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The research presented focuses on the use of Carbon-dioxide (CO₂), Nitrogen (N₂) and Argon (Ar) as purge gases for torrefaction. Torrefaction using CO₂ as a purge gas may further improve the fuel characteristics of the torrefied fuel when compared to N₂ and Ar (which are entirely inert), making it better suited for use as a fuel for co-firing with coal or gasification. Three different biomasses were investigated: Juniper wood chips, Mesquite wood chips, and forage Sorghum. Experiments were conducted using a thermo-gravimetric analyzer (TGA, TA Instruments Model Q-600) to determine the effect of the purge gas over a wide range of torrefaction temperatures (200-300°C). TGA weight traces (thermograms) showed an increased mass loss when using CO2 as a purge gas when compared to N₂. The increased mass loss when CO₂ was used is attributed to a hypothesized reaction between the CO₂ and fixed Carbon contained within the biomass. Torrefaction of biomass, using Ar as the purge gas, produced results similar to torrefaction using N₂. Derivative Thermo-Gravimetric analysis (DTG) was done to determine the temperature ranges over which the three main components of biomass (hemicellulose, cellulose, and lignin) decomposed. The DTG results are in agreement with previously published research. From TGA thermograms and DTG analysis it was determined that torrefaction at higher temperatures (>260°C) likely result in the breakdown of cellulose during torrefaction, an undesired outcome. Proximate, ultimate, and heat value analysis was done on all three biomasses. All three contain a relatively high Oxygen content, which serves to decrease the higher heating value (HHV) of the biomass. The HHV of Juniper, Mesquite, and Sorghum on a dry ash-free (DAF) basis were 20,584 kJ/kg, 20,128 kJ/kg, and 19,389 kJ/kg respectively. The HHV of the three biomasses were relatively constant as expected for agricultural biomass. From TGA analysis (thermograms and DTG), an optimal torrefaction temperature was determined (240°C) based upon the amount of mass lost during torrefaction and estimates of energy retained. Batch torrefaction of all three biomasses at the optimal torrefaction temperature was completed using a laboratory oven. All three biomasses were torrefied using CO₂, N₂, and Ar as a purge gas. Proximate, ultimate, and heat value analysis was done for each of the torrefied fuels and compared. Results of the fuel property analysis showed torrefaction reduced the moisture content and oxygen percentage of the fuel resulting in the torrefied biomass having a larger HHV when compared to raw biomass. Due to inherent mass lost during torrefaction, the amount of energy retained in the torrefied biomass was calculated to determine the percentage of the virgin biomass energy content that remained. Torrefaction using CO2 resulted in the lowest amount of energy retention of all three purge gases tested (78.86% for Juniper); conversely, Nitrogen resulted in the highest amount of energy retention (91.81% for Sorghum.) Torrefaction of the biomass also increased the fixed carbon (FC) content of the fuel. The grindability of the torrefied biomass was investigated via size distribution analysis of the raw and ground biomass. Initial size distribution analysis showed that torrefaction of Mesquite and Juniper resulted in smaller particle sizes; with a greater fraction of the torrefied biomass passing through smaller meshes. Analysis of the ground biomass samples showed that torrefaction improved the grindability of the fuel. The percent of torrefied biomass that passed through an 840 micrometer mesh increased by over 20% for both Mesquite and Juniper when ground. Sorghum exhibited similar increases; however, the amount of increase is less apparent due to the smaller particle size distribution of the raw Sorghum.

This thesis reports the systematic approaches to overcome the key drawbacks of the pure PHBV, namely low crystallisation rate, tensile strength, ductility, melt viscosity, thermal stability and high materials cost. The physical, mechanical, thermal, and rheological properties of the pure PHBV were studied systematically first to lay a solid foundation for formulation development. The influence of blending with other biopolymers, inclusion of filler, and chain extender additives in terms of mechanical properties, rheology, thermal decomposition and crystallization kinetics were then followed. Creating lightweight structures by foaming is considered to be one of the effective ways to reduce material consumption, hence the reduction of density and morphology of PHBV-based foams using extrusion foaming technique were studied comprehensively in terms of extrusion conditions (temperature profiles, screw speed and material feeding rate) and the blowing agent content. The material cost reduction was achieved by adding low-cost filler (e.g. CaCO3) and reduction of density by foaming. The thermal instability was enhanced by incorporation of chain extender (e.g. Joncryl) and blending with a high thermal stability biopolymer (e.g. PBAT). The polymer blend also improved the ductility. Adding nucleation agent enhanced the crystallization rate to reduce stickiness of extruded sheet. The final formulation (PHBV/PBAT/CaCO3 composite) was successfully extruded into high quality sheet and thermoformed to produce prototype trays in an industrial scale trial. The effect of the extrusion conditions (temperature profiles, screw speed and material feeding rate) and the blowing agent content are correlated to the density reduction of the foams. 61 and 47 % density reduction were achieved for the commercial PHBV and the PHBV/PBAT/CaCO3 composite respectively and there exists further scope for more expansion if multiple variable optimisation of the conditions are carried out.

