Composites are Key to Nano Commercialization

RBI leads the way in new, innovative ways to use nanocellulose to improve composites and replace synthetic materials.

KELLY B. SMITH
Around the world, researchers are finding more and more evidence that the frailty of our planet and the changes within its atmospheric patterns are in critical need of attention. Rapid population growth and an increasing need for landfills due to consumption of plastics and other non-biodegradable, petroleum-based materials are compounding an already alarming environmental trend.

At Georgia Tech’s Renewable Bioproducts Institute (RBI), faculty and students are engaged in a technology with tremendous potential to address some of these challenges: the pursuit of innovative use for nanocellulose and wood-derived lignin. The goal is to find more ways to replace synthetic materials in manufactured items that people around the world consume daily.
Over the past decade, RBI has identified commercial applications that include such diverse areas as automotive components, aerospace applications, electronics, cosmetic applications, food packaging, specialty paper, and polymer reinforcement.

“Nanocellulose provides a combination of properties that allows it to fill a unique niche in the nanomaterials arena,” said Meisha Shofner, RBI’s interim executive director and associate professor of materials science and engineering. “Its structural diversity, availability, and inherent properties are attractive for application-driven research.”
THE POSSIBILITIES OF NANOCELLULOSE
To prioritize its projects, RBI gathers valuable insights from the pulp and paper industry. Of particular importance is its longtime partnership with the Alliance for Pulp and Paper Technology Innovation, or APPTI (formerly known as Agenda 2020.) Among APPTI’s five working groups is a team on cellulose nanomaterials. This team is dedicated to developing new revenue streams from renewable biomaterials, with a focus on identifying knowledge gaps and barriers to commercialization of products made from nanocellulose. RBI is providing in-kind support to several projects identified by APPTI as important steps toward enabling commercially viable nanocellulose products.

RBI sponsors multiple projects that focus on taking nanocellulose from the lab to the manufacturing sector. Some of the most promising research on campus currently deals with infrastructure, composites, and both the automotive and aerospace industries. We’ll examine three of those areas here.

Concrete: The Key to Improving
Our Infrastructure
There are many ways that nanocellulose can potentially improve concrete, including increasing strength, improving dimensional stability, enhancing cement hydration and pozzolanic reaction, and improving crack resistance. Once the underlying mechanisms of the interactions between nanocellulose and cement-based materials are better understood, the composition and processing of the nanocellulose can be tailored for this potentially large application.

Dr. Kimberly E. Kurtis is a professor in the School of Civil and Environmental Engineering at Georgia Tech and interim school chair. Her innovative research on the multi-scale structure and performance of cement-based materials has resulted in more than 150 referred technical publications and three US patents. Kurtis has received funding to support her further research from P3Nano, a public-private partnership dedicated to the development of wood-based nanomaterial (see sidebar).

“Despite advances in materials, design, and construction, cracking cement-based materials including concrete remains a perennial problem,” Dr. Kurtis said. “With P3Nano funding, and in collaboration with researchers at Oregon State University, Purdue University, and University of Maine, we aim to explain the underlying mechanisms by which nanocellose can mitigate cracking, whether by increased strength, toughening, and/or internal curing.

“Concrete, as the most widely used substance on the planet (after water), is potentially an enormous market for nanocellulose. Ultimately, enhancements in concrete properties and infrastructure service life are the goals of this effort.”

High Quality Polymer Composites
Dr. Carson Meredith’s work is focused on adhesion. A professor and associate chair for graduate studies at the School of Chemical and Biomolecular Engineering, Meredith says adhesion is a key issue to be studied for nanocellulose. Understanding component interactions at their interfaces is paramount to producing high quality polymer composites containing nanocellulose.

His group has focused on modification of cellulose nanocrystals (CNCs) for use in reinforcing composites, especially polyurethanes and waterborne epoxy coating materials. The composites produced in this work have shown improved tensile strength and preserved optical clarity. The group collaborates actively with Dr. Shofner of RBI and Dr. Greg Schueneman at the USFS Forest Products Laboratory. This work is expected to lead to a more environmentally friendly coating.

“This collaborative team is using CNCs to aid in strengthening and stiffening the acrylic latex materials used in paints, in order to facilitate the development of solvent-free waterborne paint formulations,” Dr. Meredith adds.

Automotive and Aerospace:
Biomaterials and Carbon Fiber
Due to its lower density and higher specific strength and modulus as compared to other structural materials such as steel and metal alloys, carbon fibers are gaining more attention as a lightweight material for high-performance applications.

This is still very much a new frontier. Only in the past five to seven years have suppliers been producing nanocellulose with the volume and consistency needed for this type of research on this scale.
Dr. Satish Kumar, a professor in the School of Materials Science and Engineering, is conducting research to examine how forest biomaterials can be incorporated into carbon fiber technology to expand the range of carbon fibers available. The application space includes consumer goods, automotive structures, and aerospace structures.

Each application has different property and cost metrics that dictate the type of carbon fiber that would be desirable. Dr. Kumar has used lignin to replace some of the polymeric precursor and has been able to meet targets for low-cost carbon fiber from the Department of Energy (DOE). He has also used cellulose nanocrystals to displace some of the polymeric precursor. Dr. Kumar has built a comprehensive program in carbon fiber research that includes a unique pilot-scale carbon fiber production facility, and has designed routes for including forest biomaterials into the production of carbon fibers.

