Dissertation/Thesis Abstract

Mechanical Performance of Copolyester Nanocomposites and Nanolaminates
by Keane, Olivia C., Ph.D., University of Massachusetts Lowell, 2019, 355; 22623030
Abstract (Summary)

Polymer nanocomposites were produced from four different rigid, transparent, impact-resistant copolyesters in combination with an organically modified montmorillonite nanoclay. All polymers considered were based on the 2,2,4,4- tetramethyl-1,3,-cyclobutane diol (CBDO) monomer. CBDO-based polymers have shown impact resistance comparable to polycarbonate, and the addition of montmorillonite nanoclay has previously been found to simultaneously increase stiffness and elongation at break in such polymers. Two families of nanocomposites were considered: melt-blended polymer nanocomposites produced by twin-screw extrusion (containing between 0 and 1.2 vol% of inorganics, depending on composition), and highly-oriented nanolaminates produced through a solvent-assisted spray deposition process (containing between 0 and 80 vol% modified clay).

In the melt-blended systems, the addition of nanoclay was found to increase Young’s modulus, to decrease high-speed impact resistance, and to shift thermal transition temperatures.

Hansen solubility parameters were used to select chloroform as the solvent used for nanolaminate production. Dynamic mechanical analysis was used to identify the contributions of bulk polymer, bulk polymer near clay tactoids, the polymer/nanoclay interphase and the unintercalated clay to the viscoelastic response. While issues were encountered with nanolaminate production due to the lack of solubility or availability of some polymers, the addition of nanoclay was found to enhance the storage modulus in all cases where the data obtained was considered reliable. Selected nanolaminates were incorporated into multi-layer stacks with neat copolyester facing and backing material and compared to melt-blended polymer nanocomposites with similar overall clay loadings. While these stacks were found to give a lower high-speed impact resistance compared to the equivalent melt-blended nanocomposites, the addition of a nanolaminate interlayer improved impact resistance, suggesting that nanoclay reinforcement in CBDO based copolyesters may be more effective as a single, well- oriented layer than it is as a randomly distributed filler through an entire part.

Indexing (document details)
Advisor: Reynayd, Emmanuelle, Schmidt, Daniel F.
Commitee: Hansen, Christopher J.
School: University of Massachusetts Lowell
Department: Mechanical Engineering
School Location: United States -- Massachusetts
Source: DAI-B 81/4(E), Dissertation Abstracts International
Subjects: Mechanical engineering, Materials science, Plastics
Keywords: Copolyester, Hansen solubility parameters, Montmorillonite, Nanocomposite, Nanolaminate, Spray-deposition
Publication Number: 22623030
ISBN: 9781687937636
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