Getting to Green(er) Plastics

The interior of the Ford Fusion Energi plug-in hybrid research vehicle features seat cushions, seat backs, head restraints, door panel inserts and headliners filled with 30% plant-based polyethylene terephthalate (PET), the same material used in Coca-Cola’s “PlantBottle” packaging.

Johnson Controls uses a unique Compression Hybrid Molding (CHyM) process to manufacture door panel substrates, merging natural fibers with petroleum-based plastic to save weight.

NatureWorks produces 100% biobased plastic derived from corn.

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Castor beans, corn, soybeans, sugar beets, sugarcane and sweet potatoes. This is not a list of ingredients in some celebrity’s juicer, it’s a list of feedstocks used to make “green” plastic. But like a celebrity health drink, biosourced plastic is generally more expensive than the less healthy—or in this case, less sustainable—alternative. 

The push toward using more renewable plastics in the auto industry is spurred by multiple forces: the threat of rising petroleum prices negatively impacting the cost of conventional plastics; company-mandated sustainability policies; and the potential for improved performance. Yet cost remains something of an anchor to these forces pushing carmakers toward greener plastics.

“At the end of the day we want stuff to be green, but we also want it to be priced competitively,” says Craig Crawford, president and CEO of the Ontario BioAuto Council (bioautocouncil.com). Since 2007, the BioAuto Council has helped link various manufacturers in the biomaterials supply chain to potential business opportunities.

At Johnson Controls (johnsoncontrols.com), a supplier that uses natural fibers and polyols in interior components such as door panels and seating foam, there is a strong interest in biobased plastics with a discerning eye on the tradeoff between cost and performance.

Tim Spahr, who heads Johnson Controls’ advanced materials and process engineering group, cautions that he’s yet to find a biomaterial with performance that outweighs price.

This isn’t to say Spahr dismisses the potential of biobased plastics. Last year, he worked to introduce a new process technology, Compression Hybrid Molding (CHyM), which saves weight by using natural fibers with traditional petroleum-based plastic in molds for door substrates. This process combines compression molding of natural fiber-filled composites with injection molding. 

“In the past we would make a door panel substrate by taking a natural fiber mat, compression mold it, trim it, injection mold the backside detail and then glue it,” Spahr explains. 

Using the CHyM process, the mat is now roll-formed, heated, and the injection molding machine does the compression molding without needing to do it separately. If CHyM is used to form four door panels, the method saves seven pounds per vehicle. 

“This allows us to integrate details we need to attach to the body and have a further mass reduction because now we can use a lighter-weight mat and reinforce that with plastic on the backside where it’s needed,” Spahr says. 

Another area of potential for applying biobased material is as a replacement for glass or talc reinforcement in injection-molded parts. Examples of this approach already exist, such as the use of a wheat straw composite as reinforcement in the plastic bins in the Ford Flex. 

The challenge with this natural fiber-reinforced injection molding is meeting interior odor, fogging and emissions requirements. 

“What’s exciting is there’s a lot more energy and attention around this need,” says Fran Elenbaas, who heads Johnson Controls’ advanced product development group, technology scouting and partnerships efforts. “The challenge is to meet requirements while still being a structural reinforcement.”

To make this task more vexing, OEMs test biobased plastic components to standards higher than traditional, petroleum-based polymers. 

“While these extra steps ensure the consumer does not suffer any negative impact from the decision to use bio-based materials, they do increase the performance challenges bio-based plastic components must overcome in order to achieve greater penetration in the automotive industry,” according to a Center for Automotive Research (cargroup.org) report on the use of biomaterials in the automotive industry.

Elenbaas says that while Johnson Controls is actively exploring the use of biobased plastics, plastics made entirely from renewable sources are not yet seen as viable. 

“We’re keeping our eyes on bioplastics, but they are somewhat scarce and the price is not what we’re accustomed to,” she explains, noting this is likely to change as production increases. 

Ellen Lee, a plastics research technical expert at Ford, says while biobased plastics have made significant inroads in seating, floor mats and carpet, she agrees cost continues to be the biggest challenge to the wider adoption and application of organically sourced plastic in other vehicle components. 

