Sep 21 2017
Researchers at Penn State have developed an economical biomaterial that can be used to sustainably replace plastic barrier coatings in packaging and numerous other applications. The Researchers predict its implementation would significantly reduce pollution.
Jeff Catchmark began experimenting with biomaterials that might be used instead of plastics a decade or so ago out of concerns for sustainability. He became interested in cellulose because it is the largest volume sustainable, renewable material on earth. (Image: Penn State)
The material - a polysaccharide polyelectrolyte complex – is totally compostable, and comprises of approximately equal parts of treated cellulose pulp from cotton or wood, and chitosan, which is deriveded from chitin — the main ingredient in the exoskeletons of crustaceans and arthropods. The key source of chitin is the heaps of discarded shells from crabs, lobsters, and shrimp eaten by humans.
These eco-friendly barrier coatings have a number of applications ranging from coatings for wallboard and ceiling tiles, to water-resistant paper, to food coatings to seal in freshness, according to Lead Researcher Jeffrey Catchmark, Professor of Agricultural and Biological Engineering, College of Agricultural Sciences.
The material's unexpected strong, insoluble adhesive properties are useful for packaging as well as other applications, such as better performing, fully natural wood-fiber composites for construction and even flooring. And the technology has the potential to be incorporated into foods to reduce fat uptake during frying and maintain crispness. Since the coating is essentially fiber-based, it is a means of adding fiber to diets.
Jeffrey Catchmark, Lead Researcher and Professor of Agricultural and Biological Engineering, College of Agricultural Science, Pennsylvania State University
The incredibly robust and durable bond between carboxymethyl cellulose and chitosan is the key, he states. The two very low-cost polysaccharides — already used in the food sector and in other industrial sectors — have varied molecular charges and lock together in a complex that provides the base for impervious films, adhesives, coatings and more.
The potential decrease of pollution is massive if these barrier coatings replace millions of tons of petroleum-based plastic related with food packaging used annually in the United States — and a lot more worldwide, Catchmark noted.
He emphasized that the worldwide production of plastic is nearing 300 million tons annually. In a recent year, over 29 million tons of plastic became municipal solid waste in the U.S. and nearly half was plastic packaging. It is predicted that 10% of all plastic produced internationally will become ocean debris, representing a substantial human health and ecological threat.
In the research the polysaccharide polyelectrolyte complex coatings performed well. The research findings were published in Green Chemistry. Paperboard coated with the biomaterial, made up of nanostructured fibrous particles of chitosan and carboxymethyl cellulose, displayed strong water and oil barrier properties. The coating also resisted heptane, toluene, and salt solutions and displayed enhanced dry and wet mechanical and water vapor barrier properties.
These results show that polysaccharide polyelectrolyte complex-based materials may be competitive barrier alternatives to synthetic polymers for many commercial applications. In addition, this work demonstrates that new, unexpected properties emerge from multi-polysaccharide systems engaged in electrostatic complexation, enabling new high-performance applications.
Jeffrey Catchmark, Lead Researcher and Professor of Agricultural and Biological Engineering, College of Agricultural Science, Pennsylvania State University
Catchmark started working with biomaterials that might be used to replace plastics a decade or so ago out of concerns for sustainability. He became fascinated with cellulose, the key component in wood, because it is the largest volume sustainable, renewable material on earth. Catchmark analyzed its nanostructure — how it is organized at the nanoscale.
He believed he could create natural materials that are sturdier and enhance their properties, so that they could compete with artificial materials that are not sustainable and cause pollution — such as the low-density polyethylene laminate applied to Styrofoam, paper board, and solid plastic used in bottles and cups.
"The challenge is, to do that you've got to be able to do it in a way that is manufacturable, and it has to be less expensive than plastic," Catchmark explained. "Because when you make a change to something that is greener or sustainable, you really have to pay for the switch. So it has to be less expensive in order for companies to actually gain something from it. This creates a problem for sustainable materials — an inertia that has to be overcome with a lower cost."
Funded by a Research Applications for Innovation grant from the College of Agricultural Sciences, Catchmark presently is involved in developing commercialization partners in various industry sectors for a wide range of products.
We are trying to take the last step now and make a real impact on the world, and get industry people to stop using plastics and instead use these natural materials. So they (consumers) have a choice — after the biomaterials are used, they can be recycled, buried in the ground or composted, and they will decompose. Or they can continue to use plastics that will end up in the oceans, where they will persist for thousands of years.
Jeffrey Catchmark, Lead Researcher and Professor of Agricultural and Biological Engineering, College of Agricultural Science, Pennsylvania State University
Also involved in the research were Snehasish Basu, Post-Doctoral Scholar and Adam Plucinski, Master's Degree Student, current Instructor of Engineering at Penn State Altoona. Staff in Penn State's Material Research Institute offered assistance with the project.
This work was supported by the U.S. Department of Agriculture. Southern Champion Tray, of Chattanooga, Tennessee, provided paperboard and information on its production for experiments.