Development and Study of Hydrophillic Epoxy Based Adhesives.

Military equipment in general is expected to be exposed to a wide range of environments. These can range from the very cold areas of central Norway to the very hot dry regions of the Arab states. An important component when determining the life of materials is the presence of water which generally acts to enhance the rate of degradation of equipment. This is certainly true in the case of adhesively bonded systems. Water has been shown to act in many ways to degrade the performance of a joint. It can act directly upon the metal substrate and change its nature such that the adhesive is forced from the surface. An example of this would be an aluminium oxide surface which became hydrated in time. A second method is the simple displacement of the adhesive by water, as there is usually only a physical bond between the adhesive and the substrate this displacement process can proceed in time. A third method is the degradation of the adhesive composition itself, this may be of a reversible nature whereby moisture is absorbed the adhesive is plasticised and no longer has the strength to resist service loads. This plasticisation may be reversed when the adhesive is dried and the joint strength may recover. However there are effects such as microcracking of the bulk of the adhesive that cause irreversible damage. There are two general approaches to overcome these problems one is to improve the adhesive substrate interface.