• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 5
  • 1
  • 1
  • 1
  • Tagged with
  • 11
  • 11
  • 4
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

An investigation into the utilisation of recycled plastics for design applications

14 January 2014 (has links)
M.Tech. (Interior Design) / In an endeavor to achieve, the activities of many industries will need to transform and design is no exception. Commercial design has played a substantial role in contributing towards waste-generation, pollution and the exhaustion of non-renewable resources. Fundamental to achieving sustainable development is the need to determine design's contribution to economic growth in relationship to social development and environmental preservation, as these issues are completely interdependent (and need to be considered as such) if sustainability is ever to be achieved. Although much theoretical information about sustainable design has been made available, little evidence exists to prove that this theory is being put into practice, specifically in South Africa. It is also unlikely that the solutions engineered in some of the more developed countries can simply be transferred into the context of a developing nation with its own very specific social, economic and environmental conditions. This seems to justify the need to research practical and contextualized methods of implementing sustainable design theory. The main research methodology implemented in this project has taken the form of applied or practice-based research, in order to determine the feasibility of implementing established ecological design theories. Initially, theoretical research was conducted to establish the principles of sustainable design; these principles were then contextualized according to South African specific conditions and manifested in a practical application in the design and manufacture of artifacts. A consumer sampling was also undertaken to determine consumer response and economic viability of these products...

Design and development of an infrared heater for waste plastic gasification / by .

Haruon, Zuhair Eltigani Matar January 2013 (has links)
Thesis submitted in fulfillment of the requirements for the degree Master of Technology: Electrical Engineering in the Faculty of Electrical Engineering at the Cape Peninsula University of Technology 2013 / This research outlines the design, manufacturing and analysis of a far infrared ceramic heater for waste plastic gasification. The study includes the theoretical overview which concentrated on the mathematical modelling of the far infrared ceramic heater, as well as mathematical modelling of infrared gasifier. Secondly, the study presents an overview of the manufacturing process of the ceramic infrared heaters. Testing of the manufactured heaters has been performed to validate the efficacy of the heaters. The model includes non-grey radiative heat transfer between the different parts of the heaters, conduction in ceramic material, convective cooling of the surface, surface balances, and blackbody radiation theories. Using infrared module voltage as input, model predictions of temperature and wavelengths using Fourier equations were found to agree well with experimental data. The ceramic infrared heaters developed in this research are fully functional and all intended test results were obtained. The spectral analyses of different plastics (Polyethylene terephthalate, Polypropylene, Low-density polyethylene and High-density polyethylene) have been performed. ‘Heat rate’ and ‘cool rate’ of the infrared ceramic heaters have also been characterised. Gasification of plastic waste as carbonaceous material, basic reactions during gasification of plastics, and gasification products have also been discussed, including gasifier properties. The results obtained from the experiments show that using infrared heaters in gasification is practically sound because of the ability of infrared radiation to gasify waste plastics and production of syngas. This project recommended the infrared radiation because of its high efficiency in gasification of waste plastic and the production of syngas. This article reviews the infrared radiation heating and discusses the theoretical aspects of infrared radiation and the validity of infrared radiation heating in gasification of waste plastics. This research also provides a review of literature in the applications and benefits of infrared heaters.

Compatibilization of Immiscible Polymer Blends Using Polymer-Grafted Nanoparticles