Yes / Thermal degradation of polyamide 6 (PA6)/organoclay nanocomposites is a serious impediment to wider applications of these nanocomposites. In this study, a solution is proposed based on the well‐established use of chain extenders. As in PA6, thermal degradation, in the absence of moisture, produces broken polymer chains with amide end groups, a chain extender with anhydride functionalities, known to be strongly reactive with amide groups, was used to reconnect the chains. Experiments conducted using a laboratory twin‐screw extruder were first checked, through transmission electron microscopy observations, to have produced good organoclay intercalation and exfoliation into PA6. Following from this, samples with the chain extender added were produced and characterized. The data obtained were conclusive in the effectiveness of the chain extender: for the chain extended nanocomposites, there is an enhancement in the value of the complex viscosity by 7 times and in the storage modulus by 88 times, while the tensile modulus increased by 57% compared with the neat PA6. The nonchain extended nanocomposite achieved in comparison an enhancement of 2 times the value of the complex viscosity and 19 times the storage modulus while the tensile modulus increased by 53% compared to the neat PA6. These data provide conclusive proof on the rationale that anhydride functionalities should be sought when developing chain extenders for PA6 nanocomposites. / Government of Turkey

Cyanate ester thermosetting resins are a novel family of materials for high technology and aerospace applications. The high glass transition temperatures available from cured cyanate ester networks and subsequently, their resistances to corrosive materials make these resins attractive for harsh environmental applications. These features of cyanate ester resins presented a threefold opportunity for investigation, namely: 1) establish a characterization technique for the long term mechanical properties of the cured resins, 2) develop a method for determining the effect of physical and chemical aging on these mechanical properties, and 3) evaluate the AroCy® B-10 cyanate ester resin from Ciba-Geigy for use in applications where temperatures could easily reach 177°C (300°F). Dynamic mechanical analysis used in a step isothermal mode was developed to characterize the mechanical properties of the cured resin and a family of isothermal modulus curves was established. These data were then shifted, following WLF theory, to create a master curve of storage modulus with respect to measurement frequency. The resultant master curves allowed the prediction of long term mechanical behavior of the resin networks via short duration, accelerated experimental tests. The test methodology and experimental procedures were especially useful in determining the effects of physical and chemical aging on the mechanical properties of the resin. Cured resins were aged in oxidative and inert atmospheres (air and nitrogen, respectively) for varying time and temperature to study the suitability of cyanate ester resins for harsh environmental applications. After aging, the samples were tested by DMA, DSC and TGA and master curves of their mechanical behavior were generated. The results were then grouped to form a family of master curves as a function of atmosphere, time and temperature. This approach allowed for the separation of the competing chemical and physical degradation processes and established the practical application conditions for this class of cross-linked polymers. Using the techniques established above, a model cyanate ester resin was selected based upon its chemical simplicity and availability. AroCy® B-10 cyanate ester resin manufactured commercially by Ciba-Geigy was evaluated for its application where temperatures could easily reach 177C. While this material was clearly unacceptable for the stated application conditions (especially in an oxygen rich atmosphere), its investigation provided experimental confirmation of the techniques developed. The test procedures and performance evaluation techniques described allow for the systematic assessment of not only the cyanate ester class of networking polymers, but any glass forming material, and a separation methodology for their concomitant chemical and physical degradation pathways. / Ph. D.

