Polythene film outperforms aluminium

A new processing technique has produced a transparent polythene film that can be stronger than aluminium at a fraction of the weight.

By tuning temperatures, UK researchers created a clear polythene film with a resilience and tensile strength more than 10 times higher than polycarbonates and acrylics.

University of Warwick Professor Ton Peijs, who led the study, said: “It is anticipated that these lightweight, low-cost, highly transparent, high strength and high stiffness high-density polyethylene films can be used in laminates and laminated composites, replacing or strengthening traditional inorganic or polymeric glass.”

While aluminium has a higher maximum resilience, the polythene film has a lower density, meaning it can potentially outperform metals based on weight.

The technique has another advantage for plastics manufacturing. Current methods of creating high strength plastic such as hot-drawing – the process of using tensile forces to stretch metal or glass – can give materials defects and therefore an opaque appearance.

This can be a problem when manufacturing plastics that have to be completely transparent, such as for phone screens or windows, which is why additives are used in the process.

Researchers managed to achieve transparency of 90% in the visible range, without the use of additives. The best balance of strength and transparency was achieved at drawing temperatures between 90-110°C.

“We expect greater polymer chain mobility at these high drawing temperatures to be responsible for creating fewer defects in the drawn films, resulting in less light scattering by defects and therefore a higher clarity,” Professor Peijs said.

The film could be used to manufacture laminates, windscreens, glazing and high-strength shatterproof phone screens.

The team of researchers, from the University of Warwick and Queen Mary University of London, used Borealis VS4580, a high-density polyethylene, in their experiments. They detail the process in the journal Polymer.