Natural fiber composites gaining traction in automotive

As reported in the CompositesWorld March 2016 article, “Natural fiber composites: Market share, one part at a time” (see Learn More located under Editor's Picks on the top right), the natural fibers industry continues to develop. And the automotive industry has helped lead the way with its adoption of natural fibers for door panels, seat backs and trunk liners. Now the industry can add a roof frame to that list.

“When you have impregnated the fiber by crosslinking, it becomes a resolute bond between the Acrodur molecule and the fiber and thermoset,” he says.

The IAC project’s steps begin with wet-impregnating the dry natural fiber mat, in this case, bast fiber, which is done by an outside prepregger. Because Acrodur is water-based, impregnation is thorough. Wet impregnation also allows for easy application of additives, such as colorants or flame retardants. The fiber mats are dried after impregnation with a conventional convection oven or with radio frequency drying techniques. IAC then receives the prepregged fiber mat, which is still soft and flexible. The frame is then manufactured in-house by IAC in a hot molding process.

“In the specification of the IAC EcoMatHot fiber mat, as well as in terms of tooling technology and production process of this innovation, we were able to take advantage of more than 20 years of experience working with natural fiber-reinforced materials in automotive interiors,” says IAC director of advanced engineering Fritz Schweindl. “By manufacturing this product in-house in our headliner plant, we follow our strategy and expansion of vertical integration of our interior systems. Thanks to our global manu- facturing footprint and standardized processes, we are now able to adapt IAC FiberFrame to customer needs and supply it around the world.”

Schweindl says it was relatively easy to integrate the Acrodur prepreg into IAC’s production system. “The natural fiber components that are strengthened with Acrodur are ideal to mold; they are environmentally friendly and save time during the production of the composites,” he comments, adding, “Furthermore, the product is low in emissions, which means that it is safer to work with.”

FiberFrame started production in November 2015 at IAC’s Center of Excellence for overhead products in Prestice, Czech Republic, to support the Mercedes-Benz E-Class launch. The company also produces the headliner, the outer-rear wheel house liner, inner wheel house cover and rear seat cover for the vehicle.

BASF resin helps boost natural fibers

BASF says Acrodur turns natural fibers into functional and environmentally friendly materials. The company believes it’s well-suited for molded parts made from natural fiber and post-moldable nonwovens.

“Both our Acrodur families (thermoset and thermoplastic) have been developed for best bonding characteristics on these fiber types, while polypropylene acts more as a melted ‘glue’ in the voids between fibers,” Karbstein says.

Unlike other high-strength natural fiber-compatible resins, such as urea formaldehyde (UF), phenol formaldehyde (PF) or MDI resins, which are common for wood and cellulose fiber bonding, Acrodur does not emit harmful VOCs during production, handling or use. Because the only curing byproduct is water, Karbstein says these resins are suitable for safe applications in the automotive interiors and home/office furnishings industries.

In the automotive market, short wood fibers, long kenaf/ jute/hemp (bast type) fibers and glass fibers have been infused with polypropylene (PP) for a long time. Use of nonwoven fiber composites, mostly natural fiber/PP and glass/PP, has been on the rise because they perform better than simple injection molded plastics. Although PP also poses a less-critical VOC risk than formaldehyde-based resins or MDI, Karbstein says that Acrodur outdoes PP by reducing chemical use by increasing the fiber content.