Dissertations / Theses on the topic 'Kinetics of non-isothermal crystallization'

This work has mainly focused on the poly (L-lactide) (PLLA) which is a material for multiple applications with performances comparable to those of petrochemical polymers (PP, PS, PET, etc. ...), readily recyclable and also compostable. However, PLLA has certain shortcomings that limit its applications. It is a brittle, hard polymer with a very low elongation at break, hydrophobic, exhibits low crystallization kinetics and takes a long time to degrade. The properties of PLLA may be modified by copolymerization (random, block, and graft) of L-lactide monomers with other co-monomers. In this thesis it has been studied the crystallization and morphology of random copolymers poly (L-lactide-ran-ε-caprolactone) with different compositions of the two monomers since the physical, mechanical, optical and chemical properties of a material depend on this behavior. Thermal analyses were performed by differential scanning calorimetry (DSC) and thermogravimetry (TGA) to observe behaviors due to the different compositions of the copolymers. The crystallization kinetics and morphology of poly (L-lactide-ran-ε-caprolactone) was investigated by polarized light optical microscopy (PLOM) and differential scanning calorimetry (DSC). Their thermal behavior was observed with crystallization from melt. It was observed that with increasing amounts of PCL in the copolymer, there is a decrease of the thermal degradation. Studies on the crystallization kinetics have shown that small quantities of PCL in the copolymer increase the overall crystallization kinetics and the crystal growth rate which decreases with higher quantities of PCL.

L'objectiu de la tesi és estudiar la cinètica de les cristal·litzacions primàries en vidres metàl·lics mitjançant simulacions de tipus phase field. Una cristal·lització primària és una transició de fase sòlid-sòlid on la fase que cristal·litza (fase transformada o fase secundaria) té una composició química diferent de la fase precursora (fase no transformada o fase primària).
Les dades experimentals obtingudes a partir de l'estudi calorimètric de cristal·litzacions primàries s'analitzen generalment en el marc del model KJMA (Kolmogorov, Johnson & Mehl, Avrami). Aquest model proporciona l'evolució temporal de la fracció transformada basant-se en tres hipòtesis:
- Els nuclis de la fase secundaria estan distribuïts aleatòriament en tot l'espai.
- El creixement d'aquests nuclis és isotròpic.
- El creixement s'atura únicament per xoc directe (hard impingement).

En la cristal·lizació de vidres metàl·lics s'ha observat experimentalment un alentiment de la cinètica respecte del comportament calculat emprant la citada cinètica KJMA. Aquest alentiment s'explica a la literatura en base a que en aquest tipus de transformacions, controlades per difusió, la interacció entre els cristalls no és directa sinó que es produeix a través dels perfils de concentració (soft impingement) i, a més, l'evolució d'aquests perfils de concentració causa canvis en la concentració de la matriu amorfa, estabilitzant la i per tant fent que la nucleació de nous cristalls esdevingui no aleatòria. Diversos autors han proposat modificacions del model KJMA per tal d'intentar superar aquestes limitacions, basats bé en consideracions geomètriques, bé en aproximacions de camp mitjà. A pesar de tot, cap d'aquests models és capaç d'explicar satisfactòriament la cinètica observada en cristal·litzacions primàries. L'objectiu d'aquest treball ha estat la simulació realista de la cinètica de les transformacions primàries per trobar una explicació consistent a les diferències observades entre les dades experimentals i els models teòrics disponibles.
Per tal de poder descriure de forma realista el procés de cristal·lització primària s'ha d'estudiar el procés de nucleació i creixement de la fase secundaria alhora que es resol l'equació de difusió en la fase primària. En aquest treball s'ha emprat un model de simulació phase field que permet estudiar aquest sistema introduint una nova variable lligada al camp de concentració que pren dos valors diferents segons es tracti de fase transformada o no transformada. Amb aquest tipus de models també es poden introduir diferents protocols de nucleació i per tant estudiar independentment els efectes de la nucleació en la cinètica. D'aquesta manera s'han realitzat simulacions en 2 i 3 dimensions de cristal·litzacions primàries amb diferents graus de fracció transformada final). Els resultats de les simulacions s'ha comparat amb el model KJMA i, contra el que es preveia, s'ha obtingut un bon acord entre les fraccions transformades del model KJMA i de les simulacions. Donat que el model KJMA no reprodueix satisfactòriament el comportament experimental d'aquest resultat es dedueix que ni el soft impingement ni la nucleació no aleatòria son les responsables de l'alentiment de la cinètica obtingut en cristal·litzacions primàries.
Per tal de trobar una explicació físicament convincent del comportament observat experimentalment s'ha aprofundit en l'estudi teòric de les cristali·litzaciones primàries, incloent-hi l'efecte dels canvis composicionals que tenen lloc en la matriu a mesura que la transformació es produeix. Aquest fet, tot i ser conegut a la bibliografia, ha estat sistemàticament ignorat en l'elaboració de models cinètics. En concret, s'ha fet palès que canvis en la composició química de la fase primària han d'afectar de forma radical a la viscositat, que varia fortament a prop de la transició vitrea, i han de produir canvis en les propietats de transport atòmic. Això s'ha modelat a través de l'assumpció d'un coeficient de difusió depenent de la concentració, en base a la relació modificada d'Stokes-Einstein entre la viscositat i el coeficient de difusió. Les simulacions phase-field amb un coeficient de difusió d'aquest tipus donen lloc a una cinètica més lenta i que mostra un acord excel·lent amb la cinètica experimentalment observada en cristal·litzacions primàries de vidres metàl·lics. Per tant, les simulacions phase field confirmen que la cinètica de les cristal·litzacions primàries està controlada fonamentalment pel canvi en les propietats de transport atòmic, mentre que els efectes de soft impingement i nucleació no aleatoria, tot i estar presents, son secundaris.
El objetivo de la tesi es estudiar la cinética de las cristalizaciones primarias en vidrios metálicos mediante simulaciones de tipo phase field. Una cristalización primaria es una transición de fase sólido-sólido donde la fase que cristaliza (fase transformada o fase secundaria) tiene una composición química diferente a la fase precursora (fase no transformada o fase primaria).
Los datos experimentales obtenidos a partir del estudio calorimétrico de cristalizaciones primarias se analizan generalmente en el marco del modelo KJMA (Kolmogorov, Johnson & Mehl, Avrami). Este modelo proporciona la evolución temporal de la fracción transformada basándose en tres hipótesis:
- Los núcleos de la fase secundaria están distribuidos aleatoriamente en todo el espacio
- El crecimiento de estos núcleos es isotrópico
- El crecimiento se detiene únicamente por choque directo (hard impingement).

En la cristalización de vidrios metálicos se ha observado experimentalmente un retardo de la cinética respecto del comportamiento calculado usando la cinética KJMA. Este retardo se explica en la literatura en base a que en este tipo de transformaciones, controladas por difusión, la interacción entre los cristales no es directa sino que se produce a través de los perfiles de concentración (soft impingement) y, además, la evolución de estos perfiles de concentración causa cambios en la concentración de la matriz amorfa, estabilizándola y por tanto haciendo que la nucleación de nuevos cristales sea no aleatoria. Varios autores han propuesto modificaciones del modelo KJMA para intentar superar estas limitaciones, basados bien en consideraciones geométricas, bien en aproximaciones de campo medio. A pesar de todo, ninguno de estos modelos es capaz de explicar satisfactoriamente la cinética observada en cristalizaciones primarias. El objetivo de este trabajo ha sido la simulación realista de la cinética de las transformaciones primarias para hallar una explicación consistente a las diferencias entre los datos experimentales y los modelos teóricos disponibles.
Para describir de manera realista el proceso de cristalización primaria se tiene que estudiar el proceso de nucleación y crecimiento de la fase secundaria a la vez que se resuelve la ecuación de difusión en la fase primaria. En este trabajo se ha usado un modelo de simulación phase-field que permite estudiar este sistema introduciendo una nueva variable ligada al campo de concentración que toma dos valores diferentes según se trate de fase transformada o no transformada. Con este tipo de modelos también se pueden introducir diferentes protocolos de nucleación y por tanto estudiar independientemente los efectos de la nucleación en la cinética. De esta manera se han realizado simulaciones en 2 y 3 dimensiones de cristalizaciones primarias con diferentes grados de fracción transformada final. Los resultados de la simulaciones se han comparado con el modelo KJMA y, en contra de lo que se preveía, se ha obtenido un buen acuerdo entre las fracciones transformadas del modelo KJMA y de las simulaciones. Dado que el modelo KJMA no reproduce satisfactoriamente el comportamiento experimental, de este resultado se deduce que ni el soft impingement ni la nucleación no aleatoria son las responsables del retardo en la cinética obtenido en cristalizaciones primarias.
Para encontrar una explicación físicamente convincente del comportamiento observado experimentalmente se ha profundizado en el estudio teórico de las cristalizaciones primarias, incluyendo el efecto de los cambios composicionales que tienen lugar en la matriz a medida que la transformación se produce. Este hecho, aún y ser conocido en la bibliografía, ha sido sistemáticamente ignorado en la elaboración de modelos cinéticos. En concreto, se ha hecho patente que cambios en la composición química de la fase primaria tienen que afectar de forma radical a la viscosidad, que varía fuertemente cerca de la transición vítrea, y tienen que producirse cambios en las propiedades de transporte atómico. Esto se ha modelado a través de la asunción de un coeficiente de difusión dependiente de la concentración, en base a la relación de Stokes-Einstein modificada entre la viscosidad y el coeficiente de difusión. Las simulaciones phsae-field con un coeficiente de difusión de este tipo dan lugar a una cinética más lenta y que muestra un acuerdo excelente con la cinética experimentalmente observada en cristalizaciones primarias de vidrios metálicos. Por tanto, las simulaciones phase-field confirman que la cinética de las cristalizaciones primarias está controlada fundamentalmente por los cambios en las propiedades de transporte atómico, mientras que los efectos de soft-impingement y nucleación no aleatoria, aún y estar presentes, son secundarios.
The aim of this thesis is to study the kinetics of primary crystallization in metallic glasses by means of phase-field simulations. A primary crystallization is a solid-solid phase transformation where the crystallized phase (transformed phase or secondary phase) has a chemical composition different than the precursor phase (untransformed phase or primary phase).
Experimental data from calorimetric studies of primary crystallization are usually studied in the framework of the KJMA model (Kolmogorov, Johnson & Mehl, Avrami). This model yields the temporal evolution of the transformed fraction on the basis of three main assumptions:
- A random distribution of particle nuclei of the secondary phase
- The growth of these nuclei is isotropic
- The growth is only halted by direct collisions (hard impingement).

