Study of polyurethane-urea cure reaction by in-situ emission fluorescence spectroscopy

Date of Completion

January 1997

Keywords

Chemistry, Polymer

Degree

Ph.D.

Abstract

The objective of the dissertation was to study the intrinsic emission fluorescence phenomena during the in-situ curing of polyurethane-urea resin and correlate these spectral changes with the chemical and physical variation along with the reaction.^ A very strong luminescence emission was found during the cure reaction of MDI/PPO/DETDA resin at room temperature. As the cure reaction proceeded, the fluorescence emission intensity around 339nm first drastically decreased and then leveled off or slightly increased; at the same time the peak maximum underwent a small blue shift. Meanwhile, the fluorescence emission intensity around 300nm increased sharply at early stage then slightly decreased and increased again at extent of cure above 60%. A blue shift occurred at the second rising stage. By the study of model compound solution in PPO, the emission fluorescence band at 339nm can be assigned to aromatic amine. And the 300-315nm band be assigned to overlapping band of urea and urethane band. Phase separation, chromophore interaction and inner filter effect were responsible for the observed trend in intensity changes. A second order kinetics was found for the overall reaction based on isocyanate reaction. Two stage reaction of the DETDA with MDI was observed from both emission fluorescence and FTIR in-situ data and was supported by $\sp{13}$C-nmr data from the possible combination of linkage sequences.^ FTIR offer a complimentary analysis and calibration of the emission fluorescence method. The C=O stretching peaks at 1727cm$\sp{-1}$ and 1639cm$\sp{-1}$ can be used to distinguish between urethane and urea linkages while the amine is difficult to determine. Correlation of data of fluorescence and FTIR can offer chemical change information along the cure process other current techniques can not get access to. ^

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