New plastic clothing material to keep people cool

Stanford scientists have developed a low-cost, plastic-based textile that, if woven into clothing, could cool your body far more efficiently than is possible with the natural or synthetic fabrics in clothes we wear today.

The researchers suggest that this new family of fabrics could become the basis for garments that keep people cool in hot climates without air conditioning.

"If you can cool the person rather than the building where they work or live, that will save energy," said Yi Cui, an associate professor at Stanford University in the US.

This new material works by allowing the body to discharge heat in two ways that would make the wearer feel nearly 4 degrees Fahrenheit cooler than if they wore cotton clothing.

The material cools by letting perspiration evaporate through the material, something ordinary fabrics already do. But the Stanford material provides a second, revolutionary cooling mechanism: allowing heat that the body emits as infrared radiation to pass through the plastic textile.

All objects, including our bodies, throw off heat in the form of infrared radiation, an invisible and benign wavelength of light. Blankets warm us by trapping infrared heat emissions close to the body.

This thermal radiation escaping from our bodies is what makes us visible in the dark through night-vision goggles.

"Forty to 60 per cent of our body heat is dissipated as infrared radiation when we are sitting in an office," said Shanhui Fan, a professor at Stanford.

To develop their cooling textile, the researchers blended nanotechnology, photonics and chemistry to give polyethylene – the clear, clingy plastic we use as kitchen wrap – a number of characteristics desirable in clothing material.

It allows thermal radiation, air and water vapour to pass right through, and it is opaque to visible light.

The researchers found a variant of polyethylene commonly used in battery making that has a specific nanostructure that is opaque to visible light yet is transparent to infrared radiation, which could let body heat escape.

They then modified the industrial polyethylene by treating it with benign chemicals to enable water vapour molecules to evaporate through nanopores in the plastic, allowing the plastic to breathe like a natural fibre.

That success gave the researchers a single-sheet material that met their three basic criteria for a cooling fabric. To make this thin material more fabric-like, they created a three-ply version: two sheets of treated polyethylene separated by a cotton mesh for strength and thickness.

They tested the cooling potential of their three-ply construct versus a cotton fabric of comparable thickness. The comparison showed that the cotton fabric made the skin surface 3.6 Fahrenheit warmer than their cooling textile. The researchers said this difference means that a person dressed in their new material might feel less inclined to turn on a fan or air conditioner.

The research was published in the journal Science.