Materials

Plantain fibers could find use in lighter, stronger cars

Plantain fibers could find use...
A diagram showing the source, processing and end use of the plantain fibers
A diagram showing the source, processing and end use of the plantain fibers
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A diagram showing the source, processing and end use of the plantain fibers
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A diagram showing the source, processing and end use of the plantain fibers

Carbon fiber may be strong and light, but it's also expensive. South African scientists have developed a cheaper and more sustainable alternative, though, in which the carbon fibers are replaced with ones extracted from plantain plants.

Led by Prof. Tien-Chien Jen, researchers at the University of Johannesburg started by obtaining plantain "pseudo-stems" from harvested crops in Nigeria – this part of the plant is inedible, and is typically just discarded.

A process known as water-retting was then utilized to separate the individual fibers that made up those stems. Those fibers were subsequently soaked in a 3-percent caustic soda solution for four hours, dried, treated with high-frequency microwave radiation for two minutes, then dispersed in ethanol to keep them from "bunching up."

As a result, the fibers were better able to bond with an epoxy resin, which also contained a small amount of multi-walled carbon nanotubes. The best mix was a combination of one part plantain fibers and four parts resin/nanotubes, with the tubes making up just 1 percent of the material by weight. That mixture was placed in a mold and compressed at room temperature for 24 hours.

When samples of the resulting composite were lab-tested, they were found to be much stiffer and stronger than same-sized pieces of the resin on its own. More specifically, they had 31 percent more tensile strength and 34 percent more flexural strength. What's more, they also exhibited better impact strength and thermal conductivity.

It is now hoped that once the technology is developed further, the material could find use in fields such as the automotive industry.

"Using car parts made from these composites can reduce the mass of a vehicle," says postdoctoral researcher Dr. Patrick Ehi Imoisili. "That can result in better fuel efficiency and safety. These components will not rust or corrode like metals. Also, they can be stiff, durable and easily molded."

And this certainly isn't the first time we've seen a composite material made of fibers harvested from agricultural waste. Examples of other source plants have included pineapple, agave and wheat.

A paper on the Johannesburg study was recently published in the Journal of Materials Research and Technology.

Source: University of Johannesburg via EurekAlert

6 comments
windykites
I have heard of banana boats, but not banana cars!(Lol) Another good source of fibres would be sugar cane waste, also hemp!
VASRAGAVAN
Thank you for the wonderful information. I wish to inform that banana stem is regularly consumed in South India either as a salad preparation or in the form of juice as it possess certain medicinal properties. Also banana fibre is extracted from the pseudo stems to make quite a few products like sarees, strings, etc.
lee54
But how strong is it compared to conventional Fiberglass composites? Back in the 70s, some unscrupulous boat builders in Taiwan were using burlap instead of fiberglass cloth to laminate their boat hulls, so the idea of using plant-based alternatives is not new. The strength, though, was not nearly as good. And carbon fiber is far stronger than even fiberglass.
Catweazle
Duroplast, a strong light material made from cotton waste and phenolic resin, was used to construct the bodies of the East German Trabant cars.
Douglas Bennett Rogers
A lot of products, such as hardboard and fiber board are made from things like sugar cane. A problem with cellulose is that it swells when wet. This is OK for table tops, as it is bonded to a heavy base. The value of resin and glass composite is that it is a two phase material. This means that a large piece of material can exhibit a substantial fraction of the strength of a flaw free element of the strength element (glass). The matrix material must have a breaking elongation of at least 10 % more than the strength element. Thus glass in epoxy with 70 % glass makes a two phase material but cellulose in epoxy does not. Cellulose in polyethylene would work. The 70 % rule is determined by the Griffith crack length in the matrix material at maximum load.
toni24
But how well does the material in the "Banana Mobile" compare to full carbon fiber composites?