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Degradation of Polymer/Substrate Interfaces – an Attenuated Total Reflection Fourier Transform Infrared Spectroscopy Approach Degradation of polymer/substrate interfaces – an attenuated total reflection Fourier transform infrared spectroscopy approach THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Arijit Ghosh, B.Sc., M.Sc. Graduate Program in Chemistry The Ohio State University 2010 Master's Examination Committee: Heather C. Allen, Advisor Joshua E. Goldberger Gerald S. Frankel Copyright by Arijit Ghosh 2010 Abstract Organic coatings are extensively applied to protect metal structures from corrosion related damage. The durability of such polymer coated adhesively bonded joint structures depends upon the stability of the interfaces between the polymer and the substrate it is coated on. It is economically important to have a thorough understanding of how such interfaces react to a variety of aggressive media that are relevant to real life scenarios. In this thesis, attenuated total reflection Fourier transform infrared (ATR- FTIR) spectroscopy has been used to detect changes at the interfaces between poly (vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (PVB) and ZnSe upon exposure to ozone, humidity and UV-B light. Also, the response of PVB-aluminum interfaces to liquid water has been studied and compared with the same for eponol (epoxy resin, diglycidyl ether of bisphenol A)-aluminum interfaces. In the presence of ozone, humidity and UV-B radiation, an increase in carbonyl group intensity was observed at the PVB-ZnSe interface indicating structural degradation of the polymer near the interface. However, such changes were not observed when PVB coated ZnSe samples were exposed to moisture and UV-B light in the absence of ozone showing that ozone is responsible for the observed structural deterioration. Liquid water uptake kinetics for the degraded PVB monitored using ATR-FTIR indicated a degradation of the physical structural organization of the polymer film. Exposure of PVB coated aluminum thin film to de- ionized water showed water incorporation at the interface. There were evidences for ii polymer swelling, delamination and corrosion of the aluminum film under the polymer layer. On the contrary, delamination/swelling of the polymer was not observed at the eponol-aluminum interface, although water was still found to be incorporated at the interface. Al-O species were also observed to form beneath the polymer layer. A decrease of the C-H intensities was detected at the PVB-aluminum interface during the water uptake of the polymer, whereas an increase of the C-H intensities was observed for the eponol polymer under these conditions. This is assigned to rearrangement of the macromolecular polymer chains upon interaction with water. iii Dedication This document is dedicated to my parents and friends. iv Acknowledgments I would like to take this opportunity to thank the variety of people who have contributed significantly to the thesis and made it a success. First of all, I would like to thank my advisor, Dr. Heather C. Allen whose expert guidance has led to the realization of this thesis. I would then like to thank Dr. Gerald Frankel (Director, Fontana Corrosion Center) whose periodic comments have immensely helped me improve on the thesis. Next, I would like to acknowledge the constant motivation and encouragement of Dr. Ralf Posner (Department of Materials Science and Engineering) who was my second mentor in this project. I would then like to extend my heartfelt gratitude to Miss Severine Cambier (Department of Materials Science and Engineering), Mr. Tyler Frank (Undergraduate Researcher), Mr. Larry Antal (Chemistry machine shop), Mr. Tom Kelch (Nanotech West laboratory), Mr. John Sullivan (Chemistry Instrument Support Group), Mr. Alex Champagne (Department of Evolution, Ecology and Organismal Biology), Mr. Mark Andio (Department of Materials Science and Engineering), Dr. Chris Beekman, Dr. Shashi Pathak (University of Southern Missisipi) and the entire Allen group for their support in numerous important aspects related to the project and the thesis. They were always available to help me whenever there were impediments in the way. Thanks to my parents for always being my source of inspiation. v Lastly, I would like to thank the U.S. Army Aviation Applied Tech Directorate for funding this project. vi Vita March 2003 ....................................................Frank Anthony Public School, India 2006................................................................B.Sc. Chemistry, Jadavpur University, India 2008................................................................M.Sc. Chemistry, Jadavpur University, India 2008 to present ..............................................Graduate Teaching Associate, Department of Chemistry, The Ohio State University 2008 to present……………………………...Graduate Research Associate, Department of Chemistry, The Ohio State University Publications Pal, A. Chowdhury, U.K. Mondal, D. Das, B. Nayak, B. Ghosh, A. Maity, S and Chakraborti, D. Arsenic burden from cooked rice in the populations of arsenic affected and non-affected areas and Kolkata city in West Bengal, India Environ. Sci. Technol., 2009, 43 (9), pp 3349-3355 Fields of Study Major Field: Chemistry vii Table of Contents Abstract ............................................................................................................................... ii Dedication .......................................................................................................................... iv Acknowledgments............................................................................................................... v Vita .................................................................................................................................. vvii List of Tables .................................................................................................................... xx List of Figures ..................................................................................................................... x Chapter 1: Introduction ....................................................................................................... 1 Chapter 2: Instrumentation and Methods .......................................................................... 13 2.1 Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) Spectroscopy ............................................................................................................. 13 2.2 Ion sputter deposition .......................................................................................... 18 2.3 The exposure set up ............................................................................................. 19 2.4 Materials used ...................................................................................................... 20 Chapter 3: Results and Discussion: Degradation of Poly(vinyl butyral) upon exposure to ozone, UV radiation and humidity ................................................................................ 30 3.1 Exposure to ozone, UV and moisture .................................................................. 30 viii 3.2 Water uptake kinetics in degraded vs. non-degraded PVB .................................. 33 3.3 Exposure to UV and moisture .............................................................................. 35 Chapter 4: Results and Discussion: Water uptake by polymer coated Aluminum-Stability of Aluminum-polymer interfaces………………………………………………………..47 4.1 Water uptake by PVB coated Aluminum..…………………………………….47 4.2 Water retention at the PVB-Al interface………………………………………51 4.3 Water uptake by eponol coated Aluminum…………………………………...52 Chapter 5: Conclusions and recommendations………………………………………...68 References………………………………………………………………………………71 ix List of Tables Table 4.1. Parameters for the pure water OH stretch spectral fits ................................... 59 Table 4.2. Parameters for PVB confined water OH stretch spectral fits………………..59 Table 4.3. Parameters for eponol confined water OH stretch spectral fits……………...65 x List of Figures Figure 1.1.Schematic representation of a coating system .. ……………………………...10 Figure 1.2.Poly (vinyl butyral-co-vinyl alcohol-co-vinyl acetate) ................................... 11 Figure 1.3.Eponol resin 53 BH 35 .................................................................................... 12 Figure 2.1.Schematic representation of the aluminum-PVB sample configuration showing total internal reflection of the IR beam and generation of evanescent waves .................. 22 Figure 2.2a.Dispersion curve for aluminum b.Variation of IR evanescent wave penetration depths at the aluminum-PVB interface as a function of IR frequency .......... 23 Figure 2.3.Variation of IR evanescent wave penetration depths at the aluminum-eponol interface as a function of Ifrequency………………………………………………….....24 Figure 2.4.Schematic representation of the ZnSe-PVB sample configuration showing total internal reflection of the IR beam and generation of evanescent waves . ………….25 Figure 2.5.Variation of IR evanescent wave penetration depths at the ZnSe-PVB interface as a function of IR frequency ............................................................................................ 26 Figure 2.6.Schematic representation of the exposure set up (constructed by Severine Cambier, Frankel Lab) ...................................................................................................... 27 Figure 2.7a.A sample in the cell
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