The idea of a plastic material that is also magnetic sounds far-fetched. Traditional magnets depend on the alignment of electron spins; such an alignment can typically only be achieved using metallic elements. These magnets, although powerful, have several disadvantages – they are heavy, they are expensive, and they are subject to corrosion.
That’s why developing a magnetic plastic material has long been the dream of many materials scientists, including members of a team at University of Durham led by head researcher Naveed Zaidi. In 2004, that team became the first to successfully produce a magnetic plastic material that exhibited magnetic properties at room temperature (previous teams had produced magnetic plastics but they were only effective at extremely low temperatures).
The team succeeded by combining two polymers, emeraldine base polyaniline (PANi) and tetracyanoquinodimethane (TCNQ). The former can be described as a metal-like electrical conductor which remains stable in ambient conditions. The latter has a characteristic tendency to form free radicals, charged particles that can align in a certain direction just like the electron spins in traditional metallic magnets.
The team almost didn’t succeed – it was by pure luck that they discovered that previously discarded samples had slowly gained magnetic properties over the months since they were produced. Since that time, the team has found ways to increase the speed at which the polymer chains become aligned after the material was first produced, which has led the development of a practical production method.
The magnetic plastics industry has come a long way since the first crude magnets were produced at Durham in 2004. According to an infographic published in Business Wire in October 2019, the global industry is expected to experience a compound annual growth rate of 8% through 2023. Most of this growth is expected to be concentrated in the Asia-Pacific region.
Unlike traditional magnets, magnetic plastics can be molded into any shape imaginable. They can also be made flexible, transparent, and low in density. Promising applications include the production of magnetic polymer coatings which could replace traditional magnetic coatings on computer disk drives. Additional applications include mechanical medical devices such as cochlear implants. Plastic magnetic parts for implants would greatly reduce the likelihood of rejection by the body.
Continued research aims to improve our understanding of the exact influence of polymer molecular structure on the resulting magnetic properties. A better understanding of this could allow to produce magnetic plastics with highly customizable properties.