Aromatic copolyester thermosets: High temperature adhesive properties

The adhesive properties of a new family of crosslinkable aromatic copolyester resins are described in this paper. A unique method for forming an adhesive bond in the solid state through high temperature interchain transesterification reactions (ITR) between cured thin films of these copolyester thermosets is indicated. Bonds formed via this procedure yield average lap shear strengths of roughly 13 MPa to titanium adherends and invariably exhibit failure at the polymer-metal interface and not within the polymer. Various procedures to increase the strength of the bond at the interface between the polymer and the metal were tested such as the effect of surface pretreatments, primers, fillers, and the role of bondline thickness on the lap shear strength of the joints. Of these, the use of surface pretreatments and thinner bondlines has the greatest effect, raising the observed average lap shear strength of the joints to 16.5 and 20.7 Mpa, respectively. Some of the adhesive properties pertaining to the use of this new thermoset as a matrix in a graphite fiber composite are also presented.