Pablo D. Zavattieri, a Purdue University assistant professor of civil engineering, discovered that cellulose nanocrystals, which give trees and plants their strength and are extremely lightweight, are incredibly strong. These nanocrystals have been calculated to show they have a stiffness of 206 gigapascals – roughly the same as steel. The nanocrystals are expected to employed in a wide variety of applications such as strengthening construction materials and automotive components.
Zavattieri states, “This is a material that is showing really amazing properties. It is abundant, renewable and produced as waste in the paper industry.
It is very difficult to measure the properties of these crystals experimentally because they are really tiny. For the first time, we predicted their properties using quantum mechanics.”
To read the whole research paper, see the December issue of the Cellulose journal.
The nanocrystals have to be studied using quantum mechanics because they are roughly 1/1,000th of the width of the grain of sand – 3 nanometers wide x 500 nanometers long. They are too small to be studied with light microscopes and too difficult to be measured with laboratory equipment.
Along with Zavattieri, the scientists involved in the research and writing of the paper include: Fernando L. Dri, a Purdue Doctoral student who authored the paper; Louis G. Hector, Jr., a researcher from Chemical Sciences and Material Systems Laboratory at General Motors Research and Development Center; Robert J. Moon, a researchers from the U.S. Forest Services Forest Products Laboratory.
In addition to this discovery being a milestone in the research of cellulose nanocrystals, Zavattieri explains, “It is also the first step towards a multiscale modeling approach to understand and predict the behavior of individual crystals, the interaction between them, and their interaction with other materials. This is important for the design of novel cellulose-based materials as other research groups are considering them for a huge variety of applications, ranging from electronics and medical devices to structural devices for the automotive, civil and aerospace industries.”
The nanocrystals can be extracted from sources such as trees, plants, algae, tunicates, and some forms of bacteria. As for the reinforcement of materials such as polymers and concrete, the cellulose nanocrystals are a potentially “green” alternative to carbon nanotubes. Biomaterials that can be made from the crystals include biodegradable plastic bags, textiles and bandages. Also in the making are flexible batteries, filters for water purification, new types of sensors, and computer memory chips.
Moon states, “With this in mind, cellulose nanomaterials are inherently renewable, sustainable, biodegradable and carbon-neutral like the sources from which they were extracted. They have the potential to be processed at industrial-scale quantities and at low cost compared to other materials.
Some of the byproducts of the paper industry now go to making biofuels, so we could just add another process to use the left over cellulose to make a composite material. 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.”
As for the surface of the crystals being able to be chemically modified to achieve different surface properties, Moon explains, “For example you might want to modify the surface so that it binds strongly with a reinforcing polymer to make a new type of tough composite material, or you might want to change the chemical characteristics so that it behaves differently with its environment.”
In the future, Zavattieri will extend his research and study the properties of alpha-chitin – a material in the shells of lobsters, crabs, insects and other creatures – which seems to have the same properties as cellulose nanocrystals.
Zavattieri says, “This material is also abundant, renewable and waste of the food industry.”
Information: Purdue University