and CFR 2.5kPETU via differential scanning calorimetry, dynamic mechanical thermal analysis, and parallel plate rheometry resulted in an understanding of the influence of cure time and temperature on reaction progress via both reaction kinetics and monitoring of the glass transition temperature. From the rheological characterization, a two-stage, dual-Arrhenius model was developed to successfully model isothermal complex viscosity over the range of processing temperatures. Neat 2.5kPETU and CFR 2.5kPETU specimens were exposed separately to elevated temperature environments of different moisture and different oxygen concentrations to evaluate the effects of moisture absorption, moisture desorption, and thermal oxidation on material properties. Moisture absorption took place in a 90 °C / 85% relative humidity environment followed by moisture desorption in a 90 °C / 10% relative humidity environment. Thermal-oxidative aging for up to 5000 hours took place at 204 204 °C in environments of four different oxygen partial pressures: 0.0 kPa, 2.84 kPa, 20.2 kPa, and 40.4 kPa. Following exposure to the different aging environments, the specimens were tested for retention of mechanical properties. In addition, moisture sorption properties were measured. Results from the moisture sorption studies on CFR 3kPETU and CFR 2.5kPETU suggest that fully cured composites will withstand moisture absorption and desorption with negligible effects on mechanical properties, whereas, lack of full cure allows moisture sorption to permanently damage the composites. Despite a lack of mass loss or visual evidence of degradation following thermal-oxidative aging, a decline in mechanical properties was observed with the reduction becoming greater with longer aging times and higher oxygen partial pressures. / Ph. D.

Farmaceutická fakulta, Katedra farmaceutické technologie, Hradec Králové, 2014 Vypracovala: Markéta Valentová Školitel: Doc. RNDr. Milan Dittrich, CSc. ABSTRACT STUDY OF POLYESTER DRUG CARRIERS DEGRADATION USING THE DSC METHOD The aim of this work was focused on the study of relations among various parameters of degradation process, such as time-dependent range of glass transition temperature, swelling, erosion, and molar weight decrease. Two model polyesters of two type architectures of polyester molecules were used and monitored during two-week period. In the theoretical part of this diploma thesis are in details described biopolymers with stimulus responsive activity and exploitation of these materials in various biomedical applications in the topic of tissue engineering. The experimental part of this work is directed into the study of molecule degradation parameters, eventually into simulated biodegradation in the in vitro conditions of two different in the type polyesters with the contrast polyester molecule constitution. It was demonstrated that parameter Mn decreases towards the limit values. Between the values of molar weight and glass transition temperature is not Flory-Fox relation in the advanced phase of degradation process. The erosion of the material begins after the lag-time in the dependency...

La grande majorité des résines époxy utilisées aujourd’hui sont issues ou dérivées du bisphénol-A (BPA). Cependant, le BPA est soumis à de très fortes régulations, notamment vis-à-vis de sa récente classification comme substance chimique extrêmement préoccupante par l’agence européenne des produits chimiques (ECHA). Dans un but d’anticiper les évolutions de régulation, ArianeGroup a décidé de remplacer cette substance chimique de ces formulations. Ces travaux de thèse portent donc sur l’élaboration de nouvelles résines époxy biosourcées ayant des propriétés similaires voire supérieures aux références dérivées du bisphénol-A. Pour cela, une bioplatforme de monomères polyépoxydés issus de la vanilline, du méthyl vanillate, du 2,6-diméthoxyphénol et de l’eugénol a été développée. Ces précurseurs biosourcés ont ensuite été utilisés comme précurseurs de réseaux époxyde par réticulation avec des amines. Les réseaux réticulés biosourcés ainsi obtenus ont démontré des propriétés thermomécaniques remarquables bien supérieures à la référence de type DGEBA, notamment en termes de température de transition vitreuse (>300 °C) et taux de coke (>50%). En parallèle de ces travaux, la synthèse de diamines biosourcées, dérivées de la divanilline, et pouvant être utilisées comme agents de réticulation de résines époxy, a été réalisée. Des réseaux époxyde entièrement biosourcés ont ainsi été synthétisés et présentent des propriétés thermomécaniques prometteuses. / Today, most of the epoxy resins produced are derived from bisphenol-A (BPA). However, BPA is subject to strong regulations, particularly because of its recent classification as chemical of very high concern by the European Chemicals Agency (ECHA). In order to anticipate new regulations, ArianeGroup has decided to replace this substance in its applications. The aim of this thesis is to develop new bio-based epoxy thermosets with comparable thermomechanical properties as the ones issued from bisphenol-A-based materials. For this purpose, a bio-platform of epoxy monomers from vanillin, methyl vanillate, 2,6-dimethoxyphenol and eugenol was developed. These precursors were cross-linked with amines used as curing agent to obtain bio-based epoxy networks. The latter demonstrated thermomechanical properties well above the DGEBA-type reference, especially in terms of glass transition temperature (> 300 °C) and char content (> 50%). Finally, the synthesis of bio-based diamines derived from divanillin was developed and enabled the synthesis of fully bio-based epoxy networks with promising thermomechanical properties.