UV- und lichthärtenden Acrylatklebstoffen steht ein breites Anwendungsspektrum im Konstruktiven Glasbau offen. Ihr farbloses und klares Erscheinungsbild fördert eine Konstruktion, die transparent und leicht wirken soll. Kurze Aushärtezeiten, die sich im Sekunden- oder einstelligen Minutenbereich bewegen, ermöglichen eine schnelle Herstellung und reduzieren die Lagerzeiten. Die geklebten Konstruktionen können direkt weiterverarbeitet werden. Durch diese Vorteile heben sie sich von den Silikonklebstoffen ab, die für ausge-wählte Anwendungen im Fassadenbau (Structural-Sealant-Glazing-Systems - SSGS) bauaufsichtlich zugelassen sind. Gegenstand dieser Arbeit ist die Aufstellung von Empfehlungen zur Planung und Berechnung struktureller Klebungen mit strahlungshärtenden Acrylaten. Dafür werden Klebstoffe an dem reinen Material sowie in Verbindungen mit Glas und Metall untersucht. Für ein umfangreiches Bild über das Verhalten des Materials bieten sich Substanzprüfkörper an, die mit überschaubarem Aufwand eine Auswertung verschiedener Einflüsse - beispielsweise Temperatur und Prüfgeschwindigkeit - erlauben. An in-situ-Prüfkörpern kann der Klebstoff in der Verbindung betrachtet werden. Durch Wechselwirkungen zwischen Klebstoff und Fügeteil bildet sich eine sogenannte Grenzschicht aus, die gradierte Eigenschaften besitzt und die Materialkennwerte - besonders bei dünnen Klebfugen - beeinflusst. Weiterhin erlauben diese Prüfkörper eine Aussage über das Tragverhalten der Klebverbindung. Um das Potenzial der Acrylatklebungen in der Glasarchitektur aufzuzeigen und in der Anwendung zu prüfen, werden Bauteile mit punktförmig geklebten Halterungen untersucht. Absturzsicherungen werden statischen und dynamischen Belastungen unterworfen. An Überkopfverglasungen werden Trag- und Resttragfähigkeitsuntersuchungen durchgeführt. Bauteile im Freien geben Aufschluss über das Alterungsverhalten unter natürlichen klimatischen Bedingungen. / UV and light curing acrylates present a whole host of possibilities for the implementation of glass construction. Their clear and colourless appearance produces a transparent and lightweight construction. Short curing times consisting of no more than mere minutes allow for quick production with minimal downtime within the overall process. Processing can be resumed immediately once bonding has occurred. The advantages of acrylates can be compared to the characteristics and properties of adhesive silicones which have been widely approved by building authorities for specific façade applications (Structural-Sealant-Glazing-Systems - SSGS). The subject matter of this study is the development of auxiliary tools to plan and design adhesively bonded joints of UV and light curing acrylates. These adhesives are, therefore, analysed both generally as bulk material and in applications as a joint between glass and metal. The use of dog bone shaped specimens is recommended to analyze the material behaviour under a variety of influence factors such as temperature and testing rate. The bonded joints of test specimens provide an opportunity to examine the interaction between the adhesive and the materials to which they are adhered. An interface with graded properties is formed based upon the interactions between adhesive joints and each particular substrate. Further on, bonded specimens enable the development of a statement concerning the load-bearing capacity of joints. Constructions having spot bonded joints are tested to demonstrate the potential use of acrylic joints in architectural glass treatments. Safety barriers are tested under both static and dynamic loads. Sloped roof systems are tested to substantiate load-bearing capacity and to verify any residual carrying capacity. Components are exposed to natural weathering in order to examine the affects of ageing on the adhesive.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / The study described in this dissertation examines the synthesis of mainly acrylate-based surfactants and their subsequent use as emulsifiers/stabilisers in the emulsion polymerisation of styrene. Some acrylamide-based surfactants were also studied, for comparison purposes only. Two major types of surfactants, polymerisable (surfactant monomers or surfmers) and polymeric, were synthesised, characterised and used in emulsion polymerisation reactions. The prepared polymerisable surfactants, 12-acryloyloxydodecanoic acid (12-ADA) and 11-acrylamidoundecanoic acid (11-AAUA), and their sodium salts, had reactive acryloyl functionalities.

