Polymer Engineering Faculty Research

Title

Moisture Attack on Adhesive Joints: Roles of Adhesive and Interface Properties

Document Type

Article

Publication Date

Fall 2009

Abstract

It is well-known that moisture will attack many adhesive joints. A particularly interesting feature is the observation that when the moisture level in certain systems exceeds a critical concentration, the bonded joint shows a dramatic loss of strength. A number of authors have investigated this phenomenon and conclude that the interface plays a crucial role, but these studies do not explain why there is a critical concentration of moisture or exactly what role is played by the properties of the bulk adhesive. To gain a clearer picture of what controls this phenomenon, we have combined a fracture mechanics approach to determine joint strength with neutron reflectivity which provides a detailed characterization of the moisture distribution near the interface. The work uses a model system of silicon dioxide bonded to a series of polymers based on poly(n-alkyl methyl methacrylate). The results in this study suggest that the loss of adhesion is dependent on the combination of three factors: local water concentration near the interface, swelling stresses resulting from the water absorption, and water induced weakening of the interface bonds.