Interpenetrating Polymer Network (IPN) Adhesives for Electron Beam Cure

Abstract

Electron beam (e-beam) -processed polymer adhesives have historically performed poorly compared to traditional adhesive technologies due to a lack of toughness engineered into these new types of adhesive materials. Consequently, sequential-and simultaneous-interpenetrating polymer networks (seq-IPN and SIN) were developed and characterized. Seq-IPN adhesive pastes demonstrated exceptional lap-shear strengths (approaching 41 MPa) with glass transition temperatures (T g ) of 100-120° C. The sequential polymerization proceeds by first thermally curing the adhesive to the green-strength. The cure kinetics for the C-staged seq-EPNs have been investigated as a function of temperature and cure acceleration. SIN materials are being investigated to develop durable e-beam-curable film adhesives. The primary advantage of SIN film adhesives, compared to cationic e-beam systems, is insensitivity to surface contaminants (e.g., amine and water), which are known to hinder cure in cationic e-beam polymerization. Preliminary results have shown that the SIN e-beam adhesives have excellent properties. Lap-shear strengths exceeding 27.5 MPa with adhesive T g approaching 150° C have been demonstrated on primed aluminum substrates. Structural, kinetic, and adhesive performance data for both seq-IPN and SIN structural adhesives cured by e-beam irradiation are presented. u