The replacement of synthetic polymers with renewable content in emulsion polymerization latexes has been a focus of research over the past several decades. Emulsion polymerization is a more sustainable way to produce polymers for films and resins. Starch is a sustainably sourced material that has proven to be extremely useful as a filler, comonomer, and property modifier for polymer latexes. In this thesis, we attempt to incorporate high levels of starch materials into emulsion latex using waxy and dent sourced (cheaper) vinyl-functionalized regenerated starch nanoparticles (RSNPs). When fed as a batch charge, incorporation (by reaction as opposed to blending) of a grade of waxy RSNPs with 3 wt.% polymerizable sugar-based monomer (PSBM) and medium hydrophobicity (S-3-M) into the polymer matrix was 0-10 wt.% for a 15 wt.% RSNP loaded, 40 wt.% solids latex. Semi-batch feeding of the S-3-M RSNPs resulted in stable latex with the highest loadings of 40 and 50 wt.% (40 wt.% solids) with 0-10 wt.% RSNP incorporation into the synthetic particles, while 40 wt.% loading (20 wt.% incorporation) was achieved with a grade of waxy RSNPs with 6 wt.% PSBM and medium hydrophobicity (S-6-M). Strategies were developed to prepare synthetic latexes with high RSNP loadings and moderate incorporation. Dent sourced RSNPs proved difficult to use in emulsion formulations due in part to the higher percentage of water-soluble linear amylose in the nanoparticles. To reduce the chances of coagulation and minimize the viscosity of the final latex it was important to ensure monomer starved conditions, that the only initiator feed occurred at the seed stage of the reaction (to degrade the soluble starch and prevent later stage coagulation), and that a hydrophobic tie-layer was used to assist in removal of soluble starch from the water phase. Although a successful procedure was devised for creating a dent sourced RSNP loaded latex with a viscosity of 250 cp, it was significantly longer than the procedures used with waxy RSNPs (6 h polymerization + 1 h RSNP dispersion). An additional treatment of the RSNP dispersion prior to the polymerization can lower the final latex viscosity to 100 cp. Higher incorporation of vinyl-functionalized RSNPs may be achievable if the covalently bonded PSBM functional groups are resistant to hydrolysis, the amylose and other small MW starches are completely removed from the water phase, and monomers with more appropriate reactivity and hydrophobicity are employed. To this end, maleic and methacrylic anhydride modified RSNPs were prepared and tested in emulsion polymerizations. The maleic anhydride modified RSNPs were successfully loaded into an emulsion latex at 15 wt.% (40 wt.% solids content) resulting in 20-30 wt.% incorporation when utilizing 2-ethylhexyl acrylate as the tie-layer monomer with 2-ethylhexyl acrylate or butyl acrylate/methyl methacrylate/acrylic acid as the shell layer. This work presents the only comprehensive attempt to incorporate RSNPs into synthetic latexes at high loadings and solids with persulfate initiation without the need to severely reduce the RSNP molecular weight. The learning generated provides a framework for continuing research into increasing the incorporation of RSNPs into polymer particles.

Os processos industriais de polimerização em emulsão são normalmente realizados em reatores batelada ou semi batelada ou em tanques agitados contínuos (CSTR). Os reatores contínuos têm a vantagem de terem menor porte e de propiciarem melhor controle de qualidade do produto através da redução de variações de batelada a batelada. Além disso, as oscilações periódicas autosustentadas na conversão de monômero e no tamanho da partícula, que são normalmente observadas em reatores do tipo CSTR, podem ser minimizadas em reatores tubulares mediante o uso de dispositivos de mistura estáticos adequados combinados com escoamento pulsado (oscilatório). O objetivo deste trabalho é apresentar o desenvolvimento de uma copolimerização em emulsão de acetato de vinila e acrilato de butila em uma coluna pulsada com pratos perfurados (CPPP). A fim de aumentar a sua flexibilidade operacional, a coluna é composta de 5 seções, cada uma apresentando controles independentes de alimentação lateral e temperatura. Dependendo da estratégia de alimentação de monômero, pode-se notar uma deriva de composição durante o processo de copolimerização em emulsão do acetato de vinila e acrilato de butila devido às grandes diferenças entre estes monômeros em suas razões de reatividade e nas solubilidades na fase aquosa. Neste caso, a CPPP propicia diferentes possibilidades de alimentação que permitem controlar a composição do copolímero através da alimentação do monômero mais reativo ao longo da coluna. Por esta razão, foi avaliado neste estudo o efeito do número de correntes de alimentação sobre as propriedades do polímero. Diferentes números de correntes laterais de alimentação de monômero foram empregadas nos ensaios experimentais. Diferenças na uniformidade da composição do copolímero podem ser notadas dependendo do número de correntes laterais de alimentação aplicadas em cada teste. A fim de permitir variações de temperatura, somente a temperatura de entrada das camisas de resfriamento foi fixada. Para simular as reações