Researchers have converted waste sawdust into packaging foams with beeswax coatings, expected to match the strength and impact resistance of polystyrene alternatives in certain applications.
Published in ACS Applied Polymer Materials, the study – funded by the U.S. Department of Energy – sourced fine processed wood powder or coarse unprocessed mill waste from Hadley Mill Works, then incorporated cellulose binders and cross-linking ingredients.
The mixtures were poured into moulds, frozen, then freeze-dried and heat-dried. The result was used to form rigid and flexible materials, including ‘well-performing’ prototype foams.
“It can be exciting to use waste products as a starting point for materials fabrication, rather than a chemical catalogue,” says Todd Emrick, one of the study’s authors.
Different cellulose binders were found to unlock material properties; carbomethyl cellulose reportedly created stiffer foams than polystyrene, while hydroxypropyl cellulose resulted in a softer material. Processed and unprocessed sawdust were thought to yield similar results.
Stability tests used acetone to discern that the foams containing cross-linking ingredients could absorb and release water, unlike polystyrene. A beeswax coating was also applied to some of the foam samples, which was said to improve water resistance in high humidity without impacting the foam’s mechanical properties.
“We haven’t done a long-term stability study yet,” Emrick continues. “But in the weeks-to-months time frame, the liquid stability appears to be excellent, which is a useful feature during shipping in case of leakage or spills, or simply for production and storage under different environmental conditions.”
Impact tests were also conducted with a 4.5 kg weight. These apparently revealed that the foams bounced the weight 21% less distance than polystyrene of similar thickness and dispersed energy better – indicating that the foams are robust enough to replace polystyrene in conventional applications.
“The initial driver for this work was in packaging foams, which are used in abundance to protect materials in transit,” adds Emrick. “Because our initial assessment of mechanical properties appears promising, such sawdust-based foams may be examined further in all sorts of applications — including construction materials and high-end packaging for consumer electronics, where lightweight and protective packaging is essential.”
Another project saw researchers from the University of Washington 3D-print a packaging material made from coffee grounds, mushroom spores, and mycelium. It is said to perform similarly to polystyrene dunnage, but may be challenging to scale, since it requires the coffee grounds to be consistent in their granularity.
Similarly, Myco has developed a biodegradable alternative to polystyrene packaging made from mushroom mycelium and organic waste. The material is thought to maintain properties such as firmness and flexibility while unlocking a low carbon footprint and degrading without leaving microplastics behind.
In other news, Woamy’s cellulose-based foam is currently being used in Kyrö Distillery Company’s limited-edition whisky tasting set inspired by HBO’s Game of Thrones. The foam is believed to be compostable and recyclable, and is expected to protect the bottles and glassware from scratches in transit.
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