Degree Type

Dissertation

Date of Award

2014

Degree Name

Doctor of Philosophy

Department

Materials Science and Engineering

First Advisor

Michael R. Kessler

Abstract

ABSTRACT

Polyurethanes (PUs) have been widely used in coatings, adhesives, sealants, and foams. Historically, the raw materials of a PU, polyol and isocyanate, were derived from petroleum. Nowadays, the increasing concerns regarding the depletion of petroleum resources and environmental problems caused by fossil fuels, has triggered great interest in the development of monomers based on renewable resources for PU production. In this project, a novel solvent-free/catalyst-free method was developed to prepare polyols from epoxidized soybean oil and castor oil for PU production. The effects of reaction temperature, reaction time, and reaction ratios of carboxyl acid and epoxy groups on the properties of the resulting polyols were investigated. Moreover, the properties of final PUs were compared with that from castor oil and methoxylated soybean oil polyol.

To validate the versatility of this approach, this method was extended to other vegetable oils systems. Polyols with a broad functionality were prepared by castor oil fatty acid initiating ring opening reaction of various epoxidized vegetable oils, which were prepared with formic acid and hydrogen peroxide. The effect of the polyols' structure on the thermal, mechanical, and shape memory properties of the resulting PU was studied.

Possible catalysts (DBU, Pyridine) were found that could promote the ring opening reaction in this method by decreasing the reaction temperature and reaction time. The ring opening reaction kinetic for the vegetable oil systems was investigated by dynamic differential scanning calorimetry. The effect of DBU on the structure of polyols was studied as well as the properties of PU.

The polyols prepared by this novel method were used to prepare PU foam for potential application in automobile seat cushions. The compatibility between this vegetable oil-based polyol and a petroleum-based polyol was investigated by solution tests and theoretical prediction. The effect of bio-component on the physical, mechanical, thermal stability, and thermal conductivity of resulting PU was investigated.

Also, two approaches were proposed to modify lignin to compatibilize them with PU matrix for preparation of PU nanocomposites. The effects of this cheap and abundant renewable filler on the thermo-mechanical and dielectric properties of the final PU composites were studied.

In order to increase the hydroxyl numbers of vegetable oil-based polyols, another method was developed for high performance PUs. A strong reductant, LiAlH4, was used to reduce the ether and epoxy groups in epoxidized vegetable oils to prepare high functionality bio-polyols. The properties of the final PU based on those novel polyols were characterized and compared with that from a petroleum-based polyol.

Finally, carbon nanotubes were incorporated into the PU matrix to improve the thermo-mechanical properties of nanocomposites. The surface of carbon nanotube was functionalized with an amine group, which formed a covalent bond with the PUs. The loading effect of carbon nanotube on the properties of the resulting PU was investigated.

Copyright Owner

Chaoqun Zhang

Language

en

File Format

application/pdf

File Size

169 pages

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