A necessidade básica de corte de têxteis nos formatos convenientes ao posterior das peças dentro da indústria da confecção determinou o desenvolvimento dos diversos tipos de processos de corte atualmente existentes. Estes processos podem ser classificados em três grupos principais: corte mecânico, corte por laser e híbrido mecânico-térmico. O corte mecânico, que se utiliza de um agente de corte tal como faca, serra, prensa, etc., é de longe o mais empregado, devido principalmente seu baixo custo. Embora perfeitamente adequado para uma grande variedade das aplicações existentes, possui limitações específicas. O corte mecânico é adequado para cortes simultâneo de várias camadas de tecidos sobrepostas embora a velocidade de corte seja baixa. O processo de corte por laser tem sua principal vantagem na ausência de forças de corte sobre o material, permitindo um corte preciso. Além disso, permite altas velocidades de avanço. Suas principais desvantagens são o preço do equipamento e a impossibilidade de corte de várias camadas sobrepostas de tecido. O corte mecânico-térmico tem emprego bem mais limitado e consiste na degradação do material através do contato de uma ferramenta aquecida. Para têxteis tem sido usado até agora para seccionamento reto. A proposta aqui apresentada é de um novo processo de corte de têxteis apropriado ao retalhamento de tecidos dispostos em camadas sobrepostas que emprega um processo híbrido de degradação térmica do material combinada à ação mecânica de gumes de corte. Este processo consiste na utilização de uma fresa de topo eletricamente aquecida, que em decorrência da pequena área da seção transversal do circuito elétrico no comprimento de corte, da elevada resistividade elétrica do seu material e do valor elevado da corrente elétrica que o atravessa, tem a temperatura nesta região bastante elevada devido ao calor gerado pelo efeito Joule. Esta energia será absorvida pelo meio material que circunda a ferramenta, provocando a degradação localizada das fibras têxteis. Uma campânula cobre a região do contato entre a ferramenta e o tecido e em seu interior é injetado gás nitrogênio como forma de criar-se uma atmosfera inerte que iniba a combustão do tecido. O mecanismo de corte pode então ser sucintamente descrito como uma degradação térmica do material seguido da remoção mecânica dos seus resíduos pelas arestas de corte da ferramenta. Apropriado para o corte de várias camadas de tecido sobrepostas, sua maior vantagem está em sua capacidade de corte de figuras complexas que apresentem curvaturas bastante acentuadas. A combinação de um processo mecânico com o de degradação térmica permite que as forças de corte sejam baixas, garantindo desse modo a precisão do corte. Uma das áreas que possivelmente se beneficiaria deste tipo de equipamento seria o de confecção de roupas infantis, que utiliza extensivamente o recorte de figuras estampadas. Inicialmente pensado para o corte de têxteis de fibras naturais observou-se que o emprego acarretava a impregnação das peças com um persistente odor de queimado, o que se constitui uma restrição ao emprego do processo em artigos de vestuário e do lar. Contudo, no caso de têxteis sintéticos foi observado um desempenho bastante apreciável e que tenha como limitação apenas a soldagem das peças sobrepostas, o que pode ser evitado com a introdução de folhas de papel entre elas. Dos resultados obtidos no processo de corte observou-se que o seu desempenho é comparável a de outras tecnologias já estabelecidas, realçando-se que este processo pode ser certamente otimizado com o emprego de dispositivos que o levem a operar nas condições de maior rendimento e de outras medidas que diminuam as restrições atuais. / The basic necessity of cutting textiles into convenient forms for later processing within the confection industry has determined the various cutting methods in existence. These processes may be classified in three principle groups: mechanical cutting, laser cutting and hybrid mechanical-thermal cutting processes. Mechanical cutting, in which knives, saws, presses, etc. are employed, is by far the most used, due principally to the low costs involved. Although perfectly adequate for wide variety of applications, it possesses specific limitations. Mechanical cutting is adequate for straight cuts or of not very pronounced curvature and is efficient for over-layed simultaneous cuts, although the cutting velocity is low. The laser cutting process has as its principal advantage the lack of cutting forces on cut the material. As well as high advance speeds. The principal disadvantages are the price of the equipment and the impossibility of cutting various layers of material at the same time. Mechanical-thermal cutting is much less used and consists of the degradation of the material on contact with the heated cutter. The proposal here presented is of a new process of textile cutting of overlaid layers of material through the use of a hybrid process of thermal degradation of the material combined with the mechanical action of the cutting-edges. This process consists of the use of an electrically heated vertical mill which, as a result of the small cross-section of the electrical circuit formed by the length of the cut, the high resistivity of the material and of the electrical current that runs through it, possesses a high temperature in this region due the Joule effect. This energy is absorbed by the material that touches the cutting surface provoking the localized degradation of the textile fibers. A bell form covers the region of contact between cutter and material and nitrogen is injected into this space, being an inert gas that inhibits combustion of the material. The mechanism of the cut may thus be described as the thermal degradation of the material followed by the mechanical removal of the material and its residues by the tool cutting edges. Suitable for the cutting of various layers of material, the major advantage of this method is its capacity of cutting complex forms that include accentuated curvatures. The combination of mechanical process with thermal degradation permits low cutting forces, thus guaranteeing the precision of the cut. One area of use that could possibly benefit from this type of equipment is the confection of children and infant clothing, which makes extensive use of the cutting of printed designs. Initially intended for the cutting of natural textile fibers, the method is restricted to use for articles for home use due to the persistent burn odor observed during tests. For synthetic textiles was observed a good performance although occurs the edge welding of over-Iayed pieces. This may be evicted by the introduction of paper sheets between the fabric layers. The results of the tests show the performance of this process is comparable with others established technologies. However this process may be optimized with the use of devices that make the equipment to operate in the conditions of high efficiency and others that reduce the current restrictions.