foi utilizado um modelo matemático desenvolvido baseado no modelo de escoamento pistonado (plug-flow) axialmente disperso. No presente trabalho, um balanço de energia foi incluído ao modelo matemático anterior de modo que a influência de diferentes perfis de temperatura pudesse ser considerada. O efeito das correntes laterais de alimentação de monômero sobre as propriedades do copolímero puderam ser previstas com suficiente precisão pelas simulações do modelo, as quais foram também validadas pelos resultados experimentais. Com base nas simulações matemáticas, um perfil ótimo de alimentação pôde ser calculado e experimentalmente aplicado na CPPP permitindo a produção de um copolímero mais homogêneo. Os resultados também permitiram a validação do modelo matemático como uma ferramenta confiável na predição de ensaios experimentais. Além disso, as vantagens da CPPP puderam ser verificadas pelo seu desempenho adequado como reator tubular para processos contínuos de copolimerização em emulsão. Finalmente, os resultados indicaram a possibilidade de melhorias adicionais nas propriedades do polímero através do emprego de diferentes temperaturas e perfis de alimentação de outros reagentes ao longo da coluna. / Industrial emulsion polymerization processes are usually performed in batch or semi-batch stirred tanks, or in continuous stirred tank reactors (CSTR). Continuous reactors have the advantage of being smaller and providing a better product quality control by the reduction of the batch-to-batch variations. In addition, periodical self-sustained oscillations in monomer conversion and in particle size that are usually observed in CSTR can be minimized in tubular reactors presenting good radial mixing. Such conditions can be achieved in tubular reactors by using adequate static mixing devices combined with pulsed (oscillatory) flow. The aim of this work is to report the development of a continuous emulsion copolymerization of vinyl acetate and butyl acrylate performed in a pulsed sieve plate column (PSPC). In order to improve its operational flexibility, the column is composed of five sections, each one presenting independent lateral feed and temperature controls. Depending on the monomer feeding strategy, a composition drift can be noticed during the emulsion copolymerization process of vinyl acetate and butyl acrylate, due to the large differences in reactivity ratios and aqueous phase solubility between these monomers. In this case, the PSPC provides different operational feeding possibilities which allow controlling the copolymer composition by feeding the more reactive monomer along the column. For this reason, in this study the effect of the number of lateral feed streams on the polymer properties was evaluated. Different numbers of lateral monomer feed streams were employed in the experimental runs. Differences in the uniformity of the copolymer composition can be noticed along the reactor depending on the number of lateral feed streams applied in each test. In order to allow temperature variations, during each reaction only the inlet temperature of the cooling jackets was fixed. A developed mathematical model based on the axially dispersed plug-flow model was used to simulate the reactions. In the present study the energy balance was included in the mathematical model so that the influence of different temperature profiles could be taken into account. The effect of lateral monomer feed streams over the copolymer properties could be predicted with sufficient accuracy by model simulations which were also validated by the experimental results. Based on mathematical simulations, an optimal feeding profile could be calculated and experimentally applied in the PSPC allowing the production of a more homogeneous copolymer. The results also permitted the validation of the mathematical model as a reliable tool in the prediction of experimental runs. Furthermore, the advantages of the PSPC could be verified by its adequate performance as a tubular reactor for continuous emulsion copolymerization processes. Finally, the results indicate the possibility of further improvements in other polymer properties by employing different temperature and feeding profiles of other reagents along the column.

Cellulose is a potential source of nano-material not only because it possesses excellent mechanical and optical properties, but also because it is environmentally benign. In this study, nanofibres derived from wheat straw, an agriculture residue, was utilized in producing flexible and optically transparent nanocompostie films. The composites were produced using a bi-phase impregnation technique that coats the dried nanofibre films with clear polyurethane acrylate resins using UV radiation induced curing. The nanocomposite films thus produced possess excellent tensile properties (161MPa in strength and 9GPa in Young’s Modulus), superior thermal stability (above 300°C), low coefficient of thermal expansion (8-9ppm/K), good light transparency (80%), excellent flexibility and abrasion resistance. These nanocomposite films are aimed to replace the conventional glass substrates made in batches to a polymer based substrates that can be efficiently produced in a roll-to-roll process for the base of the future flexible flat panel displays.