Alkhodairi, Husam January 2022 (has links)
Recycling is one of the most important strategies for combating plastic pollution. However, before plastic waste can be converted into other items, the different types of plastic present in it must be sorted, a time-consuming and expensive process. Indeed, it is often more cost-effective to manufacture new plastic materials than to recycle existing plastic waste. Researchers are therefore attempting to eliminate the sorting process altogether and directly recycle the mixed plastic waste. While this would lead to phase-separated mixtures with temporally evolving domains and poor fracture toughness properties, these problems could be mitigated to some extent by incorporating surfactant-like macromolecular compatibilizers, such as block copolymers or random copolymers (RCPs). These compatibilizers preferentially localize at polymer/polymer interfaces, lowering droplet coalescence and interfacial tension in the process. Moreover, the macromolecular structure of these compatibilizers enables them to form entanglement networks across the interface, thus enhancing stress transfer and fracture toughness. Nanoparticle (NP)-based compatibilizers have recently attracted attention due to their significantly stronger suppression of droplet coalescence under certain conditions. Unfortunately, while these compatibilizers work relatively well in oil/water emulsions, they perform poorly in immiscible polymer blends. This is because most polymer blends consist of hydrophobic components, making the NPs gravitate toward one of the bulk phases rather than the interface. Moreover, their rigid cores function as stress concentrators in polymer matrices, causing further deterioration to the fracture toughness properties of the blend. In this dissertation, we construct hybrid compatibilizers consisting of NP cores and outer grafted polymer layers. In this manner, the desired features of both macromolecules and NPs are combined into a single compatibilizer: the NP cores suppress droplet coalescence, while the polymer grafts direct the NPs to the interface and form entanglements. We investigate the effectiveness of these hybrid compatibilizers in three critical areas: NP localization control, droplet coalescence suppression, and fracture toughness enhancement. In each area, we perform systematic studies using an immiscible polymer blend composed of poly(methyl methacrylate) (PMMA) and polystyrene (PS) in order to find the optimal compatibilizing effect as a function of graft chemistry, graft molecular weight, and grafting density. We demonstrate that the most efficient hybrid compatibilizers are those with a surfactant-like architecture. For example, silica NPs sparsely grafted with PS chains can form a dense monolayer packing at the immiscible PMMA/PS interface. In this example, surfactancy is derived from a balance of enthalpic interactions: the silica core strongly interacts with the PMMA phase, while the PS grafted layer mixes intimately with the PS phase. The hydrophilic–lipophilic balance is readily controlled by varying the contact area of each interaction through the grafting density or the graft molecular weight. Similarly, we show that silica NPs grafted with surfactant-like polymer chains, such as styrene–methyl methacrylate RCPs, can also localize at the PMMA/PS interface. Here, surfactancy is derived mainly from the RCP grafts. There are two advantages to using RCP grafts. First, it allows for interfacial localization even if the grafted layer completely encapsulates the silica core (i.e., at high grafting densities). Second, RCP grafts can entangle on both sides of the interface and thus transmit stress more efficiently than PS grafts, which only entangle on the PS side of the interface. There are two advantages to using this latter approach. First, RCP grafts can entangle on both sides of the interface and thus transmit stress more efficiently than PS grafts, which only entangle on the PS side of the interface. Second, it allows for interfacial localization even if the grafted layer completely encapsulates the silica core (i.e., at high grafting densities). Our research shows that both forms of hybrid compatibilizers significantly outperform conventional ungrafted macromolecular compatibilizers in droplet coalescence suppression. Interestingly, coalescence can be suppressed even when the hybrid compatibilizers only partially cover the dispersed droplets. We believe that this is due to the grafted layers forming strong entanglement networks around the droplets that function as barriers to coalescence. Linear rheology experiments corroborate this reasoning: the low-frequency storage moduli of the compatibilized blends approach a plateau when the NP grafting density is increased, suggesting the presence of a network structure at the interface. For fracture toughness experiments, we employ RCP-grafted NPs to exploit their entanglement on both sides of the interface. We show that when a moderate grafting density is used, the fracture toughness of the PMMA/PS interfaces exceeds that of the interfaces compatibilized with ungrafted RCP analogs. This again results from the brush entanglement network at the interface. Specifically, in the moderate grafting density zone, RCP brushes form a more connected entanglement network than ungrafted RCPs and are thus more efficient at transmitting stress across the interface. In summary, we have developed a method for accurately controlling the localization of NP-based compatibilizers in immiscible polymer blends. We have also identified the grafting conditions under which these hybrid compatibilizers outperform conventional macromolecular compatibilizers in both droplet coalescence suppression and fracture toughness enhancement.

Pre-treatment processing of household plastic packaging waste

Blackstock, Ross January 2016 (has links)
A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in fulfilment of the requirements for the degree of Masters in Engineering. Johannesburg, 2016 / The purpose of this investigation was to investigate whether or not it would be possible to separate blow moulded and injection moulded waste plastics using two techniques; air classification and ballistic separation. Air classification and ballistic separation are two techniques that separate different types of material according to size, shape and density. Previous research, together with new measurements, has suggested that blow mould plastics tend to be thinner in terms of wall thickness than injection moulded plastics meaning that air classification could be used to separate each type of plastic. The material used for the study was supplied by a Romanian recycler and was a mixture of High Density Polyethylene and polypropylene. Two additional samples, one Polyethylene rich and the other polypropylene rich, were also included in the research. The first part of the study involved measuring different characteristics of the material to determine how to go about performing the different air classification experiments. The second part of the study focused on separating the different material samples using different air classifier systems and a ballistic separation system. The third part of the study focused on processing the samples from part 2 (air classification) into test specimens for further mechanical and melt flow property measurements. After measuring the mechanical and melt flow properties of the different samples it was found that air classification did not substantially improve the mechanical or melt flow properties of the material. The study did, however, show that there is a strong correlation between polymer type and melt flow properties. High Density polypropylene is generally used for blow mould applications whereas polypropylene is generally used for injection mould applications. Separating the material according to polymer type therefore means that the material is, to an extent, also sorted according to melt flow properties. / MT2017

