Natural Engineering

Growing pressure to reduce global carbon-dioxide emissions is good news for hemp farms in France and rock quarries in central Europe.

Natural hemp fibers and those made from volcanic basalt rocks promise to reduce the weight of components made with fiber-reinforced polymers.

Linen and exotic fibers made from bananas and other plants have been gaining market share in Germany for a decade, mainly in the form of mats that are injected with resin and compressed under heat to form a vehicle part, such as a rear-package shelf or door liner.

Technilin SA, a leading French supplier of long linen fibers, began supplying linen for door panels in the Opel Astra and now provides them for the Renault Clio and Citroen C2, as well.

Mercedes-Benz has scored many ecological points for using natural fibers in rear door panels, instrument panels and other interior parts in its cars.

However, parts made by injecting plastic into a mold traditionally have used glass fibers to add strength. Natural fibers do not achieve enough standardization to be engineered properly, suppliers say.

Hemp growers in France believe they can change that and in 2001 formed a new company, AFT Plasturgie, to develop what amounts to high-tech hemp fibers.

“This year, for the first time, we have parts in production for auto makers in America, France and Germany,” says Gerard Mougin, AFT managing director at the annual JEC trade show for composites in Paris.

Most of the injection-molded parts are for the engine compartment, such as fans, radiator supports and the undercarriage, where appearance is not important.

But in the last six months since the auto industry began getting serious about saving weight, projects involving hemp fiber began multiplying.

“We are in the process of validating many automotive parts now,” Mougin says. “In three to five years, Europe will be using 10,000 tonnes (11,023 tons) a year.”

AFT Plasturgie currently is using “hundreds of tons” in its composite preparations, where it is blended with various polymers according to the requirements of the part maker and OEM client. Because cellulose degrades at 428° F (220° C), hemp must be used with low-temperature polymers like ABS, polyethylene, polypropylene, polystyrene and PVC.

The AFT hemp fiber factory now has a capacity of 5,512 tons (5,000 t) per year. Two years ago, when the first solid orders started arriving, the company began planning a plant with an annual capacity of 66,139 tons (60,000 t) that could be in production in late 2008 if the current possible orders become firm.

AFT says its advantage comes from the way it treats the fibers. Naturally, they do not bind well with polymers, but using a non-chemical thermal and mechanical treatment results in fibers with the correct mechanical properties.

Stone fibers will take longer to reach the auto industry.

ASATech, a subsidiary of the Austrian-Ukrainian Asamer Group, is just introducing its fiber to the global auto industry and as yet has no contracts to sell its product.

The family-owned firm has a 20-year strategy to create a high-tech, higher-margin product using technology developed in the former Soviet Union for space and military applications.

To make the tiny threads, just 9 microns in diameter, basalt is melted at 4,352° F (2,400° C) and spun into a monofilament that has 40% more tensile strength than glass fibers, is 60% more resistant to shocks and resistant to heat up to 1,292° F (700° C), suggesting such uses as in firewalls.

However, the first target is aimed at making high-pressure containers for natural gas or hydrogen, with a new tank system.