PVA biocomposites with reinforced cellulose microfibers from agricultural residue

Abstract

Biocomposites are finding application in several fields such as medical, automobiles and packaging industries. The cellulose fiber isolated from natural plant sources have proven to be potential reinforcements in the manufacturing of biocomposites. In the present study, cellulose microfibers are isolated from underutilized and abundantly available biofuel industrial residues: Jatropha seed shell, Pongamia seed hull and Finger millet straw, an agricultural residue. The organosolv (Method O) treatment and combined alkaline and organosolv treatments (Method IO) were carried out to isolate cellulose fibers. The cellulose fibers thus isolated by methods O and IO were further subjected to ultrasonication or enzymatic treatment. The removal of matrix components such as lignin and hemicellulose along with the isolation and defibrillation of cellulose microfibers was confirmed by analysis of chemical, thermal and morphological characteristics of the untreated and isolated fibers. The combined alkaline, organosolv and ultrasonication treatment (IOU) was found to be most effective in isolating cellulose microfibers from Jatropha seed shell, Pongamia seed hull and Finger millet straw yielding cellulose micro fibers with higher cellulose content (90%, 85% and 93%) and smallest fiber size (194, 145 and 147nm) compared to other treatments. Ultrasonication has been found to play a major role in defibrillation of the microfibers. Poly vinyl alcohol (PVA) based biocomposites with cellulose microfibers as reinforcement were prepared by solution casting. Fiber reinforcement has resulted in biocomposites with increased tensile strength and tensile modulus. The transmittance of the biocomposites film was found to be reduced as compared to that of neat PVA, which proves that the films provide protection against UV light and sunlight induced photo degradation. The cellulose fiber reinforced PVA biocomposites were found to be biodegradable in garden soil and Municipal waste dump yard soil with complete degradation being achieved in 2 weeks. Further, the biocomposites exhibited low oxygen transfer rates. Good tensile and thermal properties along with lower affinity for oxygen transfer makes these biocomposites as ideal choice in the field of food packaging. These biodegradable composites prepared from the cellulose fibers isolated from industry and agricultural residues can serve as economical 7and eco-friendly replacements for the conventional composites