The purpose of this research project is the design and optimization of complex chemical engineering problems, by employing evolutionary algorithms (EAs). EAs are optimization techniques which mimic the principles of genetics and natural selection. Given their population-based approach, EAs are well suited for solving multiobjective optimization problems (MOOPs) to determine Pareto-optimal solutions. The Pareto front refers to the set of non-dominated solutions which highlight trade-offs among the different objectives. A broad range of applications have been studied, all of which are drawn from the chemical engineering field. The design of an industrial packed bed styrene reactor is initially studied with the goal of maximizing the productivity, yield and selectivity of styrene. The dual population evolutionary algorithm (DPEA) was used to circumscribe the Pareto domain of two and three objective optimization case studies for three different configurations of the reactor: adiabatic, steam-injected and isothermal. The Pareto domains were then ranked using the net flow method (NFM), a ranking algorithm that incorporates the knowledge and preferences of an expert into the optimization routine. Next, a multiobjective optimization of the heat transfer area and pumping power of a shell-and-tube heat exchanger is considered to provide the designer with multiple Pareto-optimal solutions which capture the trade-off between the two objectives. The optimization was performed using the fast and elitist non-dominated sorting genetic algorithm (NSGA-II) on two case studies from the open literature. The algorithm was also used to determine the impact of using discrete standard values of the tube length, diameter and thickness rather than using continuous values to obtain the optimal heat transfer area and pumping power. In addition, a new hybrid algorithm called the FP-NSGA-II, is developed in this thesis by combining a front prediction algorithm with the fast and elitist non-dominated sorting genetic algorithm-II (NSGA-II). Due to the significant computational time of evaluating objective functions in real life engineering problems, the aim of this hybrid approach is to better approximate the Pareto front of difficult constrained and unconstrained problems while keeping the computational cost similar to NSGA-II. The new algorithm is tested on benchmark problems from the literature and on a heat exchanger network problem.

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.

Hydrogels are polymeric materials that have three-dimensional polymeric networks, which are able to absorb and retain a large amount of water within their structures without being dissolved. Among the synthetic hydrogel, poly(2-hydroxylethyl methacrylate) (poly(HEMA)) has been of great interest because of its excellent biocompatibility with the three-dimensional networks. Therefore, poly(HEMA) hydrogels have been widely used in many areas, especially in biomedical and pharmaceutical areas, for such applications as packing materials in chromatography, sorbents in controlled release and drug delivery, implanting materials in tissue engineering. However, the applications of poly(HEMA) are still limited because of its weak mechanical strength and network properties. Therefore, in recent decades, the challenge of how to modify and control the polymer properties and how to build highly porous structures in it has received considerable attention because these modifications could significantly improve the performance of poly(HEMA) hydrogels for more favorable applications. Although HEMA and its polymers have been studied for more than 40 years, few reports about the preparation of micro-/nano-porous poly(HEMA) hydrogel particles and the requirements of their applications have risen. Furthermore, how to control the porous structures and the properties of HEMA copolymers have not been well understood. Accordingly, the objectives of this research were to investigate the synthesis of the porous copolymeric particles of HEMA with various comonomers (MMA, St and NVP), to characterize the porous structures and particle morphology, to simulate the synthesis process and porous characteristics, to explore the effects of the polymer compositions and the porous structures on the swelling properties, and to apply the resultant polymeric particles in the controlled release of the hydrophilic model drug. In the present studies, HEMA was copolymerized with three different comonomers, methyl methacrylate (MMA), styrene (St) and N-vinyl-2-pyrrolidone (NVP), respectively, to prepare highly porous particles crosslinked using ethylene glycol dimethacrylate (EGDMA) in the presence of 1-octanol used as a porogen by means of suspension copolymerization in an aqueous phase initiated by 2,2-azobisisobutyronitrile (AIBN). Nano-pores were observed in the present studies. The pore size and the swelling properties of these particles can be successfully controlled by changing comonomers or adjusting the crosslinker and porogen concentration. The results indicate that lower crosslinker or porogen concentration favors generating smaller pores, whereas a higher concentration of a hydrophilic comonomer, higher crosslinker concentration and higher porogen volume ratio promote the generation of larger pores. In addition, the effects of the porous structures and the network properties on the swelling properties were explored. The swelling capacity of the porous particles is reduced with an increase in the EGDMA molar concentration. However, higher porosity in the particles and higher amount of hydrophilic comonomer result in a higher swelling capacity of the particles. The gel formation and the porous characteristics of HEMA/comonomer/EGDMA systems were simulated using the mathematical models combining the reaction kinetics and the thermodynamics. It was found that the model over-predicted the experimental results of the porosity because the pores and the networks are shrunk or collapsed during the porogen removal. Therefore, the model predicts the maximum porosity that the polymeric particles can reach. If the hydrophobic contents are higher, the model gives better prediction of the porosity. It is concluded that the microporous structures of HEMA related hydrogels could be controlled by a properly designed process based on the knowledge gained via this research. The output of this research helps with a better understanding for industrial production of micro-porous hydrogels and their applications.