Systematic Design of Bulk Recycling Systems under Uncertainty

Wei, Jing 13 May 2004 (has links)
The fast growing waste stream of electronic and other complex consumer products is making the bulk recycling problem an important environmental protection issue. These products must be recycled because they contain hazardous materials such as lead and mercury. The focus of this thesis is the development of systematic methods for designing systems to recover mixed plastics from electronic products such as computers and televisions. Bulk recycling systems are similar to other chemical engineering process systems. Therefore they can be synthesized and designed using some existing techniques that have been applied to distillation and reaction systems. However, the existence of various uncertainties from different sources, such as the variation of component fractions and product prices, makes it crucial to design a flexible and sustainable system, and is also a major challenge in this research. Another challenge is that plastics can be separated by different mechanisms based on different properties, but separating a mix of plastics often requires using a combination of different methods because they can have overlapping differentiating properties. Therefore many decisions are to be made including which methods to choose and how to connect them. To address the problem systematically, the design under uncertainty problem was formulated as a stochastic Mixed Integer Nonlinear Program (sMINLP). A Sample Average Approximation (SAA) method wrapped on the Outer Approximation method has been developed in this thesis to solve such problems efficiently. Therefore, large design under uncertainty problems can be solved without intractable computational difficulty. To allow making choices from separation methods by different mechanisms, this research modeled various plastics separation methods taking account of the distribution of particle properties and unified them using a canonical partition curve representation. Finally, an overall design method was proposed in this work to incorporate the design of size reduction units into the separation system. This research is the first formal development of a systematic method in this area to account for uncertainties and interactions between process steps.

Estudo da avaliação de ciclo de vida do PLA : comparação entre a reciclagem química, mecânica e compostagem / Life cycle assessment study of PLA : comparison between chemical recycling, mechanical recycling and composting

Cosate de Andrade, Marina Fernandes, 1988- 27 August 2018 (has links)
Orientadores: Ana Rita Morales, Otávio Cavalett / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-27T19:01:47Z (GMT). No. of bitstreams: 1 CosatedeAndrade_MarinaFernandes_M.pdf: 2991365 bytes, checksum: df7e463a288c5c88feea3df3157d956a (MD5) Previous issue date: 2015 / Resumo: Este projeto teve como objetivo realizar uma Avaliação do Ciclo de Vida comparando três formas de destinação do poli(ácido láctico) (PLA) e estudar a reciclagem deste polímero, que pode ser mecânica ou química. A reciclagem mecânica foi realizada por duas extrusões do PLA. No segundo processamento, o polímero proveniente da primeira extrusão foi dividido em duas partes, sendo que uma porção recebeu adição de um extensor de cadeia comercial. As amostras obtidas foram caracterizadas por Calorimetria Diferencial Exploratória (DSC), Cromatografia por Permeação em Gel (GPC), Índice de Fluidez, Análise Termogravimétrica (TGA), ensaio de resistência ao impacto Izod e ensaio de tração. Os resultados obtidos mostraram que o número de extrusões diminuiu a massa molar, o índice de fluidez e a estabilidade térmica e aumentou a cristalinidade do polímero. A presença do extensor de cadeia causou a recuperação dessas propriedades. Além disso, o módulo de elasticidade e o alongamento na ruptura sofreram alterações importantes com o aumento da cristalinidade do material. A reciclagem química foi realizada pela hidrólise do PLA, que gera ácido láctico, e posteriormente pela polimerização do ácido láctico, em que é obtido novamente PLA, através da policondensação direta. O ácido láctico foi caracterizado por Cromatografia Líquida de Alta Eficiência (HPLC) e o rendimento da reação obtido foi acima de 95%. O PLA polimerizado foi identificado por Espectroscopia do Infravermelho por Transformada de Fourier (FTIR) e sua massa molar foi medida por Cromatografia por Permeação em Gel (GPC). Os resultados da Avaliação do Ciclo de Vida para os métodos e categorias estudados mostraram que a reciclagem mecânica apresentou o menor impacto ambiental, seguida pela reciclagem química e pela compostagem. Dentre as formas de reciclagem, o insumo mais importante foi o consumo de energia elétrica / Abstract: This project aimed to conduct a Life Cycle Assessment comparing three forms of poly(lactic acid) (PLA) disposal and to study the mechanical and chemical recycling of this polymer. Mechanical recycling was performed by two extrusions of PLA. In the second extrusion, part of the material was processed with a commercial chain extender. The samples were characterized by Differential Scanning Calorimetry (DSC), Gel Permeation Chromatography (GPC), Melt Flow Index, Thermogravimetric Analysis (TGA), Izod test and Tensile test. The results showed that the molecular weight, Melt Flow Index and thermal stability decreased and the crystallinity degree of the polymer increased with the extrusion number. The presence of a chain extender recovered these properties. Furthermore, Young modulus and elongation at break undergo important changes with the crystallinity increase. The chemical recycling was performed by hydrolysis reaction, which produced lactic acid. PLA was obtained through the direct condensation polymerization from lactic acid monomer. Lactic acid was characterized by High Performance Liquid Chromatography (HPLC) and the reaction yield was above 95%. The polymerized PLA was identified by Fourier Transform Infrared Spectroscopy (FTIR) and Gel Permeation Chromatography (GPC). Considering the methods and impact categories studied, the Life Cycle Assessment showed that mechanical recycling had the lowest environmental impact, followed by chemical recycling and composting. Among the forms of recycling, the most important input was the electricity consumption / Mestrado / Ciencia e Tecnologia de Materiais / Mestra em Engenharia Química