Cellulose is a potential source of nano-material not only because it possesses excellent mechanical and optical properties, but also because it is environmentally benign. In this study, nanofibres derived from wheat straw, an agriculture residue, was utilized in producing flexible and optically transparent nanocompostie films. The composites were produced using a bi-phase impregnation technique that coats the dried nanofibre films with clear polyurethane acrylate resins using UV radiation induced curing. The nanocomposite films thus produced possess excellent tensile properties (161MPa in strength and 9GPa in Young’s Modulus), superior thermal stability (above 300°C), low coefficient of thermal expansion (8-9ppm/K), good light transparency (80%), excellent flexibility and abrasion resistance. These nanocomposite films are aimed to replace the conventional glass substrates made in batches to a polymer based substrates that can be efficiently produced in a roll-to-roll process for the base of the future flexible flat panel displays.

The phenomenon of depropagation or reverse polymerization for multicomponent polymerizations has been studied in detail. The monomer Alpha-Methyl Styrene (AMS) has been copolymerized with Methyl Methacrylate (MMA) and Butyl Acrylate (BA) at temperatures ranging from 60oC to 140oC and the kinetics have been studied in the form of propagation/cross propagation and depropagation parameters. There have been multiple attempts with varying amounts of success in the past to determine the kinetic parameters for depropagating systems including work by Lowry and Wittmer as well as other modelling methodologies that are not as mechanistic. The most recent development of the mechanistic terminal model is that of the Kruger model. The model is robust and can take into account all special cases as well as all reactions being reversible. The kinetic parameters have been estimated for each of the three binary systems using the Kruger model (MMA/AMS, MMA/BA, BA/AMS). The Alfrey-Goldfinger model is inadequate to describe depropagating terpolymer systems and in order to study them, a new model was developed based upon the binary Kruger model. This new model takes into account a fully depropagating terpolymer system leading to a total of 15 parameters to be estimated. These 15 parameters have the same definitions as those estimated from the binary Kruger model, thus making accurate analysis of the binary systems crucial since these will be used as first estimates for the terpolymer system. Extensive experimental data (composition, conversion and molecular weights) was collected and analysed for the MMA/AMS and BA/AMS systems. For the BA/AMS system both the bulk and solution copolymerizations were studied in detail with the results from the Kruger model not showing a significant difference in the reactivity ratios between the two types of polymerization. For the MMA/AMS system, a bulk study only was done which revealed an interesting phenomenon that points toward a break down of the long chain approximations used for all of the models being studied. For both of these systems, extensive ¹H NMR analysis was done to determine the copolymer composition. Data collected in previous research for the MMA/BA system was reanalysed using the Kruger model and it was found that the parameter estimates did not differ significantly from the published values. Extensive benchmarking was done with the newly developed terpolymer model on non-depropagating systems using data from the literature to ensure it worked for the simplest cases. It was found that the model matched the parameter estimates from the literature and in some cases improving upon them to fit the data better. Along with the benchmarking a sensitivity analysis was done which revealed some interesting information. For the MMA/BA/AMS terpolymer system a set of experiments (based upon practical considerations) were performed and the composition of the polymer was determined using ¹³C NMR instead of the usual ¹H NMR due to the difficulty of peak separation for the complex terpolymer. Using the depropagating terpolymer composition data in conjunction with the parameter estimates from the three binary systems allowed for estimation of the 15 kinetic parameters, which showed only minor variation from the binary estimates.