Poly(butylene succinate) (PBSu) and two poly(butylene succinate-co-propylene succinate)s (PBPSu 95/5 and PBPSu 90/10) were synthesized via the direct polycondensation reaction. The copolyesters were characterized as having 7.0 and 11.5 mol% propylene succinate (PS) units, respectively, by 1H NMR. Copolyesters were characterized as random, based on 13C NMR spectra. They were fully investigated during nonisothermal crystallization and thermal degradation through various approaches in this study. A differential scanning calorimeter (DSC) and a polarized light microscope (PLM) adopted to study the nonisothermal crystallization of these polyesters at a cooling rate of 1, 2, 3, 5, 6 and 10 ºC/min. Morphologies and the isothermal growth rates of spherulites under PLM experiments were monitored and obtained by curve-fitting, respectively. These continuous rate data were analyzed with the Lauritzen-Hoffman equation. A transition of regime II ¡÷ III was found at 95.6, 84.4, and 77.3 ºC for PBSu, PBPSu 95/5, and PBPSu 90/10, respectively. DSC exothermic curves show that all of the nonisothermal crystallization occurred in regime III. DSC data were analyzed using modified Avrami, Ozawa, Mo, Friedman and Vyazovkin equations. Ozawa equation does not accurately describe the nonisothermal crystallization kinetics of this polyester because part of the crystallization is secondary crystallization. All the results of PLM and DSC measurements indicate that incorporation of minor PS units into PBSu markedly inhibits the crystallization of the resulting polymer. The melting behavior of nonisothermally crystallized samples presents a continuous melting¡Vrecrystallization¡Vremelting process. Additionally, three absorption bands during the nonisothermal crystallization were identified for PBSu and two PBPSu copolyesters, namely, 916, 955, 1045 cm-1 in the attenuated total reflectance FTIR spectra. Thermogravimetric analysis (TGA)-FTIR was heated at 5 ºC/min under N2 to monitor the degradation products of these three polyesters. FTIR spectra revealed that the major products were anhydrides, which were obtained following two cyclic intramolecular degradation mechanisms by breaking the weak O-CH2 bonds around a succinate group. Thermal stability at heating rates of 1, 3, 5, and 10 ºC/min under N2 was investigated using TGA. The model-free methods of Friedman and Ozawa equations are useful for studying the activation energy of degradation in each period of mass loss. The results reveal that the random incorporation of minor PS units into PBSu did not markedly affect their thermal resistance. Two model-fitting mechanisms were used to determine the loss mass function f(£\), the activation energy and the associated mechanism. The mechanism of autocatalysis nth-order, with f(£\)=£\m(1-£\)n, fitted the experimental data much more closely than did the nth-order mechanism given by f(£\)=(1-£\)n. The obtained activation energy was used to estimate the failure temperature (Tf). The values of Tf for a mass loss of 5% and an endurance time of 60,000 hr are 160.7, 155.5, and 159.3 ºC for PBSu and two the copolyesters, respectively.

