The preparation method and properies of one-component epoxy powder adhesive as green adhesive

Today, adhesive joints are considered as one of the most widely used bonding methods in various industries due to their high strength-to-weight ratio, uniform stress distribution, and desirable appearance. The reduction volatile organic compound (VOC) emissions is one of the most important issues in the preparation of green adhesives. Epoxy adhesives are one of the most common reactive adhesives used in solid, liquid and paste forms due to their high mechanical and chemical resistance. These types of adhesives are used as one-component and two-component. In this paper, one-component epoxy powder adhesives prepared by solvent evaporation are investigated. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy۲(SEM) and differential scanning calorimetry (DSC) were used for characterization of this type of adhesives. Adhesive properties of this green adhesive has been evaluated in terms of the lap shear strength using aluminium adherends. The results showed that in one-component powder adhesive (green adhesive), however the epoxy chains were in contact with imidazole curing agent for long time (seven years), it was still thermoplastic. Anionic polymerization of epoxy in presence of imidazole increased the chain length of solid epoxy in one-component powder adhesive so that its melting temperature is increased. On the other hand, all the epoxy functional groups of one-component powder adhesive do not participate in the curing reaction with imidazole curing agent. This green adhesive durability in various curing temperature has also been analysed. The results indicate that this one-component epoxy powder adhesive presents a higher adhesive strength at curing temperature of ۱۵۰ oC.