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.

Hydrogels are polymeric materials that have three-dimensional polymeric networks, which are able to absorb and retain a large amount of water within their structures without being dissolved. Among the synthetic hydrogel, poly(2-hydroxylethyl methacrylate) (poly(HEMA)) has been of great interest because of its excellent biocompatibility with the three-dimensional networks. Therefore, poly(HEMA) hydrogels have been widely used in many areas, especially in biomedical and pharmaceutical areas, for such applications as packing materials in chromatography, sorbents in controlled release and drug delivery, implanting materials in tissue engineering. However, the applications of poly(HEMA) are still limited because of its weak mechanical strength and network properties. Therefore, in recent decades, the challenge of how to modify and control the polymer properties and how to build highly porous structures in it has received considerable attention because these modifications could significantly improve the performance of poly(HEMA) hydrogels for more favorable applications. Although HEMA and its polymers have been studied for more than 40 years, few reports about the preparation of micro-/nano-porous poly(HEMA) hydrogel particles and the requirements of their applications have risen. Furthermore, how to control the porous structures and the properties of HEMA copolymers have not been well understood. Accordingly, the objectives of this research were to investigate the synthesis of the porous copolymeric particles of HEMA with various comonomers (MMA, St and NVP), to characterize the porous structures and particle morphology, to simulate the synthesis process and porous characteristics, to explore the effects of the polymer compositions and the porous structures on the swelling properties, and to apply the resultant polymeric particles in the controlled release of the hydrophilic model drug. In the present studies, HEMA was copolymerized with three different comonomers, methyl methacrylate (MMA), styrene (St) and N-vinyl-2-pyrrolidone (NVP), respectively, to prepare highly porous particles crosslinked using ethylene glycol dimethacrylate (EGDMA) in the presence of 1-octanol used as a porogen by means of suspension copolymerization in an aqueous phase initiated by 2,2-azobisisobutyronitrile (AIBN). Nano-pores were observed in the present studies. The pore size and the swelling properties of these particles can be successfully controlled by changing comonomers or adjusting the crosslinker and porogen concentration. The results indicate that lower crosslinker or porogen concentration favors generating smaller pores, whereas a higher concentration of a hydrophilic comonomer, higher crosslinker concentration and higher porogen volume ratio promote the generation of larger pores. In addition, the effects of the porous structures and the network properties on the swelling properties were explored. The swelling capacity of the porous particles is reduced with an increase in the EGDMA molar concentration. However, higher porosity in the particles and higher amount of hydrophilic comonomer result in a higher swelling capacity of the particles. The gel formation and the porous characteristics of HEMA/comonomer/EGDMA systems were simulated using the mathematical models combining the reaction kinetics and the thermodynamics. It was found that the model over-predicted the experimental results of the porosity because the pores and the networks are shrunk or collapsed during the porogen removal. Therefore, the model predicts the maximum porosity that the polymeric particles can reach. If the hydrophobic contents are higher, the model gives better prediction of the porosity. It is concluded that the microporous structures of HEMA related hydrogels could be controlled by a properly designed process based on the knowledge gained via this research. The output of this research helps with a better understanding for industrial production of micro-porous hydrogels and their applications.

