Magnetism offers energy-saving alternative to oven-cured glues

Conventional adhesives like epoxy which are used to bond plastic, ceramics and wood are typically designed to cure using moisture, heat or light. The curing process is necessary to cross-link and bond the glue with the two secured surfaces as it crystallises and hardens to achieve its final strength.

The new ‘magnetocuring’ glue created by researchers at Nanyang Technological University, Singapore can cure when passed through a magnetic field. This is useful when the adhesive is sandwiched between insulating materials like rubber or wood, where traditional activators like heat, light and air cannot easily reach it.

The adhesive is made by combining a typical commercially available epoxy adhesive with specially tailored magnetic nanoparticles made by the NTU scientists. 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 such as those used in manufacturing carbon-fibre products.

For example, one gram of magnetocuring adhesive can be cured by a 200W electromagnetic device in five minutes (consuming 16.6 Watt-hours). This is 120 times less energy needed than a traditional 2000W oven which takes an hour (consuming 2000Wh) to cure conventional epoxy.

The technique was developed by Professor Raju V Ramanujan, Associate Professor Terry Steele and Dr Richa Chaudhary from the NTU School of Materials Science & Engineering, whose findings were published in the scientific journal Applied Materials Today.

Steele explained: “Our key development is a way to cure adhesives within minutes of exposure to a magnetic field, while preventing overheating of the surfaces to which they are applied. This is important as some surfaces that we want to join are extremely heat-sensitive, such as flexible electronics and biodegradable plastics.”

In one possible application, manufacturers of sports shoes often have difficulty heating up the adhesives in between the rubber soles and the upper half of the shoe, as rubber is a heat insulator and resists heat transmission to the conventional epoxy glue. An oven is needed to heat up the shoe over a long time before the heat can reach the glue.

Using magnetic-field activated glue bypasses this difficulty, by directly activating the curing process only in the glue.

The alternating magnetic field can also 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.