159 research outputs found
Development of high performance polymer blends
No full textMain aim of the project is to develop high performance polymer blends.RG 45/9
Evaluation of roughness, hardness, and strength of AA 6061 molds for manufacturing polymeric microdevices
No full textIn the manufacturing of polymeric microfluidic devices, micro-molds play a key role because they determine not only the manufacturing cost but also the quality of the molded parts. Recently, a high-quality aluminum alloy 6061 (AA6061) mold with fine features less than its grain size has been fabricated economically by a hot embossing technique. However, temperature cycling during hot embossing process in mold manufacturing reduces significantly the original tensile strength and hardness of the AA6061-T6 alloy substrate, which is not desirable. In this study, a tempering process is carried out to recover the tensile strength and hardness of the embossed mold. To evaluate the changes of these properties, surface roughness, tensile strength, and hardness values were measured in each stage: (1) before hot embossing, (2) after hot embossing, and (3) tempering to T4 and tempering to T6. The results obtained demonstrate that the original strengths and hardness can be fully recovered by a post-tempering process after hot embossing, but with an increase in surface roughness. Moreover, accelerated testing was carried out to evaluate the changes in hardness and roughness of AA6061-T4 and T6 molds under the typical hot embossing temperature cycles of manufacturing polymeric devices. The results obtained indicate that these temperature cycles have only a minor effect on the roughness of both T4 and T6 molds and will increase the hardness of T4 molds to T6 temper, and have negligible effect on the hardness of a T6 temper mold
Modeling of polycarbonate and thermotropic liquid crystalline polymer blends
No full textThe liquid crystalline polymer (LCP) belongs to a class of new polymers which were developed for their high performance properties such as tensile strength and modulus. The excellent properties of a liquid crystalline polymer can be attributed to its capacity for in-situ fiber formation during melt processing. However, LCPs are expensive. To lower costs, polymer blends containing LCP are utilized. The possibilities of using LCP as processing aids and/or for reinforcement are being explored. It has been shown that small amounts of LCPs may significantly lower the melt viscosity of many flexible polymers, thus enhancing their processability. LCPs can be blended with many common thermoplastics, without changing the processing techniques normally used for them.Master of Engineering (MPE
Polymer microfluidic devices : thermo-mechanical properties of COC polymer
No full textThis project investigates the thermo-mechanical properties of Topas Cyclic Olefin Copolymer (Topas COC) for three different grades; 8007,5013 and 6015. Experiments were conducted at temperatures ranging from room temperature to above the glass-transition temperatures of the polymer.Bachelor of Engineerin
Polymer microfluidic devices : effect of surface treatment on bonding and flow
No full textThis projects uses Topas® COC fabricated microchannels to investigate the effects of surface treatment by measuring flow of solutions under an electric current. The author made use Topas® COC Grade 6015 and 5013 in pellets to form a microchannel substrates are then bonded together using the hot embossing method. Various treatments are performed on the surface of the microchannels with the bulk being photografted samples.Bachelor of Engineering (Mechanical Engineering
Polymer micro-fluidic devices: hot embossing of topas® using molds made of different materials
No full textIn the field of hot embossing of polymers for microfluidic devices, there is a lack of research into the performance of molds (dies) made of silicon, epoxy and TOPAS® COC grade 6017 (polymer of higher Tg) under identical experimental conditions, although all 3 materials have a set of promising advantages and are all easy to fabricate. This project explores the performance of silicon, epoxy and TOPAS® COC grade 6017 molds used to create micro-channels on TOPAS® COC grade 8007 substrates by the hot embossing method. In the subsequent part of the paper, the author takes into consideration thermal conductivity and mold thickness differences between the silicon and epoxy molds, an additional step of preheating is thus introduced. The results indicate that epoxy is the ideal choice for molds meant for the hot embossing. Generally, the author finds evidence that epoxy has low adhesion between the mold and substrate and the lowest surface roughness, is rugged and the most cost-efficient to mass fabricate.Bachelor of Engineering (Mechanical Engineering
Development of polyaniline nanostructures using bio-soft-template approaches and graphene-based composites for supercapacitor applications
No full textThe focus of the current work is to develop a supercapacitor that has energy density which is comparable with high energy batteries, but with the advantages of supercapacitors such as high power density and long rechargeable cycle life. The selected approach was to enhance both the electrical double-layer capacitance and pseudo-capacitance. To achieve these, electrodes based on a graphene/polyaniline composite system that has the appropriate morphology, microstructure and composition to provide the optimum properties were developed. The 2D graphene sheets have the tendency to aggregate or stack which reduces the available surface area and limits the ion transport during electrochemical process. This makes it difficult for the stacked graphene assembly to achieve optimum device performance. Thus, we report a strategy to solve these problems by transforming the aggregated graphene sheet into an open assembly structure by introducing a spacer (p-phenylenediamine (PPD)) between the layers by covalent functionalization. Compared to stacked graphene sheet, the modified graphene sheet (GPPD) is capable of delivering a much higher specific capacitance and energy density of 232.96 F/g and 32.38 Wh/kg (almost 2-fold), respectively at the current density of 500 mA/g in aqueous 1 M H2SO4 solution. The retention of capacitance of this electrode was found to be 92.92% after 1000 charge-discharge cycles.
