Cellulose nanocrystals 'have strength of steel'
Cellulose crystals that give trees and plants their high strength, light weight and resilience have been shown to have the stiffness of steel.
The nanocrystals might be used to create a new class of biomaterials with applications that include strengthening construction materials and automotive components.
Calculations using precise models based on the atomic structure of cellulose show the crystals have a stiffness of 206 gigapascals, which is comparable to steel, said Pablo D. Zavattieri, a Purdue University assistant professor of civil engineering.
‘This is a material that is showing really amazing properties,’ he said in a statement. ‘It is abundant, renewable and produced as waste in the paper industry.’
Findings are detailed in Cellulose. The paper was authored by Purdue doctoral student Fernando L. Dri; Louis G. Hector Jr, a researcher from the Chemical Sciences and Materials Systems Laboratory at General Motors Research and Development Center; Robert J. Moon, a researcher from the U.S. Forest Service’s Forest Products Laboratory; and Zavattieri.
The nanocrystals are about 3nm wide by 500nm long, making them too small to study with light microscopes and difficult to measure with laboratory instruments.
‘For the first time, we predicted their properties using quantum mechanics,’ Zavattieri said.
Applications for biomaterials made from the cellulose nanocrystals might include biodegradable plastic bags, textiles and wound dressings; flexible batteries made from electrically conductive paper; new drug-delivery technologies; transparent flexible displays for electronic devices; special filters for water purification; new types of sensors; and computer memory.
Cellulose itself could come from a variety of biological sources including trees, plants, algae, ocean-dwelling organisms called tunicates, and bacteria that create a protective web of cellulose.
‘With this in mind, cellulose nanomaterials are inherently renewable, sustainable, biodegradable and carbon-neutral like the sources from which they were extracted,’ Moon said. ‘They have the potential to be processed at industrial-scale quantities and at low cost compared to other materials.’
Biomaterials manufacturing could be a natural extension of the paper and biofuels industries, using technology that is already well-established for cellulose-based materials.
‘Some of the by-products of the paper industry now go to making biofuels, so we could just add another process to use the leftover cellulose to make a composite material,’ Moon said. ‘The cellulose crystals are more difficult to break down into sugars to make liquid fuel. So let’s make a product out of it, building on the existing infrastructure of the pulp and paper industry.’
The research was funded by the Forest Products Laboratory through the US Department of Agriculture, the Purdue Research Foundation and the National Science Foundation.