New Hemp Bio-Material Could Rival Plastic, Say Researchers

Plastic was supposed to be the material of the future. Lighter and cheaper than glass, it made the packaging and shipment of products a breeze. Unfortunately, it is also very literally the material of the future, as less than 10% of global plastic is actually recycled.

Theoretically, a much larger proportion of plastics are recyclable, but much of this material ends up being sent to landfill due to logistical or economic factors. This natural breaking down of plastics is a leading source of microplastics in the environment, which are increasingly being recognized as dangerous pollutants that can harm wildlife and aquatic ecosystems.

Creating safer alternatives to traditional plastics has become a key area of research in recent years in order to stem the tide of microplastics being introduced to the environment.

Now, in a new paper published in the Journal of Polymer Science, researchers from Western University, Canada, report the development of new biodegradable hemp-reinforced co-polyesters that could serve as a sustainable substitute for traditional plastic packaging.

Creating an effective co-polyester-hemp blend

In this study, the researchers set out to find alternatives to industrial plastics. These alternatives had to still work with the same manufacturing processes used to make plastic packaging, however, meaning they needed to demonstrate good enough thermal and mechanical properties to allow for injection molding and thermal processing.

To this end, the researchers looked at composites based on poly(butylene 2,5-furandicarboxylate) (PBF), a well-known and highly-promising biobased polymer. The researchers synthesized a small library of PBF-based copolymers made with various dicarboxylic acids, before testing the thermal and mechanical properties of each material.

They then synthesized and tested a further group of co-polymers, this time using a twin-screw compounder to incorporate amounts of hemp powder into each biomaterial.

Upon testing, the researchers found that the incorporation of the hemp increased the stiffness of the biomaterials and reduced their ductility while leaving their thermal properties unaffected.

“When it comes to packaging, plastic replaces things like metal and glass. Those are heavy and expensive,” senior study author Professor Elizabeth Gilles said in a press statement. “Glass recycling is not a very profitable business and while many plastics are potentially recyclable, it often doesn’t happen in practice.”

“Depending on the form, hemp can have a fibrous structure, which acts perfectly as a reinforcement for materials,” Gillies explained. “Basically, hemp is stronger and more malleable than many other biomaterials.”

Hemp bio-composites are more biodegradable

PBF, the core biopolymer used in this study, is popular due to it being a biopolymer. However, while biopolymers are generally seen as more sustainable options, PBF itself is in fact non-biodegradable.

To test the biodegradability of the new hemp bio-composites, the researchers next examined the behavior of the best-performing materials identified in the thermal and physical tests. These were made with PBF incorporating either succinic acid (PBFSc40) or sebacic acid (PBFSe40) at a 40% feed ratio and were tested both with and without the inclusion of 10 percentage by weight (%wt) hemp powder.

The biodegradability of these materials was studied by incubating a melt-pressed film of each PBFSc40 and PBFSe40 sample in a buffer solution containing the enzyme lipase. After 28 days, the researchers found that the PBFSe40 sample had lost around 9% of its total weight; the PBFSu40 sample measured a 3% weight loss. Both samples were determined to be similarly biodegradable both with and without the incorporation of hemp.

Having shown that the inclusion of hemp in these bio-composites can strengthen the materials while leaving favorable thermal properties and a material’s biodegradability unaffected, the researchers say that such hemp-based material could one day be used as a promising alternative to traditional plastics and non-biodegradable biomaterials.

Hemp materials could be an affordable material for the future

Since the passage of the 2018 Farm Bill, industrial hemp production in the United States has skyrocketed. Similarly, other regions with a strong CBD or cannabis market, such as Canada and the European Union, also produce significant amounts of hemp material as a feedstock for various cannabinoid products. This increased production has led to plummeting prices for unprocessed hemp. The CBD extract industry also produces large volumes of hemp waste material as a byproduct of its processes.

The increasing affordability of hemp combined with its structural integrity has played a significant role in making hemp a realistic candidate for further research and commercial development when searching for new eco-friendly materials.

Unsurprisingly, then, this is not the only study to have successfully produced a hemp-based next-generation bioplastic. In late 2022, researchers from the University of Connecticut and Purdue University published a new study describing the creation of a new CBD-based polyester, poly(CBD-Adipate).

After creating polymer strands from a polycondensation reaction between CBD and adipoyl chloride, the researchers were able to successfully cast a poly(CBD-Adipate) polymer film onto glass. In addition to its “exceedingly high stretchability”, the new bioplastic also performed well in a melt processability test.

Notably, the bioplastic also appeared to have some antioxidant activity, which the researchers said might be desirable in some biomedical and food storage applications.