A new method could turn refinery byproducts into high-value, ultralight structural materials for cars, aircraft, and spacecraft.

As the world struggles to improve the efficiency of cars and other vehicles in order to curb greenhouse gas emissions and improve the range of electric vehicles, the search is on for ever-lighter materials that are strong enough to be used in the bodies of cars.

Researchers at MIT have come up with a way of making lightweight fibres out of an ultracheap feedstock: the heavy, gloopy waste material left over from the refining of petroleum.

The material is currently used only for low-value applications such as asphalt, or eventually treated as waste.

But MIT says the refinery byproducts can produce carbon fibre that is cheap to make, and offers advantages over the traditional carbon fibre materials because it can have compressional strength, meaning it could be used for load-bearing applications.

Composites made from carbon fibres are not a new idea, but so far in the automotive world they have only been used in a few very expensive models. 

The new research aims to turn that around by providing a low-cost starting material and relatively simple processing methods.

Traditional carbon fibres are typically made from polymers (such as polyacrilonitrile) derived petroleum, but using a costly intermediate step of polymerising the carbon compounds. 

Instead of using a refined and processed petroleum product to start with, the MIT team’s new approach uses what is essentially the dregs left after the refining process, a material known as petroleum pitch. 

“It’s what we sometimes call the bottom of the barrel,” says research scientist Dr Nicola Ferralis.

“Pitch is incredibly messy,” he says. 

“It’s a hodgepodge of mixed heavy hydrocarbons, and “that’s actually what makes it beautiful in a way, because there’s so much chemistry that can be exploited. That makes it a fascinating material to start with.

“The process that you need to actually make a carbon fibre [from pitch] is actually extremely minimal, both in terms of energy requirements and in terms of actual processing that you need to do,” Dr Ferralis says.

Part of the complication of making conventional fibre composites is that the fibres have to be made into a cloth and laid out in precise, detailed patterns. 

The reason for that, he says, “is to compensate for the lack of compressive strength”, but with the new process all that extra complexity would not be needed.

More details are accessible here.