Giving a plastic useful new properties does not necessarily mean changing the whole material. Researchers at the University of Leicester have developed a technique that anchors nanoparticles in a polymer’s surface, leaving enough of each particle exposed to do its job.
The approach could give familiar plastics and coatings new functions while preserving properties such as low weight, strength and chemical resistance. Tests on a commercial wind-turbine blade coating showed improved resistance to degradation, suggesting a possible application in protecting renewable-energy equipment.
Nanoparticles can provide materials with useful abilities, from controlling chemical reactions to interacting with light or resisting microbial growth. Keeping them in the right place, however, presents a problem. Particles left on a surface can wash or rub away, while those buried inside a material lose contact with the environment they are supposed to affect.
The Leicester team’s method uses gentle heating to strike a balance between the two. Particles touching a warmed polymer sink part-way into its surface, then stop. Loose particles above them can be washed away, leaving a tightly packed layer just one particle thick. The polymer itself holds them in place, without an additional adhesive, binder or chemical-grafting step.
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‘The idea is simple: rather than making a completely new material, we give the surface of an existing one a new functional skin,’ said Dr Shengfu Yang, who led the research. ‘The polymer holds the nanoparticles in place, but leaves enough exposed to do their job.’
To test the technique, the researchers applied cerium oxide nanoparticles to a commercial epoxy coating used on wind-turbine blades. The particles settled roughly halfway into the surface and remained attached after vigorous washing, ultrasound treatment and repeated tape peeling.
Their exposed surfaces also remained chemically active. Cerium oxide can react with damaging oxidising chemicals and subsequently recover its chemical state, allowing its protective action to be renewed.
In accelerated laboratory tests, the treated coating suffered less damage than untreated material. Short-term outdoor weathering and tests in artificial seawater also showed improved resistance to degradation, although the results do not yet establish how much longer a coating would last in service.
The team also embedded silver nanoparticles in two common forms of polyethylene, indicating that the process could work with different combinations of particles and polymers. Potential applications include sensing, antimicrobial surfaces and materials that carry out useful chemistry.
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The university has filed a patent covering the technique and is seeking industrial partners to develop it further.
The study, ‘Self-limiting thermal embedding creates surface-accessible nanoparticle monolayers on polymers’, is published in Communications Materials.