In the crystallization of metallic glasses, a slowing down of the kinetics respect the behavior calculated with the KJMA kinetics has been observed. This delay is explained in the literature by the fact that in this kind of transformations, that are diffusion controlled, the interaction between the crystals is not direct but through the concentration profiles (soft impingement) and moreover, the evolution of these profiles causes changes in the concentration of the amorphous matrix, stabilizing it and thus, the nucleation of new nuclei become non random. Several authors had proposed modifications to the KJMA model to try to overcome these limitations, based either on geometrical considerations or in mean field approaches. However, none of these models is able to explain the observed kinetics in primary crystallizations. The aim of this work has been the realistic simulation of the kinetics of primary crystallization to find a explanation to the differences between the experimental data and the available theoretical models.
In order to describe in a realistic way the process of a primary crystallization, the nucleation and growth process of the secondary phase has to be studied at the same time that the diffusion equation is solved in the primary phase. In this work, it has been used a phase field model for the simulations that allows to study this system introducing a new variable, coupled to the concentration field, that takes two different values in each of the existing phases. With these kinds of models, different nucleation protocols can also be introduced and thus, independently study the effects of the nucleation in the kinetics. Therefore, 2 and 3 dimensional simulations of primary crystallization have been performed with several degrees of final transformed fraction. The simulation results have been compared with the KJMA model and, unexpectedly, a good agreement between the simulations and the KJMA model has been obtained. As the KJMA model does not reproduce satisfactorily the experimental behavior, from this result can be deduced that neither the soft impingement nor the non random nucleation are the responsible of the slowing down observed in the kinetics of primary crystallization.
In order to find a physical convincing explanation of the observed experimental behavior, the theoretical study of primary crystallization has been extended, including the effects of the compositional changes that take place in the matrix as the transformation proceed. This fact, notwithstanding being known in the literature, has been systematically ignored in the development of the kinetics models. In particular, it has become clear that changes in the chemical composition of the primary phase have to radically affect the viscosity, that strongly varies near the glass transition, and some changes in the atomic transport properties must occur. This has been modeled through the assumption of a compositional dependent diffusion coefficient, on the basis of a modified Stokes-Einstein relation between viscosity and diffusion coefficient. Phase field simulations with a diffusion coefficient of this type yield a slower kinetics and show an excellent agreement with the kinetics experimentally observed in primary crystallization of metallic glasses. Thus, phase field simulations confirm that the kinetics of primary crystallization is fundamentally controlled by the changes in the atomic transport properties, while the soft impingement and non random effects, although being present, are secondary.

The aim of submitted diploma thesis is the study of non-isothermal crystallization kinetics of polylactide (PLA) with selected agents (1 %) and observation of the emerging crystalline structure under polarizing optical microscope. The agents were talc, a mixture of organic salts with the addition of amorphous SiO2 (HPN 68L) and zinc stearate (HPN 20E) and LAK-301 (potassium salt of 5-dimethylsulfoisophtalate), which is a nucleating agent developer for PLA. The PLA matrix served as a reference. Non-isothermal crystallization took place on a differential scanning calorimeter at cooling rates () 0,3; 0,5; 0,7; 1; 1,5; 2 °C/min After non-isothermal crystallization, the crystalline fraction (Xc) od PLA was evaluated from X-ray diffraction analysis, and the supramolecular structure was observed after chemical degradative etching using confocal laser scanning microscope. The crystallization kinetics were evaluated by the methods of Jeziorny and Mo and the activation energy of the crystallization was determined according to the Friedmann method. All prepared materials were amorphous (Xc 40 % for up to 1,5 °C/min). However, for LAK-301, Xc decreased to 30 % already at the = 2 °C/min and it can be assumed that with increasing its nucleation activity will decrease. A spherulitic structure was observed in all samples, but the number and size of spherulites decreased with increasing and the appearance varied according to the type of agent. Both kinetic models proved to be unsuitable for materials with low Xc and the highest because the rate of crystallization did not change. With the Jeziorny method, it was possible to evaluate the kinetics only for the relative crystallinity Xt = 29–50 % and with the Mo method it was not possible to evaluate the data for the highest for PLA matrix and sample with HPN 68L. The samples with LAK-301 and HPN 68L showed the lowest activation energy.

No presente trabalho, foram processados compósitos de polietileno de alta densidade (PEAD) com hidroxiapatita deficiente de cálcio (HA), com o objetivo de obter materiais com melhores propriedades mecânicas e bioatividade. A adição da HA deficiente de cálcio proporcionou um aumento no módulo de elasticidade (maior rigidez), menor resistência ao impacto e decréscimo do grau de cristalinidade do PEAD, proporcionando uma maior bioatividade ao material. A análise térmica exploratória (sistema não isotérmico) foi realizada por meio da técnica de calorimetria exploratória diferencial (DSC) e foram avaliados os teores de fosfato de cálcio e a velocidade de rotação da rosca no processamento dos materiais. No estudo da cristalização não-isotérmica observou-se uma diminuição da temperatura de cristalização com o aumento da taxa de resfriamento para todos os materiais sintetizados. A energia de ativação (Ea) da cristalização dos materiais foi avaliada por meio dos métodos Kissinger e Ozawa. A amostra com 5% de HA deficiente de cálcio e velocidade de processamento de 200 rpm foi a que apresentou menor valor de energia de ativação, 262 kJ/mol, menor desvio da linearidade e a que mais se assemelhou à matriz de PEAD sem HA. O teor de hidroxiapatita deficiente de cálcio não favorece o processo de cristalização devido à alta energia de ativação determinada pelos métodos descritos. Provavelmente, a velocidade de rotação, favorece a dispersão da carga na matriz de PEAD, dificultando o processo de cristalização. Na aplicação do método de Osawa-Avrami, os coeficientes de correlação indicaram perda na correlação linear. Estas perdas podem estar associadas a uma pequena percentagem de cristalização secundária e/ou à escolha das temperaturas utilizadas para determinar a velocidade de cristalização. Na determinação dos parâmetros pelo método de Mo, as menores percentagens de cristalização apresentaram um grande desvio da linearidade, com coeficiente de correlação bem menor que 1 e com o aumento da percentagem de cristalização, o desvio da linearidade diminui, ficando próximo de 1. Os resultados obtidos mostraram que o modelo de Mo e de Osawa-Avrami não foram capazes de definir o comportamento cinético dos materiais produzidos neste trabalho.
In this work, composites of high density polyethylene HDPE with calciumdeficient hydroxyapatite were synthesized in order to obtain materials with good mechanical properties and bioactivity. The addition of calcium-deficient hydroxyapatite resulted in an increase in elastic modulus (high rigidity), lower impact resistance and lower HDPE crystallinity degree, promoting, in these materials, a higher bioactivity. Scanning thermal analysis (non-isothermal system) was carried out by differential scanning calorimetry (DSC), and it was evaluated the calcium phosphate content added and the screw speed in the processing. In non-isothermal crystallization studies it was observed a decrease in crystallization temperature as the cooling rate was increased for all produced materials. The activation energy of crystallization was evaluated by Kissinger and Ozawa methods. The sample with 5 wt.% of calcium-deficient hydroxyapatite and processed at 200 rpm screw speed showed the lower value of activation energy (262 kJ/mol) and the lower deviation from linearity. Calcium-deficient hydroxyapatite does not promote the crystallization process due to the high activation energy determined by the described methods. Probably the screw speed promotes the dispersion of the filler in the HDPE matrix and hinders the crystallization process. Correlation coefficients in Osawa-Avrami method indicated loss in the linear correlation. These losses might be associated with a small percentage of secundary crystallization and/or the temperatures chosen to determine the crystallization rate. The parameters obteined from Mo method, the lower percentages of crystallization showed a great deviation from linearity, with correlation coefficient much smaller than 1, when increasing the percentage of crystallization, the deviation from linearity decreases, getting closer to 1.The results of Mo and Osawa-Avrami models were not able to set the kinetic behavior of the materials produced in this study.