Poly(butylene succinate) (PBSu), poly(2-methyl-1,3-propylene succinate) (PMPSu), and their two novel poly(butylene succinate-co-2-methyl-1,3-propylene succinate)s (PBMPSu 95/05 and PBMPSu 90/10) were synthesized by a two-stage esterification reaction. PBMPSu 95/05 and PBMPSu 90/10 were characterized as having 6.5 and 10.8 mol% 2-methyl-1,3-propylene succinate (MPS) units, respectively, by 1H NMR. These copolymers were characterized to be random from the 13C NMR spectra. In this study, the nonisothermal crystallization and thermal degradation behaviors of the polyesters were investigated via different approaches. A differential scanning calorimeter (DSC) and a polarized light microscope (PLM) were employed to investigate the nonisothermal crystallization of these copolyesters and neat PBSu. Morphology and the isothermal growth rates of spherulites under PLM experiments at three cooling rates of 1, 2.5 and 5 ¢XC/min were monitored and obtained by curve-fitting. These continuous rate data were analyzed with the Lauritzen-Hoffman equation. A transition of regime II ¡÷ III was found at 96.2, 83.5, and 77.9 ¢XC for PBSu, PBMPSu 95/05, and PBMPSu 90/10, respectively. DSC exothermic curves at five cooling rates of 1, 2.5, 5, 10 and 20 ¢XC/min show that almost all of the nonisothermal crystallization occurred in regime III. DSC data were analyzed using modified Avrami, Tobin, Ozawa, Mo, Friedman and Vyazovkin equations. All the results of PLM and DSC measurements reveal that incorporation of minor MPS units into PBSu markedly inhibits the crystallization of the resulting polymer. The nonisothermal crystallization behavior of these polyesters was also investigated using a Fourier-transform infrared spectrometer (FTIR) with an attenuated total reflection (ATR). The absorbance peaks of crystals for the £\ form (918, 955, and 1045 cm-1) of PBSu and PBMPSu copolyesters were observed by ATR-FTIR under nonisothermal crystallization. When these semicrystalline polyesters started to be solidified from the melt state, these characteristic absorption bands for PBSu and its copolyesters crystals have been detected. In this study, the thermal degradation mechanisms of PBSu, PMPSu, PBMPSu 95/05, and PBMPSu 90/10 were investigated using a thermogravimetric analyzer combined Fourier-transform infrared spectrometer (TGA-FTIR) and a pyrolysis-gas chromatography¡Vmass spectrometry (Py-GC-MS). The volatile products evolved from the thermal degradation of these two copolyesters were identified to be anhydride, ether, ester, alcohol, alkene, aldehyde, and CO2. FTIR spectra displayed that the main degradation products for these four polymers were anhydrides. Moreover, PBSu-rich PBMPSu copolymers exhibited the same thermal degradation mechanism as that of PBSu at lower thermal degradation temperatures (< 403 ºC) and as that of PMPSu at higher thermal degradation temperatures (> 403 ºC) by the TGA-FTIR analysis. The results of the TGA-FTIR analysis clearly demonstrates that the influence of MPS units on the thermal degradation process is gradually increased as the temperature increases for PBMPSu copolymers. The degradation mechanism of PBMPSu at lower thermal degradation temperatures and PBSu mainly follows the £]-hydrogen bond scission mechanism and the back-biting process from the polymer chains. Moreover, the degradation mechanism of PBMPSu at higher thermal degradation temperatures and PMPSu occurred mainly through the £]-hydrogen bond scission and secondarily through £\-hydrogen bond scission. Finally, the thermal stability and degradation kinetics of these polyesters were investigated using a TGA at heating rates of 1, 3, 5, and 10 ºC/min under dynamic nitrogen. The activation energies of thermal degradation in elective conversions were estimated using the Friedman and Ozawa methods. The results clearly demonstrated that the thermal stabilities of these PBMPSu copolyesters were slightly reduced with the incorporation of minor MPS units into PBSu. Two model-fitting methods of nth-order and autocatalysis nth-order reaction mechanisms were adopted to determine the mass loss function f(£\), the activation energy and the associated degradation parameters. The results revealed that the mechanism of autocatalysis nth-order fitted the experimental data much more closely than did the nth-order mechanism for PBSu, PMPSu and PBMPSu copolymers.

Thermal degradation of linear thermoplastics is modeled at several scales. High-density polyethylene (HDPE) is chosen as an example material. The relevant experimental data is surveyed. At the molecular scale, pyrolysis chemistry is studied with reactive molecular dynamics. Optimization is used to calibrate several pyrolysis mechanisms with thermogravimetric analysis (TGA) data. It is shown that molecular scale physics may be coupled to continuum scale transport equations through a population balance equation (PBE). A PBE solution method is presented and tested. This method has the advantage of preserving detailed information for the small species in the molecular weight distribution with minimal computational expense. The mass transport of these small species is modeled at the continuum scale with a bubble loss mechanism. This mechanism includes bubble nucleation, growth, and migration to the surface of the condensed phase. The bubble loss mechanism is combined with a random scission model of pyrolysis to predict TGA data for HDPE. The modeling techniques developed at these three scales are used to model two applications of engineering interest with a combined pyrolysis and devolatilization PBE. The model assumes a chemically consistent form of the random scission pyrolysis mechanism and an average, parameterized form of the bubble loss mechanism. This model is used to predict the piloted ignition of HDPE. Predictions of the ignition times are reasonable but the model over predicts the ignition temperature. This discrepancy between model and data is attributed to surface oxidation reactions. The second application is the prediction of differential scanning calorimetry (DSC) data for HDPE. The model provides detailed information on the energy absorption of the thermally degrading sample, but the literature data is too variable to validate the model. / text