The phenomenon of depropagation or reverse polymerization for multicomponent polymerizations has been studied in detail. The monomer Alpha-Methyl Styrene (AMS) has been copolymerized with Methyl Methacrylate (MMA) and Butyl Acrylate (BA) at temperatures ranging from 60oC to 140oC and the kinetics have been studied in the form of propagation/cross propagation and depropagation parameters. There have been multiple attempts with varying amounts of success in the past to determine the kinetic parameters for depropagating systems including work by Lowry and Wittmer as well as other modelling methodologies that are not as mechanistic. The most recent development of the mechanistic terminal model is that of the Kruger model. The model is robust and can take into account all special cases as well as all reactions being reversible. The kinetic parameters have been estimated for each of the three binary systems using the Kruger model (MMA/AMS, MMA/BA, BA/AMS). The Alfrey-Goldfinger model is inadequate to describe depropagating terpolymer systems and in order to study them, a new model was developed based upon the binary Kruger model. This new model takes into account a fully depropagating terpolymer system leading to a total of 15 parameters to be estimated. These 15 parameters have the same definitions as those estimated from the binary Kruger model, thus making accurate analysis of the binary systems crucial since these will be used as first estimates for the terpolymer system. Extensive experimental data (composition, conversion and molecular weights) was collected and analysed for the MMA/AMS and BA/AMS systems. For the BA/AMS system both the bulk and solution copolymerizations were studied in detail with the results from the Kruger model not showing a significant difference in the reactivity ratios between the two types of polymerization. For the MMA/AMS system, a bulk study only was done which revealed an interesting phenomenon that points toward a break down of the long chain approximations used for all of the models being studied. For both of these systems, extensive ¹H NMR analysis was done to determine the copolymer composition. Data collected in previous research for the MMA/BA system was reanalysed using the Kruger model and it was found that the parameter estimates did not differ significantly from the published values. Extensive benchmarking was done with the newly developed terpolymer model on non-depropagating systems using data from the literature to ensure it worked for the simplest cases. It was found that the model matched the parameter estimates from the literature and in some cases improving upon them to fit the data better. Along with the benchmarking a sensitivity analysis was done which revealed some interesting information. For the MMA/BA/AMS terpolymer system a set of experiments (based upon practical considerations) were performed and the composition of the polymer was determined using ¹³C NMR instead of the usual ¹H NMR due to the difficulty of peak separation for the complex terpolymer. Using the depropagating terpolymer composition data in conjunction with the parameter estimates from the three binary systems allowed for estimation of the 15 kinetic parameters, which showed only minor variation from the binary estimates.

Magnetic particles have attracted increasing attention in fields ranging from separation processes to electromagnetic information storage an medical application. Various approaches for their synthesis have been developed and studied to satisfy the criteria of production. Improvement and optimization of size, stability, and functionality is of vital importance in biological applications. The main aspect of project, initially, was to study the application of aqueous functionalized magnetic nanoparticles coupled with high gradient magnetic separation technique for the removal of trace residue of organic contaminants from drinking water. However, the importance of synthesizing stable ferrofluid for this purpose became clear later and took precedence over the initial objective. Different approaches were adopted, such as the incorporation of poly(ethylene glycol) methacrylate, ethylenediamine, and chitosan, to enhance the stability of magnetic particles. However, these surface modifications had unfavorable effect on the stability of initial particles. In accord with the initial objective of the project, the possibility of utilization of β-cyclodextrin, as organic pollutant entrapment agent, was investigated in preliminary studies conducted on its interaction with a model compound, procaine hydrochloride. The outcomes of these experiments suggest its potential as a biocompatible removal agent for the elimination of organic pollutant in drinking water system, or other applications that require selective separation of organic compounds.

This study was aimed to synthesize low molecular weight hydroxyl terminated polyurethane acrylate polymers that can be used in biomedical applications. Acrylate end capping via inter-esterification reaction was successfully achieved with the methacryloyl chloride addition to the hydroxyl ends of the polyurethane at low temperatures. Isocyanate terminated polyurethane acrylates were also synthesized for the sake of comparison. TDI, HDI and MDI were used as diisocyanates for urethane synthesis and they were end capped with MMA and HEMA. Nature of the monomers used had an effect on thermal, morphological, and rheological properties that were interpreted in terms of the level of hydrogen bonding and degree of phase separation. Synthesized polymers were characterized by NMR, FTIR-ATR, DSC, TGA, GPC, Mass Spectroscopy, SEM and rheometry. In the literature, polyurethane acrylate polymers have been synthesized from the isocyanate terminated polyurethanes in which the urethane chains were ended with isocyanate groups. However, the toxicity of the isocyanate groups limited their biomedical applications especially in prosthetic dentistry as a soft lining material. Therefore, it is inevitable to explore the cytotoxicity of polyurethane acrylate polymers. For this purpose, silver nanoparticles that have an average particle size of 40 nm, were incorporated to the synthesized polymers. This addition, which intends to improve the degree of cytotoxicity, was successful to a certain extent.