Technologie výroby tělesa konektoru z recyklátu / Production technology of the connector body from recykled material

Brhel, Michal January 2016 (has links)
Study developed during the Master's degree studies of Mechanical Engineering deals with the use of recycled plastic in the injection molding and its influence on the mechanical properties of the mold. Examined product is used in the automotive industry as a connector body. The housing is manufactured from a plastic material, polyamide. The annual production volume of 3 000 000 pieces. According to tests specified in standard USCAR2 regrind influence on mechanical properties and dimensions was evaluated. After the technical evaluation of the project, research was also judged from economic point of view. In this task, savings with the different content of the recycled material during production was calculated. The final chapters justify change of properties and they are proposing the use of recycled materials in practice.

Surface Topography and Aesthetics of Recycled Cross-Linked Polyethylene Wire and Cable Coatings

Xie, Wa 12 1900 (has links)
Our research focuses on re-using a waste a material, cross-linked polyethylene abbreviated XLPE, which is a widely used coating for wires. XLPE is strong and has excellent thermal properties due to its chemical structure - what leads to the significance of recycling this valuable polymer. Properties of XLPE include good resistance to heat, resistance to chemical corrosion, and high impact strength. A wire is usually composed of a metal core conductor and polymeric coating layers. One creates a new coating, including little pieces of recycled XLPE in the lower layer adjacent to the wire, and virgin XLPE only in the upper layer. Industries are often wasting materials which might be useful. Mostly, some returned or excess products could be recycled to create a new type of product or enable the original use. This method helps cleaning the waste, lowers the costs, and enhances the income of the manufacturing company. With the changing of the thickness of the outer layer, the roughness changes significantly. Moreover, different processing methods result in surfaces that look differently.

<strong>Synthesis, Recycling, and Processing of Topochemical Polymer Single Crystals</strong>

Zitang Wei (16325274) 15 June 2023 (has links)
<p>  </p> <p>Plastics play crucial rules in almost every aspect of life. Unique properties of plastics like chemical and light resistant, strong, moldable, and low cost make plastic materials useful in many aspects of our global society. However, largely relying on feedstock resources like fossil fuels, plastics production is not sustainable. Thus, plastic recycling could be an efficient alternative to save feedstock resources as well as to reduce production cost.</p> <p>Recently, a series of polymer materials synthesized via topochemical polymerization are considered as strong candidates for next generation recyclable plastics. It is well-known that topochemical polymerization has high efficiency and environment-friendly features, such as solvent-free and catalyst-free reaction conditions, high reaction yield without side reactions, and atom economy. Yet, there exist few studies on depolymerizing and recycling those polymers. A unique topochemically polymerizable polyindenedione derivative [2,2'-Bi-1H-indene]-1,1'-dione-3,3'-diyl dialkylcarboxylate (polyBIT) with rapid and quantitative depolymerization was discovered via breakage of elongated carbon-carbon (C-C) bonds with bond length of 1.57∼1.63 Å. The elongated C-C bonds have been proven theoretically and experimentally to have significantly lower bond dissociation energies than normal C-C bonds, and it is the major driving force to depolymerize polyBIT polymer single crystals. </p> <p>Different from most traditional polymers that can be dissolved or melt processed, topochemical polymer single crystals are not soluble in most common solvents due to their highly crystalline and ordered nature. This unique feature inhibited topochemical polymer crystals from practical applications. To convert needle-like polyBIT crystals into useful forms, I developed an ultrasonication method to break large polymer crystals into small fibers that can be uniformly suspended in organic solvents. Followed by vacuum filtration and heat press, polyBIT crystals can be processed into robust and freestanding polymer thin films. The processed thin films presented reasonable mechanical properties with Young’s modulus of over 600MPa and are stable under harsh conditions.</p> <p>Topochemical polymerization reactions require specific monomer packings before applying external stimuli, and a small change in monomer structure may completely alter the reactivity. Therefore, functionalizing monomer structures for topochemical reactions is quite challenging. In the polyBIT system, we attempted to functionalize BIT monomer with several linear and branched side chains. After preparing monomer crystals, only needle-like 1D monomers can be photopolymerized, while plate-like 2D monomer crystals became photostable. Introducing heteroatoms (such as oxygen, sulfur, bromine, chlorine) can induce different non-bonding interactions and interactions, which combined can push monomers away from one another to make them unreactive. Introducing branched side chains will also change the distances between two BIT monomers and leads to unreactive crystals when the branched side chain is too bulky (such as when tertbutyl group is on the end of side chain). Functionalizing side chains for polyBIT crystals can further tune the mechanical properties of the crystals: swapping end methyl group with a simple bromine atom can induce multiple intermolecular and interchain interaction including weak hydrogen bonding and C−H···Br interactions. These interactions bind all the polymer chains together to provide a strong 1D polymer fiber with elastic modulus over 10.6 GPa. These results suggest that the crystalline polymers synthesized from simple photochemistry and without expensive catalysts are promising for practical applications with complete materials circularity and wide range of structural and mechanical turnabilities.</p>

