A New Way to Cure Adhesives on Demand? Magnets.

Conventional adhesives require light or heat to bond.

Scientists from Nanyang Technological University, Singapore (NTU Singapore), have developed a new way to cure adhesives: passing them through a magnetic field. The non-contact method of curing leads to adhesives that can be activated on demand.

The "magnetocuring" adhesive is made by combining a typical commercially available epoxy adhesive with specially tailored magnetic nanoparticles created by the NTU scientists. Unlike the two-component adhesives that require the mixing of two liquids before use, the NTU-developed coating does not need to be mixed with any hardener or accelerator.

The ease of use, according to the NTU SIngapore researchers, can be especially helpful for manufacturers of high-end sports equipment, automotive products, electronics, and medical devices.

The adhesive activates material bonding once it is passed through a magnetic field, which is generated by a small electromagnetic device. The process uses less energy than a large conventional oven.

One magnetocuring adhesive, for example, can be 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," said Professor Raju V. Ramanujanin in a December 2020 news release from Nanyang Technological University  .

The bond also has a high adhesive strength comparable to conventional adhesives and commercial epoxy glue: 7 megapascals.

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

After filing a patent through NTUtive, the university's innovation and enterprise company, the team hopes to engage adhesive manufacturers to collaborate on commercializing their technology.

In a short Q&A with Tech Briefs below, Professor Ramanujan reveals what kinds of companies are already attracted to the idea of magnetocuring.

Tech Briefs: Why is magnetocuring better than other types of adhesive options?

Raju Ramanujan: Magnetocuring adhesives are a new class of one-pot adhesives that are activated by magnetic field. Previous related work has potential drawbacks of overheating the substrates and hotspot formation within the adhesive. Typically, one-component adhesives cure using moisture, heat and light. These approaches limit applications to specific substrates and can only be indirectly activated. Our methodology overcomes the previous failures and offers a method for remote and contactless curing of adhesives under a magnetic field.

Tech Briefs: How easy is it to pass glue through a magnetic field. What is that process like?

Raju Ramanujan: It is an easy process since the magnetic field generated devices can be a hollow cylinder or a planar surface. You just need to pass the object through these devices. The strength of the magnetic field can be varied by changing the input current or by changing the position of the object from the AMF device.

The new adhesive is made of two main components – a commercially available epoxy that is cured through heat, and oxide nanoparticles made from a chemical combination of manganese, zinc and iron oxides (Mn_xZn_1-xFe₂O₄). These nanoparticles are designed to heat up when electromagnetic energy is passed through them, activating the curing process. The maximum temperature and rate of heating can be controlled by these special nanoparticles, eliminating overheating and hotspot formation.

Tech Briefs: Can you walk me through a theoretical application? Let’s say I’m making high-end sports equipment. What would the process be like, to use your glue?

Raju Ramanujan: This glue needs to applied to the region where curing is required and then magnetic field has to applied to that region. A magnetic coil can be employed on the part where glue has been applied. Or the complete object can be slid on the planar surface of a magnetic coil. Furthermore, it is also possible to customize the magnetic coil as per the desired application.

Tech Briefs: What inspired this work? Are there a lot of magnetocured materials out there?

Raju Ramanujan: This invention was inspired by the goal of overcoming the many limitations associated with conventional thermal curing. Here we can cure the material without placing it into a furnace/oven/autoclave. Magnetocuring can be employed to join nonmetallic materials. There are several materials which are magnetocured at laboratory scale for example, glass, wood, polymer/plastic, carbon fiber, etc.

Tech Briefs: What’s next regarding your research?

Raju Ramanujan: Magnetocuring provides a new way of 3D printing that we are just starting to explore. Magneto-adhesive can be printed out of a specially designed nozzle that applies magnetic field at the printing tip and substrate and cures the adhesive as it is printed. 3D printing provides design freedom and manufacturing advantages to customize products.

Would you use this adhesive? Share your questions and comments below.

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