Green manufacturing can save new energy, time and space.
Scientists at Nanyang Technological University in Singapore (NTU Singapore) have developed a new way to cure adhesives using a magnetic field.
Conventional adhesives such as epoxy used to bond plastic, ceramics and wood are often designed to cure using moisture, heat or light. They often require specific inlet temperatures, ranging from room temperature to 80 degrees Celsius.
The curing process is necessary to cross and bond the glue to the two fixed surfaces, as the glue crystallizes and hardens to obtain the final strength.
The new “magnetocuring” glue of the NTU can be cured by passing it through a magnetic field. This is very useful in some environmental conditions where current adhesives do not work well. Moreover, when adhesive is embedded in insulating materials such as rubber or wood, traditional activators such as heat, light and air cannot reach the adhesive easily.
Products such as composite bike frames, helmets, and golf clubs are now made with two-part epoxy adhesives, where resin and hardener are mixed and the reaction begins immediately.
For manufacturers of carbon fiber (thin carbon tape glued layer by layer) and carbon fiber-related sports equipment manufacturers, factories use large high-temperature furnaces to cure epoxy glue for many hours. This energy-intensive curing process is the main reason for the high cost of carbon fiber.
The new commercially available magnetic magnetomagnetic adhesive is made in combination with custom-made magnetic nanoparticles made by NTU scientists. It should not be mixed with any hardener or accelerator, unlike two-component adhesives (it contains two liquids that need to be mixed before use) to make it easier to manufacture and apply.
When activated it binds materials through a small magnetic field that is easily generated by a small electromagnetic device. This uses less energy than a large conventional furnace.
For example, a gram of magnetocurtion adhesive can easily cure a 200 Watt electromagnetic device in five minutes (consuming 16.6 Watt hours). This requires 120 times less energy than a 2000 watt oven that consumes one hour (consuming 2000 watts hours) of conventional epoxy.
The findings were published in the scientific journal by Professor Raju V. Ramanujan, Associate Professor Terry Steele and Dr. Richa Chaudhary of the NTU School of Materials Science and Engineering. Applied Materials Today and provide potential application in a wide range of areas.
It includes state-of-the-art sports equipment, automotive products, electronics, energy, aerospace and medical manufacturing processes. Laboratory tests have shown that the new adhesive has a strength of up to 7 megapascals, comparable to many epoxy adhesives on the market.
The Steele Association of Professors, experts in various types of advanced adhesives, explained: “Our key development is a way to cure adhesives by causing a magnetic field and a few minutes to prevent the applied surfaces from heating up. This is important because some surfaces we want to join are very heat sensitive. such as flexible electronics and biodegradable plastics. “
How glue “magnetizing” works
The new adhesive consists of two main components: heat-cured commercial epoxy and manganese, oxide nanoparticles composed of a chemical combination of zinc and iron (MnxZn1-xFe2O4).
These nanoparticles are designed to heat electromagnetic energy as it passes through them, activating the curing process. Through these special nanoparticles the maximum temperature and heating rate can be controlled, creating heating and hot spot.
Without the need for large industrial kilns, activating glue has a smaller footprint in space and energy consumption. The energy efficiency of the curing process is crucial for green manufacturing, the products are made at lower temperatures and use less energy for heating and cooling.
For example, sports shoe manufacturers have difficulty heating adhesives between rubber soles and the upper half of the shoe because the rubber is heat insulating and transmits heat to conventional epoxy glue. The shoe needs to be heated in the oven for a long time before the hot glue arrives.
The use of activated field magnetic glue avoids this difficulty by activating the curing process only with glue.
The replacement magnetic field can also be inserted at the bottom of the conveyor belt systems, so that products with pre-applied glue can be cured when they cross the magnetic field.
Improving manufacturing efficiency
Professor Raju Ramanujan, internationally recognized for advances in magnetic materials, led the project and predicted that this technology could increase manufacturing efficiency where adhesive joints are needed.
“Temperature-controlled magnetic nanoparticles are designed to be mixed with single-pot adhesive formulations, so many epoxy adhesives on the market could be converted to magnetic field-activated glue,” said Professor Ramanujan.
“The speed and temperature of curing can be adjusted so that manufacturers of existing products can redesign or improve existing manufacturing methods. as they move along the chain, without the kiln, it would lead to much fewer downtime and more efficient production. ”
The first author of the study, Dr. Richa Chaudhary, said, “It takes a few hours to cure the newly developed magnetic adhesive instead of a few hours, and yet it is able to secure surfaces with high strength bonds, which is of great interest in sports, medicine, automotive and aerospace industry. This efficient process can also lead to cost savings, as the space and energy required to cure conventional heat are significantly reduced. “
This three-year project was supported by the Science, Technology and Research Agency (A * STAR).
In previous work, an electric current was passed through a coil to work with heat-activated glue, known as induction curing, where the glue is heated and cured from the outside. However, its drawbacks are surface heating and uneven bonding due to the generation of heat inside the adhesive.
Going forward, the group hopes to work with adhesive manufacturers to commercialize their technology. They have filed a patent through NTUitive University for Innovation and Business. Manufacturers of sports products have already received interest in their research.
Reference: By Richa Chaudhary, Varun Chaudhary, Raju V. Ramanujan, and Terry WJ Steele, “Magnetization of Epoxy Adhesives for Vacuum Temperatures,” September 15, 2020, Applied Materials Today.
DOI: 10.1016 / j.apmt.2020.100824