Low-carbon hydrogen production from waste plastics via pyrolysis and in-line catalytic cracking process / Vätgasproduktion med låga kolutsläpp av plastavfall via pyrolys kombinerad med katalytisk reformering

Jin, Yanghao January 2022 (has links)
This study develops a novel pyrolysis process combined with in-line catalytic reforming toproduce high purity hydrogen and carbon products from waste plastics. The input resource is waste plastic material in the form of discarded Covid masks. Results show that for the optimized pyrolysis followed by in-line biochar-based catalytic reforming process, the hydrogen yield is 98.2 mg/g-mask (up to 87% purity), and the carbonyield is 642.4 mg/g-mask, with over 70% of the waste plastic being completely cracked to elemental carbon and hydrogen. The overall process has virtually no CO2 emissions. The use of biomass char catalysts has been studied to contribute to increased hydrogen yield. This is because the unique porous structure of the biochar catalyst increases the residence time of the pyrolysis vapor in the catalytic layer, allowing sufficient cracking of the macromolecular vapor, therefore, increasing the hydrogen yield. The process is also facilitated by the cracking temperature, which increases the cracking of the pyrolysis vapor, resulting in an increase in char yield. However, high temperatures may breakdown the structure of the biomass char catalyst, causing more of the pyrolysis vapor to be converted to CH4, reducing the hydrogen yield. The optimum hydrogen yield was obtained at process parameters of a Biochar catalyst-to-Maskratio (C/M ratio) of 2 and a cracking temperature of 900 oC. / Detta examensarbete utvecklar en ny pyrolysprocess kombinerad med en katalytisk reformeringsprocess i följd för att producera högrenade väte- och kolprodukter från plastavfall. Resursen till processen består av avfallsprodukter i form av kasserade munskydd. Resultaten visar att för den optimerade pyrolys- och biokol-katalytiska reformeringsprocessen är vätgasavkastningen 98,2 mg/g plastavfall (upp till 87 % renhet) och kolavkastningen 642,4 mg/g plastavfall, med över 70 % av plastavfallet fullständigt knäckt till enkla kol- och vätemolekyler. Den genomgripande processen har praktiskt taget inga koldioxidutsläpp. Användningen av biokol-katalysatorer av biomassa har studerats för att bidra till ett ökat vätgasutbyte. Detta beror på att biokolkatalysatorns unika porösa struktur ökar uppehållstiden för pyrolysångorna i det katalytiska skiktet, vilket möjliggör tillräcklig krackning av de makromolekylära ångorna och därmed ökar vätgasutbytet. Processen underlättas också av krackningstemperaturen, som ökar krackningen av pyrolysångorna, vilket leder till ökad kolavkastning. Höga temperaturer kan dock bryta ned strukturen hos katalysatorn för biomassakol, vilket gör att en större del av pyrolysångorna omvandlas till CH4, vilket minskar vätgasutbytet. Det optimala vätgasutbytet uppnåddes vid C/M-parameter (katalysator-till-munskydd förhållande) = 2och en krackningstemperatur på 900 0C.

Page generated in 0.1707 seconds