Processing-Structure-Property Relationships in Polymer Carbon Nanocomposites
| Autor: | Danda, kranthi Chaitanya |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
Analytical Chemistry
Chemistry Design Engineering Materials Science Nanoscience Nanotechnology Polymer Chemistry Polymers Polymer Composites Twin screw extrusion Polymer processing TPU Thermoplastic polyurethane Polypropylene Graphene oxide Carbon black Carbon nanotubes POSS Graphene nanoplatelets Aerogels Rheology Hydrogel Computational Simulation DPD |
| Druh dokumentu: | Text |
| Popis: | This dissertation has a primary focus on design and development of composites by employing processing methods aimed at improving filler dispersion in polymers. Mixing elements taking advantage of extensional dominated flows are adopted. Several such mixing elements, extensional mixing elements (EMEs) to be specific, with varying degree of ability to impose extensional dominated flows, have been experimentally validated. A first attempt is made to enhance the dispersion of carbon black (CB), graphene nano platelets (GNP) and carbon nano tubes (CNT) in polypropylene (PP). Enhanced dispersion does translate into improved mechanical properties. A more comprehensive approach is adopted with an integrated computational and processing method on thermoplastic polyurethane (TPU) graphene oxide (GO) composites. The role of filler functionalization in exfoliation and TPU hard block crystallization is established. A difference in anisotropy and phase separation is observed between material processed with EME and kneading blocks. A significantly enhanced ductility is obtained by employing EME during processing. Improved abrasion and strength is also observed. A secondary focus of the thesis includes synthesis of composites by wet chemical and other processes to end up with composite materials with enhanced properties and/or improved material behavior. Hydrogels of poly(ethylene glycol) methyl ether methaycrylate filled with graphene oxide are made via a reversible assisted fragmentation termination (RAFT) approach. Reinforcement and lubrication effects are studied with the incorporation of covalent bonds between filler and matrix. Aerogels obtained from hydrogels of graphene oxide (GO) and montmorillonite (MMT) clay nanocomposites in poly(vinyl alcohol) are synthesized. Hence, obtained aerogels have improved compressive strength and further silylation makes them functional materials for oil-water separation. Twin-screw reactive extrusion of Thermoplastic polyurethane (TPU) compounded with trisilanol isooctyl polyhedral oligomeric silsesquioxane (POSS) chain extender results in a composite with covalently tethered filler on the polymer backbone. Morphological, spectroscopic and rheological characterization is performed to understand the relevant changes in composites as a function of concentration. Lastly, cyclodextrin based polymers are synthesized and tailored for their ability to deliver corticosteroids into knee cavity. The polymer system has been successfully formulated to mimic the synovial fluid behavior under shear imposed from bio-mechanical motion. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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