Session: 03-09-03: Design of Engineering Materials

Paper Number: 99069

99069 - Development of Recyclable and Biodegradable Additively Manufactured Corn-Based Composites 

Petroleum-based plastics have a wide range of applications in construction, automobiles, aviation, packaging, and civilian uses. However, most of these plastics take hundreds of years to degrade due to extremely low degradation rates. Both the raw materials used to make them and their disposal after their service life poses environmental concerns. Apart from that, most petroleum-based composites face key challenges in recycling, such as separating fibers and matrix from their structures after service life. As a result, only 18% of plastics are recyclable, with the real recycling rate being 6 to 8.4%, out of 400 million tons of plastic wastes produced every year. Furthermore, plastic recycling faces numerous obstacles, including the use of chemicals, energy, complex manufacturing processes associated with high costs, and degraded material properties over a few recycling cycles. To find an efficient alternative solution, emerging researchers propose to develop sustainable high-performance structural materials that are biodegradable, easy to recycle with minimal processing cost, and more environmentally friendly using bio-based natural materials. Recent advancements in extrusion-based additive manufacturing techniques further advance the development of such sustainable composites with tunable properties for a diverse array of applications. In this study, the recyclable and biodegradable performance of additively manufactured corn-based composites are investigated. These 3D printable biocomposites are derived from low-cost corn starch and husks and exhibit thermally tunable mechanical properties from preparation and 3D printing. The composites demonstrate a comparable mechanical performance with commonly used 3D printed thermoplastics and their composites, such as Polylactic acid (PLA)-wood fiber composites. The recycling process, harnessing the gelatinization and retrogradation of the starch molecules, requires simple mechanical grinding and thermal treatments with water at moderate temperature (120 ^oC) and short duration (10 minutes). The recycled materials are 3D re-printable from the direct ink writing (DIW) method. Multiple recycling experiments, mechanical testing, and microstructural characterization were conducted on the 3D printed recycled composites, and show minimal changes in mechanical properties and similar microstructures to the pristine materials after more than 10 cycles. Furthermore, the corn-based materials demonstrate excellent biodegradability compared to PLA and PLA-wood composites in compost tests under controlled temperature and moisture environment. The biocomposites degrade more than 3 times faster than the PLA-based composites, and the products are fully degraded within 25 days. This environment-friendly, recyclable, and biodegradable composite materials from low-cost corn products can be used as alternatives to petroleum-based plastics in engineering applications for the benefit of the environment, sustainable growth, energy-saving, and lower carbon footprint.

Presenting Author: Md Nurul Islam University of North Texas

Presenting Author Biography: I'm a third-year Ph.D. student in mechanical engineering at the University of North Texas, working on extrusion-based 3D printing. My primary research interests are in developing 3D printable bio composites entirely from natural resources. In particular, I aspire to develop corn-based printable mechanically-robust engineering-grade materials and investigate their multifunctional properties such as thermally strengthening mechanisms for tunable mechanical properties, harnessing self-healing properties for reversing fatigue behavior, and engineering composite microstructure via thermomechanical treatment integrated with 3D printing for biomedical and microfluidics applications. I also have broad interests in topics around 3D printed Zn-air batteries, piezo and dielectric sensors as well as electrospun nanofibers and their functional application.

Authors:

Md Nurul Islam University of North Texas
Yijie Jiang University of North Texas
Sheldon Shi University of North Texas
Yu Fu University of North Texas