Metallic glasses possess attractive properties, such as high strength, good corrosion resistance, and superior soft magnetic performance. They also serve as precursors for synthesizing nanocrystalline materials. In addition, a new class of composites having crystalline phases embedded in amorphous matrix is evolving based on selective crystallization of metallic glasses. Therefore, crystallization of metallic glasses and its effects on properties has been a subject of interest. Previous investigations from our research group related to laser assisted crystallization of Fe-Si-B metallic glass (an excellent soft magnetic material by itself) showed a further improvement in soft magnetic performance. However, a fundamental understanding of crystallization and mechanical performance of laser treated metallic glass was essential from application point of view. In light of this, the current work employed an integrated experimental and computational approach to understand crystallization and its effects on tensile behavior of laser treated Fe-Si-B metallic glass. The time temperature cycles during laser treatments were predicted using a finite element thermal model. Structural changes in laser treated Fe-Si-B metallic glass including crystallization and phase evolution were investigated with the aid of X-ray diffraction, differential scanning calorimetry, resistivity measurements, and transmission electron microscopy. The mechanical behavior was evaluated by uniaxial tensile tests with an InstronTM universal testing machine. Fracture surfaces of the metallic glass were observed using scanning electron microscopy and site specific transmission electron microscopy. Fe-Si-B metallic glass samples treated with lower laser fluence (<0.49 J/mm2) underwent structural relaxation while higher laser flounces led to partial crystallization. The crystallization temperature experienced an upward shift due to rapid heating rates of the order of 104 K/s during laser treatments. The heating cycle was followed by termination of laser upon treatment attainment of peak temperature and rapid cooling of the similar order. Such dynamic effects resulted in premature arrest of the crystallite growth leading to formation of fine crystallites/grain (~32 nm) of α-(Fe,Si) as the major component and Fe2B as the minor component. The structural relaxation, crystallization fractions of 5.6–8.6 Vol% with α-(Fe,Si) as the main component, and crystallite/grain size of the order of 12 nm obtained in laser fluence range of 0.39-0.49 J/mm2 had minimal/no influence on tensile behavior of the laser treated Fe-Si-B metallic glass foils. An increase in laser fluence led to progressive increase in crystallization fractions with considerable amounts of Fe2B (2-6 Vol%) and increase in grain size to ~30 nm. Such a microstructural evolution severely reduced the strength of Fe-Si-B metallic glass. Moreover, there was a transition in fracture surface morphology of laser treated Fe-Si-B metallic glass from vein pattern to chevron pattern. Tensile loading lacked any marked influence on the crystallization behavior of as-cast and structurally relaxed laser-treated metallic glass foils. However, a significant crystallite/grain growth/coarsening of the order of two and half times was observed in the fractured region compared to the region around it for the laser-treated partially crystallized metallic glass foils. The simultaneous effects of stress generation and temperature rise during tensile loading were considered to play a key role in crystallite/grain growth/coarsening.

This thesis is concerned with the development of methods and models to aid in optimization and development of new materials for Fused Filament Fabrication (FFF). We demonstrate a novel FFF nozzle design to enable the first measurements of in-situ rheology inside FFF nozzles, which is critical for part performance by ensuring that the polymer extrudate is flowing at an appropriate temperature and flow rate during the part build process. Testing was performed using Acrylonitrile butadiene styrene filament and a modified Monoprice Maker Select 3D printer. Tests using the default temperature control settings of the printer showed an 11 °C drop in temperature and significant fluctuations in pressure, during printing and while idle, of ± 2 °C and +/-14 kPa. These deviations were eliminated at lower flow rates with a properly calibrated proportional–integral–derivative (PID) system. At high flow rates, drops in temperature as high as 6.5 °C were observed even with a properly calibrated PID, providing critical input to the impact of flow rate and PID calibration on polymer melt temperature inside FFF nozzles. Pressure readings ranging from 140-6900 kPa were measured over the range of filament feed rates and corresponding extrusion flow rates. Theoretical predictions of pressure profiles, assuming a powerlaw fluid model, matched well with experimental results. Our nozzle prototype succeeded in measuring internal conditions of FFF nozzles for the first time, thereby providing several important insights into the printing process which are vital for monitoring and improving FFF printed parts. Furthermore, finite difference simulations based on first principles analysis are presented which are capable of quantifying the effect of processing conditions on the properties of semicrystalline parts made by FFF. Each layer was modelled as a rectangular cross section which was broken down into smaller elements for modelling. Crystallinity of each element was calculated using a parallel Avrami model which accounts for changes in crystallization rate due to temperature and multiple crystallization mechanisms. The amount of polymer diffusion, also referred to as the degree of healing, was calculated using a novel incremental diffusion model which accounted for not only changes in reptation time due to temperature but also restrictions to healing due to crystallinity. To the authors knowledge, this is the first healing model capable of accounting for the effect of crystallinity on healing and is relevant to any process involving healing of crystalline interfaces; not just FFF. Cumulative shear stresses between each layer and at the bottom of the part were also calculated for the first time using a force balance model by assuming constant shear strain throughout each layer. Simulations were performed using typical printing conditions for polyether ether ketone. In the first layer of a 24 layer part, the average degree of crystallinity, healing, and shear stress were 25.0%, 53.8% and 19.4 MPa respectively. The degree of crystallinity and healing at layer 22 (which represented the steady state values) were 18.4-25.0% and 51.4% respectively. When crystallinity was not accounted for, varying the printing parameters and material properties supported the use of high temperatures and specific heat in addition to a low printing speed, heat transfer coefficient, and thermal conductivity to maximize part properties. These conditions also supported crystallization, however, which led to a simultaneous reduction in the part properties when crystallinity was taken into account. These contradictory effects will need to be considered when optimizing the printing parameters, though the optimal balance will be highly dependent on the material used and the limitations of the printer. Experimental validation of the accuracy of the heat transfer and polymer diffusion models was performed using an amorphous polymer (polyether imide). Single road wide parts were printed at various nozzle temperatures, bed temperatures, and printing speeds and the results were compared to the simulated results. The predicted shear stress in the bottom of the part ranged from 2.3-3.8 MPa and correlated to warpages at the corners of each part of 1.2-2.4 mm. A linear increase in warpage with predicted shear stress was observed supporting the shear stress model. Predicted degrees of healing ranged from 2-90% but the experimental results ranged from 15-36%. Results of the healing model underpredicted strength at low printing speeds and over predicted strength at high printing speeds. The experimental validations showed the capabilities of the models, but the effect of printing speed will need to be investigated further to improve the accuracy of the healing model.
MS

