The synergistic effects of lignin and cellulose nanofibers on the properties of starch/zein blends

The study aimed to develop cornmeal-based thermoplastic composites by using corn starch and zein (the two major components of cornmeal) as the matrix and lignin as the compatibilizer, while cellulose nanofibrils (CNFs) served as the reinforcement. The research examined the individual effects of lignin and CNFs on the mechanical properties of the composites. Two parts of lignin decreased the domain size of the blend and increased the strength and modulus by 31% and 44%, respectively. Six parts of CNFs led to a 137% and 399% increase in strength and modulus, respectively. The addition of two parts of powder lignin and six parts of CNFs resulted in the largest increases in strength (236%) and modulus (510%), suggesting a strong synergy between lignin and CNFs in reinforcing the corn-based thermoplastic. This study differentiates itself from previous research on thermoplastic starch composites by using a starch/zein blend as the matrix instead of pure starch. It demonstrates a novel method for producing cornmeal-based thermoplastics with significantly enhanced mechanical properties by separately controlling the contents of lignin and CNFs and optimizing the formulations to achieve desired composite properties. Furthermore, the research revealed the strong compatibilizing effect of lignin on the starch/zein blend. The results obtained in this research could facilitate the direct use of low-cost cornmeal as a feedstock for producing sustainable materials which could find application in the packaging and household plastic industries, among others.