Polymer Diffusion Processes and the Evolution of Adhesive Bond Strength

摘要

One of the contributing mechanisms to polymer adhesion is said to be the diffusion of chain elements across a polymer/polymer interface. The concept makes sense intuitively, when polymers in close contact are above their respective Tg. Nevertheless, relatively little credence is attributed to it. The reason is the limited experimental evidence to support the diffusion mechanism, one of the few cases where it seems applicable being the auto-adhesion of rubbery materials. In this work we set out to show whether or not further support for the inherently logical diffusion supposition could be garnered. Polymer pairs were bonded, the selection being such as to limit interfacial forces in one case to the universal dispersion force, and in other cases to the presence both of favorable and unfavorable specific, or acid-bases forces. Following the determination of initial lap-shear bond strengths, the joints were aged for controlled periods above their Tg values, and bond characteristics were re-evaluated. Any measured changes in bond strength then could be considered in terms of possible diffusion events.