Le développement de nanomatériaux à propriétés optiques et fonctionnalisés pour un marquage spécifique est en plein essor dans le domaine de l'imagerie biologique. Parmi les agents de contraste exogènes déjà utilisés, les marqueurs fluorescents tels que les nanocristaux semi-conducteurs (CdSe/ZnS,...) et les molécules organiques naturelles (GFP,...) ou synthétiques (fluorescéine,...) souffrent respectivement de clignotements (blinking) et de photo-blanchiment (bleaching) c'est-à-dire d'une faible tenue au rayonnement lumineux incident. Récemment, la microscopie de Génération de Second Harmonique (GSH) à partir de structures non-centrosymétriques de certains matériaux ou molécules optiquement non linéaires (ONL), s'est révélée un outil particulièrement prometteur. Les inconvénients du clignotement et du photo-blanchiment sont en effet absents pour le processus non linéaire de GSH. De plus, le principe de fonctionnement des marqueurs ONL repose sur un processus non résonant, contrairement aux marqueurs fluorescents, ce qui est un avantage décisif pour le choix de la longueur d'onde d'excitation des nanosondes. Pour des illuminations dans le proche infrarouge, cela permet de limiter l'énergie déposée dans le milieu biologique, d'augmenter la profondeur d'imagerie et enfin de bien séparer spectralement les signaux des marqueurs ONL de l'auto-fluorescence naturelle de certains échantillons. Notre objectif, dans ce contexte, était la synthèse et la caractérisation de nouvelles nanosondes ONL de forme sphérique et de taille inférieure à 100nm. Le matériau de structure cristalline non centrosymétrique retenu est l'iodate de fer (Fe(IO3)3) car ses éléments chimiques sont peu toxiques et que ses propriétés paramagnétiques peuvent également donner un contraste en imagerie par résonance magnétique (IRM) ce qui est potentiellement intéressant par rapport à d'autres cristaux ONL tels que ZnO, KNbO3, BaTiO3 et KTP. D'un point de vue synthèse, les microémulsions inverses sont bien référencées dans la littérature pour leur rôle de gabarit permettant un bon contrôle de la taille et de la morphologie des nanomatériaux obtenus par co-précipitation. Dans ce travail, les nano-réacteurs ont été préparés à partir des systèmes AOT/alcane/eau et Triton/1-hexanol/cyclohexane/eau. De manière très originale et pratique, le développement d'un banc optique de diffusion Hyper-Rayleigh (HRS) a permis de suivre in-situ et en temps réel les cinétiques de cristallisation des nanoparticules de Fe(IO3)3 en fonction de conditions expérimentales variables. Les mécanismes de croissance et de cristallisation des nano-bâtonnets de Fe(IO3)3 ont été élucidés en combinant d'autres techniques physico-chimiques usuelles comme la diffraction des rayons X, la diffusion dynamique de la lumière et la microscopie électronique en transmission. Nous avons démontré que la température et la nature du tensioactif influencent les forces d'interaction à l'interface organique-inorganique ce qui permet, pour certaines conditions expérimentales, de réduire la taille et la polydispersité des nanocristaux en fin de processus. Toutefois, avant d'envisager l'utilisation de ces derniers en tant que marqueurs optiques spécifiques, il est nécessaire d'encapsuler ces nanocristaux en raison de la faible stabilité du composé aux pH physiologiques. Les premiers essais de stabilisation en microémulsions par une couche de silice ont permis d'obtenir des nanoparticules de taille ~ 10 nm avec une forte réponse ONL. La caractérisation complète et la fonctionnalisation de ces nanostructures ainsi qu'une optimisation des interactions à l'interface particules - films de tensioactifs constituent les perspectives de ce travail.

Poly(ethylene terephthalate) (PET) is a semi-crystalline polymer that has mechanical and thermal properties suitable for many applications. The rate of crystallization in manufacturing environments influences the final physical, mechanical, and optical properties of PET. Many industrial PET processes occur under dynamic or non-isothermal conditions and in the melt phase. The final material properties are influenced by the size, dimension, and distribution of crystallites and morphology that develop upon cooling from the melt. PET films of varying thickness for optical applications require clarity and transparency. One way achieving clarity and transparency in PET films is to limit or inhibit the quiescent crystallization, while not completely eliminating useful strain-induced crystals. The crystallization behavior of PET is influenced by many things including molecular weight, catalyst remnants, nucleating additives, and the addition of linear and multifunctional comonomers (i.e. branching agents). Branching agents have been reported to inhibit the crystallization of PET. It is of interest to study the effects of branching agents on branched PET (BPET).

In this investigation the influence of branching agent concentration and geometry on the non-isothermal crystallization behavior and kinetics of BPET was studied. To study the influence of branching agent concentration and geometry, two structural isomers of benzenetricarboxylic acid ( n=3) were used at concentrations of 0.10, 0.25, 0.50, and 1.00 mol% (with respect to purified terephthalic acid). The branching agents used were 1,3,5-benzenetricarboxylic acid (trimesic acid, TMA) and 1,2,4-benzenetricarboxylic acid (trimellitic acid, TMLA). TMA and TMLA were used to study the influence of branching agent geometry because TMA is planar and TMLA is non-planar. Two different series of BPET were made to evaluate the influence of catalyst remnants and process on the non-isothermal crystallization behavior of BPET. The Jeziorny-modified Avrami model, the Ozawa model, and the Mo model were applied to study the effects of the branching agent concentration and geometry on the non-isothermal crystallization kinetics of BPET at various cooling rates (5, 10, 20, 50 °C/min).

The results from the study showed that equivalent amounts of TMA and TMLA produced different non-isothermal crystallization results even though the molecular weight and catalyst concentration remained approximately constant. Increasing branching agent content did not produce a systematic decrease in the crystallization peak temperatures Tc. The Mo model was successful in characterizing the non-isothermal crystallization behavior and kinetics of BPET. The crystallization rate was inhibited at concentration of 0.25 and 0.50 mol% TMA and 0.50 and 1.00 mol% TMLA. However, the crystallization rate was enhanced at 0.10 and 1.00 mol% TMA and 0.10 and 0.25 mol% TMLA. It is thought that at small concentrations of the branching agents, regardless of geometry, the branching agents act as nucleating agents. At other branching agent concentrations it is thought that the branching agent geometry influenced the non-isothermal crystallization behavior.

Master thesis deals with the influence of polyvinylacetate, polycaprolactone, poly(butylene-adipate-co-terephtalate) and talc, ethylenevinylacetate, polyethylene glycol and monosodium citrate on the flow properties, mechanical properties and crystallization ability of PLA. The flow properties were studied using the melt flow index and mechanical properties were studied using a tensile test. The crystallinity was studied by differential scanning calorimetry and on a polarization optical microscope equipped with hot stage. Isothermal crystallization was performed at 95 and 105 °C for 3 h and non-isothermal crystallization was performed with a calorimeter at two cooling rates (1 and 10 °C/min). Upon the isothermal crystallization at 95 °C, the formation of denser crystalline structure was observed and the content of crystalline phase increased in most of the samples. The formation of spherulitic structure was observed at 105 °C in samples with 30 % PVAc, 30 % EVA and PEG. Reducing the cooling rate to 1 °C/min at non-isothermal crystallization had nearly no effect on the crystallization process of the most samples; the content of crystalline phase increased in the samples containing PBAT and PEG, which revealed double melting peak during subsequent heating. The crystalline fraction was the most significantly affected by the addition of PEG. All added polymers except PVAc affected the mechanical properties; PBAT, PCL, EVA and PEG increased the strain and decreased the strength and modulus of elasticity. The samples containing monosodium citrate showed unsatisfactory mechanical properties and could not be measured. The samples containing higher concentration of EVA copolymer showed the phase separation.

The thesis is divided into four chapters. They are: introduction, experimental, results and discussion about the free ligands and results and discussion about the complexes. The First Chapter, the introductory chapter, is a general introduction to the study of solid state reactions. The Second Chapter is devoted to the materials and experimental methods that have been used for carrying out the experiments. The Third Chapter is concerned with the characterisations of free ligands (Picolinic acid, nicotinic acid, and isonicotinic acid) by using elemental analysis, IR spectra, X-ray diffraction, and mass spectra. Additionally, the thermal behaviour of free ligands in air has been studied by means of thermogravimetry (TG), derivative thermogravimetry (DTG), and differential scanning calorimetry (DSC) measurements. The behaviour of thermal decomposition of the three free ligands was not identical Finally, a computer program has been used for kinetic evaluation of non-isothermal differential scanning calorimetry data according to a composite and single heating rate methods in comparison with the methods due to Ozawa and Kissinger methods. The most probable reaction mechanism for the free ligands was the Avrami-Erofeev equation (A) that described the solid-state nucleation-growth mechanism. The activation parameters of the decomposition reaction for free ligands were calculated and the results of different methods of data analysis were compared and discussed. The Fourth Chapter, the final chapter, deals with the preparation of cobalt, nickel, and copper with mono-pyridine carboxylic acids in aqueous solution. The prepared complexes have been characterised by analyses, IR spectra, X-ray diffraction, magnetic moments, and electronic spectra. The stoichiometry of these compounds was ML2x(H20), (where M = metal ion, L = organic ligand and x = water molecule). The environments of cobalt, nickel, and copper nicotinates and the environments of cobalt and nickel picolinates were octahedral, whereas the environment of copper picolinate [Cu(PA)2] was tetragonal. However, the environments of cobalt, nickel, and copper isonicotinates were polymeric octahedral structures. The morphological changes that occurred throughout the decomposition were followed by SEM observation. TG, DTG, and DSC measurements have studied the thermal behaviour of the prepared complexes in air. During the degradation processes of the hydrated complexes, the crystallisation water molecules were lost in one or two steps. This was also followed by loss of organic ligands and the metal oxides remained. Comparison between the DTG temperatures of the first and second steps of the dehydration suggested that the water of crystallisation was more strongly bonded with anion in Ni(II) complexes than in the complexes of Co(II) and Cu(II). The intermediate products of decomposition were not identified. The most probable reaction mechanism for the prepared complexes was also Avrami-Erofeev equation (A) characteristic of solid-state nucleation-growth mechanism. The tempemture dependence of conductivity using direct current was determined for cobalt, nickel, Cl.nd copper isonicotinates. An activation energy (ΔΕ), the activation energy (ΔΕ ) were calculated. The temperature and frequency dependence of conductivity, the frequency dependence of dielectric constant, and the dielectric loss for nickel isonicotinate were determined by using altemating current. The value of s parameter and the value of density of state [N(Ef)] were calculated.