Polyaniline (PANI) nanostructures (viz. nanotubes and nanofibers) networks with different morphology were synthesized by chemical oxidative polymerization method using the bio-molecules like vitamin C and heparin. We report the discovery of an unprecedented behavior of vitamin C which forms a rod-like assembly through hydrogen-bonding in water, which produced PANI nanotubes upon the addition of aniline monomer. The tubular growth of PANI at the nanometer scale can be controlled by the variation of molar ratio of vitamin C to aniline. The polymerization rate became slower at higher molar ratio, whereas at lower molar ratio of 0.25 (i.e. [Vitamin C]/[Aniline] = 0.25), uniform nanotubes (PANIV-0.25) were observed. The outer diameter of the nanotube was in the range of 80 - 120 nm. Surprisingly, no polymerization was observed at an equal molar ratio of vitamin C to aniline. Besides this, with heparin template, uniform nanofibers were also synthesized when the weight ratio of heparin to aniline was 0.25 (PANIH-0.25). The uniform nanofibers obtained had average diameters of between 80 - 110 nm. No uniform PANI nanofibers were formed at other weight ratios. We have further studied the novelty of PANI nanotubes and nanofibers as nanostructured electrode materials for supercapacitor applications. The PANIV-0.25 nanotube based electrodes showed higher capacitance and energy density values of 619.76 F/g and 86.14 Wh/kg at 500 mA/g current density in aqueous 1 M H2SO4 solution, respectively, with a cyclic stability of 76.74% capacitance retention after 1000 cycles. On the other hand, the PANI nanofiber electrode (PANIH-0.25) yielded a higher specific capacitance and energy density values of 732.18 F/g and 101.77 Wh/kg, respectively, where the retention of capacitance was 72.28% after 1000 cycles at the same current density. The observed capacitances were also elucidated and justified based on theoretical considerations, which showed the good agreement between the observed and theoretical values. The graphene/PANI nanostructures (nanotubes and nanofibers) based composites were then fabricated and evaluated. The graphene nanosheet/PANI nanotube composites were fabricated by in situ chemical oxidative polymerization of aniline using vitamin C as a template. The G20PNT80 composite showed the best current-voltage response and the maximum specific capacitance was found to be 671.79 F/g at 500 mA/g current density in aqueous 1 M H2SO4 solution. The composite presented an excellent cycle life with 89.33% specific capacitance retention after 1000 cycles. The specific energy density was calculated to be 93.38 Wh/kg.
Next, graphene/PANI nanofibers composites were synthesized using a novel in situ chemical oxidative polymerization of aniline using heparin as a template.The novel G25PNF75 composite showed a high specific capacitance of 690.68 F/g and an excellent energy density of 96 Wh/kg at a discharge current density of 500 mA/g. When the current density was reduced to 250 mA/g, the composite showed specific capacitance and energy density values of 890.79 F/g and 123.81 Wh/kg, respectively. This energy density is comparable to that of high energy batteries. Moreover, the composite exhibited excellent cycle life with 88.78% specific capacitance retained after 1000 cycles. The significantly improved specific capacitance is due to the synergistic effect in the composite. The excellent cyclic stability over the entire cycle life can be attributed to the good mechanical stability of the composite electrode. Thus, this composite with such a high specific capacitance is a very promising electrode material for supercapacitor applications.DOCTOR OF PHILOSOPHY (MAE
Surface modification and characterisation of high performance thermotropic liquid crystalline polymer fibres
No full textVectran fibre is a high-performance thermotropic multifilament yarn spun from
Vectra® liquid crystal polymer (LCP). This fibre is the only commercially available
melt spun LCP fibre in the world. Its exceptional strength and rigidity render itself for good market penetration. This body of work aimed to characterise Vectran fibre and study the effects of surface
modification on this fibre. Before the surface modification attempt, Vectran fibre' s inherent bulk properties were carefully analysed utilising scanning electron microscopy (SEM), thermal analysis and
tensile test. Two important types of Vectran fibres, Vectran HS (VHS) and Vectran
M(VM) fibre, were characterised and the structure-property relationship was
investigated by Spectroscopy Analysis, Element Analysis, Thermal Analysis and
Tensile Test. Spectroscopy and CHNO analysis found that VHS has higher HNA/HBA
ratio than VM fibre. Thermal analysis and tensile test results show that VHS fibre has
higher rigidity and crystallinity than VM fibre. The Module of VHS fibre is twice than
that of VM fibre and the crystalline-nematic transition temperature of VHS is also
higher than that of VM. The Morphology and microstructure of Vectran fibre were
studied by Scanning Electron Microscopy (SEM). The apparently banded structure was
seen on the surface of Vectran fibres.Master of Applied Scienc
Strength and toughness of bonded joints in thermoplastic polymer microfluidic devices
No full textIn the field of hot embossing of polymers for microfluidic, there is a lack of study into the relationships of bonding strength and bonding toughness with regard to the different bonding parameters.
This project aims to explore the relationship of bonding strength and toughness under different parameters, which are identified as bonding temperature, time and loading. The material that is used for the entire course of experiment is TOPAS® COC grade 8007. Although this thermoplastic copolymer is a relatively new polymer material, it is a low-cost alternative that has been gaining popularity due to its excellent physical and chemical properties. Injection molding process will be carried to produce the polymer substrates due to its fast production rate and high output accuracy.Bachelor of Engineering (Mechanical Engineering
Composites for marine and offshore applications : thermal and mechanical characterization of epoxy matrix
No full textTo enhance toughness and to reduce the brittleness character of epoxy by varying percentage of curing agent DDM. To investigate the thermal and Mechanical characterization of epoxy resin after curing with different percentage of curing agent.Bachelor of Engineering (Mechanical Engineering
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