Adhesive-bonded joints

The influence of type and size of filler particles and viscosity of the cyanoacrylate component on the volume resistivity, conductivity mechanism and adhesive strength of the resultant bond has been investigated. Various carbon and metal fillers were used to make conductive cyanoacrylate adhesive compositions and the best results were obtained when Ag, Ni or Mo powders (5–10 μm) were incorporated in thickened ethyl 2-cyanoacrylate with a viscosity of 50–100 cP

The introduction of high molecular weight poly(methyl methacrylate) or poly(butadiene-co-acrylonitrile) into ethyl 2-cyanoacrylate produced viscous adhesives with a homogeneous or heterogeneous structure after cure. Steel joints bonded with these adhesives are shown to have improved tensile shear strength, deformability and stress relaxation of bonds compared with pure cyanoacrylate adhesive. Poly(methyl methacrylate)-modified adhesive is recommended for static load-bearing joints while poly(butadiene-co-acrylonitrile)-modified adhesive is more suited to cyclic or vibrating loads.

The lap shear strengths of stell joints bonded with ethyl 2-cyanoacrylate adhesive containing various amounts of acetic acid have been determined, and an optimum adhesion promoting effect was found at an acetic acid content of 0.25% by weight. Further tests showed that adhesion promotion with acetic acid was dependent on the nature and surface treatment of various metal adherends, with selectivity being shown towards steel, stainless steel and duraluminium.