L'existence de différentes phases, polymorphes, sels, solvates et co-cristaux génère de nombreuses questions concernant la caractérisation des matériaux à l'état solide, en particulier pour l'industrie pharmaceutique. Les problématiques relatives à l'identification des phases et à la surveillance des processus de crist(allisation et de transitions de phase ne peuvent toutefois pas toujours être résolues à l'aide de techniques d'analyse conventionnelles. Dans ce travail, nous développons une approche analytique basée sur le phénomène d'optique non-linéaire de génération de seconde harmonique (GSH). La GSH est une technique sensible et précise pour détecter l'absence de centre d'inversion au sein d'une structure cristalline et pour suivre des modifications subtiles de symétrie. A travers plusieurs exemples, nous montrons comment les mesures de GSH résolues en température (TR-SHG) peuvent être utilisées pour étudier les diagrammes de phases et pour suivre les mécanismes et cinétiques des transitions de phase, y compris pour des transitions de type ordre-désordre. La combinaison de la TR-SHG avec les techniques classiques (XRPD, DSC et microscopie) permet ainsi de démontrer l'utilité et le potentiel de l'optique non-linéaire dans la caractérisation des propriétés physico-chimiques des matériaux
The existence of different phases, including polymorphs, salts, solvates and co-crystals generates concerns in the characterization of solid-state materials, especially for the pharmaceutical industry. Issues related to the identification of phases and the monitoring of phase transitions and crystallisation processes cannot be always solved using conventionnal techniques. In this work, a complementary analytical approach based on the nonlinear optical phenomena of second harmonic generation (SHG) is developed. SHG is a sensitive and accurate technique to detect the absence of inversion center in the crystalline structure and to capture subtle symmetry changes. Herein, through several examples we show how Temperature-Resolved SHG (TR-SHG) measurements van be used to study phase diagrams and for tracking mechanisms and kinetics of phase transitions including order-disorder phase transitions. The combination of TR-SHG with classical techniques (XRPD, DSC and microscopy) reveals in this study the usefulness and the potentials of nonlinear optics in material characterization

This diploma thesis deals with study of crystalline structure of polyhydroxybutyrate (PHB), which contains different types of additives for studying of their nucleation activity and which were prepared by mixing. It is about boronitrid (BN), sacharin, hydroxapatit, plasticizer Tegmer a tree types of talc. Crystal structure was analysed by differential scanning calorimetry and x-ray diffraction, supramolecular structure was observed by optical microscopy (polarized and confocal laser scanning). Nucleating activity was evaluated by isothermal and non-isothermal crystallization made on calorimeter and heated table of optical microscope. There is not influence of additives on crystallographic structure, but additives affects number and size of spherulites including crystal domains defects, which can have impact on final mechanical properties. BN and talcs react as nucleating agents, other additives during low and high cooling speeds (vc) inhibit nucleation and in middle cooling speeds are without effect. Nucleating activity is not evaluated by numerically, because decrease of crystallization temperature together with vc is not linear. Results of direct methods are based on picture analysis, which is great benefit for understanding of crystal behaviour of PHB.

The influence of seven additives on the crystallization ability of polylactide (PLA), melt flow index (MVR) and mechanical tensile properties was studied. Pressed plates with a thickness of 0.8 mm were tested. Selected additives added in amounts of 0.5 and 1.0% were as follows: talc, sodium benzoate, mixtures of organic salts with amorphous SiO2 and zinc stearate, metal salt, phosphate salt, and potassium salt of 5-dimethylsulfoisophthalate (LAK-301 - nucleating agent developed for PLA). Non-isothermal crystallization measurements were performed at different cooling rates (0.3; 0.5; 0.7; 1.0 and 1.5 ° C). All nucleation agents increased the MVR of PLA except talc; the largest increase (9-fold and 24-fold) was the addition of metal salt. The additives did not fundamentally change the mechanical properties. All samples were rather brittle (the most brittle with LAK-301), the modulus of elasticity was around 1.2 GPa for all samples, the strength of PLA was increased the most by the addition of 1% talc (by 12%) and the elongation at break was increased by organic salt with SiO2. All samples with nucleating agents content of 1% were amorphous (crystalline content did not exceed 2%). Thus, the addition of reagents did not support the crystallization process during rapid cooling, even in the case of LAK-301. However, LAK-301 was acting as an excellent nucleating agent at slow cooling rates (1.5 °C / min and below). The nucleation activity of the additives decreased in the following order: LAK-301, organic salt with zinc stearate, talc, organic salt modified with amorphous SiO2 and phosphate salt. Samples with sodium benzoate and metal salt were crystallizing on cooling in several steps and it was not possible to use the method of Dobrev and Gutzow to evaluate the nucleation activity.

Selon leur formulation et leur mise en forme et grâce à leur complexité microstructurale induite, les polymères thermoplastiques bénéficient d’une grande diversité de propriétés thermomécaniques. Cependant, l’évolution de la microstructure de ces matériaux au cours de leur utilisation reste difficile à identifier. Afin de mieux comprendre les modifications microstructurales ayant lieu au cours de sollicitations thermomécaniques, différentes techniques non destructives de caractérisation en temps réel et in situ ont été développées. Dans ce contexte, un Poly (Ethylène Téréphtalate) (PET) amorphe et semi-cristallin a été étudié afin de mettre en évidence l’effet de la microstructure sur les propriétés macroscopiques du matériau. Pour ce faire, plusieurs couplages de techniques expérimentales de caractérisation ont été mis en œuvre tels que la spectroscopie Raman et la diffraction/diffusion des rayons X couplées au système de VidéoTraction™ ou la spectroscopie Raman couplée à la calorimétrie différentielle à balayage (DSC) pour une caractérisation des micromécanismes de déformation et du comportement thermique du matériau respectivement. Le suivi de différentes bandes vibrationnelles judicieusement identifiées a permis d’établir un nouveau critère robuste et capable de mesurer avec exactitude le taux de cristallinité du matériau ou de remonter aux températures caractéristiques de sa morphologie (Tg, Tc, Tcc, Tf) grâce aux informations extraites d’un spectre Raman. De plus, un système de caractérisation relaxationnelle par un couplage de la spectroscopie diélectrique dynamique avec un essai de traction a été utilisé afin de mettre en évidence l’effet de la mobilité moléculaire sur la déformation élasto-visco-plastique du PET. D’un point de vue mécanique, les principaux micromécanismes de déformation ont été étudiés en temps réel pendant un essai de traction à différentes températures et vitesses de déformation vraies constantes : l’orientation macromoléculaire, l’endommagement volumique, le développement de mésophase et la cristallisation induite sous contrainte, ont été observés et quantifiés in situ en utilisant les couplages précédents au synchrotron Petra III de Hambourg et au synchrotron Elettra de Trieste. En parallèle, une étude de la mobilité moléculaire (paramètre déterminant à la prédominance de tel ou tel micromécanisme de déformation) a été menée via des analyses relaxationnelles réalisées au cours de la déformation du matériau. En complément, des expériences en temps réel, des études post mortem par les techniques précédemment citées et par radiographie X, microscopie électronique à balayage et tomographie X ont été réalisées afin d’apprécier l’influence de la relaxation mécanique du PET
According to their formulations and forming processes and thanks to the complexity of their induced microstructure, thermoplastic polymers show a wide range of thermomechanical properties. However, the identification of the evolution of the microstructure of these materials during their use remains difficult. To better understand the microstructural changes occurring during thermomechanical loadings, various in situ and non-destructive techniques of characterization have been used. In this context, a Poly (Ethylene Terephthalate) (PET) amorphous and semi-crystalline was studied in order to highlight the effect of the microstructure on the macroscopic properties of the material. This way, different coupling systems combining several experimental characterization techniques have been implemented such as Raman spectroscopy and X-rays diffraction/scattering coupled to the VidéoTraction™ system or Raman spectroscopy coupled with differential scanning calorimetry (DSC) for the characterization of the deformation micro-mechanisms and the thermal behavior of the material respectively. Monitoring specific vibrational bands thoroughly identified allowed the establishment of a new robust criterion which enables to accurately measure the crystallinity ratio of the material and the identification of the characteristic temperatures of its morphology (Tg, Tc, Tcc, Tm). In addition, a relaxational characterization system by coupling dynamic dielectric spectroscopy to a tensile test has been used in order to highlight the effect of molecular mobility on the elasto-visco-plastic deformation of PET. From a mechanical point of view, the main deformation micro-mechanisms have been studied in real time during a tensile test at different temperatures and constant true strain rates: macromolecular orientation, volume damage, development of mesophase and strain induced crystallization were observed and quantified in situ using the coupled characterization technics presented previously at Petra III (Hambourg) and Elettra (Trieste) synchrotrons. In parallel, a study of the molecular mobility (a determining parameter for the predominance of one deformation micromechanism to another) was conducted via relaxational analysis performed during the deformation of the material. In addition to in situ experiments, post mortem analysis by the previously mentioned technics and by X radiography, scanning electron microscopy and X tomography were performed to assess the influence of the mechanical relaxation of the polymer

