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Full-Text Articles in Engineering
Synthesis Of Zeolites With Controlled Defects By Understanding The Role Of Charge Balance In Zeolite Crystallization, Song Luo
Doctoral Dissertations
Zeolites are well-defined and ordered microporous crystalline materials constructed by the continuous linkage of corner sharing TO4 tetrahedra (taking T atoms (e.g., Si or Al) as the tetrahedral center). Due to the structural and compositional diversities and superior hydrothermal stability, zeolites have been broadly utilized to many industrial fields, including gas separation and catalysis heterogeneous catalysis. However, understanding zeolite crystallization mechanisms remains a tantalizing challenge, which causes challenges in tailoring this material for advanced applications. Raman spectroscopy has emerged as a powerful tool for probing medium-range (0.35 - 1 nm) structures. Since this scale is consistent with the micropore size …
The Role Of Chain Configuration In Governing The Rational Design Of Polymers For Adhesion, Onyenkachi Wamuo
The Role Of Chain Configuration In Governing The Rational Design Of Polymers For Adhesion, Onyenkachi Wamuo
Doctoral Dissertations
ABSTRACT THE ROLE OF CHAIN CONFIGURATION IN GOVERNING THE RATIONAL DESIGN OF POLYMERS FOR ADHESION SEPTEMBER 2017 ONYENKACHI C. WAMUO, B.Eng., FEDERAL UNIVERSITY OF TECHNOLOGY, OWERRI (FUTO), NIGERIA M.S., UNIVERSITY OF MASSACHUSETTS AMHERST Ph.D., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor Shaw Ling Hsu The chain configurational control of polymers used in adhesion can be utilized as a means of tuning the cohesive properties of hot melt adhesives (HMAs). The cohesive properties control the solidification, strength, setting speed. Propylene-Ethylene copolymers (PP-co-PE) and thermoplastic polyurethanes (TPUs) were studied. In the first project, the effects of sequence distribution of the two types …
Solution, Interfacial, And Interlayer Studies Of Electronically Active Polymers, Hsin-Wei Wang
Solution, Interfacial, And Interlayer Studies Of Electronically Active Polymers, Hsin-Wei Wang
Doctoral Dissertations
This thesis describes the solution behavior and interfacial properties of electronically active polymers. The performance of such polymers in devices is often determined by their chain conformation and morphology in solution and in thin films. For example, the intricate balance between polymer domain size and crystalline packing of electron donor and acceptor components, as well as the properties at the polymer-metal interface, are crucial for achieving optimal performance in devices, such as solar cells. Chapter 1 presents the current progress in polymer-based solar cells, their fundamental principles, and key factors to improve their efficiency. Literature precedents on the development of …
Process-Structure-Property Relationship In Ultra High Molecular Weight Polytetrafluoroethylene And Double Network Epoxies, Ranadip Ganguly
Process-Structure-Property Relationship In Ultra High Molecular Weight Polytetrafluoroethylene And Double Network Epoxies, Ranadip Ganguly
Doctoral Dissertations
The focus of this dissertation is to develop a fundamental understanding of process-structure-property relationship in two different classes of polymers: semi-crystalline Ultra High Molecular Weight Polytetrafluoroethylene (UHMWPTFE) and amorphous glassy double network (DN) epoxies. Conventional melt processing techniques such as extrusion and injection molding cannot be applied to UHMWPTFE due to its very high melt viscosity (1010-1011 poise). Therefore, UHMWPTFE is industrially processed by a modified metallurgy technology-sintering. However, the fundamental mechanism for UHMWPTFE sintering is unknown. Further, this process is highly time consuming, cost inefficient and hinders the recyclability of the material. The first part of …
Investigation Of Hydration Induced Structural Rearrangements Of Poly(Lactic Acid), Omkar Vidyadhar Vyavahare
Investigation Of Hydration Induced Structural Rearrangements Of Poly(Lactic Acid), Omkar Vidyadhar Vyavahare
Doctoral Dissertations
A comprehensive analysis of microstructural changes associated with hydration of Poly(lactic acid) (PLA) and their effect on the macroscopic properties has been provided. Although water absorbed in PLA is extremely small (~0.5% by weight or 1 water molecule per 30 PLA monomer units), we found significant increase in the kinetics of physical aging and crystallization in the presence of water. The fact that water has such a strong effect on PLA structure is attributed to the polar nature of water, strong intermolecular interactions present in PLA and their changes in the hydrated state. Using vibrational spectroscopy, features associated with bound …
On The Morphology Of Polymer-Based Solar Cells To Achieve Higher Device Performance, Yu Gu
On The Morphology Of Polymer-Based Solar Cells To Achieve Higher Device Performance, Yu Gu
Doctoral Dissertations
It has been recognized that the morphology of the active layer of the polymer-based solar cells has a great influence on the device performance. To push the efficiency to a higher level, morphology design and control by varying processing conditions are crucial. The theme of this dissertation is to characterize and understanding of the morphology of the active layer of polymer-based solar cells and the role that the morphology plays on device performance, so as to develop routes by which the morphology can be optimized. The focus of this dissertation is first on a binary system consisting of poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b’]-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) …
Effects Of Molecular Architecture On Crystallization Behavior Of Pol(Lactic Acid) And Ethylene-Vinyl Acetate, Jeffrey Paul Kalish
Effects Of Molecular Architecture On Crystallization Behavior Of Pol(Lactic Acid) And Ethylene-Vinyl Acetate, Jeffrey Paul Kalish
Open Access Dissertations
The relationship between polymer chain architecture, crystallization behavior, and morphology formation was investigated. The structures formed are highly dependent on chain configuration and crystallization kinetics. Poly(lactic acid) (PLA) and Poly(ethylene-co-vinyl acetate) (EVA) random copolymers were studied. Sample characterization was performed using a variety of techniques, including spectroscopy, scattering, and calorimetry. In PLA, structural differences between α’ and α crystalline phases were analyzed using cryogenic infrared and Raman spectroscopy. Compared to the crystal, the ’ crystal has slightly looser packing and weaker intermolecular interactions involving carbonyl and methyl functional groups. Simulations in conjunction with Raman scattering analyzed the …
Structure-Property Evolution During Polymer Crystallization, Deepak Arora
Structure-Property Evolution During Polymer Crystallization, Deepak Arora
Open Access Dissertations
The main theme of this research is to understand the structure-property evolution during crystallization of a semicrystalline thermoplastic polymer. A combination of techniques including rheology, small angle light scattering, differential scanning calorimetry and optical microscopy are applied to follow the mechanical and optical properties along with crystallinity and the morphology. Isothermal crystallization experiments on isotactic poly-1-butene at early stages of spherulite growth provide quantitative information about nucleation density, volume fraction of spherulites and their crystallinity, and the mechanism of connecting into a sample spanning structure. Optical microscopy near the fluid-to-solid transition suggests that the transition, as determined by time-resolved mechanical …