Polyethylene-co-methacrylic acid healing agents for mendable epoxy resins

A new thermoplastic healing agent and associated healing agent delivery mechanism have been investigated. Polyethylene-co-methacrylic acid (EMAA) particles were mixed into an epoxy resin, resulting in an increase in the fracture strength of the resin. Damaged single edge notched bars and tapered double cantilever beams were healed at 150 °C for 30 min to achieve up to an 85% recovery in critical stress intensity and over 100% recovery in sustainable peak load. Optical and scanning electron microscopy revealed that strength recovery in the damaged resin was achieved via EMAA particle healing as well as the formation of an adhesive EMAA layer between adjacent epoxy fracture surfaces. Microscopy also showed that small bubbles in the EMAA particles act as a new healing agent delivery mechanism wherein expansion during heating forced larger volumes of healing agent into the damaged region of the resin.