碩士
國立清華大學
材料科學工程學系
93
We apply gamma ray irradiation from 250 kGy to 1000 kGy on Poly(4-methyl-l-pentene) (commercial name is TPX) specimens in air and oxygen environment. During DSC tests, we set different cooling rates to measure the data of TPX specimens. We proceeded the cooling rate by 1℃、2.5℃、5℃、10℃、20℃、40℃ and 60℃ per minute. The DSC data indicated that the specimens with low gamma-ray dose have large peak which is clear to see, and in high gamma-ray dose the peak become small and not easy to see, especially the specimens irradiated in oxygen environment. In order to proceed the non-isothermal crystallization kinetics of irradiated Poly(4-methyl-1-pentene), we separate the double peak curve by modified Gaussian equation with gama distribution . For TPX non-isothermally crystallized by cooling at constant rates, we can find exponent n in Ozawa plots with two tendencies. One is that Ozawa exponent n decreases with decreasing crystallization temperature for the same interval of cooling rates, the other is the exponent n increasing with increasing cooling rates. We have a conclusion that Ozawa apparach method can not meet the high cooling rates data. For the study of Poly(4-methyl-l-pentene), it can be seen that Ozawa exponent n increases with increasing crystallization temperature, n is almost from 1.0 to 3.0, which means the pre-determined nuclei might exist before cooling.

碩士
高雄醫學大學
醫藥暨應用化學研究所碩士在職專班
96
Biodegradable aliphatic polyesters were synthesized by Showa Highpolymer company, trademarked “BIONOLLE”. BIONOLLE is a white crystalline thermoplastic such as poly(butylene succinate), poly(ethylene succinate) and polybutylene succinate adipate copolymer. The mechanical properties of BIONOLLE were similar to that of polyethylene. Avrami and Ozawa equations were used to analyze the experiment data in this study. Because the melting point of PBS is high and the mechanical properties are worse. In addition, the PTS is uncrystallized. Therefore, PBS and PTS were mixed to improve their properties. PBS containing 5wt% PTS can be able to reduce the crystallization performance, and make the polymer strength to enhance. Furthermore, the brittle fracture situation of PBS is also improved simultaneously. The thermostability of PBS/PTS (90/10) is similar to that of PBS/PTS (95/05). With PTS percentage increasing under the same condition, the thermal degradation temperature was decrease. Increasing the PTS percentage is helpful to the thermal degradation of PBS.

碩士
國立清華大學
化學工程學系
92
The morphology of block copolymer can be tailored by blending with the corresponding homopolymer if the homopolymer is uniformly solubilized in the microdomain. Depending on the molecular weight of the homopolymer, the blend system may exhibit “wet-brush” phase behavior or “dry-brush” phase behavior in the melt. In this report, we study the morphology and crystallization kinetics of a series of wet-brush blends of a symmetric polybutadiene-block-poly( ε -caprolactone) （ PB-b-PCL ） and a low molecular weight homopolymer PB. In the study of melt state morphology, we found that as the weight fraction of PB increases, the microdomain structure of the blend system changes from lamellae(wPB=0.5~0.6) to hexagonally-packed PCL cylinder(wPB=0.7~0.75) and liquid-like packed PCL sphere (wPB=0.8~0.85). The crystallization behavior of PCL is strongly affected by this morphological transformation; their crystallization rate was highly sensitive to the microdomain morphology. The fixed cooling rate experiment in the DSC revealed that freezing temperature exhibits one to one correlation with the meet to the melt state morphology. The isothermal crystallization kinetics in wPB=0.7 was properly described by the classical Avrami equation, indicating that the crystallization started from heterogeneous nucleation followed by long-range crystal growth. There has a maximum in crystallization rate Due to the competition between crystallization driving force and mobility of PCL block. We also found an unusual increase in crystallization rate at –41 ℃ ,because at very low crystallization temperature, homogeneous nucleation dominated crystallization rate and increased overall crystallization rate. After PCL crystallized, melt state morphology were all destroyed and become the morphology consisting of alternating amorphous PB and crystalline PCL lamellae, show the “breakout” crystallization mode.

碩士
國立成功大學
資源工程學系碩博士班
96
The major electric power supply is thermal power plant in Taiwan, instead of nuclear power plant. It is estimated that above 2,000,000 tons of coal ash was produced annually in Taiwan, the other fly ash of 80% and another bottom ash of 20%. Coal ash has been investigated continuously in the world in order to reduce effect of coal ash on environment. Reuse of fly ash has rather fruitage in ten years, treatment of bottom ash is restricted in landfill, lack of place is produced in the further. Therefore, resource recycle of the bottom ash has become an urgent subject recently. The chemical composition of bottom ashes are the same with the raw materials of glasses. The research used bottom ashes as materials to produce glass by melt after adding network modifier (15wt%CaCO3, 10wt%Na2CO3). Base on Differential Thermal Analysis, the glass transition temperature is 801℃ and the softing point appears in 832℃. There is a crystallization exothermic peaks in 931℃ before 1200℃. After heat treated on the glass and analyzed by X-ray diffraction, the crystal phase is anorthite, but has different composition in several temperatures. Representative DTA thermographs taken at different heating rates can get the volume fraction of crystallites, χ. This study find that the mean value of the kinetic exponent, n, is three and the growth mechanism of crystal particles, m, is two using the equation derived by K. Matusita. From the kinetic exponent, the activation energies of crystallization were caculated to be 524.5kJ mol-1 for Marotta`s equation and 378.3kJ mol-1 for Kissinger`s equation. It shows that the activation energies have deviation without considering the crystallization and heat treated mechanism. The growth mechanism of crystal particles is two, so the crystal habit is tabular. The surface and cross-section of the glass ceramic show the tabular crystal`s growth by scanning electron microscopy, and the calculation was proved by this. The cross-section of the glass ceramic by optical microscopy shows that it is denser and more porous than the initial glass.

碩士
國立臺北科技大學
分子科學與工程系有機高分子碩士班
107
This study used various instruments to analyze and identify the properties and crystallization behavior of a series of Polybutylene terephthalate/Polytetramethylene Ether Glycol thermoplastic Polyester Elastomer (TPEE) synthesized in this laboratory. The first part is the identification of components and properties. Firstly, the results of PBT and PTMEG copolymerization were confirmed by FTIR and NMR spectroscopy. The actual peak ratio of PTMEG in each material was calculated from the corresponding characteristic peak area of NMR spectrum. When the Tg point was tested by DMA, it was found that the Tg point decreased significantly with the increase of PTMEG content. The same trend appeared when the Tm test by DSC. Indicating that the softness of the whole molecular chain was obtained with the increase of the soft chain PTMEG content And the Tm and Tg decrease. However, there was no significant difference between pure PBT and other copolymers at the Td test (5%) by TGA, indicating that the initial cracking step was dominated by the hard segment PBT. The second part is non-isothermal crystallization kinetics. The temperature is raised and lowered by DSC at 2, 5, 10, 20 °C/min. The crystallization curve is observed. It is found that under the same cooling condition, when the proportion of PTMEG increases, the temperature range of the crystallization peak was lowered. And then analyzed and compared using the Avrami and Mo models, and the crystallization activation energy was calculated by the Kissinger equation. The third part is a temperature-controlled hot plate with a polarizing microscope to make the materials isothermally crystallize and observe the behavior and crystallization rate changes. Similar to the DSC non-isothermal crystallization, at the same temperature, the crystal growth rate decreases as the PTMEG content increases. The crystal morphology, with the increase of PTMEG content, the more obvious the color of negative spherulite field. Indicating that the soft segment increases the flexibility of the molecular chain, and the stack is more regular. In the same material, as the crystallization temperature increases, the molecular chain kinetic energy is enhanced and it is difficult to form a stack, the color different becomes inconspicuous, and the shape of the crystal deviates from the spherical shape.