“That’s not to say we’re going to stop using biobased materials,” Lee says. “We see that our customers are very interested when we make improvements with sustainability—they like it—but they’re not yet willing to pay more for it.”

Regulation, investment required?
Ramani Narayan, a Michigan State University chemical engineering and materials science professor, who researches bioplastics, says greater proliferation of bioplastic materials in the auto industry may require buy-in from government and industry alike.

“I think bioplastics are going to grow on the strength of  performance, but more importantly on the commitment of companies and government regulations toward sustainability,” Narayan says. “That’s the bottom line right there. The time will come when it will become a part of the automotive resin composition. It will be required as part of procurement.” 

Last year, Ford joined Coca-Cola, Danone, H.J. Heinz, Nestle, Nike, Procter & Gamble, Unilever, and the World Wildlife Fund to form the Bioplastic Feedstock Alliance (BFA). 

BFA is intended to be a “precom-petitive” forum to help guide the responsible selection of feedstocks for biobased plastics, with an emphasis on encouraging a more sustainable flow of materials. 

The introduction of biobased polyethylene in packaging such as Coca-Cola’s PlantBottle technology has been successful. This lightweight plastic, polyethylene terephthalate (PET), is now being used in the interior fabric of the Ford Fusion Energi plug-in hybrid research vehicle. This material, which is found in the seat cushions, seat backs, head restraints, door panel inserts and headliners contains 30% plant-based material. 

Bioplastic manufacturing
NatureWorks (natureworksllc.com), a company that began as a Cargill research project in 1989, makes 100% biosourced plastics. The company has successfully manufactured and marketed its packaging plastics with an affordable price tag of around 90 cents-per-pound. Automakers and suppliers are interested in NatureWorks’ materials, but an automotive application may still be a few years away.

“We’re focusing on getting into more injection-molded, durable products,” says Steve Davies, the director of corporate communications and public affairs for NatureWorks. “Due to the long lead times, we don’t yet have an automotive focus specifically. All plastics are different, so we’re looking at where the grades we make fit.”

While biobased polyethylene plastics work well in packaging applications, the material is not robust enough to make its way into more structural auto parts. An affordable biobased polypropylene, however, could spark a great deal of interest from automakers and suppliers. 

“We’ve seen more interest from the auto industry for green polypropylene than the green polyethylene we’re currently producing,” says James Kahn, the U.S. commercial manager for chemical-maker Braskem’s (braskem.com) biosourced polyethylene material. 

Braskem plans to open a sugarcane-based polypropylene facility in Brazil, but company officials say that the time table has not been finalized and the plan has yet to be approved by its board. Last year, Dow Chemical and Mitsui postponed plans to open a sugarcane-based ethanol plant, also in Brazil. 

Fracking a threat?
Increased access to natural gas liquid from shale buried beneath parts of the United States and Canada is slowing the opening of additional “green plastic” production facilities, according to industry observers. By leveraging hydraulic fracturing, or fracking, to extract natural gas liquids such as ethane, propane, butane and methane, fossil-fuel derived plastic becomes potentially less expensive due in large part to reduced transportation costs. This domestically sourced feedstock can be pipelined to production facilities now under construction in North America.

Craig Crawford of the BioAuto Council explains: “What’s happening is the chemical industry in the United States is pumping about $80 billion over a decade [2010 to 2020] into putting in new ethylene crackers and on-purpose propane-to-propylene production facilities, which leads to low-cost polypropylene, low-cost polyethylene, and low-cost PVC. That’s about 75% of the plastics we use in the automotive industry.”

Future opportunity
Cheaper polyethylene and polypropylene doesn’t necessarily mean biobased materials lose out completely, however. 

Crawford notes that when the chemical industry switches from using an oil-based feedstock, the co-products produced in the process are significantly reduced. 

For example, butadiene, a key ingredient in ABS plastic and nylon, is not produced in abundance when natural gas liquids are used as feedstock. 

“This is a business opportunity for biobased products,” says Crawford. 

Ford’s Lee says, “Since biobased materials and biobased plastics are still relatively young as a field, I think in general people have leaned toward being risk adverse and looked at things that aren’t quite as meaty, or have huge structural requirements, to them,” she says. “But we’re starting to see some good success in the interior components we’re working on, so we are beginning to look at things that require more function.”