Low-Density Polyethylene Films Containing Cellulose-Encapsulated Thymol With Prolonged Anti-Mold Activity and Its Potential in Hay Preservation

Abstract

The use of many pesticides in agricultural crop protection has been banned due to their harmful effects on health and the environment, leaving farmers with limited crop protection options. A natural nontoxic alternative is thymol (TY), the main component in thyme essential oil (EO), which is known to have pesticidal and anti-mold properties. TY can be incorporated into plastic films, widely used in agricultural applications. However, its volatility and susceptibility to heat limits its use in polymeric systems. By encapsulating TY using natural biopolymer such as cellulose, TY can be protected during high-temperature plastic processing, thus enabling to achieve an active plastic packaging. In this study, cellulose-encapsulated TY was melt-compounded with low-density polyethylene (LDPE) and 100 μm-thick films were fabricated and compared with similar compounds containing free TY. Scanning electron microscopy with energy dispersive X-ray spectroscopy confirmed the presence of TY-loaded particles and demonstrated that they had no significant effects on the LDPE matrix morphology. LDPE films containing encapsulated TY offered higher anti-mold protection functionality to postharvest alfalfa plants, in comparison to films containing free TY. Fourier transform infrared spectroscopy supported by thermo gravimetric analysis further confirmed successful incorporation of TY-loaded particles in the LDPE films. Taken together, the application range of EOs and their synthetic compounds such as TY, can be broadened by encapsulation with cellulose. Incorporation of cellulose-encapsulated TY in plastic composites can serve as a useful natural alternative to toxic pesticides in agricultural applications.