The present study employs a standardized progressive load scratch test (ASTM D7027/ISO 19252) to investigate the fundamental physical and mechanistic origins of scratch deformation in styrene-acrylonitrile (SAN) random copolymers. Previous findings from numerical simulation using finite element methods are used to establish correlation between mechanical properties and key scratch deformation mechanisms of the SAN model systems. For SAN, the acrylonitrile (AN) content and molecular weight (MW) can be changed to alter mechanical properties such as tensile strength and ductility. The key scratch deformation mechanisms are identified as: scratch groove formation, scratch visibility, periodic micro-cracking and plowing. Groove formation has been correlated to the secant modulus at the compressive yield point while micro-cracking and plowing are related to the tensile strength of the material. The fundamentals and physical origins of scratch visibility are discussed. It is explained how unbiased evaluation is accomplished by means of an automatic digital image analysis software package (ASV®). Frictional behavior and the effects of scratch speed and moisture absorption are also addressed. Increasing the AN content and/or the MW of the SAN random copolymers generally enhances the scratch resistance of the material with regard to the onset of the key deformation mechanisms. Increasing the scratch speed increases the brittleness of the material, resulting in failure at lower applied loads. Moisture absorption increases with AN content and imparts a degree of plasticization as the moisture diffuses into the sub-surface. This plasticization initially results in a degradation of scratch resistance with respect to the key deformation mechanisms, but then, after saturation, the moisture on the surface provides lubrication and improves the scratch resistance. It is important to note that polymers are fundamentally different in nature, but the findings of this study serve as an important stepping stone down the path to a deeper understanding of polymer scratch behavior.

During a risk assessment undertaken in a factory dealing with fiber reinforced plastic products in the northwestern part of Peninsular Malaysia, styrene was identified as the most potential hazard in the factory. It was therefore chosen to focus the rest of the risk assessment on this chemical. The purpose of this risk assessment was to find out which negative health effects styrene could have on the factory workers, especially on the laminators who are dealing daily with styrene at a close range during lamination through hand lay-up. This was investigated theoretically through a literature research and practically through measurements of styrene in the air in the factory. The styrene doses were measured on two occasions at several distances away from the potential sources. These measurements were high compared with dose-response relationships found in the literature and various national occupational exposure limit values with regards to styrene. The calculated risk quotient (RQ) was also greater than one and it is therefore likely that styrene has negative health effects on the workers in the factory. The various negative health effects identified in the literature were then included in a risk matrix were they were ranked according to the probability that they would have a negative effect on the factory workers. Hearing- and colourvision effects were ranked as very likely, effects on the central nervous system and the respiratory system as well as livertoxicity were classified as likely and genotoxicity was ranked as a possible negative health effect. In the future it would be interesting to talk to the current laminators and do health check-ups to see if they are suffering from any of the suggested negative health effects. It would also be interesting to follow them on a longterm basis to see if their health is changing and if this can be linked to the styrene handling in the factory. / Vid en riskbedömning i en fabrik i nordvästra Malaysia identifierades styren som den största hälsofaran för fabriksarbetarna, framförallt laminerarna eftersom de ofta hanterar styren på nära håll. Det valdes därför att fokusera den resterande riskbedömningen just på styren och dess möjliga negativa hälsoeffekter. Syftet med studien var att ta reda på om styren kan ha en negativ effekt på fabriksarbetarnas hälsa. Detta undersöktes teoretiskt genom en litteraturstudie och praktiskt genom mätningar av styrenhalten i fabriken. Vid två tillfällen mättes styrenhalten i fabriken. De uppmätta halterna jämfördes sedan med de dos-responssamband som funnits vid litteraturstudien, samt med olika nationella hygieniska gränsvärden för styren. De uppmätta värdena visade sig vara höga jämfört med de funna i litteraturen. Det bidrog tillsammans med den beräknade riskkvoten som visade sig vara större än ett, till slutsatsen att styren har en negativ effekt på fabriksarbetarnas hälsa. De möjliga negativa hälsoeffekter som identifierats i litteraturen rangordnas med hjälp av en riskmatris enligt sannolikheten att de skulle utgjöra en risk för arbetarna i fabriken. Effekter på hörseln och färgseendet ansågs vara mycket sannolikt, effekter på centrala nervsystemet (CNS) och levern samt irritation av andningssystemet ansågs sannolika och att styren skulle vara genotoxiskt ansågs möjligt. Övriga hälsoeffekter ansågs osannolika eller mycket osannolika. I framtida studier skulle det vara intressant att diskutera med de nuvarande laminerarna och undersöka dem medicinskt för att se om de har påverkats utav några av de förväntade hälsoeffekterna. Det vore också intressant att följa dessa arbetare under en längre tid för att se om deras hälsa ändras på något sätt som skulle kunna kopplas till styrenhanteringen i fabriken.

