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Thermwood

Polyurethane Class A Finish Possible with LFI

12 February 2010

Attendees of Composites 2010 were given a first-hand look at an example of a Long Fiber Injection formed component that displayed a Class A finish direct from the mould.

Despite the fact that Long Fiber Injection (LFI) is a proven and efficient method for forming large and lightweight polyurethane composite parts, companies have found difficulties when attempting to producing a part with a decorated, Class A surface right out of the mould. Michigan-based Romeo RIM has produced what they believe to be the first such component in NAFTA – the knotter shield for a baler.

The shield is produced utilizing Baydur STR 675 polyurethane system, which is marketed through BaySystems.

“The ability to create a part with a high-gloss, zero-defect surface has great implications,” said Craig Snyder, market channel representative, Bayer MaterialScience LLC. “At Bayer MaterialScience LLC, we expect that it may open up new markets and new applications to the many benefits of LFI technology.”

A baler is a piece of farm machinery used to compress a cut and raked crop, such as hay, into compact bales. The knotter plays a critical role in a baler: It ties off bales when they reach the appropriate length. The shield that was produced is on the end cap of the knotter, covering up the knotter drive mechanism to protect it from the elements, as well as crop build-up. This external shield is serviced regularly, and therefore needs to be both durable and aesthetically pleasing.

To produce the part, an inmould coating is sprayed into the mould, followed by a barrier coat. Next, the Baydur polyurethane material, which is specially formulated by Bayer MaterialScience LLC for the LFI process, and fibreglass are simultaneously dispensed into the mould cavity. Use of the polyurethane barrier spray in conjunction with LFI shortens demould time and also improves the surface quality by preventing the glass from showing through the surface.

The LFI shield replaces a vacuum moulded shield made of acrylonitrile butadiene styrene (ABS) resin and reinforced by a steel frame. Replacing the previous shield with the LFI-produced part results in a strong, yet lighter component that is more cost- and time-efficient to produce because it eliminates the need for post-applied paint and the use of rivets and reinforced brackets.

“This advancement marks the next step in the evolution of Long Fiber Injection technology,” said Matt Getty, product engineer, Romeo RIM. “This was a team effort achieved through our close working relationship with Bayer MaterialScience LLC.”