Adhesion Mechanism between Metal and Polymer Interface

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Title: Adhesion Mechanism between Metal and Polymer Interface
Author: Uner, Birol
Advisors: M. Hubbe, Committee Member
John F. Kadla, Committee Co-Chair
S. Zauscher, Committee Member
M. K. Ramasubramanian, Committee Chair
Abstract: The creping process is used to develop bulk, stretch, absorbency and softness in tissue paper. Typically, an adhesive material, e.g. polyvinyl alcohol and polyamidoamine, is used to attach paper on to the drum surface. The severity of the creping process is dependent upon a number of factors, including the adhesion between the adhesive and the metal surface of the Yankee Dryer. Therefore, the objective of this project is to understand the interaction mechanism between the adhesive and metal surface specifically with respect to acid-base interactions, in order to have better control in the creping process. Using well-characterized polymers and surfaces, the role of surface energy of the polymer, radius of gyration, and chemical composition on adhesion has been investigated. Through the use of microscopic and spectroscopic analyses of the surface chemistry at the polymer-metal interface, in conjunction with creping experiments, the role of the chemical constituents in the microstructural and the physiochemical development of adhesion, and the critical parameters for processing operations have been studied. Acid-base interactions between substrates and adhesives appear to affect surface wetting and the resulting adhesive bond strength. Atomic force microscopy with chemically functionalized colloidal probes--mounted on the end of the force sensing cantilever--were used to study 'acid-base' interactions between adhesives and metal/paper surfaces. The probes used in our experiments were silica spheres decorated with mixed, self-assembled monolayers of hydroxyl- and methyl-terminated thiols. Cast iron was used as the substrate. Force vs. distance curves, recorded in air and in water, showed that adhesive force depends strongly on the chemical functionality of the tip and the degree of acetylation of the intervening poly(vinyl-alcohol), an adhesive used in paper creping. These results suggest that adhesion forces in the paper creping process likely can be controlled through tailoring 'acid-base' interactions. It was observed that with an increase acetyl content of the poly(vinyl-alcohol) adhesion force decreased. There results were support by other empirical and theoretical force measurements. Cast iron is a porous material. When adhesive is applied to this surface, it may penetrate into the pores. After evaporation of solvent, adhesive solidifies and may act as a mechanical anchor. We used optical microscopy and crystalline polymer to observe this relationship. The results indicated that some penetration occurred, but that it was sparse and not uniform. There results were supported by the comparison of the cast iron surface roughness and polymer radius of gyration. Therefore, it does not appear that mechanical interlocking plays a significant role in the adhesion of polymer to cast iron surface.
Date: 2003-10-04
Degree: PhD
Discipline: Wood and Paper Science

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