Acrylic resins, synthesized from a mixture of monomers selected from the methacrylate, acrylate and styrene families, are the base polymer components for many automotive coatings due to their excellent chemical and mechanical properties. The low molecular weight polymers with reactive functionalities are made via high-temperature starved-feed free-radical solution semibatch terpolymerization, operating conditions that greatly promote the importance of secondary reactions, such as methacrylate depropagation, and acrylate backbiting, chain scission and macromonomer propagation. In this work, a generalized model for styrene/methacrylate/acrylate terpolymerization has been developed and formulated in the PREDICI software package and poorly understood high temperature mechanisms have been studied. Unknown rate coefficients for methacrylate depropagation, reactivity of acrylate macromonomer and penultimate copolymerization kinetics were determined via separate kinetic experiments. The generality of the terpolymerization mechanistic model was verified against data obtained under a range of polymerization conditions, and provides an exclusive insight into the kinetic complexity of methacrylate/styrene/acrylate terpolymerization at high temperatures. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2010-04-28 19:56:36.906

One of the current problems faced by mankind is the problem of safe disposal of waste rubber. Statistics show that the number of waste tires is continuously increasing at a very rapid rate. Since rubber materials do not decompose easily (due to their crosslinked structure), they end up being a serious ???environmental problem???. An intuitive solution to prevent the accumulation of the scrap tires is to continuously reuse them. A new patented reclamation method was discovered in our laboratory, which makes use of a twin screw extruder (TSE) in order to produce reclaimed rubber (referred as devulcanized rubber (DR) from here on) of very high quality. Also, this method has proven to be more economical than other commercial reclaiming methods. Products made solely from a reclaimed material face challenges from those made by virgin materials because of relatively poor properties. However, the striking advantage of using reclaimed rubbers is the cost reduction. Hence, it is important to work on establishing methods by which these reclaimed rubbers could be efficiently used and incorporated into present day products. The deterioration of properties could be minimized by blending them with varying amounts of other materials. A possibility in this direction is manufacturing of thermoplastic vulcanizates (TPVs) using reclaimed rubber and general purpose thermoplastics. In accordance with this idea, the focus of this research is to prepare DR and polypropylene (PP) based TPVs. DR is unique as the rubber itself consists of two phases- one phase consisting of uncrosslinked (including devulcanized rubber molecules), and the other phase consisting of crosslinked (un-devulcanized) rubber. These un-devulcanized crumbs act as stress concentrators because they do not break-up easily, and lead to poor physical properties. Hence, this project tries to find out ways to increase the interfacial adhesion between the rubber and PP by using reactive and non-reactive techniques. Preliminary experiments were carried out in a batch mixer to compare DR and rubber crumb (CR). DR based TPVs showed better properties than CR based TPVs, however, the properties were not useful for commercial applications. Sulphur based dynamic vulcanization was studied in a batch mixer and found to be not effective in improving the properties of DR based blends. On the other hand, DCP/ sulphur based curing system was found to show significant improvement in properties. Therefore, DCP/sulphur based curing package was studied in detail on the blends consisting of DR and PP. The optimum ratio of DCP/sulphur was found to vary depending on the ratio of DR/PP. A hypothesis regarding the mechanism of DCP/sulphur curing has been proposed, which seem to correlate well with the experimental results observed. Additionally, it was determined that DR prepared from tire rubber (DRT) performed better than DR prepared from waste EPDM (DRE) for the curing system used. Accordingly, experiments on a TSE were carried out using DRT and a combination of compatibilizing resins and curatives. This combination showed a drastic improvement in blends properties and once again the optimum ratio of compatibilizing resins seemed to depend on the ratio of DRT/PP. As a result of the work, successful strategies based on reactive compatibilization techniques were developed in order to prepare useful TPVs having up to 70% DR. A series of compatibilization techniques has been evaluated using design of experiments and various characterization techniques such as mechanical tests, scanning electron microscopy, thermal analysis and crosslink density measurements. This led to the development of a formulation, which could improve the blend properties significantly. A tensile strength of around 10 MPa and an elongation-at-break of 150-180 % could be achieved for devulcanized rubber (70%) based TPVs, which has broadened the scope for its commercial applications. In addition to that, the process was established on a TSE that has enabled a continuous and steady production of these TPVs with reasonable throughputs.

No description available.