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THE MOLECULAR STRUCTURE OF INTERFACES FORMED BETWEEN PLASMA POLYMERIZED SILICA-LIKE FILMS AND EPOXY ADHESIVES

BENGU, BASAK
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1195657609

Abstract Details

2007, PhD, University of Cincinnati, Engineering : Materials Science.
The molecular structure of the interphase formed by curing a model adhesive system consisting of the diglycidyl ether of bisphenol-A (DGEBA) and dicyandiamide (DDA) against inorganic substrates, including mechanically polished aluminum, electrogalvanized steel (EGS) and plasma polymerized silica-like primer films, was determined using reflection–absorption infrared spectroscopy (RAIR) and X-ray photoelectron spectroscopy (XPS). RAIR analysis suggested that DGEBA/DDA mixtures created an interphase with a different molecular structure from the bulk of the adhesive when cured in contact with aluminum. The formation of this unique interphase was mainly due to interactions between DDA and the Al surface. XPS analysis indicated that aluminum ions exposed by heating the substrate surface were necessary for this interaction. DDA was found to adsorb onto the aluminum surface via the lone pair of electrons on the nitrogen atoms of the nitrile groups. A slight decrease in the nitrile stretching frequency indicated an additional back-bonding interaction between aluminum ions and the nitrile groups. Slight back donation of electrons from the metal to DDA resulted in a reduction product that led to the formation of the carbodiimide form of DDA. This specific reaction caused a decrease in the concentration of nitrile groups in the interphase and changed the network structure of the epoxy adhesive in the regions close to the oxide surface. The interaction of DDA with EGS surfaces followed a similar trend. However, the effects were much more pronounced with EGS and the path of the curing reaction and the network structure near the metal surface were strongly affected by EGS/DDA interactions. Two types of plasma polymerized silica-like films were prepared from hexamethyldisiloxane (HMDSO) monomer and oxygen by varying the gas compositions. One of the films was high and the other was low in hydroxyl content. XPS results showed that adjacent to the silica-like primer films, the adhesive had a composition enriched in DDA, indicating that curing agent was preferentially adsorbed onto the silica-like films. The preferential adsorption of the curing agent was lower in the case of low-hydroxyl silica like films, probably due to fewer active sites present on the low-hydroxyl silica like films.
F Boerio (Advisor)
139 p.
Engineering, Materials Science
Dicyandiamide; Diglycidyl ether of bisphenol-A; Plasma polymerized silica-like films; Interfaces; Aluminum; XPS; RAIR

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Citations

  • BENGU, B. (2007). THE MOLECULAR STRUCTURE OF INTERFACES FORMED BETWEEN PLASMA POLYMERIZED SILICA-LIKE FILMS AND EPOXY ADHESIVES [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1195657609

    APA Style (7th edition)

  • BENGU, BASAK. THE MOLECULAR STRUCTURE OF INTERFACES FORMED BETWEEN PLASMA POLYMERIZED SILICA-LIKE FILMS AND EPOXY ADHESIVES. 2007. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1195657609.

    MLA Style (8th edition)

  • BENGU, BASAK. "THE MOLECULAR STRUCTURE OF INTERFACES FORMED BETWEEN PLASMA POLYMERIZED SILICA-LIKE FILMS AND EPOXY ADHESIVES." Doctoral dissertation, University of Cincinnati, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1195657609

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Cincinnati and OhioLINK.