Polymer research could lead to scratch-resistant coatings

A new analytical method for determining the optimal composition of polymer surfaces could lead to lightweight windows and scratch-resistant coatings for cars and mobile phones.

The research used a polymer called poly(methyl methacrylate) (PMMA), which is widely used as a glass substitute, under trademarks such as Lucite or Plexiglas — although is far more brittle and is less scratch-resistant than glass.

Previous work has succeeded in adding silica particles to PMMA, which can create a polymer-particle nanocomposite with better strength; however, the particles tend to clump and the resulting materials are inconsistent in terms of performance.

A team at MIT has found a way to analyse the particle-polymer interactions at the nanoscale, which could facilitate the discovery of improved coatings.

‘We demonstrated that putting a small amount of particles on the surface increases the stiffness,’ said Dr Meng Qu of MIT, adding that ‘any surface that needs coating’ is potentially a candidate for such a process.

The team first treated the silica particles with other functional groups of molecules, changing their surface chemistry so it disperses evenly on the polymer surface.

Then it heated the polymer to soften it slightly and used an atomic force microscope to observe the particles as they slowly sank into the surface.

The resulting data allowed the team to figure out the optimal coating materials and particle densities for strengthening the polymer surface.

The work could make a difference in many current uses of PMMA, such as the windows used in aquarium tanks. At present, such windows are made very thick to resist the enormous water pressure in large tanks. But if the material is stronger, the windows could be made thinner and lighter, and therefore less expensive.

The work was a collaboration between MIT’s Department of Materials Science and Engineering, and several researchers at DuPont Nanocomposite Technologies in Delaware and was partly funded by the DuPont-MIT Alliance.