Adhesives Based on Poly(glycidyl methacrylate-co-butyl acrylate) with Controlled Structure: Curing Behavior and Adhesion Properties on Metal Substrates

Abstract

The adhesion properties of poly(glycidyl methacrylate (GMA)-co-butyl acrylate (BA)) statistical copolymers, synthesized by atom transfer radical polymerization (ATRP), are investigated employing three different curing agents or hardeners, such as diethanolamine (DEA), dicyandiamide (DICY), and 2-cyanoacetamide (2-CA) on copper, iron, brass, aluminum, and titanium metal surfaces. This work describes the treatment of the different surfaces, establishes the optimal curing conditions from differential scanning calorimetry (DSC) analysis of these novel adhesive systems, and evaluates the results of the single-lap shear test for metal joints. Thus, by dynamic DSC measurements of the mixtures, a low curing temperature of 90 °C is defined when DEA is used as a curative; while systems based on DICY and 2-CA require temperatures of 150 °C and 160 °C, respectively. In addition, the curing process of this controlled acrylic copolymer with DICY exhibits a singular behavior, possibly due to the curing reaction mechanism, where multiple epoxy-amine ring-opening polyaddition reactions take place between DICY's active hydrogens and epoxy groups of poly(GMA-co-BA). This latter curing system shows the highest adhesion features with lap-shear strength at room temperature of 15.5 MPa, using copper as metallic substrate; however, the best results are obtained using 2-CA as curing agent with aluminum and iron.