<p> This thesis is based on the studies of cross-linked network polymerization by
measurements of dielectric permittivity and a study of the polymers formed by dynamic
mechanical analysis. The network polymers are formed by reacting a trifunctional epoxy
with three primary amines, namely, aniline, 3-chloroaniline and 4-chloroaniline. The
manner in which the dielectric permittivity changes on polymerization was followed from
the monomeric to the ultimately polymeric state, and the relaxation time and the
distribution of reaction times was followed with reaction time. Isothermal measurements
of the heat evolved during the reaction led to a determination of the number of covalent
bonds formed at any instant of reaction time, thus the dielectric relaxation time was
related to the number of covalent bonds formed during polymerization. The relaxation
time increased progressively more rapidly with the increase in the number of covalent
bonds formed under isothermal conditions as the reaction progressed towards completion.
As the number of covalent bonds increased, a high-frequency, or low-temperature, relaxation process emerged. This was observed for both the time-variant (fixed frequency) and time-invariant (dielectric spectra) dielectric data.</p> <p> The extent of reaction at the gelation time deduced from the irreversible decrease in the dc conductivity on polymerization was 50% lower than anticipated from Flory-Stockmayer theory, but, the extent of reaction at the point of singularity agreed with the theory. As polymerization reactions occurred, both the static and high-frequency dielectric permittivities decreased with time. Data simulated for the dielectric behaviour for a fixed frequency during the course of polymerization were analyzed to confirm that the two analysis procedures (time-invariant and time-variant) yield the same parameters within 2-3%.</p> <p> The three, new, network polymers thus produced had unrelaxed and relaxed moduli that were in the ranges of 1.35-1.51GPa and 6.6-10.6MPa, respectively. GU of the three polymers decreased with increasing temperature and GR increased. The former effect has been attributed to mainly a decrease in the GR of the low-temperature, or high-frequency, β-relaxation process, and the latter to the increase in the temperature, and consequently, the increase in the entropy, as discussed in the entropy theories of the rubber modulus. The spectrum of the shear modulus cannot be superposed by shifting the spectra along the frequency scale alone. The three reasons discussed are; (1) GU and GR change with temperature, therefore the spectra differ in magnitude for each measurement temperature, (2) the presence of a temperature-dependent, frequency-independent background loss changes the magnitude of tan∅ with the temperature, and (3) the influence of secondary-, β-, or Johari-Goldstein relaxations causes deviations in the shape of the spectrum such that they cannot be superposed. It was determined that none of the three effects described contribute significantly to the changes in the isothermal spectra, and hence, the principle of the time-temperature superposition does not apply to the three polymers in this study. The three polymers produced have a mechanical loss peak at room temperature that is attributed to the β-relaxation process and whose magnitude is greater than that of polycarbonates. This suggests that the three new polymers produced here can absorb more energy at room temperature than the polycarbonates.</p> / Thesis / Master of Engineering (MEngr)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/19279 |
| Date | 05 1900 |
| Creators | Wasylyshyn, Dwayne Andrew |
| Contributors | Johari, G. P., Materials Science and Engineering |
| Source Sets | McMaster University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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