Professor Raju of NTU grabbed and bent two pieces of wood by magnet uring crushing glue to demonstrate its strong bonding strength. Credit: NTU Singapore
A potential boon for green production, new glue saves on energy, time and space.
Scientists at Nanyang Technological University in Singapore (NTU Singapore) have developed a new way to treat adhesives using a magnetic field.
Traditional adhesives such as epoxy used to seal plastics, ceramics and wood are usually made to treat using moisture, heat or light. They often require a special remedy of temperatures up to 80 degrees at room temperature Celsius.
The glue requires a curing process to close the cross-links and glue with two protected surfaces as the glue crystallizes and hardens to achieve its final strength.
NTU’s new “magnet curing” glue can cure it by passing it through a magnetic field. This is very useful in certain environmental situations where current adhesives do not work well. Also, when sandwiched between insulating materials such as adhesive rubber or wood, conventional workers such as heat, light and air cannot easily reach the adhesive.
Products such as composite bike frames, helmets and golf clubs are currently made by two-part epoxy adhesives, where a resin and hardness are mixed and the reaction begins immediately.
For manufacturers of carbon fiber – thin ribbons of carbon glued together by a layer – and manufacturers of sporting goods, which include carbon fiber, their factories use large, high-temperature ovens to cure epoxy glue for many hours. This energy-intensive treatment process is the main reason for the high cost of carbon fiber.
The new “Magnetoc Curing” adhesive is made by combining specially commercially available epoxy adhesives with specially formulated magnetic nanoparticles made by NTU scientists. It does not need to be mixed with any hardness or accelerator, unlike two-component adhesives (which are two liquids that must be mixed before use), making it easy to manufacture and apply.
When it is activated by passing through a magnetic field it shuts off the material, which is easily generated by a small electromagnetic device. This uses less energy than large conventional ovens.
Associate Prof Steele (left) and Dr .. Richa healing magnet oc curing glue on a cotton mesh using an electromagnetic field. Credit: NTU Singapore
For example, one gram of magnet oc curing adhesive can be easily cured in five minutes (taking 16.6 watt hours) by a 200-watt electromagnetic device. This requires 120 times less energy than the traditional 2000-watt oven which takes one hour (2000 watts) to heal a conventional epoxy.
Professor Raju V. Dr. Ramanujan, Associate Professor Terry Steele and NTU School of Materials for Materials Science and Engineering. Developed by Richa Choudhury, these findings were published in the scientific journal. Content applied today And offers potential application in a wide range of fields.
These include state-of-the-art sports equipment, automotive products, electronics, energy, aerospace and medical manufacturing processes. Laboratory tests show that the new adhesive has a strength of up to 7 megapascals compared to many epoxy adhesives on the market.
Associate Professor Steele, who specializes in various types of advanced adhesives, explains: “Our key development is a way to cure adhesives in the minutes that come in contact with the magnetic field, while preventing excessive heat from being applied to surfaces. This is important because some of the surfaces we want to join are extremely sensitive to heat, such as flexible electronics and biodegradable plastics. “
How “magnet curing” glue works
The new adhesive is made up of two main components – commercially available epoxy that is heat treated, and oxide nanoparticles made from a chemical compound including manganese, zinc and iron (MNXZN1-XFE2O4).
These nanoparticles are designed to heat when the electromagnetic energy radiation passes through them, activating the healing process. The maximum temperature and heating rate can be controlled by these special nanoparticles, eliminating overheating and hotspot formation.
(Left to right) NTU Associate Professor Terry Steele, Prof. Raju V. Ramanujan and Dr. Richa Choudhury has a variety of soft and hard materials bound by his new magnet uring crushing glue. Credit: NTU Singapore
Without the need for a large industrial oven, glue activation is a small step in terms of space and energy consumption. Energy efficiency in the treatment process is crucial for green production, where products are made at low temperatures, and use less heat for heating and cooling.
For example, manufacturers of sports shoes often have difficulty heating adhesives between rubber soles and the upper part of the shoe, as rubber is a heat insulator and resists the transmission of heat in conventional epoxy glue. No longer does the oven need to heat the shoes, while the heat reaches the glue.
The use of magnetic-field activated glue simply bypasses this difficulty by directly activating the healing process in the glue.
The optional magnetic field can also be embedded in the bottom of conveyor belt systems, so pre-applied glue products can recover when they pass through the magnetic field.
Improve product efficiency
Pro. Raju Ramanujan, who is internationally recognized for advancing in magnetic materials, jointly led the project and predicted that the technology could increase production efficiency where adhesive joints are needed.
“Our temperature-controlled magnetic nanoparticles are designed to be blended with existing one-pot adhesive formulations, so many epoxy-based adhesives on the market can be converted into magnetic field-activated glues,” said Professor Ramanujan.
“The speed and temperature of the treatment can be adjusted, so manufacturers of existing products can redesign or improve their existing production methods. For example, instead of applying glue to a conventional assembly line and treating it as part, the new procedure might be to pre-apply glue to all parts and then treat them as they move along the conductor chain. Without an oven, it would lead to much less downtime and a more efficient product. “
The first author of the study, Dr. Richa Choudhury said, “Our newly developed magnet curing adhesive solution takes only a few minutes instead of hours, and yet, is able to protect surfaces with high strength restrictions, which is of considerable interest in sports. , Medical, automotive and aerospace industries. This efficient process can also bring cost savings as the space and energy required for conventional heat treatment is significantly reduced. “
The three-year project was supported by the Science, Technology and Research Agency (A * STAR).
Previous work on heat-activated glue used electric current flowing from the coil, known as induction-curing, where the glue is heated and cured from the outside. However, its drawbacks include overheating and uneven bonding of surfaces due to the formation of hotspots in the adhesive.
Going forward, the team hopes that adhesive manufacturers will be involved in collaborating in the commercialization of their technology. They have filed a patent through the university’s innovation and enterprise company NTutive. They have already received interest from sports goods manufacturers for their research.
References: Richa Chowdhury, Varun Chowdhury, Raju V. Ramanujan and Terry W.J. Steele, 15 September 2020, “Magnet net curing of temperature failed epoxy adhesives” Content applied today.
DOI: 10.1016 / j.apmt.2020.100824