碩士
國立清華大學
材料科學工程學系
93
Non-isothermal crystallization kinetics of Poly(4-methyl-1-pentene) samples irradiated by γ-ray in air and vacuum with 100-400 kGy was studied using Differential Scanning Calorimeter (DSC). Different cooling rates at 2.5, 5, 7.5, 10, 15 and 20 ℃/min were applied to investigate the exothermic behavior of crystallization. According to the heat flow along the continuous cooling temperature, the heat flow is related to the degree of crystallization. However, we found double peaks in the diagram of the heat flow versus the cooling temperature. Two crystalline processes were expected to coexist. It is possible that the phenomenon comes from the up-down disorder in crystal structure. In this research, we separated the double peaks by curve fitting. We used the probability density function of the inverse Gaussian distribution to separate two peaks with different parameters. After that, Avrami approach modified by Jeziorny and Ozawa approach were applied to analyze the non-isothermal crystallization kinetics. Generally speaking, the exponent n of Avrami approach is around 1.5~2 for Peak 1 and 1~1.5 for Peak 2 at different cooling rates when TPX samples are irradiated by γ-ray with different doses in air and vacuum. The exponent n of Ozawa approach decreases from 2~3 to 0.5~1 for peak 1 and peak 2 with the decreasing crystallization temperature. The activation energy of non-isothermal crystallization were computed by Kissinger’s approach. The crystallization activation energy for peak 1 decreases from 667.01 KJ/mol to 452.63 KJ/mol and 407.75 KJ/mol with the increasing dose of γ-ray in air and in vacuum, respectively. The crystallization activation energy for peak 2 decreases from 484.18 KJ/mol to 420.97 KJ/mol and to 342.17 KJ/mol with the increasing dose of γ-ray in air and in vacuum, respectively.

碩士
國立中山大學
材料科學研究所
91
Non-isothermal crystallization of the PET/PTT copolyesters was studied at five different cooling rates over 1-20oC/min by means of differential scanning calorimetry (DSC). Both the Ozawa equation and the modified Avrami equation have been used to analyze the crystallization kinetics. The non-isothermal kinetics of most copolymers cannot be described by the Ozawa analysis, except the copolyester with a composition of 66.3% trimethylene- (TT) and 33.7 %ethylene- terephthalates (ET). It may be due to the inaccuracy of the Ozawa assumptions, such as the secondary crystallization is neglected. From the kinetic analysis using the modified Avrami equation, the Avrami exponents, n, were found to be in the range of 2.43-4.67 that are dependent on the composition of the copolyesters. The results indicated that the primary crystallization of the PET/PTT copolymers followed a heterogeneous nucleation and a spherulitic growth mechanism during the non-isothermal crystallization. In the cases of the copolyesters with either TT or ET less than 10%, we found the molten temperature is a key factor to decide whether the Ozawa equation can be succeeded in analyzing the dynamic crystallization. For the non-isothermal crystallization, a single exothermic peak was detected in each DSC curve regardless of the composition and the cooling rate. It indicated that a single-mode distribution of the crystallite sizes was formed during the cooling process. After the non-isothermal crystallization, the melting behavior of the specimens was monitored by temperature modulated DSC (TMDSC) in the conventional mode and the modulated mode. Multiple endothermic peaks were observed in both modes. The wide-angle X-ray diffraction (WAXD) patterns of these copolymers showed that the peak height became sharper and sharper as the crystallization temperature increased, but the position of the diffraction peaks did not change apparently. It indicated that the multiple melting behaviors did not originate from the melting of the crystals with different structures. The melting behavior of these PET/PTT copolyesters can be explained logically by using the melt-recrystallization model. From the reversing and non-reversing signals of TMDSC, the melting-recrystallization-remelting phenomena were further verified. In addition, a small endothermic peak was found at the highest melting temperature in the reversing thermogram for TT-enriched copolyesters. It is reasonably to believe that this endotherm is attributed to the melting of the crystals that are formed in regime I during the heating scan. The cocrystallization of the PET/PTT copolyesters was studied using DSC and WAXD. A clear endothermic peak in the DSC thermogram was detected over the entire range of copolymer composition. A minimum melting temperature was found for the copolyester with 50% ET. The WAXD patterns of these copolymers can be divided into two groups with sharp diffraction peaks, i.e., PET type and PTT type crystals. The transition of crystal structure between PET type and PTT type occurred around the eutectic composition (50 % ET and TT), determined from the variation of the melting temperature with the composition. In addition, the fiber diagram and the WAXD pattern of the copolyester with the eutectic composition showed a different crystalline structure. These results indicated that the cocrystallization behavior of the PET/PTT copolyesters was isodimorphic.

碩士
義守大學
材料科學與工程學系碩士班
93
Recently, a number of amorphous alloy systems with a wide supercooled liquid region (ΔTx is above 50 K, ΔTx is defined as the difference between the glass transition temperature Tg and the onset crystallization temperature Tx) and high glass forming ability (have bulk dimensions in the range of 5 to 50 mm) have been discovered. These amorphous alloys promise to allow the production of large-scaled bulk glassy materials by casting at low cooling rates. In addition, availability of these bulk metallic glasses (BMGs) enables unique approaches to form complex-shaped precision components by viscous flow forming at the temperature within the supercooled liquid region. In order to control the precision forming process at the temperature of supercooled liquid region and avoid the occurrence of crystallization, it is important to investigate the kinetics of crystallization by isothermal annealing the amorphous alloy at the temperature within the supercooled liquid region. The Zr-Cu-Al-Ni metallic glass system is one of the most promising BMGs with exceptional wide super cooled liquid region exceeding 100K, high glass-formation ability, and superior engineering properties. In addition, Jang and some other scholars also reported that adding silicon into the Zr65Al7.5Cu17.5Ni10 base alloy can significant increase the thermal stability of the Zr65Al7.5Cu17.5Ni10 base alloy. The highest activation energy of crystallization, 370 kJ/mole, and relatively long incubation time during isothermal annealing at the supercooled temperature region were found to occur at the Zr61Al7.5Cu17.5Ni10Si4 alloy. Therefore, the Zr61Al7.5 Cu17.5Ni10Si4 alloy was selected for studying its crystallization kinetics under isothermal annealing. According the result of non-isothermal DSC analysis, both of the Avrami n values of Zr61Cu17.5Al7.5Ni10Si4 and Zr65Cu17.5Al7.5Ni10 amorphous alloys exhibited decreasing trend with increasing temperature as well as increasing crystallization ratio. The n value varies from 4 to 2 with increasing temperature and crystallization ratio. In addition, the transition point of nucleation-crystal growth occurred at about 64% crystallization for Zr61Cu17.5Al7.5Ni10Si4 alloy and about 47% crystallization for the Zr65Al7.5Cu17.5Ni10 alloy. This demonstrates that the Zr61Cu17.5Al7.5Ni10Si4 amorphous alloy has better thermal stability than the base alloy. After isothermal annealing Zr61Cu17.5Al7.5Ni10Si4 and Zr65Cu17.5Al7.5Ni10 amorphous alloys, the Zr2Cu crystal was observed at the early stage for both of alloys. Then the Zr2Ni crystal、the ZrNi2Al crystal and the ZrCu crystal were also observed term by term with increasing crystallization ratio. Moreover, the Zr3Al crystal and the Zr3Al2 crystal were found after isothermal annealed the Zr61Cu17.5Al7.5Ni10Si4 amorphous alloy at 703K for 2500 s (which corresponds to 70 % crystallization). Finally, the Zr2Si was crystallized after 4 hours isothermal annealing at 703 K. The result of line scan analysis revealed that Si atoms tend to segregate around the Zr2Cu crystal at the early stage of crystallization. This increases the difficulty of grain growth for Zr2Cu. Additionally, the result of TEM observation also revealed that the grain growth Zr2Cu crystal in these two amorphous alloys is controlled by a thermal activated process of Arrhenius type, which is described by Dt3 – D03 = k0 tg exp (-Q/R•Ta).This kinetics shows that the crystalline grain grows in three dimensions at the initial crystallization stage. The activation energy for the grain growth of Zr2Cu is 155 ± 20 kJ/mole in the Zr61Al7.5Cu17.5Ni10Si4 amorphous alloy, which is larger than that, 100 ± 10 kJ/mole, in Zr65Cu17.5Al7.5Ni10 amorphous alloy. This also indicates that the Zr61Cu17.5Al7.5Ni10Si4 amorphous alloy has higher thermal stability than the base alloy.

碩士
高苑科技大學
化工與生化工程研究所
98
The purpose of this research is on the study of thermal degradation and isothermal crystallization of PLA for the neat PLA and the PLA/Starch blends. All the results are based on the combination of characterizations of the Fourier Transform Infrared Spectroscopy (FTIR), the thermogravimetry analyzer (TGA) and the Polarizing Microscope (POM). The FTIR spectra show that there are only physical interactions between the PLA matrix and the starch. The TGA analysis gives that both the thermal degradation reaction and the activation energy of starch are higher that those of PLA but the former requires higher thermal degradation temperature for the same degradation percentage. Finally, the examinations of polarizing microscope (POM) illustrate that the diameter growth rate of PLA spherulite is increased as the addition of starch is small (e.g. 5 %). When the larger amount of starch are used to produce blends, the diameter growth rate of PLA spherulite of the resulting blends us reduced. This result may be due to hindrance of steric effect of excess starch.

