Versatile polymer that can be manipulated by magnets and cured into shape by microwaves

Australian researchers have created a versatile new polymer material that can be used to purify water or used as a recyclable construction material, and even formed into lightweight machine components.

According to research published in Polymer Chemistry, the material is made by hot-pressing together magnetic iron nanoparticles and a sulphur-rich polymer – made from canola oil and elemental sulphur.

The iron particles allow the material to be manipulated with a magnet and to be heated very rapidly with microwaves, which allows it to be cured into a solid shape within seconds.

This versatile material is also recyclable and easy to repurpose because it can be ground up and re-shaped multiple times.

Senior author of the study, Justin Chalker, who is a Professor of Chemistry at Flinders University, says the new research provides important additional evidence of the potential and versatility of sulphur-rich polymers.

“This study illustrates the expanding utility and reach of sulphur-rich polymers,” says Chalker. “Heavy metal remediation, novel construction materials and light-weight and recyclable machine components were all made from this single, versatile material.”

It can be used in mercury remediation

The sulphur-rich polymer is made by combining the sulphur by-product of petroleum refining and unsaturated plant oil, which is then ground up into particles about 0.5 millimetres to 3 mm in diameter. Hundreds of kilograms of this can be made industrially, making it readily available to be integrated into new technologies.

Magnetic nanoparticles of Maghemite (γ-Fe2O3) – an iron oxide – were hot pressed and integrated into the polymer at 100 °C, then repeatedly milled and hot-pressed for a more uniform distribution throughout the material.

Read more: Explainer: What is a polymer?

The researchers demonstrated that the magnetic-responsive material can be used to remove mercury from contaminated water; it soaks up the toxic metal because the sulphur in the polymer binds heavy metals.

And, instead of having to filter the mixture, the magnetic nanoparticles allow the material to be easily picked up with the use of a magnet. They could reduce the mercury concentration in the water to less than 7 parts per billion – a 99.9% reduction in mercury from the original mixture.

“This is a simple way to remove toxic metals from complex mixtures,” says lead author Dr Nic Lundquist, a research associate in Chemistry at Flinders University.

Manufacturing light-weight machine components

The material can also be manufactured into solid objects through microwave curing, which the team demonstrated by fashioning a solenoid valve.

By upping the iron nanoparticle content of the composite, they were able to create a valve that, when an electric current was passed through the solenoid coil to produce a magnetic force, could be made to open.

A. magnetic responsive composite cylinder was prepared by curing 2.0 g of the magnetic composite powder in a syringe. The magnetic responsive cylinder (green box) was then used to replace a metal valve in solenoid. B. The solenoid in operation. The magnetic field generated when the power is on is sufficient to move the cylinder against the spring and open the valve. When the power is turned off, the cylinder no longer experiences a magnetic force, the spring forces the cylinder back into a position where the flow of the liquid is stopped. Credit: Lundquist et al. 2022/Polymer Chemistry

Their magnetic sulphur rich-polymer version was just one-tenth of the mass of the original commercial all-metal component.

“This is a demonstration of how polymer-based composites can be lightweight replacements of machine components that are traditionally composed entirely of metal. Such capabilities are important in soft robotics as well as machines that require lighter weight for more efficient transport,” the authors write in their study.

The magnetic-responsive material was also demonstrated to be an effective binder for new construction materials, charting new paths for converting waste.

“I’m very excited about the possible new applications of these polymers and can envision uptake in different fields, from environmental remediation to robotics,” says Dr Lundquist.

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