He notes, “The research we are doing is still in the early stages, but if successful, these low cost and renewable carbon fibers could have a tremendous impact on a diverse set of industries—including aerospace, where we have already seen the Boeing 787, which was rolled out in 2010, use a record amount of carbon fiber-reinforced plastic and other composites.”

Dr. Kyriaki Kalaitzidou, an associate professor in Georgia Tech’s School of Mechanical Engineering, has been looking into the benefits of nanocellulose in the automotive industry for several years, including lightweight PNCs for automotive applications, or PNCs made from biodegradable polymers instead of petroleum-based polymers.

In her small-scale manufacturing setup housed in Georgia Tech’s Manufacturing Institute, which she designed herself, some of Dr. Kalaitzidou’s work combines resin with glass fibers. Nanocellulose is then incorporated and the polymer is compressed into a panel. In other instances it is used to coat the glass fibers. This cellulose-infused polymer composite could someday significantly reduce the weight of a car (to improve fuel efficiency), or replace more expensive carbon fiber-based polymers in in an aerospace application.

CAPITALIZING ON THE POTENTIAL OF NANOCELLULOSE
Though the types of matrices are different in each of these projects, the goal is the same—using forest biomaterials to produce new composites. There is much work remaining, including further exploring the market potential of cellulose nanomaterial applications and addressing the challenges hindering the speed of cellulose nanomaterials commercialization in the US. There are also issues of cost in industrial applications in comparison to non-renewable materials.
Kalaitzidou remains optimistic that this generation will push the scientific community and industry toward more renewable materials. “This generation is all about making this world a better place, whether it’s using less water in manufacturing or creating less waste for landfills. And if the performance gain is significant, consumers—even if there is a small cost increase—will also move in that direction.”
Kelly B. Smith is the manager of marketing and communications for Georgia Tech’s Renewable Bioproducts Institute.
In Dr. Satish Kumar’s Carbon and Multi-functional Fiber Center, researchers are utilizing gel spinning technology of polyacrylonitrile (PAN) and polyacrylonitrile/carbon nanotube (PAN/CNT) fibers in an effort to produce the next generation carbon fiber.
Dr. Carson Meredith with Dr. Zihao Qu, a post-doctoral fellow, in Meredith’s lab. The Meredith group studies the important roles of surfaces and interfaces in renewable materials critical to sustaining human societies through food security, renewables, and energy efficiency.
PHOTO BY RANDALL FROSTIG/BROWNIELAND PICTURES/GEORGIA TECH.
Dr. Carson Meredith uses characterization techniques to understand component interfaces. PHOTO BY RANDALL FROSTIG/BROWNIELAND PICTURES/GEORGIA TECH.

---

Understanding Cellulose Nanomaterial
The nanoscale is very small—the prefix “nano” means one-billionth. A standard sheet of writing paper is about 100,000 nanometers thick, and there are 25,400,000 nanometers in one inch. The website nano.gov reports that “nanotechnology is the understanding and control of matter at the nanoscale, at dimensions between approximately 1 and 100 nanometers, where unique phenomena enable novel applications.” Visualization at the nanoscale requires high-powered equipment, such as scanning electron microscopes or the newer atomic force microscopes.

Cellulose is the most abundant organic polymer on earth. It can be found in plant cell walls together with other renewable polymers such as lignin and hemicellulose. Products made from cellulose store atmospheric carbon throughout their service until the end of life. Cellulose has demonstrated great promise for commercial applications across an array of industrial sectors; are renewable and environmentally sustainable; and have the potential to be produced in large volumes (i.e., millions of tons per year). The commercialization of cellulose nanomaterials has the capacity to create hundreds of thousands of direct and indirect jobs.

Cellulose nanomaterial is an innovative nanoscale material that is abundant, renewable, sustainable, and originates from natural resources. These materials have unique properties with broad application potential as platform materials in multiple market sectors and products such as packaging, automotive components, paper and paperboard, cement, polymer composites, medical applications, defense applications, electronics, aircraft components and rheology modifiers, to name a few. Cellulosic nanomaterial has exceptional strength and is considerably lighter weight compared with many other competing materials. Cellulose nanomaterial is expected to be lower cost than most nanomaterial and have piezoelectric, photonic, and self-assembly properties.

P3Nano has been a key player in numerous nanocellulose projects directed by RBI-affiliated faculty on Georgia Tech’s campus. Its leadership and financial support has been critical in moving many of these projects forward. A community of public-private partnerships for nanotechnology, P3Nano begins with the hypothesis that wood-based cellulosic nanotechnology can be developed in ways that are safe for people and the planet. P3Nano’s focus is to assist in and oversee the development of commercial production of cellulosic nanomaterial in the US by:
• Identifying and prioritizing critical business and technical barriers;
• Determining the resulting technical, economic, engineering, material property, applications, materials standards, and EHS information gaps that arise from these critical barriers; and
• Bringing together the needed resources from government, industry and academia to generate the information required to overcome these critical barriers.