碩士
國立中山大學
材料科學研究所
92
The crystallization kinetics and the melting behavior of a random copolyester with equal amounts of ethylene- and trimethylene- terephthalate units were studied by using a modulated differential scanning calorimeter in both conventional mode (DSC) and modulated mode (TMDSC). Polarizing light microscope (PLM) was used to study the spherulite growth rates and spherulite patterns. Isothermal crystallization was performed at temperatures (TC) between 115 and 142℃. The Avrami exponents, n1, were found to increase from 3.00 to 3.22 with an increasing TC. At the highest TC, it should be a sporadic nucleation with spherical growth, i.e. n1 = 4. The value of n1 less than 4 and the slow rate of crystallization indicate that both primary and secondary crystallization occurs in parallel rather than in series. Triple- and double- melting peaks were observed for the melting behavior of DSC at 10℃/min and of TMDSC at 2℃/min. The results of WAXD, DSC and TMDSC indicate the coexistence of two melting mechanisms, i.e., dual morphologies and the recrystallization process. The Hoffman-Weeks plot gave an equilibrium melting temperature of 176.6℃ from the reversing curves of TMDSC. In this study, the regime II→III transition temperature can be estimated from the inverse of the half-time of crystallization as overall growth rate and the growth rate. Meanwhile, a clear change in morphology from negative regular to banded spherulites was also observed around 132℃ by using PLM. The heat of fusion of polymer is customarily evaluated through the melting point depression measurements with the thermodynamic melting points. Application of the Flory equation to the PET/PTT random copolyesters diluted with di-n-butyl phthalate gave the values of the heat of fusion to be 4.48, 3.43 and 3.07 kcal/mole, respectively, for the random copolyesters containing 28, 38 and 50 mole % of ethylene terephthalate unit. The corresponded values of the interaction energy of mixing at infinite dilution were 3.90, 2.85 and 2.75 cal/cc.

碩士
國立成功大學
化學工程學系碩博士班
98
This research was accomplished to investigate the effect of the incorporation of silver nanoplates on both the isothermal and non-isothermal crystallization of poly(ethylene oxide) (PEO)/nanoplate composites. In isothermal crystallization of composites, it was obtained that the addition of the nanoplates into the PEO causes an increase in the spherulite growth rate. In addition, the silver nanoplates hinder the primary nucleation of PEO and thus reduce the crystallization rate. This result suggests that silver nanoplates act as an anti-nucleation agent for the crystallization of composites. By analyzing the experimental data using the Lauritzen-Hoffman’s theory, both the nucleation constant (Kg) and surface free energy (σσe) decrease with the incorporation amount of nanoplates. This is because the nanoplates promote the creation of the corresponding free polymer crystal surface more dominant than that of the interface between polymer crystals and substrate. Additionally, the neat PEO and its composites exhibit similar q, indicating that the existence of silver nanoplates has no significant effect on the formation of the secondary nuclei of PEO, but induce the formation of free polymer crystals. Differential scanning calorimetry (DSC) was employed to investigate the non-isothermal crystallization of these composites. The Avrami exponent (n) for neat PEO ranged from 2.51 to 2.53 whereas that for composites showed slightly higher values between 2.54 to 3.16, indicating that these composites exhibit spherical crystal morphology. The half time for crystallization (t1/2) showed that the crystallization rate of neat PEO and its composites increase with increasing cooling rate and the crystallization rate of neat PEO is faster than that of composites. By analyzing the nucleation activity, we obtained that the nucleation ability increases with an increase in the content of silver nanoplates. Derived from the comparison with a few previous researches, the crystallization behavior of polymer with the addition of nanoparticles with different shape and size is atypical. It depends highly on the interaction between the polymer chains and the fillers.

碩士
大同大學
化學工程學系(所)
95
Studies of non-isothermal decomposition of a new diamine monomer led to a series of novel polyimide polymer (a)-(f) when reacted with six dianhydrides were measured by thermogravimetric analysis (TGA) at a heating rate of 20℃/min in nitrogen and air atmospheres. Three single heating-rate integral methods by Coats-Redfern, Horowitz-Metzger and Van Krevelen that were analysed using the non-isothermal data with different expressions of solid state reactions, i.e., g(a) would be used to estimate the activation energy (E), pre-exponential factor (A), and order of reaction (n). The F1 and R2 models were selected as the best mechanisms for solid-state reactions to fit experimental TG curves in nitrogen and air atmospheres, individually. Mathematical verification of using different integral methods shows that the Coats-Redfern method is more precise than the Horowitz-Metzger and Van Krevelen methods since the other two methods are dependent on the arbitrary selection of the reference temperatures. From the molecular structure point of view, the order of the activation energy of polyimide under nitrogen is PI-e(DSDA) =PI-f(6FDA) >PI-a(PMDA) >PI-d(ODPA) =PI-b(BPDA) >PI-c(BTDA); however, under air it is PI-f(6FDA) >PI-a(PMDA) >PI-d(ODPA) =PI-c(BTDA) >PI-b (BPDA) =PI-e(DSDA). In this study, it is found that the activation energy and pre-exponential factor show the same trend, i.e., both values increase with increasing the order of reaction for each sample, i.e., polyimide (a)-(f). On the other hand, the parameter values in air are lower than those in N2. It can be attributed to that not only the molecular structure but also combustion of oxygen would affect the value of activation energy.

碩士
崑山科技大學
綠色材料研究所
98
In this work, we provided insights into effect of paraffin content and isothermal temperature on the thermal properties, isothermal crystallization kinetic, nanotemplet assembled and morpholries transition behaviors of polyethylene-block-poly(ethylene glycol)/paraffin (PE-b-PEG/PAF) binary blends by means of differential scanning calorimetry (DSC), wide-angle X-ray diffractions (WAXD), transmission electron microscope (TEM), polarized optical microscopy (POM), and in situ small-angle and wide-angle X-ray scattering (SAXS and WAXS). Herein, the melting temperature of PEGb、Paraffin、PEb is 32, 53, and 103oC, respectively. However, the isothermal crystallization mechanisms of PE-block and paraffin, PEG-block in PE-b-PEG/PAF binary blends preceded by unconfined and confined crystallizations, respectively, to form the interlamellar to the breakout lamellar morphology with increased paraffin content. It maybe the paraffin was dry brushed between PE-b-PEG interlamellar domains and preceded the multi-crystallization behaviors during isothermal crystallization at various Tcs. The characteristic parameters of the Avrami exponent; n-bPE, and n-bPEG are ca. 2.0, implying it hinted a thermal nucleation process followed by the two-dimensional growth or self-assemble. While that of n-PAF is ca. 2.2-2.8 attributed to hint a thermal nucleation process followed by two- to three-dimensional growth depended on paraffin content. Although the microstructures of PE-b-PEG/PAF blends combined the monoclinic crystal of PEG and orthorhombic crystal of PE together and independent up the paraffin contents. The results of TEM and SAXS indicated that the effects of paraffine content on the morphology of the PE-b-PEG/Paraffin binary blend present the lamellar structure, the long-perior of the lamellar structure is about 9.6-12.3nm, which independent of paraffine content. The result indicated that the morphology of the PE-b-PEG/Paraffin binary blend was a macro-phase separation system. In the results of in situ SAXS-WAXS, however during heating cycle, the SAXS profile of pure PE-b-PEG indicated morphology transition; crystalline lamella (belower than melting temperature of block-PEG), cylinder (temperature between melting points of block PEG and PE), and amorphase lamella (higher than melting point of PE). On the other hand, the SAXS profile of PE-b-PEG/Paraffin binary blend presented another morphology transition; crystalline lamella (belower than melting temperature of block-PEG), cylinder (temperature between melting points of block PEG and PE), and amorphase sphere phases (higher than melting point of PE) during heating cycle. However, the reversible of the morphology transition was observed in cooling cycle. The SAXS profile of PE-b-PEG/Paraffin binary blend presented that the q value of the primary scattering peak of PE-b-PEG diblock copolymer is ca. 0.052Å-1, which means the average thickness of interlamellar morphology is ca. 12.08nm, whereas, the q value of the scattering peak of paraffin is ca. 0.17Å-1, which means the average thickness of interlamellar morphology is ca. 3.7nm. However, the q values of primary scattering peak of PE-b-PEG diblock copolymer and scattering peak of paraffin independent, while the intensities of that dependent of paraffine content provided that the PE-b-PEG/Paraffin binary blend was a macro-phase separation system. Moreover, The WAXS profiles indicated that the combined the scattering peaks at q values at 1.5 and 1.68Å-1 attributed to crystal planes (110) and (200) of crystalline block PE and that at 1.34 and 1.62Å-1 attributed to crystal planes (120) and (032) of crystalline block PEG together at temperature belower than meltinf point of block PEG. The crystal planes (120) and (032) of crystalline block PEG decreased as temperature around 60oC, and the crystal planes (110) and (200) of crystalline block PE also melting as temperature rised to 105oC, therefore, we obtented a full amorphase phase at temperature above 105oC. The WAXS profile changed remarkable with paraffine content, expecially, WAXS profile showed a near paraffine pattem at over 50wt% paraffine maybe due to paraffine and block PE acted as an effectively confined agent role for block PEG during both heating and crystallization.