Conventional adhesives like epoxy that are used to bond plastic, ceramics, and wood are typically designed to cure using moisture, heat, or light. They often require specific curing temperatures, ranging from room temperature up to 80 °C. The curing process is necessary to cross-link and bond the glue with the two secured surfaces as the glue crystallizes and hardens to achieve its final strength.
Scientists have developed a “magnetocuring” glue that can cure by passing it through a magnetic field. This is very useful in certain environmental conditions where current adhesives do not work well. Also, when the adhesive is sandwiched between insulating material like rubber or wood, traditional activators like heat, light, and air cannot easily reach the adhesive.
Products such as helmets, composite bike frames, and golf clubs are currently made with two-part epoxy adhesives, where a resin and a hardener are mixed and the reaction starts immediately. For manufacturers of carbon fiber — thin ribbons of carbon glued together layer by layer — and makers of sports equipment involving carbon fiber, their factories use large, high-temperature ovens to cure the epoxy glue over many hours. This energy-intensive curing process is the main reason for the high cost of carbon fiber.
The new adhesive is made by combining a typical commercially available epoxy adhesive with specially tailored magnetic nanoparticles. It does not need to be mixed with any hardener or accelerator, unlike two-component adhesives (which have two liquids that must be mixed before use), making it easy to manufacture and apply.
It bonds the materials when it is activated by passing through a magnetic field, which is easily generated by a small electromagnetic device. This uses less energy than a large conventional oven; for example, one gram of magnetocuring adhesive can be easily cured by a 200-Watt electromagnetic device in five minutes (consuming 16.6 Watt-hours). This is 120 times less energy needed than a traditional 2000-Watt oven, which takes an hour (consuming 2000 Watt-hours) to cure conventional epoxy.
The new adhesive is made of two main components: the commercially available epoxy that is cured through heat, and oxide nanoparticles made from a chemical combination including manganese, zinc, and iron. These nanoparticles heat up when electromagnetic energy is passed through them, activating the curing process. The maximum temperature and rate of heating can be controlled by the nanoparticles, eliminating overheating and hotspot formation.
The alternating magnetic field can be embedded at the bottom of conveyor belt systems, so products with pre-applied glue can be cured when they pass through the magnetic field.