Polymer fibres: light, strong and tough

A research team from the University of Bayreuth has developed polymer fibres designed to be strong and tough yet as light as a feather — an exceptional combination of properties that is urgently needed in many industrial sectors and in medicine, as well as being of great interest for scientific research. The fibres were characterised together with partners in Germany, China and Switzerland, and have since been described in the journal Science.

“The fibres we discovered can be produced easily using high-tech processes that are already established in the industry — and on the basis of polymers that are readily available worldwide,” explained Prof Dr Andreas Greiner from the University of Bayreuth, who guided the research work.

“One individual fibre is as thin as a human hair, weighs less than a fruit fly, and yet is very strong: it can lift a weight of 30 grams without tearing. This corresponds to about 150,000 times the weight of a fruit fly. Experiments on the high tensile strength of these fibres have furthermore revealed their high toughness. This means that each individual fibre can absorb a lot of energy.”

Getting prepared for electrospinning. Image ©University of Bayreuth/Jürgen Rennecke.

The chemical basis of the fibres is polyacrylonitrile. A single fibre with a diameter of about 40,000 nm consists of up to 4000 ultrathin fibrils. These fibrils are linked by small amounts of an additive. Three-dimensional X-ray images show that the fibrils within the fibre are almost always arranged in the same longitudinal direction.

“We prepared these multifibrillar polyacrylonitrile fibres in a laboratory for electrospinning at the University of Bayreuth and extensively tested them for their properties and behaviour,” said Bayreuth polymer scientist Prof Dr Seema Agarwal. “Their unique strength in combination with high toughness never ceased to fascinate us.”

Electrospinning of a multifibrillar polyacrylonitrile fibre. Image ©University of Bayreuth/Jürgen Rennecke.

Due to their impressive properties, the polymer fibres are suitable for technical components that are exposed to high loads. They enable innovative applications in a wide variety of fields, for example, in the textile industry or medical technology, in automotive engineering or in the aerospace industry. In addition, the polymer fibres can be recycled.

“We are certain that our research results have opened the door to a new, forward-looking class of materials,” Prof Dr Greiner said. “Practical applications on the part of industry can be expected in the near future. In polymer science, our fibres will be able to provide valuable services in the further research and development of high-performance functional materials.”

Top image: Stretching of a multifibrillar polyacrylonitrile fibre. Image ©University of Bayreuth/Jürgen Rennecke.

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