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Plant-based, a novel alternative to aluminum has arrived

A team of MIT researchers has succeeded in designing a composite made primarily of cellulose nanocrystals mixed with a low percentage of synthetic polymer, which could be a substitute for aluminum. They discovered that the strongest part of a tree is in its microscopic cell walls. The material is composed of 60 to 90% CNC, to date the highest portion of CNC achieved in a composite.

The wall of a wood cell is made up of cellulose fibers, nature's most abundant polymer and the main structural component of all plants and algae. Within each fiber are reinforcing cellulose nanocrystals, or CNCs, described as chains of organic polymers arranged in near-perfect crystalline patterns. At the nanoscale, CNCs are stronger and stiffer than Kevlar.

If these crystals could be transformed into materials in significant portions, CNCs could be a path to stronger, more sustainable, naturally occurring plastics.

The cellulose-based composite becomes stronger and tougher than some types of bone, harder than typical aluminum alloys. In addition, the material possesses a brick-and-mortar-like microstructure that matches the structure of mother-of-pearl.

"By creating composites with CNC at high loading, we can give polymer-based materials mechanical properties they've never had before," commented A. John Hart, professor of mechanical engineering, "If we can replace some petroleum-based plastic with naturally occurring cellulose, that's arguably better for the planet as well."

The research team managed to come up with the formula for the CNC-based composite, which can be used with both 3D printing and traditional casting. They used the size of a coin to test strength and hardness, and the shape of a tooth to demonstrate that it could be used as a dental implant, based on cellulose. They could eventually replace any plastic product-that are stronger, tougher and more sustainable.

"Basically, we deconstructed the wood and rebuilt it," Rao says. "We took the best components of the wood, which are the cellulose nanocrystals, and rebuilt them into a new composite material."

To get the composite tested, the team managed to turn it into a gel, which allowed it to be used in a 3D printer or poured into a mold to be cast. When the samples dried, the material shrunk, resulting in a solid composite consisting mainly of cellulose nanocrystals.

For now, the team continues to work on achieving large-scale strength, preventing large objects from bending or cracking as the drying process occurs.

To read more about the progress of the project, please visit https://news.mit.edu/2022/plant-derived-composite-0210

29 de Marzo, 2022