|Early version of CRP-based armrest piece under development. Source: Weyerhaeuser. Click to enlarge.|
A three-year collaboration between Lincoln, Weyerhaeuser and auto parts supplier Johnson Controls has resulted in the creation of a tree-based, renewable alternative to fiberglass for use in auto parts. (Earlier post.) The 2014 Lincoln MKX features the use of Cellulose Reinforced Polypropylene (called “THRIVE” composites by Weyerhaeuser) in the floor console armrest substrate—a structural piece located within the center console armrest.
Pieces made from CRP are roughly 6% lighter, and decrease the reliance on less-environmentally friendly fiberglass parts. The use of Cellulose Reinforced Polypropylene in the MKX, while relatively small, marks an advancement that has the potential to play a more impactful role in the future, suggested Dr. Ellen Lee, plastics research technical expert for Ford Motor Company. Ford engineers are using the company’s development and deployment of soy-based foam as an model—i.e., starting out small, then improving the material and widening the application.
Unlike soy-based foam, CRP can have exterior applications as well as interior, Lee noted. Some potential applications for CRP include:
Under hood: potential for blow molded shapes (vs. glass); battery tray enclosures; cold air canisters in air induction systems; brackets for bottle/canister holders; radiator fan shroud assemblies
Weatherseal carriers (with TPE)
Trunk area: inserts for spare tire hold-downs; spacers/bumper support
Firewall: two shot grommets; housing for cable routing
Interior: door bolster inserts; arm rest/consoles; headliner close-outs; HVAC flapper door structures; replace ABS, glass-filled PP; seat backs/frame components; pedal assemblies for brake/clutches; knee bolsters; glovebox housings
If we transfer its use to larger parts, it could really benefit the vehicle weight, which benefits fuel economy. Cellulose has good reinforcement, so we looked at fiberglass-reinforced materials for this project.—Ellen Lee
In its work with Weyerhaeuser, Ford found that cellulose-based plastic composite materials could meet the automaker’s stringent requirements for stiffness, durability, temperature resistance—and odor. In addition to being lighter weight, components can be produced 20 to 40% faster and with less energy when made with cellulose-based materials compared with fiberglass-based materials. These weight and process savings can enable equivalent or reduced component costs.
One of the obstacles the Ford engineers faced was appearance, Lee said. Small particles of cellulose can be seen through the composite. While that doesn’t affect the material properties, it’s something Lincoln customers might not want to see, she observed. Hence, the first production applications is as the substrate; the CRP part is covered by foam and the cover. The next-generation of materials, however, has a much improved appearance, Lee said.
Cellulose Reinforced Polypropylene has been used on Ford Motor Company prototype vehicles in the past, but its use on Lincoln MKX marks its first application on a production vehicle.
|Weyerhaeuser sees THRIVE as a platform opportunity. Click to enlarge.|
THRIVE. Weyerhaeuser officially launched THRIVE thermoplastic composites using sustainably sourced cellulose fiber as a reinforcement additive in September 2012. Weyerhaeuser is doing its own compounding, Lee said, and is looking to increase its capacity. Ford urged the inclusion of Johnson Controls in the partnership due to that company’s expertise with interior components
The specially engineered cellulose fiber is extracted from pulp. THRIVE composites offer several advantages over short glass fibers or naturally occurring fibers, such as sisal, hemp and kenaf, Weyerhaeuser says:
|Benefits over alternative materials|
|Compared to short glass-filled composites||Compared to other natural fibers (sisal, hemp and kenaf)|
THRIVE composites are currently available as cellulose blended with polypropylene with both high and low melt flow indices. Because cellulose fibers are compatible with various “workhorse” polymers, Weyerhaeuser plans to expand the THRIVE line of products beyond polypropylene to a range of hydrocarbon and non-hydrocarbon polymers.
Ford is using a THRIVE blend with 20 wt% cellulose; Ford is also looking at 20% and 40% blends for other applications, Lee said.
Rob Banning (2013) Unique benefits from a new class of polypropylene/cellulose fiber (GPEC 2013 presentation)