Adhesion Interface Studied by Neutron Reflectometry

Abstract

In recent years, there has been a strong demand for more advanced adhesion technologies. Neutron reflectometry (NR) is a powerful tool to examine the structure of the adhesion interface because of the large penetration depth to materials and the isotope-dependent contrast mechanism. Examining the effects of absorbed water on epoxy adhesives at their interfaces with solid substrates is crucial because of their adhesive applications in various fields. The spatial distribution of absorbed water in epoxy resin thin films under high humidity was investigated by NR. The in situ NR measurement revealed the formation of an ~1 nm-thick condensed water layer at the interface with an adherend in a humid atmosphere at a relative humidity of 85%. Water absorbed by epoxy adhesives from a humid atmosphere considerably influences their structure and properties; therefore, the results of NR indicate that the effect of water at the adhesion interface should be considered to develop the adhesion technology. The recent advances in NR overcome the limitation in the applicable field in the conventional NR measurements and would unveil the further information on the fundamental mechanism of the adhesion phenomena.